0001060955-23-000007 | 20-F | XBRL Viewer

Print Document View Excel Document

Employee Benefits - Components of Net Periodic Benefit Cost (Details) - United Kingdom - ICON Development Solutions Limited pension plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 117	$ 134	$ 100
Interest cost	672	665	746
Expected return on plan assets	(1,258)	(1,171)	(1,214)
Amortization of net loss	228	625	160
Net periodic benefit cost	$ (241)	$ 253	$ (208)

Investments

12 Months Ended

Dec. 31, 2022

Investments, Debt and Equity Securities [Abstract]

Investments

(a) Available for sale investments (short-term)

The Company held $1.7 million of available for sale investments at both December 31, 2022 and December 31, 2021. The Company classifies its investment in short term investments as available for sale. Short term investments comprise highly liquid investments with maturities of greater than three months and minimum "A-" rated fixed term deposits.

Short term investments at December 31, 2022 have an average maturity of 2.8 years compared to 2.7 years at December 31, 2021. The contractual maturity of certain investments in the portfolio is greater than 12 months; however, classification as short-term investments reflects the Company practice and intention in respect of these investments. The Company recognizes the unrealized losses at fair value in equity as these unrealized losses on short term investments have been considered as temporary.

(b) Available for sale investments (long-term)

The Company entered into subscription agreements with a number of funds. Capital totaling $20.6 million had been advanced under the terms of the subscription agreements at December 31, 2022 (December 31, 2021: $16.9 million). The Company determined that the interests in the funds meet the definition of equity securities without readily determinable fair values. The Company concluded that the interests held at December 31, 2022 qualify for the NAV practical expedient in ASC 820 'Fair value measurements and disclosures'. These are therefore measured at Level 3 of the fair value hierarchy. There was an increase in fair value of $6.3 million (December 31, 2021: $3.2 million) recognized in net income during the year bringing the carrying value of the subscriptions to $32.6 million at December 31, 2022 (December 31, 2021: $22.6 million). At December 31, 2022, the Company had committed to future investments of $23.3 million in respect of these funds.

The Company has invested $4.9 million to obtain a 49% interest in the voting share capital of Oncacare. The Company’s investment in Oncacare is accounted for under the equity method due to the Company's ability to exercise significant influence over Oncacare that is considered to be greater than minor. The Company records its pro rata share of the earnings/losses of this investment in 'Share of equity method investments' in the Consolidated Statement of Operations.

The majority investor has the right to sell the 51% majority voting share capital exclusively to the Company in an eighteen month period, commencing January 1, 2023 and ICON also has the right to acquire the 51% majority voting share capital from August 1, 2025.

The following table represents our equity method investments at December 31, 2022:


	Ownership Percentage		Carrying Value		Carrying Value

	December 31, 2022		December 31, 2022		December 31, 2021
			(in thousands)
Oncacare Limited	49	%	$	—	$	2,373

During the year ended December 31, 2021, the Company provided a loan of $10 million to Oncacare in order to fund the continued development of the business operations. The loan accrues annual interest at 1.6% and the loan is repayable on June 30, 2025.

The Company has recorded losses of $3.1 million and $2.2 million representing its pro rata share of the losses in Oncacare during the year ended December 31, 2022 and December 31, 2021, respectively. The carrying value of the Company's investment in Oncacare was reduced by $2.3 million of pro rata losses. The remaining $0.8 million in pro rata losses served to reduce the carrying value of the Company's loan receivable from Oncacare. The outstanding balance of the Company's loan receivable with Oncacare at December 31, 2022 is $9.2 million.

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Litigation We do not expect any litigation to have a materially adverse effect on our financial condition or results of operations. However, from time to time, we may become involved in various lawsuits and legal proceedings which arise in the ordinary course of business. Litigation is subject to inherent uncertainties, and an adverse result in these or other matters may arise from time to time that may harm our business. Operating Leases The Company has several non-cancelable operating leases, primarily for facilities, that expire over the next twelve years. These leases generally contain renewal options and require the Company to pay all executory costs such as maintenance and insurance. See note 15 - Operating leases for rental expense pursuant to ASC 842 for the years ended December 31, 2022 and December 31, 2021 and future minimum rental commitments as of December 31, 2022.

Fair Value

12 Months Ended

Dec. 31, 2022

Fair Value Disclosures [Abstract]

Fair Value

The Company records certain assets and liabilities at fair value. Fair value is defined as the price that would be received to sell an asset, or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. A three-level fair value hierarchy that prioritizes the inputs used to measure fair value is described below. This hierarchy requires entities to maximize the use of observable inputs and minimize the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows:

•Level 1 — Quoted prices in active markets for identical assets or liabilities.

•Level 2 — Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data.

•Level 3 — Unobservable inputs that are supported by little or no market activity. This includes certain pricing models, discounted cash flow methodologies, and similar techniques that use significant unobservable inputs.

The carrying amounts of financial instruments, including cash and cash equivalents, accounts receivable, unbilled services, contract assets, accounts payable, and unearned revenue approximate fair value due to the short maturities of these instruments.

As of December 31, 2022, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows (in thousands):


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
Assets:
Available for sale securities (short-term) (a)	1,713		—		—		—		1,713
Available for sale investments (long-term) (b)	—		—		—		32,663		32,663
Derivative instruments (c)	—		12		—		—		12
Total assets	$	1,713	$	12	$	—	$	32,663	$	34,388

Liabilities:
Derivative instruments (c)	—		3,670		—		—		3,670
Total Liabilities	$	—	$	3,670	$	—	$	—	3,670

As of December 31, 2021, the fair value of the major classes of the Company's assets measured at fair value on a recurring basis were as follows (in thousands):


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
Assets:
Available for sale securities (short-term) (a)	1,712		$	—	$	—	—		1,712
Available for sale investments (long-term) (b)	—		$	—	$	—	20,579		20,579
Total assets	$	1,712	$	—	$	—	$	20,579	$	22,291

(a) Represents the fair value of investments in highly liquid investments with maturities of greater than three months and a minimum "A-" rated fixed term deposits and are based on quoted market prices.

(b) To determine the classification of its interests in long-term investments, the Company considered the nature of its investment, the extent of influence over operating and financial decisions and the availability of readily determinable fair values. The Company determined that the interests in funds at December 31, 2022 and December 31, 2021 meet the definition of equity securities without readily determinable fair values. The Company concluded that the interests held at December 31, 2022 and December 31, 2021 qualify for the Net Asset Value (NAV) practical expedient in ASC 820 'Fair value measurements and disclosures'. Any increases or decreases in fair value are recognized in net income in the period.

(c) Represents the fair value of interest rate cap and interest rate swap agreements. The fair value of the agreements are the estimated amount that the Company would receive or pay to terminate such agreements, taking into account market interest rates and the remaining time to maturities or using market inputs with mid-market pricing as a practical expedient for bid-ask spread. The Company held no derivative instruments at December 31, 2021.

Non-recurring Fair Value Measurements

Certain assets and liabilities are carried on the accompanying Consolidated Balance Sheet at cost and are not re-measured to fair value on a recurring basis. These assets include finite-lived intangible assets that are tested for impairment when a triggering event occurs and goodwill that is tested for impairment annually or when a triggering event occurs. As of December 31, 2022, assets carried on the balance sheet and not re-measured to fair value on a recurring basis totaled approximately $13,250.4 million and are identified as Level 3 assets. These assets are comprised of goodwill of $8,971.7 million and identifiable intangible assets, net of $4,278.7 million.

As of December 31, 2022 and 2021, the fair value of total debt approximated $4,650.3 million and $5,507.2 million, respectively, as determined under Level 2 measurement for these financial instruments.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Non-current Bank Credit Lines and Loan Facilities - Schedule of Maturities of Long-term Debt (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Debt Disclosure [Abstract]
2023	$ 55,150
2024	55,150
2025	55,150
2026	55,150
2027 and thereafter	4,480,613
Total long-term debt, net	$ 4,701,213

- Definition

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Employee Benefits - Change in Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
United Kingdom \| ICON Development Solutions Limited pension plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 36,198	$ 34,612
Expected return on plan assets	1,258	1,171	$ 1,214
Actual return on plan assets	(7,305)	1,176
Employer contributions	70	91
Plan participants' contributions	19	23
Benefits paid	(514)	(489)
Foreign currency exchange rate changes	(3,676)	(386)
Fair value of plan assets at end of year	26,050	36,198	34,612
Switzerland \| Aptiv Solutions pension plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	6,964	7,601
Expected return on plan assets	29	15
Actual return on plan assets	(987)	(238)
Scheme contributions	114	128
Plan participants' contributions	82	95
Benefits paid and transferred balances	182	(76)
Settlement	(218)	(483)
Foreign currency exchange rate changes	(121)	(230)
Fair value of plan assets at end of year	5,681	6,964	7,601
Switzerland \| PRA Switzerland AG pension plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	3,017	2,849
Expected return on plan assets	29	15
Actual return on plan assets	87	0
Employer contributions	325	135
Plan participants' contributions	2,396	135
Benefits paid	(946)	(113)
Settlement	(844)	0
Foreign currency exchange rate changes	(5)	(4)
Fair value of plan assets at end of year	$ 4,059	$ 3,017	$ 2,849

Equity Incentive Schemes and Stock Compensation Charges - Summary of Stock Option Activity (Details) - Stock Option and Award Plans - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Options Granted Under Plans
Beginning balance (in shares)	1,695,460	553,746	656,107
Assumed through business combination (in shares)		2,177,130
Granted (in shares)	108,643	100,299	107,737
Exercised (in shares)	(348,286)	(1,065,529)	(193,417)
Canceled/expired (in shares)	(77,698)	(70,186)	(16,681)
Ending balance (in shares)	1,378,119	1,695,460	553,746
Vested and exercisable at end of period (in shares)	1,047,803
Weighted Average Exercise Price
Beginning balance (USD per share)	$ 110.38	$ 108.53	$ 87.80
Assumed through business combination (USD per share)		108.78
Granted (USD per share)	229.94	177.76	159.83
Exercised (USD per share)	102.87	111.29	68.19
Canceled/expired (USD per share)	143.08	128.46	92.21
Ending balance (USD per share)	119.86	$ 110.38	$ 108.53
Vested and exercisable at end of period (USD per share)	$ 102.29

Operating Leases Operating Leases - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net operating lease costs	$ 52,715	$ 49,862
Right-of-use assets obtained in exchange for lease obligations	28,700	10,200
Impairment of long lived assets	$ 24,800	$ 15,400
Weighted average remaining lease term	6 years 10 months 24 days	6 years 10 months 28 days
Weighted average discount rate (in percent)	2.45%	2.51%
Operating lease liabilities	$ 43,657	$ 49,949
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other liabilities (Note 12)	Other liabilities (Note 12)
Selling, general and administrative
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net operating lease costs	$ 48,300	$ 47,500
Cost of Sales
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net operating lease costs	$ 4,400	$ 2,400

Disaggregation of Revenue

12 Months Ended

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

Revenue disaggregated by customer profile is as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Top client	$	683,546	$	441,173	$	337,904
Clients 2-5	1,506,087		1,291,946		754,906
Clients 6-10	1,112,636		752,325		350,865
Clients 11-25	1,585,739		1,077,073		501,643
Other	2,853,378		1,918,309		851,970
Total	$7,741,386		$5,480,826		$2,797,288

Our customers have similar profiles and economic characteristics, and therefore have similar degrees of risk and growth opportunities.Contract Balances

Accounts receivable and unbilled revenue are as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Billed services (accounts receivable)	$	1,751,950	$	1,349,851
Allowance for credit losses (note 5)	(20,562)		(7,081)
Accounts receivable (net)	1,731,388		1,342,770
Unbilled services (unbilled revenue)	$	957,655	$	623,121
Accounts receivable and unbilled revenue, net	$	2,689,043	$	1,965,891

Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows:


(in thousands, except percentages)	December 31, 2022		December 31, 2021		$ Change		% Change

Unbilled services (unbilled revenue)	$	957,655	$	623,121	$	334,534	53.7	%
Unearned revenue (payments on account)	(1,507,449)		(1,323,961)		(183,488)		13.9	%
Net balance	$	(549,794)	$	(700,840)	$	151,046	21.6	%

Timing may differ between the satisfaction of performance obligations and the invoicing and collection of amounts related to our contracts with customers. We record assets for amounts related to performance obligations that are satisfied but not yet billed and/or collected. These assets are recorded as unbilled revenue and therefore contract assets rather than accounts receivable when receipt of the consideration is conditional on something other than the passage of time. Liabilities are recorded for amounts that are collected in advance of the satisfaction of performance obligations or billed in advance of the revenue being earned.

Unbilled services/revenue balances arise where invoicing or billing is based on the timing of agreed milestones related to service contracts for clinical research. Contractual billing arrangements in respect of certain reimbursable expenses (principally investigators) require billing by the investigator to the Company prior to billing by the Company to the customer. As there is no contractual right of set-off between unbilled services (contract assets) and unearned revenue (contract liabilities), each are separately presented gross on the Consolidated Balance Sheet.

The Company is the contract principal in respect of both direct services and in the use of third parties (principally investigator services) that support a clinical trial. The progress towards completion for clinical service contracts is measured based on total project costs (including reimbursable costs). Amounts owed to investigators and others in respect of reimbursable expenses at December 31, 2022 and December 31, 2021 were $406.3 million and $323.6 million (see note 12 - Other liabilities).

Unbilled services as at December 31, 2022 increased by $334.5 million as compared to December 31, 2021. Unearned revenue increased by $183.5 million over the same period resulting in a decrease of $151.0 million in the net balance of unbilled services and unearned revenue or payments on account between December 31, 2021 and December 31, 2022. These fluctuations are primarily due to the completion of the Merger on July 1, 2021 but are also partially due to timing of payments and invoicing related to the Group's clinical trial management contracts. Billings and payments are established by contractual provisions including predetermined payment schedules which may or may not correspond to the timing of the transfer of control of the Company's services under the contract. Unbilled services arise from long-term contracts when a cost-based input method of revenue recognition is applied and revenue recognized exceeds the amount billed to the customer.

The credit loss expense recognized on the Group's receivables and unbilled services was $17.8 million and $0.9 million for the twelve months ended December 31, 2022 and 2021, respectively.

As of December 31, 2022 approximately $13.7 billion of revenue is expected to be recognized in the future in respect of unsatisfied performance obligations compared to $13.3 billion as of December 31, 2021. As of December 31, 2022 the Company expects to recognize revenue on approximately 52% of the unrealized performance obligation over the next twelve months compared to 48% as of December 31, 2021, with the remainder recognized thereafter over the duration of the customer contracts.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI https://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

+ Details

Summary of Significant accounting policies - Estimated Useful Lives of Intangible Assets (Details)	12 Months Ended
	Dec. 31, 2022
Customer relationships
Indefinite-lived Intangible Assets [Line Items]
Amortization period	23 years
Order backlog
Indefinite-lived Intangible Assets [Line Items]
Amortization period	3 years
Trade names & brands
Indefinite-lived Intangible Assets [Line Items]
Amortization period	3 years
Patient database
Indefinite-lived Intangible Assets [Line Items]
Amortization period	7 years
Technology assets
Indefinite-lived Intangible Assets [Line Items]
Amortization period	5 years

Derivatives - Effect of Derivative Financial Instruments on Statement of Financial Position (Details) - Total derivatives designated as hedging instruments	Dec. 31, 2022 USD ($)
Interest Rate Caps
Derivative [Line Items]
Derivative Asset	$ 12,000
Derivative Liability	3,363,000
Notional	2,100,606,000
Interest Rate Swap
Derivative [Line Items]
Derivative Asset	0
Derivative Liability	307,000
Notional	1,100,606,000
Interest rate cap and interest rate swap
Derivative [Line Items]
Derivative Asset	12,000
Derivative Liability	3,670,000
Notional	$ 3,201,213,000

Non-current Bank Credit Lines and Loan Facilities - Narrative (Details) - USD ($) $ in Thousands								12 Months Ended
	Dec. 30, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 29, 2021	Sep. 27, 2021	Jul. 01, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Total financing costs								$ 229,731	$ 182,423	$ 13,019
Cash paid for interest								210,918	106,205	$ 13,062
Long-term debt at fair value								4,650,300	5,507,200
PRA Health Sciences, Inc
Debt Instrument [Line Items]
Total financing costs								$ 17,700	$ 86,700
Senior Secured Term Loan \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								0.50%
Senior Secured Term Loan \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)							2.25%
Senior secured revolving loan facility \| Variable rate component one \| Base rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								0.60%
Senior secured revolving loan facility \| Variable rate component one \| Base rate \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								1.00%
Senior secured revolving loan facility \| Variable rate component one \| Base rate \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								0.25%
Senior secured revolving loan facility \| Variable rate component two \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								1.60%
Senior secured revolving loan facility \| Variable rate component two \| London Interbank Offered Rate (LIBOR) \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								2.00%
Senior secured revolving loan facility \| Variable rate component two \| London Interbank Offered Rate (LIBOR) \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								1.25%
Credit Facilities: \| Senior secured credit facility and senior secured notes
Debt Instrument [Line Items]
Debt discount paid							$ 27,600
Credit Facilities: \| Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, face amount							$ 5,515,000
Debt instrument, interest rate (in percent)							1.00%	7.092%	2.75%
Repayments of senior debt	$ 200,000	$ 200,000	$ 100,000	$ 300,000	$ 500,000	$ 13,800
Cash paid for interest	66,100	53,600	39,400	35,100	40,800	$ 40,400
Payments of debt restructuring costs	$ 1,800	$ 1,900	$ 900	$ 3,200	$ 5,600
Credit Facilities: \| Senior Secured Revolving Credit Facility
Debt Instrument [Line Items]
Remaining borrowing capacity								$ 300,000
Line of credit \| Senior secured revolving loan facility \| Revolving loan facility
Debt Instrument [Line Items]
Maximum borrowing capacity							$ 300,000
Senior Secured Notes \| Senior Secured Notes
Debt Instrument [Line Items]
Debt instrument, face amount							$ 500,000
Debt instrument, interest rate (in percent)							2.875%	2.875%	2.875%

Allowances for Credit Losses

12 Months Ended

Dec. 31, 2022

Accounts Receivable, after Allowance for Credit Loss [Abstract]

Allowances for Credit Losses

Allowance for Credit Losses

The Company does business with most major international pharmaceutical companies. Provision for credit losses at December 31, 2022 and December 31, 2021 comprises:


	December 31, 2022		December 31, 2021
	(in thousands)
Opening provision	$	7,081	$	7,149
Amounts used during the year	(3,913)		(116)
Amounts provided during the year	17,800		705
Amounts released during the year	—		(544)
Foreign exchange	(406)		(113)
Closing provision	$	20,562	$	7,081

Business Segment and Geographical Information (Tables)

12 Months Ended

Dec. 31, 2022

Segment Reporting [Abstract]

Schedule of Distribution of Net Revenue by Geographical Area

Reportable geographic information at December 31, 2022 and December 31, 2021 and for the years ended December 31, 2022, December 31, 2021 and December 31, 2020 is as follows:

a) The distribution of revenue by geographical area was as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020

	(in thousands)
Ireland	$	1,984,567	$	1,365,909	$	1,181,292
Rest of Europe	1,618,350		1,175,515		416,884
U.S.	3,574,610		2,581,007		925,563
Other	563,859		358,395		273,549
Total	$	7,741,386	$	5,480,826	$	2,797,288

Schedule of Distribution of Income from Operations by Geographical Area

The distribution of income from operations (including Restructuring) by geographical area was as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Ireland *	$	218,088	$	131,961	$	276,478
Rest of Europe	253,799		177,863		35,765
U.S.	254,849		39,132		58,018
Other	68,501		29,573		21,239
Total	$	795,237	$	378,529	$	391,500

* Includes the full amount of the amortization charge associated with the intangible asset acquired in the Merger.

Schedule of Distribution of Long-lived Assets, Net, by Geographical Area

The distribution of long-lived assets (property, plant and equipment and operating right-of-use assets), net, by geographical area was as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Ireland	$	143,025	$	118,253
Rest of Europe	99,721		121,174
U.S.	213,311		239,828
Other	48,095		55,312
Total	$	504,152	$	534,567

Equity Incentive Schemes and Stock Compensation Charges - Outstanding and Exercisable Share Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum Range Exercise Price (USD per share)	$ 14.88
Maximum Range Exercise Price (USD per share)	231.68
Range 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum Range Exercise Price (USD per share)	14.88
Maximum Range Exercise Price (USD per share)	96.15
Range 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum Range Exercise Price (USD per share)	103.81
Maximum Range Exercise Price (USD per share)	124.00
Range 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum Range Exercise Price (USD per share)	125.74
Maximum Range Exercise Price (USD per share)	147.26
Range 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum Range Exercise Price (USD per share)	159.33
Maximum Range Exercise Price (USD per share)	$ 231.68
Stock Option and Award Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares (in shares)	1,378,119
Weighted Average Remaining Contractual Life	4 years 8 months 8 days
Weighted average exercise price (USD per share)	$ 119.86	$ 110.38	$ 108.53	$ 87.80
Number of Shares (in shares)	1,047,803
Vested and exercisable at end of period (USD per share)	$ 102.29
Stock Option and Award Plans \| Range 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares (in shares)	494,565
Weighted Average Remaining Contractual Life	2 years 8 months 12 days
Number of Shares (in shares)	494,565
Stock Option and Award Plans \| Range 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares (in shares)	226,489
Weighted Average Remaining Contractual Life	5 years 6 months 29 days
Number of Shares (in shares)	203,605
Stock Option and Award Plans \| Range 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares (in shares)	386,518
Weighted Average Remaining Contractual Life	5 years 7 months 24 days
Number of Shares (in shares)	303,054
Stock Option and Award Plans \| Range 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares (in shares)	270,547
Weighted Average Remaining Contractual Life	6 years 2 months 26 days
Number of Shares (in shares)	46,579

Share Capital	12 Months Ended
Share Capital	Dec. 31, 2022
Equity [Abstract]
Share Capital	Share CapitalHolders of ordinary shares are entitled to receive such dividends as may be recommended by the Board of Directors of the Company and approved by the shareholders and/or such interim dividends as the Board of Directors of the Company may decide. On liquidation or a winding up of the Company, the par value of the ordinary shares are repaid out of the assets available for distribution among the holders of the ordinary shares of the Company. Holders of ordinary shares have no conversion or redemption rights. On a show of hands, every holder of an ordinary share present in person or proxy at a general meeting of shareholders shall have one vote, for each ordinary share held with no individual having more than one vote. (a)Employee share based payments During the year ended December 31, 2022, 348,286 options were exercised by employees at an average exercise price of $102.87 per share for total proceeds of $35.8 million. During the year ended December 31, 2022, 195,029 ordinary shares were issued in respect of certain RSUs and 46,087 ordinary shares were issued in respect of PSUs previously awarded by the Company. During the year ended December 31, 2021, 1,065,529 options were exercised by employees at an average exercise price of $111.29 per share for total proceeds of $118.6 million. During the year ended December 31, 2021, 446,404 ordinary shares were issued in respect of certain RSUs and 44,132 ordinary shares were issued in respect of PSUs previously awarded by the Company. On July 1, 2021, the Company completed the Acquisition of PRA. In accordance with the terms of the Merger Agreement, the Company issued 27,372,427 shares of the Company’s ordinary share capital at par value in exchange for all outstanding PRA shares of common stock. During the year ended December 31, 2020, 193,417 options were exercised by employees at an average exercise price of $68.19 per share for total proceeds of $13.2 million. During the year ended December 31, 2020, 144,172 ordinary shares were issued in respect of certain RSUs and 63,516 ordinary shares were issued in respect of PSUs previously awarded by the Company. (b)Share Repurchase Program A resolution was passed at the Company’s Annual General Meeting (“AGM”) on July 22, 2016, which authorized the Directors to purchase (buyback) up to 10% of the outstanding shares in the Company. This authorization was renewed at the Company's AGM on each of July 25, 2017, July 24, 2018, July 23, 2019, July 21, 2020, July 20, 2021 and July 26, 2022. On October 3, 2016, the Company commenced a share buyback program of up to $400 million. The share buyback program was completed during the year ended December 31, 2018 with a total of 4,026,576 ordinary shares redeemed for a total consideration of $372.1 million. On January 8, 2019, the Company commenced a further share buyback program of up to 1.0 million ordinary shares which was completed during the year ended December 31, 2019. These shares were redeemed by the Company for a total consideration of $141.6 million. On October 22, 2019, the Company commenced a further share buyback program. At December 31, 2019, 35,100 ordinary shares were redeemed by the Company for a total consideration of $5.3 million. During the year ended December 31, 2020, 1,235,218 ordinary shares were redeemed by the Company under this buyback program for a total consideration of $175.0 million. On February 18, 2022, the Company commenced a share buyback program which was fully complete at March 31, 2022. Under this buyback program, 420,530 ordinary shares were redeemed by the Company for total consideration of $100.0 million. All ordinary shares that were redeemed under the buyback program were canceled in accordance with the Constitution of the Company and the nominal value of these shares transferred to other undenominated capital as required under Irish Company law. Under the repurchase program, a broker purchased or may purchase the Company's shares from time to time on the open market or in privately negotiated transactions in accordance with agreed terms and limitations. The program was and may be in the future designed to allow share repurchases during periods when the Company would ordinarily not be permitted to do so because it may be in possession of material non-public or price-sensitive information or due to applicable insider trading laws or self-imposed trading blackout periods. The Company's instructions to the broker in such cases were or may in the future be irrevocable and the trading decisions in respect of the repurchase program were made or will be made independently of and uninfluenced by the Company. The Company confirms that on entering the share repurchase plans it had no material non-public, price-sensitive or inside information regarding the Company or its securities. Furthermore, the Company will not enter into additional plans whilst in possession of such information. The timing and actual number of shares acquired by way of the redemption will be dependent on market conditions, legal and regulatory requirements and the other terms and limitations contained in the program. In addition, acquisitions under the program may be suspended or discontinued in certain circumstances in accordance with the agreed terms. Therefore, there can be no assurance as to the timing or number of shares that may be acquired under the program.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-URI https://asc.fasb.org/topic&trid=2208762

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI https://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 16
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496180-112644

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126731327&loc=SL126733271-114008

+ Details

Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Finite-Lived Intangible Assets

Intangible assets are amortized on a straight-line basis over the expected useful life, as set forth in the table below:


			Estimated Useful Life
Customer relationships			23 years
Order backlog			3 years
Trade names			3 years
Patient database			7 years
Technology assets			5 years

The carrying amount of Intangible Assets for the years ended December 31, 2022 and 2021 is as follows:


	December 31, 2022		December 31, 2021
Cost	(in thousands)
Customer relationships	$	4,076,435	$	4,056,642
Order backlog	536,934		528,022
Trade names & brands	204,621		204,685
Patient database	170,238		170,525
Technology assets	120,984		121,507
Total cost	5,109,212		5,081,381

Accumulated amortization	(830,553)		(370,538)
Net book value	$	4,278,659	$	4,710,843

Schedule of Future Intangible Asset Amortization Expense

Future intangible asset amortization expense for the years ended December 31, 2023 to December 31, 2027 is as follows:


	Year Ended December 31, 2022
	(in thousands)
2023	$	460,711
2024	339,940
2025	223,674
2026	209,681
2027	198,300
	$	1,432,306

Non-current Bank Credit Lines and Loan Facilities

12 Months Ended

Dec. 31, 2022

Debt Disclosure [Abstract]

Non-current Bank Credit Lines and Loan Facilities

The Company had the following debt outstanding as of December 31, 2022 and 2021:


					Principal amount
	Interest rate as of		Interest rate as of		December 31,		December 31,
(in thousands)	December 31, 2022		December 31, 2021		2022		2021		Maturity Date
Credit Facilities:
Senior Secured Term Loan	7.092	%	2.750	%	$	4,201,213	$	5,001,213	July 2028

Senior Secured Notes	2.875	%	2.875	%	500,000		500,000		July 2026



Total debt					4,701,213		5,501,213

Less current portion of long-term debt and debt issuance costs					(55,150)		(55,150)
Total long-term debt					4,646,063		5,446,063
Less long-term portion of debt issuance costs and debt discount					(47,026)		(64,901)
Total long-term debt, net					$	4,599,037	$	5,381,162

The Company paid a $27.6 million debt discount in connection with the Senior Secured Credit Facility and Senior Secured Notes on July 1, 2021.

The Company incurred interest costs from various financing arrangements during the years ended December 31, 2022, December 31, 2021 and December 31, 2020 as set out in the table below. These costs have been charged in the interest expense line of the Consolidated Statement of Operations. In the years ending December 31, 2022 and December 31, 2021, the Company expensed $17.7 million and $86.7 million of transaction related financing costs (inclusive of the amortization of financing fees which were previously capitalized) associated with the debt facilities used to finance the Merger.


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)

Interest expense on drawn facilities	$	209,189	$	93,809	$	13,406
Amortization of financing costs	17,749		12,890		523
Transaction and one time financing costs	—		75,391		—
Other financing costs/(credits)	2,793		333		(910)
Total financing costs	$	229,731	$	182,423	$	13,019

As of December 31, 2022, the contractual maturities of the Company's debt obligations were as follows:


Current maturities of long-term debt:	(in thousands)
2023	55,150
2024	55,150
2025	55,150
2026	55,150
2027 and thereafter	4,480,613
Total	$	4,701,213

The Company's primary financing arrangements are its senior secured credit facilities (the "Senior Secured Credit Facilities"), which consists of a senior secured term loan and a revolving credit facility, and the senior secured notes (the "Senior Secured Notes").

Senior Secured Credit Facilities

In conjunction with the completion of the Merger Agreement, on July 1, 2021, ICON entered into a credit agreement providing for a senior secured term loan facility of $5,515 million and a senior secured revolving loan facility in an initial aggregate principal amount of $300 million (the "Senior Secured Credit Facilities"). The proceeds of the senior secured term loan facility were used to repay in full (i) PRA’s existing credit facilities and (ii) the Company's notes and fund, in part, the Merger. The senior secured term loan facility will mature in July 2028 and the senior secured revolving loan facility will mature in July 2026. The credit agreement governing the Senior Secured Credit Facilities provides that borrowings denominated in U.S. Dollars will bear interest based on LIBOR or the base rate (as elected by the borrower), plus an applicable margin. On the 29th of November 2022, the Company agreed with its lenders to the early adoption of Term SOFR as the reference rate within the Credit Agreement ahead of the June 2023 USD LIBOR cessation date. LIBOR is no longer an applicable reference rate available to the Company under the terms of the Credit Agreement.

Borrowings under the senior secured term loan facility amortize in equal quarterly installments in an amount equal to 1.00% per annum of the principal amount, with the remaining balance due at final maturity. The interest rate margin applicable to borrowings under the senior secured term loan facility is USD Term SOFR and a Term SOFR Adjustment depending on the interest period chosen plus an applicable margin of 2.25%. The senior secured term loan facility is subject to a floor of 0.50%.

The interest rate margin applicable to borrowings under the revolving loan facility will be, at the option of the borrower, either (i) the applicable base rate plus an applicable margin of 1.00%, 0.60% or 0.25% based on ICON’s current corporate family rating assigned by S&P of BB- (or lower), BB or BB+ (or higher), respectively, or (ii) Term SOFR plus a Term SOFR Adjustment on the interest period chosen plus an applicable margin of 2.00%, 1.60% or 1.25% based on ICON’s current corporate family rating assigned by S&P of BB- (or lower), BB or BB+ (or higher), respectively. In addition, lenders under the revolving loan facility are entitled to commitment fees as a percentage of the applicable margin at the time of drawing and utilization fees dependent on the proportion of the facility drawn. At December 31, 2022, $300.0 million remained undrawn under the senior secured revolving loan facility.

The Borrowers’ (as defined in the Senior Secured Credit Facility) obligations under the Senior Secured Credit Facilities are guaranteed by ICON and the subsidiary guarantors. The Senior Secured Credit Facilities are secured by a lien on substantially all of ICON’s, the Borrowers’ and each of the subsidiary guarantor’s assets (subject to certain exceptions), and the Senior Secured Credit Facilities will have a first-priority lien on such assets, which will rank pari passu with the lien securing the Senior Secured Notes, subject to other permitted liens. The Company is permitted to make prepayments on the senior secured term loan without penalty.

On December 30, 2022, the Company repaid $200.0 million of the senior secured term loan facility and made a quarterly interest payment of $66.1 million. This repayment resulted in an additional charge associated with previously capitalized fees of $1.8 million.

On September 30, 2022, the Company repaid $200.0 million of the senior secured term loan facility and made a quarterly interest payment of $53.6 million. This repayment resulted in an additional charge associated with previously capitalized fees of $1.9 million.

On June 30, 2022, the Company repaid $100.0 million of the senior secured term loan facility and made a quarterly interest payment of $39.4 million. This repayment resulted in an additional charge associated with previously capitalized fees of $0.9 million.

On March 31, 2022, the Company repaid $300.0 million of the senior secured term loan facility and made a quarterly interest payment of $35.1 million. This repayment resulted in an additional charge associated with previously capitalized fees of $3.2 million.

On December 29, 2021, the Company repaid $500.0 million of the senior secured term loan facility and made a quarterly interest payment of $40.8 million. This repayment resulted in an additional charge associated with previously capitalized fees of $5.6 million.

On September 27, 2021, the Company repaid $13.8 million of the senior secured term loan facility and made a quarterly interest payment of $40.4 million.

Senior Secured Notes

In addition to the Senior Secured Credit Facilities, on July 1, 2021, a subsidiary of the Company issued $500 million in aggregate principal amount of 2.875% senior secured notes due 2026 in a private offering (the “Offering”). The Senior Secured Notes will mature on July 15, 2026.

Fair Value of Debt

The estimated fair value of the Company’s debt was $4,650.3 million and $5,507.2 million at December 31, 2022 and December 31, 2021, respectively. The fair values of the Senior Secured Credit Facilities and Senior Secured Notes were determined based on Level 2 inputs, which are based on rates at which the debt is traded among financial institutions.

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 505,304	$ 153,185	$ 332,964
Other comprehensive income, net of tax
Currency translation adjustment	(89,530)	(60,617)	46,526
Unrealized capital loss - investments	0	0	(231)
Actuarial gain/(loss) on defined benefit pension plan	12,657	4,266	(4,138)
Amortization of cash flow hedge	0	113	(910)
(Loss)/gain on cash flow hedge	(3,728)	778	(905)
Total comprehensive income	424,703	97,725	373,306
Less net income attributable to noncontrolling interest	0	0	(633)
Total comprehensive income attributable to the Group	$ 424,703	$ 97,725	$ 372,673

Fair Value - Measurement of Fair Value of Major Asset and Liability classed (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments (Note 8a)	$ 1,713	$ 1,712
Available for sale investments (long-term) (b)	32,663	20,579
Total assets	34,388	22,291
Total Liabilities	3,670
Interest rate cap and interest rate swap \| Total derivatives designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments (c)	12
Derivative instruments (c)	3,670
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments (Note 8a)	1,713	1,712
Available for sale investments (long-term) (b)	0	0
Total assets	1,713	1,712
Total Liabilities	0
Level 1 \| Interest rate cap and interest rate swap \| Total derivatives designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments (c)	0
Derivative instruments (c)	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments (Note 8a)	0	0
Available for sale investments (long-term) (b)	0	0
Total assets	12	0
Total Liabilities	3,670
Level 2 \| Interest rate cap and interest rate swap \| Total derivatives designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments (c)	12
Derivative instruments (c)	3,670
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments (Note 8a)	0	0
Available for sale investments (long-term) (b)	0	0
Total assets	0	0
Total Liabilities	0
Level 3 \| Interest rate cap and interest rate swap \| Total derivatives designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments (c)	0
Derivative instruments (c)	0
Fair Value Measured at Net Asset Value Per Share
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments (Note 8a)	0	0
Available for sale investments (long-term) (b)	32,663	20,579
Total assets	32,663	$ 20,579
Total Liabilities	0
Fair Value Measured at Net Asset Value Per Share \| Interest rate cap and interest rate swap \| Total derivatives designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments (c)	0
Derivative instruments (c)	$ 0

Fair value - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	$ 34,388	$ 22,291
Long-term debt at fair value	4,650,300	5,507,200
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	$ 0
Fair value, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Identifiable intangible assets, net	4,278,700
Fair value, nonrecurring \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	13,250,400
Goodwill	$ 8,971,700

Income Taxes - Reconciliation of Beginning and Ending Amount of Total Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at start of year	$ 202,065	$ 19,078	$ 20,156
Increase related to acquired tax positions		170,047	0
Increase related to prior year tax positions	16,098	204	401
Decrease related to prior year tax positions	(5,442)	(1,695)	(1,271)
Increase related to current year tax positions	5,701	18,613	2,931
Settlements	0	(844)	(369)
Lapse of statute of limitations	(838)	(3,338)	(2,770)
Unrecognized tax benefits at end of year	$ 217,584	$ 202,065	$ 19,078

Operating Leases

12 Months Ended

Dec. 31, 2022

Leases [Abstract]

Operating Leases

Lease costs recorded under operating leases as of December 31, 2022 and 2021 were as follows:


	Year ended
	December 31, 2022		December 31, 2021
	(in thousands)

Operating lease costs	$	53,880	$	51,200
Income from sub-leases	(1,165)		(1,338)
Net operating lease costs	$	52,715	$	49,862

Of the total cost of $52.7 million incurred in the year ended December 31, 2022, $48.3 million is recorded within selling, general and administration costs and $4.4 million is recorded within direct costs. Of the total cost of $49.9 million incurred in the year ended December 31, 2021, $47.5 million is recorded within selling, general and administration costs and $2.4 million is recorded within direct costs.

Right-of-use assets obtained, in exchange for lease obligations, net of early termination options now reasonably certain to be exercised, during the years ended December 31, 2022 and December 31, 2021 totaled $28.7 million and $10.2 million, respectively.

During the years ended December 31, 2022 and December 31, 2021, impairments of operating right-of-use assets were recognized within restructuring charges for $24.8 million and $15.4 million, respectively, as part of an office consolidation program (see note 19 - Restructuring Charges).

The weighted average remaining lease term and weighted-average discount rate at December 31, 2022 were 6.90 years and 2.45%, respectively. The weighted average remaining lease term and weighted-average discount rate at December 31, 2021 were 6.91 years and 2.51%, respectively.

Future minimum lease payments under non-cancelable leases as of December 31, 2022 were as follows:


	Minimum rental
	payments
	(in thousands)
2023	$	47,479
2024	34,400
2025	25,045
2026	20,430
2027	17,249
Thereafter	45,065
Total future minimum lease payments	189,668
Lease imputed interest	(14,367)
Total	$	175,301

Operating lease liabilities are presented as current and non-current. Operating lease liabilities of $43.7 million and $49.9 million have been included in other liabilities as at December 31, 2022 and December 31, 2021, respectively.

Goodwill (Tables)

12 Months Ended

Dec. 31, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

The change in the carrying amount of Goodwill for the years ended December 31, 2022 and 2021 is as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Opening goodwill	$	9,037,931	$	936,257
Current year acquisitions (note 6)	—		8,120,006
Prior period acquisition (note 6)	(35,692)		—
Foreign exchange movement	(30,569)		(18,332)
Closing goodwill	$	8,971,670	$	9,037,931

- Definition

Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1A
-URI https://asc.fasb.org/extlink&oid=121556970&loc=SL108378252-109267

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13854-109267

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 55
-Paragraph 24
-URI https://asc.fasb.org/extlink&oid=122137925&loc=d3e14258-109268

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

Contract Balances - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Amounts due to third parties for reimbursable expenses	$ 406,300	$ 323,600
Change in unbilled receivables	334,534
Change in unearned revenue (payments on account)	183,488
Increase in advance payments netted against unbilled contracts receivable	151,046
Bad debt expense	17,800	900
Revenue, remaining performance obligation, amount	$ 13,700,000	$ 13,300,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation (in percent)		48.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period		12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation (in percent)	52.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months

Accumulated Other Comprehensive Income

12 Months Ended

Dec. 31, 2022

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Accumulated Other Comprehensive Income


	Year ended
	December 31, 2022		December 31, 2021
	(in thousands)
Currency translation adjustments	$	(175,369)	$	(85,840)

Actuarial gain/(loss) on defined benefit pension plan (note 21)	7,559		(5,098)
Loss on cash flow hedge	(3,728)		—
Amortization of loss on cash flow hedge	—		1
Total	$	(171,538)	$	(90,937)

Employee Benefits - Summary of plan assets and liabilities (Details) - Pension Plan - United States - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Other receivables	$ 6,492	$ 0
Non-current other liabilities (note 16)	$ (13,033)	$ (16,262)

Business Segment and Geographical Information - Distribution of Income from Operations, Excluding Restructuring, by Geographical Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Income from operations, excluding restructuring and other items	$ 795,237	$ 378,529	$ 391,500
Ireland
Segment Reporting Information [Line Items]
Income from operations, excluding restructuring and other items	218,088	131,961	276,478
Rest of Europe
Segment Reporting Information [Line Items]
Income from operations, excluding restructuring and other items	253,799	177,863	35,765
U.S.
Segment Reporting Information [Line Items]
Income from operations, excluding restructuring and other items	254,849	39,132	58,018
Other
Segment Reporting Information [Line Items]
Income from operations, excluding restructuring and other items	$ 68,501	$ 29,573	$ 21,239

Employee Benefits - Net Periodic Pension Benefit Cost Assumptions (Details) - ICON Development Solutions Limited pension plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Expected rate of return on plan assets	3.80%	3.80%
United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.80%	1.50%	2.10%
Rate of compensation increase	3.70%	3.40%	3.30%
Expected rate of return on plan assets	3.80%	3.40%	4.00%
Other comprehensive income
Actuarial (gain)/loss - benefit obligation	$ (18,636)	$ (2,097)	$ 5,294
Actuarial loss/(gain) – plan assets	7,305	(1,176)	(878)
Actuarial loss recognized in net periodic benefit cost	(228)	(625)	(160)
Total	$ (11,559)	$ (3,898)	$ 4,256

Equity Incentive Schemes and Stock Compensation Charges - Schedule of Non-cash Stock Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation costs	$ 70,523	$ 133,844	$ 26,271
Direct costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation costs	22,854	18,551	8,557
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation costs	47,669	41,457	17,714
Transaction and integration related
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation costs	$ 0	$ 73,836	$ 0

Summary of Significant accounting policies (Policies)

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Basis of Consolidation

Basis of consolidation

The consolidated financial statements include the financial statements of the Company and all of its subsidiaries. All significant intercompany profits, transactions and account balances have been eliminated. The results of subsidiary undertakings acquired in the period are included in the Consolidated Statement of Operations from the date of acquisition.

Use of Estimates

Use of estimates

The preparation of financial statements in conformity with generally accepted accounting principles in the United States requires management to make estimates and judgments that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reported period. Actual results could differ from those estimates. The principal management estimates and judgments used in preparing the financial statements relate to revenue recognition and intangible assets acquired in a business combination.

Disclosure of Fair Value of Financial Instruments

Disclosure of fair value of financial instruments

Cash, cash equivalents, other receivables, available for sale investments, accounts receivable, accounts payable, investigator payments and income taxes payable have carrying amounts that approximate fair value due to the short term maturities of these instruments. Other liabilities' carrying amounts approximate fair value based on net present value of estimated future cash flows. Debt is measured at historical cost.

Financial instruments are measured in the Consolidated Balance Sheet at amortized cost or fair value using a fair value hierarchy of valuation inputs. The fair value hierarchy prioritizes the inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market. Each fair value measurement is reported in one of three levels, which is determined by the lowest level input that is significant to the fair value measurement in its entirety. These levels are:

•Level 1: Inputs are based upon unadjusted quoted prices for identical instruments traded in active markets.

•Level 2: Inputs are based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

•Level 3: Inputs are generally unobservable and typically reflect management’s estimates of assumptions that market participants would use in pricing the asset or liability.

The Company classifies its investments in short term debt or equity investments as available for sale, as it does not actively trade such securities nor does it intend to hold them to maturity. The fair value of short term investments are represented by level 1 fair value measurements – quoted prices in active markets for identical assets. The unrealized movements in fair value are recognized in equity until disposal or sale, at which time, those unrealized movements from prior periods are recognized in the Consolidated Statement of Operations. Losses other than temporary, which reduce the carrying amount below cost are recognized in Consolidated Statement of Operations.

Business Combinations

Business combinations

The cost of a business combination is measured as the aggregate of the fair value of assets received, liabilities assumed and equity instruments issued in exchange for control. The Company records and allocates to its reporting units the excess of the cost over the fair value of the net assets acquired, known as goodwill. Where a business combination agreement provides for an adjustment to the cost of the acquisition which is contingent upon future events, the amount of the estimated adjustment is recognized at the acquisition date at the fair value of the contingent consideration. Any changes to this estimate outside the measurement period will depend on the classification of the contingent consideration. If the contingent consideration is classified as equity it shall not be re-measured and the settlement shall be accounted for within equity. If the contingent consideration is classified as a liability any adjustments will be accounted for through the Consolidated Statement of Operations or Other Comprehensive Income depending on whether the liability is considered a financial instrument.

The assets, liabilities and contingent liabilities of businesses acquired are measured at their fair values at the date of acquisition. In the case of a business combination which is completed in stages, the fair values of the identifiable assets, liabilities and contingent liabilities are determined at the date of each exchange transaction. When the initial accounting for a business combination is determined provisionally, any subsequent adjustments to the provisional values allocated to the identifiable assets, liabilities and contingent liabilities are made within twelve months of the acquisition date and presented as adjustments to goodwill in the reporting period in which the adjustments are determined.

The Company allocates a share of net income to the noncontrolling interest holders based on percentage ownership.

Transaction and integration-related expenses

Transaction and integration-related expenses are the incremental costs directly attributable to the completion and integration activities associated with the Company’s recent acquisitions. The costs consist of investment banking fees, advisory costs, retention agreements with employees, accelerated share compensation charges, contingent consideration valuation adjustments and ongoing integration activities. The Company accounts for these transaction and integration-related costs as expenses in the period in which the costs are incurred and the services are received.

Foreign Currencies and Translation of Subsidiaries

Foreign currencies and translation of subsidiaries

The Company's financial statements are prepared in United States dollars. The financial statements of subsidiaries with other functional currencies are translated at period end rates for the Consolidated Balance Sheets and average rates for the Consolidated Statements of Operations. Translation gains and losses arising are reported as a movement on accumulated other comprehensive income.

Transactions in currencies other than the functional currency of the subsidiaries of the Company are recorded at the rate ruling at the date of the transaction. Monetary assets and liabilities denominated in currencies other than the functional currency of the subsidiaries of the Company are translated into the functional currency of that entity at exchange rates prevailing at the Balance Sheet date. Adjustments resulting from these translations are charged or credited to income. Foreign currency gains and losses on intercompany transactions classified as long-term investments are reported in other comprehensive income as currency translation adjustments. Amounts charged or credited to the Consolidated Statements of Operations for the years ended December 31, 2022, December 31, 2021 and December 31, 2020 were as follows:


	Year ended December 31,
	2022		2021		2020
	(in thousands)
Amounts (credited)/charged	$	(25,997)	$	(14,316)	$	5,979

Revenue recognition

The Company earns revenues by providing a number of different services to its customers. These services, which are integral elements of the clinical development process, include clinical trials management, consulting, contract staffing, data services and laboratory services. These services, which are described below, can be purchased collectively or individually as part of a clinical trial contract. There is not significant variability in how economic factors affect these services. Contracts range in duration from a number of months to several years.

ASC 606 requires application of five steps: (1) identify the contract(s) with a customer; (2) identify the performance obligation in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the entity satisfies the performance obligation(s), which have been applied to revenue recognized from each service described below.

Clinical trial service revenue

A clinical trial service is a single performance obligation satisfied over time, i.e. the full-service obligation in respect of a clinical trial (including those services performed by investigators and other parties) is considered a single performance obligation. Promises offered to the customer are not distinct within the context of the contract. ICON is the contract principal in respect of both direct services and in the use of third parties (principally investigator services) that support the clinical research projects. The transaction price is determined by reference to the contract or change order value (total service revenue and pass-through/ reimbursable expenses) adjusted to reflect a realizable contract value. Revenue is recognized over time as the single performance obligation is satisfied. The progress towards completion for clinical service contracts is measured based on an input measure being total project costs incurred (inclusive of pass-through/ reimbursable expenses) at each reporting period as a percentage of forecasted total project costs.

Laboratory services revenue

Revenue is recognized when, or as, obligations under the terms of a contract are satisfied, which occurs when control of the products or services are transferred to the customer. Revenue for laboratory services is measured as the amount of consideration we expect to receive in exchange for transferring products or services. Where contracts with customers contain multiple performance obligations, the transaction price is allocated to each performance obligation based on the estimated relative selling price of the promised good or service. Service revenue is recognized over time as the services are delivered to the customer based on the extent of progress towards completion of the performance obligation. The determination of the methodology to measure progress requires judgment and is based on the nature of services provided. This requires an assessment of the transfer of value to the customer. The right to invoice measure of progress is generally related to rate per unit contracts, as the extent of progress towards completion is measured based on discrete service or time-based increments, such as samples tested or labor hours incurred. Revenue is recorded in the amount invoiced since that amount corresponds to the value of the Company's performance and the transfer of value to the customer.

Contracting services revenue

The Company has availed of the practical expedient which results in recognition of revenue on a right to invoice basis. Application of the practical expedient reflects the right to consideration from the customer in an amount that corresponds directly with the value to the customer of the performance completion to date. This reflects hours performed by contract staff.

Consulting services revenue

Our consulting services contracts represent a single performance obligation satisfied over time. The transaction price is determined by reference to contract or change order value. Revenue is recognized over time as the performance obligation is satisfied. The progress towards completion for consulting contracts is measured based on total project inputs (time) at each reporting period as a percentage of forecasted total project inputs.

Data services revenue

The Company provides data reports and analytics to customers based on agreed-upon specifications, including the timing of delivery, which is typically either weekly, monthly, or quarterly. If a customer requests more than one type of data report or series of data reports within a contract, each distinct type of data report is a separate performance obligation. The contracts provide for the Company to be compensated for the value of each deliverable. The transaction price is determined using list prices, discount agreements, if any, and negotiations with the customers, and generally includes any out-of-pocket expenses. Typically, the Company bills in advance of services being provided with the amount being recorded as unearned revenue.

When multiple performance obligations exist, the transaction price is allocated to performance obligations on a relative standalone selling price basis. In cases where the Company contracts to provide a series of data reports, or in some cases data, the Company recognizes revenue over time using the “units delivered” output method as the data or reports are delivered. Expense reimbursements are recorded to revenue as the expenses are incurred as they relate directly to the services performed.

Certain arrangements include upfront customization or consultative services for customers. These arrangements often include payments based on the achievement of certain contractual milestones. Under these arrangements, the Company contracts with a customer to carry out a specific study, ultimately resulting in delivery of a custom report or data product. These arrangements are a single performance obligation given the integrated nature of the service being provided. The Company typically recognizes revenue under these contracts over time, using an output-based measure, generally time elapsed, to measure progress and transfer of control of the performance obligation to the customer. Expense reimbursements are recorded to revenue as the expenses are incurred as they relate directly to the service performed.

The Company enters into contracts with some of its larger data suppliers that involve non-monetary terms. The Company issues purchase credits to be used toward the data supplier's purchase of the Company's services based on the fair value of the data obtained. In exchange, the Company receives monetary discounts on the data received from the data suppliers. The fair value of the revenue earned from the customer purchases is recognized as services are delivered as described above.

At the end of the contract year, any unused customer purchase credits may be forfeited or carried over to the next contract year based on the terms of the data supplier contract.

Commissions

Incremental costs of obtaining a contract are recognized as an asset on the Consolidated Balance Sheet in respect of those contracts that exceed one year. Where commission costs relate to contracts that are less than one year, the practical expedient is applied as the amortization period of the asset which would arise on deferral would be one year or less.

Reimbursable expenses and Direct costs

Reimbursable expenses

Reimbursable expenses comprise investigator payments and certain other costs which are reimbursed by clients under terms specific to each contract to the investigators. The Company includes reimbursed expenses in revenue and direct costs as the Company is primarily responsible for fulfilling the promise to provide the specified service, including integration of the related services into a combined output to the customer.

Direct costs

Direct costs consist of compensation, associated employee benefits and share-based payments for project-related employees and other direct project-related costs.

Reimbursable expenses are presented within direct costs. This presentation is to align the presentation of costs with our assessment that our clinical trial service is a single performance obligation satisfied over time. Reimbursable expenses are recorded once the activity which forms the basis for the cost has occurred. Payments are made based on predetermined contractual arrangements. Timing of payments may differ from the timing of the expense.

Cash and Cash Equivalents

Cash and cash equivalents

Cash and cash equivalents include cash and highly liquid investments with initial maturities of three months or less and are stated at cost, which approximates market value.

Investment in Debt, Equity and Other

Investments in debt, equity and other

Available for sale investments

The Company classifies short-term investments as available for sale. The investments are reported at fair value, with unrealized gains or losses reported in a separate component of shareholders' equity. Any differences between the cost and fair value of the investments are represented by accrued interest and unrealized gains/losses. Realized gains and losses are determined using specific identification

Long term investments

The Company classifies its interests in funds having considered the nature of its investment, the extent of influence over operating and financial decisions and the availability of readily determinable fair values. The Company determined that the interests in funds at December 31, 2022 meet the definition of equity securities without readily determinable fair values. The Company concluded that the interests held at December 31, 2021 and December 31, 2022 qualify for the NAV practical expedient in ASC 820 'Fair value measurements and disclosures'. Any increases or decreases in fair value are recognized in net income in the period. These are therefore measured at Level 3 of the fair value hierarchy.

Equity method investments

The Company’s investments that are not consolidated are accounted for under the equity method if the Company exercises significant influence that is considered to be greater than minor. These investments are classified as equity method investments on the accompanying Consolidated Balance Sheet. The Company records its pro rata share of the earnings/losses of these investments in Share of equity method investments in the Consolidated Statement of Operations. The Company reviews these for impairment whenever events or changes in circumstances indicate that the carrying amounts may not be recoverable.

Accounts Receivable, Net and Unbilled Revenue

Accounts receivable, net and unbilled revenue

Accounts receivable and unbilled revenue are recorded at fair value less an estimate of the credit losses expected to be incurred on the Company's accounts receivable portfolio. The Company's estimate of expected credit losses considers historical credit loss information that is adjusted, where necessary, for current conditions and reasonable and supportable forecasts. Historical credit loss experience provides the basis for the estimation of expected credit losses. The Company's receivables and unbilled services are predominantly due from large and mid-tier pharmaceutical and biotechnology companies that share similar risk characteristics. The Company monitors their portfolio of receivables and unbilled services for any deterioration in current or expected credit quality (for example, expected delinquency level), and adjusts the allowance for credit losses as required.

Changes in the allowance for credit losses are recorded as a provision for (or reversal of) credit loss expense in the Consolidated Statement of Operations. Losses are charged against the allowance when management believes the uncollectibility of a previously provisioned amount is confirmed.

Accounts receivable early payment discounting

Where the Company enters into an agreement to sell certain portfolios of its accounts receivable balances, the sale is accounted for in accordance with ASC Topic 860 'Transfers and Servicing' (ASC 860). Agreements which result in true sales of the transferred receivables, as defined in ASC 860, which occur when receivables are transferred without recourse to ICON, are excluded from amounts reported in the Consolidated Balance Sheet. Cash proceeds received from such sales are included in operating cash flows.

Property, Plant and Equipment

Property, plant and equipment

Property, plant and equipment is stated at cost less accumulated depreciation. Depreciation of property, plant and equipment is computed using the straight line method based on the estimated useful lives of the assets as listed below:


			Years
Building			40
Computer equipment and software			2-8
Office furniture and fixtures			8
Laboratory equipment			5
Motor vehicles			5

Leasehold improvements are amortized using the straight line method over the estimated useful life of the asset or the lease term, whichever is shorter.

Leases

The Company determines if an arrangement is a lease at inception and reassess if there are changes in terms and conditions of the contract. Finance leases, if any, are depreciated on the same basis as property, plant and equipment. At December 31, 2022 and December 31, 2021, the Company did not account for any leases as finance leases.

Operating leases are included in operating right-of-use assets, other liabilities and non-current operating lease liabilities on our Consolidated Balance Sheet with the lease charge recognized on a straight-line basis over the lease term. ROU assets and lease liabilities are recognized based on the present value of future minimum lease payments over the lease term at commencement date or date of transition. Our lease terms may also include options to extend or terminate. The Company actively reviews options to extend or terminate leases and adjusts the ROU asset and lease liability when it is reasonably certain the option will be exercised. The ROU asset is adjusted for any prepayments made at the date of commencement and any initial direct costs incurred. As most of the Company's leases do not provide an implicit rate, the discount rate used is based on the rate of traded corporate bonds available at the commencement date adjusted for country risk, liquidity and lease term.

The Company accounts for lease and non-lease components separately with lease components flowing through the Consolidated Balance Sheet and non-lease components expensed directly to the Consolidated Statements of Operations.

Leasehold improvements are amortized over the shorter of the depreciable lives of the corresponding fixed assets or the lease term including any applicable renewals. Certain property leases include variable lease payments resulting from periodic rent increases based on an index which cannot be reasonably estimated at the lease commencement date. These costs are expensed as incurred on the Consolidated Statements of Operations.

In some cases, the Company enters into sublease agreements and becomes both a lessee and a lessor for the same underlying asset. Subleases are accounted for as operating leases separately from the lease they relate to, but similar in manner as all other leases.

ROU assets for operating leases are occasionally reduced by impairment losses. The Company uses the long-lived assets impairment guidance in Subtopic 360-10, Property, Plant, and Equipment – Overall, to determine whether an ROU asset is impaired, and if so, the amount of the impairment loss to recognize.

Intangible Assets

Intangible assets

Intangible assets are measured at their fair value when acquired and amortized on the straight line basis over their respective useful lives. The Company has no indefinite life intangibles other than goodwill. The Company evaluates its intangibles for impairment when indicators of impairment exist.

Intangible assets are amortized on a straight-line basis over the expected useful life, as set forth in the table below:


			Estimated Useful Life
Customer relationships			23 years
Order backlog			3 years
Trade names			3 years
Patient database			7 years
Technology assets			5 years

The Company periodically assesses the useful lives of intangible assets to evaluate whether what was established at acquisition continues to be appropriate.

Impairment of goodwill and long-lived assets

Goodwill is tested for impairment annually or more frequently if an event or circumstance indicates that an impairment loss may have been incurred. The annual impairment test for goodwill includes an option to perform a qualitative assessment of whether it is more likely than not that a reporting unit's fair value is less than its carrying value. Reporting units are businesses with discrete financial information that is available and reviewed by management. If the Company determines that it is more likely than not that the fair value of a reporting unit is less than its carrying value, then the Company performs the quantitative goodwill impairment test. The Company may also chose to bypass the qualitative assessment for any reporting unit in its goodwill assessment and proceed directly to performing the quantitative assessment. The Company recognizes an impairment charge for the amount by which the reporting unit's carrying amount exceeds its fair value.

Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Fair value is determined through various valuation techniques including discounted cash flow models and third-party independent appraisals, as considered necessary. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of the asset to future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured at the amount by which the carrying amount of the asset exceeds the fair value of the asset. Assets to be disposed of are reported at the lower of the carrying amount of the asset or fair value less selling costs.

Debt Issuance Costs

Debt issuance costs

Debt issuance costs relating to the Company’s long-term debt are recorded as a direct reduction of long-term debt; these costs are deferred and amortized to interest expense using the effective interest method, over the respective terms of the related debt. Debt issuance costs relating to the Company’s revolving credit facilities are recorded as an asset; these costs are deferred and amortized to interest expense using the straight-line method. Early repayment of debt facilities can result in modification of the debt and the acceleration of the amortization of debt issuance costs.

Derivative Financial Instruments

Derivative financial instruments

The Company uses derivative financial instruments to reduce exposures to interest rates and foreign currencies. Derivatives are recorded on the balance sheet at fair value at each balance sheet date utilizing pricing models for non-exchange-traded contracts.

Our accounting policies for derivative financial instruments are based on whether they meet the criteria for designation as cash flow or fair value hedges. A designated hedge of the exposure to variability in the future cash flows of an asset or a liability, or of a forecast transaction, is referred to as a cash flow hedge. A designated hedge of the exposure to changes in fair value of an asset or a liability is referred to as a fair value hedge. The criterion for designating a derivative as a hedge includes the assessment of the instrument's effectiveness in risk reduction, matching of the derivative instrument to its underlying transaction and the probability that the underlying transaction will occur. For derivatives with cash flow hedge accounting designation, we report the gain or loss from the effective portion of the hedge as a component of Other Comprehensive Income

and reclassify it into earnings in the same period or periods in which the hedged transaction affects earnings and within the same Consolidated Statement of Operations line item as the impact of the hedged transaction. For derivatives with fair value hedge accounting designation, we recognize gains or losses from the change in fair value of these derivatives, as well as the offsetting change in the fair value of the underlying hedged item, in earnings. Fair value gains and losses arising on derivative financial instruments not qualifying for hedge accounting are reported in our Consolidated Statement of Operations.

The company has entered into certain put and call arrangements to purchase equity in unconsolidated entities at a future date. These arrangements are accounted for at fair value at the balance sheet date.

Income Taxes

Income taxes

The Company applies the asset and liability method of accounting for income taxes. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amount of existing assets and liabilities and their respective tax bases and for operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which these temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Deferred tax assets are reduced by a valuation allowance to the amount that is more likely than not to be realized. The Company recognizes the effect of income tax positions only if those positions will more likely than not be sustained. Recognized income tax positions are measured at the largest amount of tax benefit that is greater than 50 percent likely of being realized upon settlement. Interest and penalties related to income taxes are included in income tax expense and classified with the related liability on the Consolidated Balance Sheet. The Company accounts for the impact of GILTI (“global intangible low-taxed income”) in the period it arises and has therefore not provided for deferred taxes in respect of this item.

Government grants

Government grants received relating to capital expenditures are shown by deducting the grant from the asset's carrying amount and crediting them to income on a basis consistent with the depreciation policy of the relevant assets. Grants relating to categories of operating expenditures are shown as deferred income and credited to income in the period in which the expenditure to which they relate is charged.

Under the grant agreements amounts received may become repayable in full should certain circumstances specified within the grant agreements occur, including downsizing by the Company, disposing of the related assets, ceasing to carry on its business or the appointment of a receiver over any of its assets. The Company has not recognized any loss contingency having assessed as remote the likelihood of these events arising.

Research and development credits

Research and development credits are available to the Company under the tax laws in certain jurisdictions, based on qualifying research and development spend as defined under those tax laws. Research and development credits may be recognized as a reduction of income tax expense. However, certain tax jurisdictions provide refundable credits that are not wholly dependent on the Company's ongoing income tax status or income tax position. In these circumstances the benefit of these credits is not recorded as a reduction to income tax expense, but rather as a reduction of operating expenditure.

Pension Costs

Pension costs

The Company contributes to defined contribution plans covering all eligible employees. The Company contributes to these plans based upon various fixed percentages of employee compensation and such contributions are expensed as incurred.

The Company operates, through certain subsidiaries, a defined benefit plan for certain employees located in the United Kingdom and Switzerland. The Company accounts for the costs of these plans in accordance with ASC 715-30 'Defined Benefit Plans – Pension'. These plans are presented in accordance with the requirements of ASC 715-60 'Defined Benefit Plans – Other Postretirement'. The Company also maintains various retirement plans across the Group, many of which are required by local employment laws.

Share-Based Compensation

Share-based compensation

The Company accounts for its share options, Restricted Share Units ("RSUs") and Performance Share Units ("PSUs") in accordance with the provisions of ASC 718 'Compensation – Stock Compensation'. Share-based compensation expense for equity-settled awards made to employees and directors is measured and recognized based on estimated grant date fair values. These equity-settled awards include employee share options, RSUs and PSUs.

Share-based compensation expense for share options awarded to employees and directors is estimated at the grant date based on each option's fair value as calculated using the Black-Scholes option-pricing model. Share-based compensation for RSUs and PSUs awarded to employees and directors is calculated based on the market value of the Company's shares on

the date of award of the RSUs and PSUs. The value of awards expected to vest is recognized as an expense over the requisite service periods. Forfeitures are estimated on the date of grant and revised if actual or expected forfeiture activity differs materially from original estimates.

Estimating the grant date fair value of share options as of the grant date using an option-pricing model, such as the Black-Scholes model, is affected by the Company's share price as well as assumptions regarding a number of complex variables. These variables include, but are not limited to, the expected share price volatility over the term of the awards, risk-free interest rates and the expected term of the awards.

Liability classified awards are measured at the fair value of the award on the grant date and remeasured at each reporting period at fair value until the award is settled.

Replacement awards

In connection with the completion of the Merger, the company issued replacement awards to the holders of PRA equity awards on July 1, 2021. An exchange of share-based compensation awards in a business combination is treated as a modification under ASC 718. The replacement awards and the original acquiree awards are measured at fair value at the acquisition date and calculated using the fair-value-based measurement principles in ASC 718. Amounts attributable to pre-combination vesting are accounted for as part of the consideration transferred for the acquiree. Amounts attributable to post-combination vesting are accounted for separate from the business combination and are recognized as compensation cost in the post-combination period.

Transaction and Integration-related Expenses

Business combinations

The Company allocates a share of net income to the noncontrolling interest holders based on percentage ownership.

Transaction and integration-related expenses

Restructuring

Restructuring charges reflect certain one-time costs arising from reorganization programs announced by Company management. These programs generally result in asset impairments and workforce reductions in order to optimize the Company’s structure and facilitate improved long-term performance. Impairment charges are taken when the value-in-use of the asset is less than the asset’s carrying value. Workforce related charges are taken when an approved reorganization program is communicated to the relevant employee groups.

Redeemable non-controlling interests and equity

Redeemable noncontrolling interests and equity

The Company acquired a majority ownership interest in MeDiNova during the year ended December 31, 2019. Included in the purchase agreement were put and call option arrangements with the noncontrolling interest holders that required (put option) or enabled (call option) the Company to purchase the remaining minority ownership at a future date. The option was accounted for as temporary equity, which is presented separately as redeemable noncontrolling interest on the Consolidated Balance Sheet. This classification reflects the assessment that the instruments are contingently redeemable in accordance with ASC 480-10-S99 'Distinguishing Liabilities from Equity'. On March 9, 2020, ICON exercised its option to call the remaining shares and took 100% ownership of MeDiNova.

Redeemable noncontrolling interests are accreted to their redemption value over the period from the date of issuance to the first date on which the option is exercisable. The change in the option's redemption value is recorded against retained earnings. In a computation of earnings per share, the accretion of redeemable noncontrolling interests to their redemption value is a reduction of net income attributable to the Group. Basic and diluted net income per ordinary share attributable to the Group includes the adjustment to reflect the accretion of the noncontrolling interest to its redemption value until the redemption of the noncontrolling interest on March 9, 2020.

Net Income per Ordinary Share

Net income per ordinary share

Basic net income per ordinary share attributable to the Company has been computed by dividing net income available to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period. Diluted net income per ordinary share is computed by adjusting the weighted average number of ordinary shares outstanding during the period for all potentially dilutive ordinary shares outstanding during the period and adjusting net income for any changes in income or loss that would result from the conversion of such potential ordinary shares. There is no difference in net income used for basic and diluted net income per ordinary share. Basic and diluted net income per ordinary share attributable to the Company includes the adjustment to reflect the accretion of the noncontrolling interest in MeDiNova to its redemption value.

Reclassifications

Certain prior period amounts in the consolidated financial statements and accompanying notes have been reclassified to conform to the current period’s presentation. Most notably, the Company has presented transaction and integration-related expenses as a separate line in the Consolidated Statement of Operations and reclassified certain costs incurred in the year ended December 31, 2020 within this line. These costs consist of transaction and integration-related expenses and contingent consideration valuation adjustments related to ICON's prior period acquisitions. These costs were previously presented in the selling, general and administrative expenses but have been reclassified to transaction and integration-related expenses to conform to the current period’s presentation.

Impact of Recently Issued or Adopted Accounting Standards

No new accounting pronouncement issued or effective has had, or is expected to have, a significant impact on the Company’s consolidated financial statements.

Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Other Liabilities Disclosure [Abstract]
General trade and overhead liabilities	$ 530,204	$ 459,814
Personnel related liabilities	395,862	413,185
Operating lease liabilities	43,657	49,949
Facility related liabilities	16,896	12,055
Other liabilities	12,852	7,204
Restructuring liabilities	5,512	7,377
Short term government grants	42	45
Other liabilities	1,005,025	949,629
Amounts due to third parties for reimbursable expenses	$ 406,300	$ 323,600

Employee Benefits - Narrative (Details) - USD ($)	12 Months Ended
Employee Benefits - Narrative (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	May 07, 2014
Other retirement plans
Defined Benefit Plan Disclosure [Line Items]
Non-current other liabilities (note 16)	$ 11,600,000	$ 8,000,000
ICON Development Solutions Limited pension plan
Defined Benefit Plan Disclosure [Line Items]
Expected rate of return on plan assets	3.80%	3.80%
Aptiv Solutions pension plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.30%	0.40%
PRA Switzerland AG pension plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.30%	0.40%
United States
Defined Benefit Plan Disclosure [Line Items]
Participant's contributions percentage of annual compensation (in percent)	4.50%
Defined contribution plan, cost	$ 30,200,000	$ 23,700,000	$ 17,000,000
United Kingdom \| ICON Development Solutions Limited pension plan
Defined Benefit Plan Disclosure [Line Items]
Non-current other liabilities (note 16)	19,558,000	$ 41,813,000	$ 43,988,000
Net loss that will be amortized	300,000
Net prior service cost for defined benefit pension plan that will be amortized	$ 0
Pension plan period	19 years
Expected rate of return on plan assets	3.80%	3.40%	4.00%
Contribution to pension fund in the year ending December 31, 2021	$ 100,000
Retirement period used as a basis to estimate expected cash flows	10 years
Discount rate	4.90%	1.80%
Switzerland \| Aptiv Solutions pension plan
Defined Benefit Plan Disclosure [Line Items]
Non-current other liabilities (note 16)	$ 5,806,000	$ 7,643,000	$ 8,620,000
Switzerland \| Aptiv Solutions pension plan \| Aptiv Solutions
Defined Benefit Plan Disclosure [Line Items]
Percentage of share capital acquired (in percent)				100.00%
Switzerland \| PRA Switzerland AG pension plan
Defined Benefit Plan Disclosure [Line Items]
Non-current other liabilities (note 16)	$ 5,345,000	$ 4,990,000	$ 4,890,000

Disaggregation of Revenue (Tables)

12 Months Ended

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

Schedule of Disaggregation of Revenue

Revenue disaggregated by customer profile is as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Top client	$	683,546	$	441,173	$	337,904
Clients 2-5	1,506,087		1,291,946		754,906
Clients 6-10	1,112,636		752,325		350,865
Clients 11-25	1,585,739		1,077,073		501,643
Other	2,853,378		1,918,309		851,970
Total	$7,741,386		$5,480,826		$2,797,288

Goodwill

12 Months Ended

Dec. 31, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill

The change in the carrying amount of Goodwill for the years ended December 31, 2022 and 2021 is as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Opening goodwill	$	9,037,931	$	936,257
Current year acquisitions (note 6)	—		8,120,006
Prior period acquisition (note 6)	(35,692)		—
Foreign exchange movement	(30,569)		(18,332)
Closing goodwill	$	8,971,670	$	9,037,931

There were no goodwill impairment losses for the years ended December 31, 2022 and 2021.

Summary of Significant accounting policies

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Summary of Significant accounting policies

Summary of Significant Accounting Policies

The accounting policies noted below were applied in the preparation of the accompanying financial statements of the Company and are in conformity with accounting principles generally accepted in the United States.

Basis of consolidation

Use of estimates

Disclosure of fair value of financial instruments

•Level 1: Inputs are based upon unadjusted quoted prices for identical instruments traded in active markets.

•Level 3: Inputs are generally unobservable and typically reflect management’s estimates of assumptions that market participants would use in pricing the asset or liability.

Business combinations

The Company allocates a share of net income to the noncontrolling interest holders based on percentage ownership.

Foreign currencies and translation of subsidiaries


	Year ended December 31,
	2022		2021		2020
	(in thousands)
Amounts (credited)/charged	$	(25,997)	$	(14,316)	$	5,979

Revenue recognition

Clinical trial service revenue

Laboratory services revenue

Contracting services revenue

Consulting services revenue

Data services revenue

At the end of the contract year, any unused customer purchase credits may be forfeited or carried over to the next contract year based on the terms of the data supplier contract.

Commissions

Reimbursable expenses

Direct costs

Direct costs consist of compensation, associated employee benefits and share-based payments for project-related employees and other direct project-related costs.

Cash and cash equivalents

Cash and cash equivalents include cash and highly liquid investments with initial maturities of three months or less and are stated at cost, which approximates market value.

Investments in debt, equity and other

Available for sale investments

Long term investments

Equity method investments

Accounts receivable, net and unbilled revenue

Accounts receivable early payment discounting

Property, plant and equipment


			Years
Building			40
Computer equipment and software			2-8
Office furniture and fixtures			8
Laboratory equipment			5
Motor vehicles			5

Leasehold improvements are amortized using the straight line method over the estimated useful life of the asset or the lease term, whichever is shorter.

Leases

Intangible assets

Intangible assets are amortized on a straight-line basis over the expected useful life, as set forth in the table below:


			Estimated Useful Life
Customer relationships			23 years
Order backlog			3 years
Trade names			3 years
Patient database			7 years
Technology assets			5 years

The Company periodically assesses the useful lives of intangible assets to evaluate whether what was established at acquisition continues to be appropriate.

Impairment of goodwill and long-lived assets

Debt issuance costs

Derivative financial instruments

Income taxes

Government grants

Research and development credits

Pension costs

Share-based compensation

Liability classified awards are measured at the fair value of the award on the grant date and remeasured at each reporting period at fair value until the award is settled.

Replacement awards

Transaction and integration-related expenses

Restructuring

Redeemable noncontrolling interests and equity

Net income per ordinary share

Reclassifications

Impact of Recently Issued or Adopted Accounting Standards

No new accounting pronouncement issued or effective has had, or is expected to have, a significant impact on the Company’s consolidated financial statements.

Share Capital (Details)					12 Months Ended
Share Capital (Details)	Feb. 18, 2022 USD ($) shares	Jul. 01, 2021 shares	Dec. 31, 2019 USD ($) shares	Jul. 22, 2016	Dec. 31, 2022 USD ($) vote $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) shares	Jan. 08, 2019 shares	Oct. 03, 2016 USD ($)
Equity, Class of Treasury Stock [Line Items]
Number of votes \| vote					1
Total proceeds from exercise of stock options by employees \| $					$ 35,844,000	$ 118,589,000	$ 13,203,000
Ordinary shares redeemed, value \| $					$ 99,983,000		$ 175,000,000
Buyback program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount \| $											$ 400,000,000
Ordinary shares redeemed (in shares)	420,530		35,100				1,235,218		4,026,576
Ordinary shares redeemed, value \| $	$ 100,000,000		$ 5,300,000				$ 175,000,000	$ 141,600,000	$ 372,100,000
Number of shares authorized to be repurchased (in shares)										1,000,000
Maximum \| Buyback program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized percentage (in percent)				10.00%
Employee Stock Option
Equity, Class of Treasury Stock [Line Items]
Options exercised by employees (in shares)					348,286	1,065,529	193,417
Average exercise price of option per share (USD per share) \| $ / shares					$ 102.87	$ 111.29	$ 68.19
Total proceeds from exercise of stock options by employees \| $					$ 35,800,000	$ 118,600,000	$ 13,200,000
Restricted Stock Units (RSUs)
Equity, Class of Treasury Stock [Line Items]
Ordinary shares issued in respect of certain RSUs previously awarded by the Company (in shares)					195,029	446,404	144,172
Performance Share Unit (PSUs)
Equity, Class of Treasury Stock [Line Items]
Ordinary shares issued in respect of certain PSUs previously awarded by the Company (in shares)					46,087	44,132	63,516
Ordinary Shares
Equity, Class of Treasury Stock [Line Items]
Options exercised by employees (in shares)					348,286	1,065,529	193,417
Issue of shares associated with a business combination (in shares)		27,372,427				27,372,427
Ordinary shares redeemed (in shares)					420,530		1,235,218
Ordinary shares redeemed, value \| $					$ 28,000		$ 82,000

Property, Plant and Equipment, net

12 Months Ended

Dec. 31, 2022

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment, net

The carrying amount of Property, Plant and Equipment for the years ended December 31, 2022 and 2021 is as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Cost
Land	$	3,724	$	3,724
Building	70,880		82,017
Computer equipment and software	500,135		506,322
Office furniture and fixtures	50,600		107,507
Laboratory equipment	59,946		29,210
Leasehold improvements	65,167		70,123
Motor vehicles	41		65

	750,493		798,968
Less accumulated depreciation and asset write offs	(400,173)		(462,524)

Property, plant and equipment (net)	$	350,320	$	336,444

Property, Plant and Equipment depreciation expense is as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Depreciation expense	$	106,426	$	75,484

The Company regularly updates its register of property, plant and equipment and during the year ended December 31, 2022 and the year ended December 31, 2021, certain fully depreciated assets were written off as they were no longer used in the Company.

Operating Leases - Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Operating lease costs	$ 53,880	$ 51,200
Income from sub-leases	(1,165)	(1,338)
Net operating lease costs	$ 52,715	$ 49,862

Income Taxes - Components of Income Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]
Income before income tax expense	$ 567,851	$ 196,680	$ 381,205
Ireland
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]
Income before income tax expense	432,963	231,893	280,310
United States
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]
Income before income tax expense	(270,440)	(278,413)	41,950
Other
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]
Income before income tax expense	$ 405,328	$ 243,200	$ 58,945

Supplemental Disclosure of Cash Flow Information (Tables)

12 Months Ended

Dec. 31, 2022

Supplemental Cash Flow Elements [Abstract]

Schedule of Supplemental Disclosure of Cash Flow Information


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Cash paid for interest	$	210,918	$	106,205	$	13,062
Cash paid for income taxes (net of refunds)	$	116,322	$	55,105	$	27,604

Supplemental Disclosure of Cash Flow Information

12 Months Ended

Dec. 31, 2022

Supplemental Cash Flow Elements [Abstract]

Supplemental Disclosure of Cash Flow Information


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Cash paid for interest	$	210,918	$	106,205	$	13,062
Cash paid for income taxes (net of refunds)	$	116,322	$	55,105	$	27,604

Equity Incentive Schemes and Stock Compensation Charges - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended			24 Months Ended	252 Months Ended
	Feb. 14, 2017	May 11, 2015	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2017	May 18, 2020	May 16, 2019	May 31, 2018	Feb. 13, 2017	Sep. 23, 2013
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Weighted average contractual term of options outstanding			4 years 8 months 8 days	5 years 4 months 20 days
Exercisable - weighted average remaining contractual life			4 years 3 months	4 years 6 months 18 days
Total compensation costs			$ 70,523	$ 133,844	$ 26,271
Income tax benefit related to stock compensation			12,900	22,700	6,900
Cash tax benefit related to stock options exercised			$ 7,700	23,900	$ 2,500
The 2018 Legacy PRA Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)										2
2013 Legacy PRA Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)												2,052,909
Percentage of outstanding shares authorized												12.50%
The 2020 Legacy PRA Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)								2,500,000
Consultants Stock Plan, 2008 Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)	1,000,000										400,000
Limit of shares issued or to be issued pursuant to options granted (in shares)	1,000,000
Employee Stock Plan, 2008 Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)	6,000,000
Maximum number of shares per employee (in shares)	400,000
Option Plans 2008 \| Minimum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Percentage of option price for fair value of ordinary share (in percent)	100.00%
Employee Stock Option
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Shares vesting period			5 years
Employee Stock Option \| Award date, prior to 2018
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Shares expiration period							8 years
Shares vesting period							5 years
Restricted Stock Units 2013
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)		4,100,000
Additional number of ordinary shares which have been reserved for issuance (in shares)		2,500,000
Consultants Restricted Stock Units 2019
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)									250,000
Consultants Restricted Stock Units 2019 \| Non-executive director
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Shares vesting period						12 months
Restricted Stock Units (RSUs)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Fair value of stock units vested			$ 34,100	$ 83,500
Restricted Stock Units (RSUs) \| Minimum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share price of equity instruments other than options, vested in period (in USD per share)			$ 137.47	$ 115.11
Restricted Stock Units (RSUs) \| Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share price of equity instruments other than options, vested in period (in USD per share)			$ 265.96	$ 206.71
Performance Share Unit (PSUs)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Fair value of stock units vested			$ 6,500	$ 5,100
Performance Share Unit (PSUs) \| Minimum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share price of equity instruments other than options, vested in period (in USD per share)			$ 137.47	$ 115.11
Performance Share Unit (PSUs) \| Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share price of equity instruments other than options, vested in period (in USD per share)			$ 166.51	$ 125.74
PSUs Based on Service and EPS Targets \| Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock units to be granted (in shares)			76,210

Equity Incentive Schemes and Stock Compensation Charges - Summary of RSU and PSU Activity (Details)	12 Months Ended
	Dec. 31, 2022 $ / shares shares
Performance Share Unit (PSUs)
Outstanding number of shares [Roll Forward]
Outstanding at beginning of period (in shares) \| shares	154,190
Granted (in shares) \| shares	64,682
Shares vested (in shares) \| shares	(46,087)
Forfeited (in shares) \| shares	(20,365)
Outstanding at ending of period (in shares) \| shares	152,420
Weighted Average Fair Value
Outstanding at beginning of period (USD per share) \| $ / shares	$ 160.23
Granted (USD per share) \| $ / shares	229.79
Shares vested (USD per share) \| $ / shares	140.48
Forfeited (USD per share) \| $ / shares	185.90
Outstanding at end of period (USD per share) \| $ / shares	$ 192.29
Restricted Stock Units (RSUs)
Outstanding number of shares [Roll Forward]
Outstanding at beginning of period (in shares) \| shares	572,785
Granted (in shares) \| shares	302,307
Shares vested (in shares) \| shares	(195,029)
Forfeited (in shares) \| shares	(97,451)
Outstanding at ending of period (in shares) \| shares	582,612
Weighted Average Fair Value
Outstanding at beginning of period (USD per share) \| $ / shares	$ 191.20
Granted (USD per share) \| $ / shares	216.85
Shares vested (USD per share) \| $ / shares	174.35
Forfeited (USD per share) \| $ / shares	205.25
Outstanding at end of period (USD per share) \| $ / shares	$ 207.73

Income Taxes - Tax Effects of Temporary Differences That Give Rise to Significant Portions of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax liabilities:
Property, plant and equipment	$ 10,927	$ 19,606
Operating right-of-use-assets	23,260	33,449
Goodwill	37,150	33,354
Intangible assets	1,078,302	1,201,086
Other	9,054	1,761
Total deferred tax liabilities recognized	1,158,693	1,289,256
Deferred tax assets:
Operating loss and tax credits carryforwards	88,697	86,893
Property, plant and equipment	6,010	5,846
Operating lease liabilities	27,593	36,106
Intangible assets	3,602	4,596
Accrued expenses and unbilled revenue	64,016	69,198
Stock compensation	21,862	25,557
Deferred compensation	2,917	3,445
Unearned revenue	66,565	64,924
Other	9,155	602
Total deferred tax assets	290,417	297,167
Valuation allowance for deferred tax assets	(43,379)	(45,495)	$ (32,800)
Deferred tax assets recognized	247,038	251,672
Overall net deferred tax asset/(liability)	$ (911,655)	$ (1,037,584)

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Currency translation adjustments	$ (175,369)	$ (85,840)
Actuarial gain/(loss) on defined benefit pension plan (note 21)	7,559	(5,098)
Loss on cash flow hedge	3,728	0
Amortization of loss on cash flow hedge	0	1
Total	$ (171,538)	$ (90,937)

- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References + Details

Employee Benefits - Annual Benefit Payments (Details) - United Kingdom - ICON Development Solutions Limited pension plan $ in Thousands	Dec. 31, 2022 USD ($)
Defined Benefit Plan Disclosure [Line Items]
2023	$ 302
2024	371
2025	402
2026	703
2027	643
Years 2028 - 2032	$ 3,614

Goodwill - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Goodwill - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill impairment charge	$ 0	$ 0

Income Taxes - Expected Expiry Dates of NOL's (Details) - United States $ in Thousands	Dec. 31, 2022 USD ($)
State NOL's
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, not subject to expiration	$ 6,736
Net operating loss carryforwards	401,898
State NOL's \| 2023-2036
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, subject to expiration	249,530
State NOL's \| 2033-2041
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, subject to expiration	145,632
Federal NOL's
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, not subject to expiration	95
Net operating loss carryforwards	5,363
Federal NOL's \| 2023-2036
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, subject to expiration	5,268
Federal NOL's \| 2033-2041
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, subject to expiration	$ 0

Intangible Assets - Future Intangible Asset Amortization Expense (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2023	$ 460,711
2024	339,940
2025	223,674
2026	209,681
2027	198,300
Finite lived intangible assets, amortization expense, net, total	$ 1,432,306

Intangible Assets - Narrative (Details) - USD ($) $ in Thousands		12 Months Ended	18 Months Ended
	Jul. 01, 2021	Dec. 31, 2022	Dec. 31, 2022
Customer relationships
Indefinite-lived Intangible Assets [Line Items]
Amortization period		23 years
Order backlog
Indefinite-lived Intangible Assets [Line Items]
Amortization period		3 years
Trade names & brands
Indefinite-lived Intangible Assets [Line Items]
Amortization period		3 years
Patient database
Indefinite-lived Intangible Assets [Line Items]
Amortization period		7 years
Technology assets
Indefinite-lived Intangible Assets [Line Items]
Amortization period		5 years
PRA Health Sciences, Inc
Indefinite-lived Intangible Assets [Line Items]
Value of intangible assets acquired	$ 4,919,000
Amortization of intangible assets		$ 453,600	$ 677,100
PRA Health Sciences, Inc \| Minimum
Indefinite-lived Intangible Assets [Line Items]
Amortization period	3 years
PRA Health Sciences, Inc \| Maximum
Indefinite-lived Intangible Assets [Line Items]
Amortization period	23 years
PRA Health Sciences, Inc \| Customer relationships
Indefinite-lived Intangible Assets [Line Items]
Value of intangible assets acquired	$ 3,938,000
PRA Health Sciences, Inc \| Order backlog
Indefinite-lived Intangible Assets [Line Items]
Value of intangible assets acquired	500,000
PRA Health Sciences, Inc \| Trade names & brands
Indefinite-lived Intangible Assets [Line Items]
Value of intangible assets acquired	202,000
PRA Health Sciences, Inc \| Patient database
Indefinite-lived Intangible Assets [Line Items]
Value of intangible assets acquired	168,000
PRA Health Sciences, Inc \| Technology assets
Indefinite-lived Intangible Assets [Line Items]
Value of intangible assets acquired	$ 111,000

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsThe Company has evaluated subsequent events from the Balance Sheet date through February 24, 2023, the date at which the consolidated financial statements were available to be issued. The Company has determined that there are no items to disclose.

Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Supplemental Cash Flow Elements [Abstract]
Cash paid for interest	$ 210,918	$ 106,205	$ 13,062
Cash paid for income taxes (net of refunds)	$ 116,322	$ 55,105	$ 27,604

Business Combinations - Schedule of Acquisitions, PRA Acquisition (Details) - USD ($)	18 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Jul. 01, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill	$ 8,971,670,000	$ 9,037,931,000		$ 936,257,000
PRA Health Sciences, Inc
Business Acquisition [Line Items]
Cash and cash equivalents			$ 259,971,000
Accounts receivable and unbilled revenue			934,308,000
Other current assets			125,156,000
Fixed assets			156,851,000
Operating lease right-of-use assets			180,601,000
Goodwill			8,084,314,000
Intangible assets			4,919,000,000
Deferred tax assets			25,190,000
Other assets			33,928,000
Accounts payable			(50,259,000)
Accrued expenses and other current liabilities			(380,048,000)
Current portion of operating lease liabilities			(36,506,000)
Unearned revenue			(739,278,000)
Non-current portion of operating lease liabilities			(147,204,000)
Deferred tax liabilities			(1,119,762,000)
Other non-current liabilities			(204,291,000)
Net assets acquired			12,041,971,000
Goodwill, expected tax deductible amount			$ 0
Cash and cash equivalents	$ 0

Business Combinations - Fair Value of Identified Intangible Assets Acquired, PRA Acquisition (Details) - PRA Health Sciences, Inc $ in Thousands	Jul. 01, 2021 USD ($)
Business Acquisition [Line Items]
Estimated Fair Value	$ 4,919,000
Customer relationships
Business Acquisition [Line Items]
Estimated Fair Value	$ 3,938,000
Estimated Useful Life	23 years
Order backlog
Business Acquisition [Line Items]
Estimated Fair Value	$ 500,000
Estimated Useful Life	3 years
Trade names
Business Acquisition [Line Items]
Estimated Fair Value	$ 202,000
Estimated Useful Life	3 years
Patient database
Business Acquisition [Line Items]
Estimated Fair Value	$ 168,000
Estimated Useful Life	7 years
Technology assets
Business Acquisition [Line Items]
Estimated Fair Value	$ 111,000
Estimated Useful Life	5 years

Equity Incentive Schemes and Stock Compensation Charges

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Equity Incentive Schemes and Stock Compensation Charges

Share Options

On July 21, 2008 the Company adopted the Employee Share Option Plan 2008 (the "2008 Employee Plan") pursuant to which the Compensation and Organization Committee of the Company's Board of Directors may grant options to any employee, or any Director holding a salaried office or employment with the Company or a Subsidiary for the purchase of ordinary shares. On the same date, the Company also adopted the Consultants Share Option Plan 2008 (the "2008 Consultants Plan"), pursuant to which the Compensation and Organization Committee of the Company's Board of Directors may grant options to any consultant, adviser or non-executive Director retained by the Company or any Subsidiary for the purchase of ordinary shares.

On February 14, 2017 both the 2008 Employee Plan and the 2008 Consultants Plan (together the "2008 Option Plans") were amended and restated in order to increase the number of options that can be issued under the 2008 Consultants Plan from 0.4 million to 1.0 million and to extend the date for options to be granted under the 2008 Option Plans.

An aggregate of 6.0 million ordinary shares have been reserved under the 2008 Employee Plan, as reduced by any shares issued or to be issued pursuant to options granted under the 2008 Consultants Plan, under which a limit of 1.0 million shares applies. Further, the maximum number of ordinary shares with respect to which options may be granted under the 2008 Employee Option Plan, during any calendar year to any employee shall be 0.4 million ordinary shares. There is no individual limit under the 2008 Consultants Plan. No options may be granted under the 2008 Option Plans after February 14, 2027.

Each option granted under the 2008 Option Plans is an employee stock option, or Nonqualified Stock Option ("NSO"), as described in Section 422 or 423 of the Internal Revenue Code. Each grant of an option under the 2008 Options Plans is evidenced by a Stock Option Agreement between the optionee and the Company. The exercise price is specified in each Stock Option Agreement, however option prices are not less than 100% of the fair market value of an ordinary share on the date the option is granted. Share option awards are granted with an exercise price equal to the market price of the Company's shares at date of grant. Share options typically vest over a period of five years from date of grant and expire eight years from date of grant.

PRA Equity Incentive Plans

The following represent the PRA equity incentive plans, that have been terminated as of July 1, 2021, as to grants of future awards.

Pursuant to the Merger Agreement, effective on July 1, 2021, each stock option and restricted stock unit under the PRA Plans was assumed by the Company and converted into a stock option or Restricted Share Unit exercisable for or payable in Ordinary Shares based on the ratio of the average trading price per Ordinary Share for the ten days prior to July 1, 2021, and the corresponding value of the Merger consideration for each PRA Share. Accordingly, the plans as detailed below were assumed by the Company.

PRA Health Sciences, Inc. 2020 Stock Incentive Plan (the "2020 Plan”), 2018 Stock Incentive Plan (the "2018 Plan"), 2014 Omnibus Incentive Plan (the "2014 Plan"), and 2013 Stock Incentive Plan (the "2013 Plan") were amended and restated and assumed by the Registrant effective as of July 1, 2021.

The 2020 Stock Incentive Plan, was approved by the PRA stockholders at their annual meeting on May 18, 2020. The 2020 Plan allowed for the issuance of stock options, stock appreciation rights, restricted shares and restricted stock units, other stock-based awards, and performance compensation awards as permitted by applicable laws. The 2020 Plan authorized the issuance of 2.5 million shares of common stock plus all shares that remained available under the prior plan on May 18, 2020.

The 2018 Stock Incentive Plan (the “2018 Plan”), was approved by the PRA stockholders at their annual meeting on May 31, 2018. The 2018 Plan allowed for the issuance of stock options, stock appreciation rights, restricted shares and restricted stock units, other stock-based awards, and performance compensation awards as permitted by applicable laws. The 2018 Plan authorized the issuance of 2 million shares of common stock plus all shares that remained available under the 2014 Plan on May 31, 2018 (which included shares carried over from the 2013 Plan).

On November 23, 2014, the PRA Health Sciences, Inc. Board of Directors approved the formation of the 2014 Plan for Key PRA Employees. The 2014 Plan allowed for the issuance of stock options, stock appreciation rights, restricted shares and restricted stock units, other stock-based awards, and performance compensation awards as permitted by applicable laws.

On September 23, 2013, the PRA Health Sciences, Inc. Board of Directors approved the formation of the 2013 Plan for Key Employees of Pinnacle Holdco Parent, Inc. and its subsidiaries. The 2013 Plan allowed for the issuance of stock options and other stock-based awards as permitted by applicable laws. The number of shares available for grant under the 2013 Plan was 12.5% of the outstanding shares at closing on a fully diluted basis. The 2013 Plan authorized the issuance of 2,052,909 shares of common stock.

The following table summarizes the transactions for the Company's share option plans for the years ended December 31, 2022, December 31, 2021 and December 31, 2020:


	Options Granted Under Plans	Weighted Average Exercise Price
Outstanding at December 31, 2019	656,107	$	87.80
Granted	107,737	$	159.83
Exercised	(193,417)	$	68.19
Canceled	(16,681)	$	92.21
Outstanding at December 31, 2020	553,746	$	108.53
Assumed through business combinations *	2,177,130	$	108.78
Granted	100,299	$	177.76
Exercised	(1,065,529)	$	111.29
Canceled/expired	(70,186)	$	128.46
Outstanding at December 31, 2021	1,695,460	$	110.38
Granted	108,643	$	229.94
Exercised	(348,286)	$	102.87
Canceled/expired	(77,698)	$	143.08
Outstanding at December 31, 2022	1,378,119	$	119.86
Vested and exercisable at December 31, 2022	1,047,803	$	102.29

*Represents stock options issued as replacement awards in connection with the Merger.

The weighted average remaining contractual life of options outstanding and options exercisable at December 31, 2022, was 4.69 years and 4.25 years respectively (2021: 5.39 years and 4.55 years respectively).

Outstanding and exercisable share options:

The following table summarizes information concerning outstanding and exercisable share options as of December 31, 2022:


Options Outstanding					Options Exercisable
Range Exercise Price	Number of Shares	Weighted Average Remaining Contractual Life	Weighted Average Exercise Price		Number of Shares	Weighted Average Exercise Price

14.88 - 96.15	494,565	2.70	—		494,565	—
103.81 - 124.00	226,489	5.58	—		203,605	—
125.74 - 147.26	386,518	5.65	—		303,054	—
159.33 - 231.68	270,547	6.24	—		46,579	—

14.88 - 231.68	1,378,119	4.69	$	119.86	1,047,803	$	102.29

Options outstanding include both vested and unvested options as at December 31, 2022. Options exercisable represent options which have vested at December 31, 2022. From the date of grant, substantially all options vest over a five year period.

Fair value of Stock Options Assumptions

The weighted average fair value of options granted during the years ended December 31, 2022, December 31, 2021 and December 31, 2020 was calculated using the Black-Scholes option pricing model. The weighted average fair values and assumptions were as follows:


	Year Ended
	December 31, 2022			December 31, 2021			December 31, 2020
Weighted average fair value	$	68.42		$	49.15		$	42.43

Assumptions:
Expected volatility	31		%	30		%	30		%
Dividend yield	—		%	—		%	—		%
Risk-free interest rate	1.86		%	0.78		%	0.57		%
Expected life	5.0 years			5.0 years			5.0 years

The weighted average fair value of options assumed on the date of the Merger was calculated using the Black-Scholes option pricing model. The weighted average fair values on the date of the Merger and assumptions used were as follows:


	July 1, 2021
Weighted average grant date fair value	$	107.21
Assumptions:
Expected volatility	30		%
Dividend yield	—		%
Risk-free interest rate	0.56		%
Expected life	3.5 years

Expected volatility is based on the historical volatility of our common stock over a period equal to the expected term of the options; the expected life represents the weighted average period of time that options granted are expected to be outstanding given consideration to vesting schedules and our historical experience of past vesting and termination patterns. The risk-free rate is based on the U.S. government zero-coupon bonds yield curve in effect at time of the grant for periods corresponding with the expected life of the option.

Restricted Share Units and Performance Share Units

On April 23, 2013 the Company adopted the 2013 Employees Restricted Share Unit and Performance Share Unit Plan (the "2013 RSU Plan") pursuant to which the Compensation and Organization Committee of the Company's Board of Directors may select any employee, or any Director holding a salaried office or employment with the Company, or a Subsidiary to receive an award under the plan. On May 11, 2015 the 2013 RSU Plan was amended and restated in order to increase the number of shares that can be issued under the RSU Plan by 2.5 million shares. Accordingly, an aggregate of 4.1 million ordinary shares have been reserved for issuance under the 2013 RSU Plan. The shares are awarded at par value and vest over a service period. Awards under the 2013 RSU Plan may be settled in cash or shares at the option of the Company. No awards may be granted under the 2013 RSU Plan after May 11, 2025.

On April 30 2019, the Company approved the 2019 Consultants and Directors Restricted Share Unit Plan (the “2019 Consultants RSU Plan”), which was effective as of May 16, 2019, pursuant to which the Compensation and Organization Committee of the Company’s Board of Directors may select any consultant, adviser or non-executive Director retained by the Company, or a Subsidiary to receive an award under the plan. 250,000 ordinary shares have been reserved for issuance under the 2019 Consultants RSU Plan. The awards are at par value and vest over a service period. Awards granted to non-executive directors during 2020 and 2021 vest over twelve months.

The Company has awarded RSUs and PSUs to certain key individuals of the Group. The following table summarizes RSU and PSU activity for the year ended December 31, 2022:


	PSU Outstanding Number of Shares	PSU Weighted Average Grant Date Fair Value		RSU Outstanding Number of Shares	RSU Weighted Average Grant Date Fair Value
Outstanding at December 31, 2021	154,190	$	160.23	572,785	$	191.20

Granted	64,682	$	229.79	302,307	$	216.85
Shares vested	(46,087)	$	140.48	(195,029)	$	174.35
Forfeited	(20,365)	$	185.90	(97,451)	$	205.25

Outstanding at December 31, 2022	152,420	$	192.29	582,612	$	207.73

The fair value of RSUs vested for the year ended December 31, 2022 totaled $34.1 million (2021: $83.5 million). The share price range for the year was $137.47 - $265.96 (2021: $115.11 - $206.71).

The fair value of PSUs vested for the year ended December 31, 2022 totaled $6.5 million (2021: $5.1 million). The share price range for the year was $137.47 - $166.51 (2021: $115.11 - $125.74).

The PSUs vest based on service and specified EPS targets over the period 2021 – 2023 and 2022 – 2024. Depending on the actual amount of EPS from 2021 to 2024, up to an additional 76,210 PSUs may also be granted.

Non-cash stock compensation expense

Income from operations for the year ended December 31, 2022 is stated after charging $70.5 million in respect of non-cash stock compensation expense. Non-cash stock compensation expense has been allocated as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Direct costs	$	22,854	$	18,551	$	8,557
Selling, general and administrative	47,669		41,457		17,714
Transaction and integration related *	—		73,836		—
Total compensation costs	$	70,523	$	133,844	$	26,271

* Represents the post combination portion of the accelerated vesting of awards following the completion of the Merger

The income tax expense for the year ended December 31, 2022 reflects a net income tax benefit of $12.9 million in connection with stock compensation (including excess tax benefits) and the total tax benefit in connection with stock options exercised during 2022 was $7.7 million. The income tax expense for the year ended December 31, 2021 reflects a net income tax benefit of $22.7 million in connection with stock compensation (including excess tax benefits) and the total tax benefit in connection with stock options exercised during 2021 was $23.9 million. The income tax expense for the year ended December 31, 2020 reflects a net income tax benefit of $6.9 million in connection with stock compensation (including excess tax benefits) and the total tax benefit realized in connection with stock options exercised during 2020 was $2.5 million.

Investments - Equity Method Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Jul. 24, 2020
Debt Securities, Available-for-sale [Line Items]
Equity method investments	$ 0	$ 2,373	$ 4,900
Oncacare
Debt Securities, Available-for-sale [Line Items]
Ownership Percentage	49.00%

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Summary of Components of Income Before Provision for Income Taxes

The components of income before income tax expense are as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Ireland	$	432,963	$	231,893	$	280,310
United States	(270,440)		(278,413)		41,950
Other	405,328		243,200		58,945
Income before income tax expense	$	567,851	$	196,680	$	381,205

Summary of Components of Provision for Income Taxes

The components of income tax expense are as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Income tax expense:
Current tax expense:
Ireland	$	53,248	$	18,469	$	28,963
United States	60,753		35,478		3,022
Other	70,395		48,003		14,963
Total current tax expense	184,396		101,950		46,948

Deferred tax (benefit)/expense:
Ireland	(6,166)		553		1,654
United States	(118,475)		(52,717)		4,577
Other	(344)		(8,452)		(5,304)
Total deferred tax (benefit)/expense	(124,985)		(60,616)		927

Income tax expense allocated to continuing operations	59,411		41,334		47,875

Income tax expense was allocated to the following components of other comprehensive income:

Currency impact on long term funding	7,211		1,776		68


Total	$	66,622	$	43,110	$	47,943

Schedule of Reconciliation of Consolidated Reported Provision for Income Taxes and Statutory Rate

The Company's consolidated reported income tax expense differed from the amount that would result from applying the Irish statutory rate as set forth below:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Taxes at Irish statutory rate of 12.5% (2021:12.5%; 2020:12.5%)	$	70,980	$	24,586	$	47,651
Rate differential from amortization of intangible assets	(59,330)		(31,228)		(2,298)
Foreign and other income taxed at higher rates	52,464		51,273		10,241
Research & development tax incentives	(2,608)		(3,120)		(1,243)
Movement in valuation allowance	(777)		3,101		3,581
Effects of change in tax rates	(300)		(128)		108
Change in unrecognized tax benefits	8,392		5,246		(1,672)
Impact of stock compensation	(8,756)		(9,083)		(5,150)

Other	(654)		687		(3,343)
Income tax expense	$	59,411	$	41,334	$	47,875

Schedule of Tax Effects of Temporary Differences that Give Rise to Significant Portions of Deferred Tax Assets and Deferred Tax Liabilities

The tax effects of temporary differences that give rise to significant portions of deferred tax assets and deferred tax liabilities are presented below:


	December 31, 2022		December 31, 2021
	(in thousands)
Deferred tax liabilities:
Property, plant and equipment	$	10,927	$	19,606
Operating right-of-use-assets	23,260		33,449
Goodwill	37,150		33,354
Intangible assets	1,078,302		1,201,086
Other	9,054		1,761
Total deferred tax liabilities recognized	1,158,693		1,289,256

Deferred tax assets:
Operating loss and tax credits carryforwards	88,697		86,893
Property, plant and equipment	6,010		5,846
Operating lease liabilities	27,593		36,106
Intangible assets	3,602		4,596
Accrued expenses and unbilled revenue	64,016		69,198
Stock compensation	21,862		25,557
Deferred compensation	2,917		3,445
Unearned revenue	66,565		64,924
Other	9,155		602
Total deferred tax assets	290,417		297,167
Valuation allowance for deferred tax assets	(43,379)		(45,495)
Deferred tax assets recognized	247,038		251,672
Overall net deferred tax asset/(liability)	$	(911,655)	$	(1,037,584)

Schedule of Expected Expiry Dates of NOL's

The expected expiry dates of the US NOLs are as follows:


	Federal NOL's		State NOL's
	(in thousands)
2023-2036	$	5,268	$	249,530
2033-2041	—		145,632
Indefinite	95		6,736

	$	5,363	$	401,898

Schedule of Reconciliation of Beginning and Ending Amount of Total Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of total unrecognized tax benefits is as follows:


	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Unrecognized tax benefits at start of year	$	202,065	$	19,078	$	20,156
Increase related to acquired tax positions			170,047		—
Increase related to prior year tax positions	16,098		204		401
Decrease related to prior year tax positions	(5,442)		(1,695)		(1,271)
Increase related to current year tax positions	5,701		18,613		2,931
Settlements	—		(844)		(369)
Lapse of statute of limitations	(838)		(3,338)		(2,770)
Unrecognized tax benefits at end of year	$	217,584	$	202,065	$	19,078

Contract Balances

12 Months Ended

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

Contract Balances

Disaggregation of Revenue

Revenue disaggregated by customer profile is as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Top client	$	683,546	$	441,173	$	337,904
Clients 2-5	1,506,087		1,291,946		754,906
Clients 6-10	1,112,636		752,325		350,865
Clients 11-25	1,585,739		1,077,073		501,643
Other	2,853,378		1,918,309		851,970
Total	$7,741,386		$5,480,826		$2,797,288

Our customers have similar profiles and economic characteristics, and therefore have similar degrees of risk and growth opportunities.Contract Balances

Accounts receivable and unbilled revenue are as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Billed services (accounts receivable)	$	1,751,950	$	1,349,851
Allowance for credit losses (note 5)	(20,562)		(7,081)
Accounts receivable (net)	1,731,388		1,342,770
Unbilled services (unbilled revenue)	$	957,655	$	623,121
Accounts receivable and unbilled revenue, net	$	2,689,043	$	1,965,891

Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows:


(in thousands, except percentages)	December 31, 2022		December 31, 2021		$ Change		% Change

Unbilled services (unbilled revenue)	$	957,655	$	623,121	$	334,534	53.7	%
Unearned revenue (payments on account)	(1,507,449)		(1,323,961)		(183,488)		13.9	%
Net balance	$	(549,794)	$	(700,840)	$	151,046	21.6	%

The credit loss expense recognized on the Group's receivables and unbilled services was $17.8 million and $0.9 million for the twelve months ended December 31, 2022 and 2021, respectively.

- Definition

+ References

+ Details

Employee Benefits - Change in Benefit Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
United Kingdom \| ICON Development Solutions Limited pension plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 41,813	$ 43,988
Service cost	117	134	$ 100
Interest cost	672	665	746
Plan participants' contributions	19	23
Benefits paid	514	489
Actuarial gain	(18,636)	(2,097)
Foreign currency exchange rate changes	(3,913)	(411)
Benefit obligation at end of year	19,558	41,813	43,988
Switzerland \| Aptiv Solutions pension plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	7,643	8,620
Service cost	146	150
Interest cost	30	12
Plan participants' contributions	82	95
Settlement	(218)	(483)
Prior service cost	(23)	(82)
Benefits paid and transferred balances	(182)	76
Actuarial gain	(1,527)	(484)
Foreign currency exchange rate changes	(145)	(261)
Benefit obligation at end of year	5,806	7,643	8,620
Switzerland \| PRA Switzerland AG pension plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	4,990	4,890
Service cost	404	207
Interest cost	20	19
Plan participants' contributions	2,396	135
Settlement	(844)	0
Benefits paid	946	113
Actuarial gain	(627)	1
Foreign currency exchange rate changes	(48)	(149)
Benefit obligation at end of year	$ 5,345	$ 4,990	$ 4,890

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY AND COMPREHENSIVE INCOME - USD ($) $ in Thousands	Total	Ordinary Shares	Additional Paid-in Capital	Other Undenominated Capital	Accumulated Other Comprehensive Income	Retained Earnings	Redeemable Noncontrolling Interest
Beginning balance (in shares) at Dec. 31, 2019		53,622,206
Beginning balance at Dec. 31, 2019	$ 1,618,055	$ 4,635	$ 577,961	$ 1,052	$ (75,819)	$ 1,110,226
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	332,331					332,331
Currency translation adjustment	46,526				46,526
Unrealized capital loss - investments	(231)				(231)
Actuarial gain (loss) on defined benefit pension plan	(4,138)				(4,138)
Amortization of cash flow hedge	(910)				(910)
Loss on cash flow hedge	(905)				(905)
Total comprehensive income attributable to the Group	372,673
Exercise of share options (in shares)		193,417
Exercise of share options	13,189	$ 13	13,176
Issue of restricted share units / performance share units (in shares)		207,688
Issue of restricted share units / performance share units	14	$ 14
Share based compensation expense	25,981		25,981
Share issue costs	(14)		(14)
Repurchase of ordinary shares (in shares)		(1,235,218)
Repurchase of ordinary shares	(175,000)	$ (82)		82		(175,000)
Share repurchase costs	(140)					(140)
Noncontrolling interest adjustment to redemption amount	(4,522)					(4,522)	$ 4,522
Ending balance (in shares) at Dec. 31, 2020		52,788,093
Ending balance at Dec. 31, 2020	1,850,236	$ 4,580	617,104	1,134	(35,477)	1,262,895
Beginning balance at Dec. 31, 2019							39,510
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income							633
Noncontrolling interest adjustment to redemption amount	(4,522)					(4,522)	4,522
Exercise of call option on noncontrolling interest shares							(44,665)
Ending balance at Dec. 31, 2020							$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	153,185					153,185
Currency translation adjustment	(60,617)				(60,617)
Unrealized capital loss - investments	0
Actuarial gain (loss) on defined benefit pension plan	4,266				4,266
Amortization of cash flow hedge	113				113
Loss on cash flow hedge	778				778
Total comprehensive income attributable to the Group	97,725
Exercise of share options (in shares)		1,065,529
Exercise of share options	118,589	$ 77	118,512
Issue of restricted share units / performance share units (in shares)		328,634
Issue of restricted share units / performance share units	23	$ 23
Share based compensation expense	133,553		133,553
Share issue costs	(853)		(853)
Issue of shares associated with a business combination (in shares)		27,372,427
Issue of shares associated with a business combination	5,658,155	$ 1,960	5,656,195
Replacement share-based awards issued to acquiree employees	$ 209,399		209,399
Ending balance (in shares) at Dec. 31, 2021	81,554,683	81,554,683
Ending balance at Dec. 31, 2021	$ 8,066,827	$ 6,640	6,733,910	1,134	(90,937)	1,416,080
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	505,304					505,304
Currency translation adjustment	(89,530)				(89,530)
Unrealized capital loss - investments	0
Actuarial gain (loss) on defined benefit pension plan	12,657				12,657
Amortization of cash flow hedge	0
Loss on cash flow hedge	(3,728)				(3,728)
Total comprehensive income attributable to the Group	424,703
Exercise of share options (in shares)		348,286
Exercise of share options	35,828	$ 21	35,807
Issue of restricted share units / performance share units (in shares)		241,116
Issue of restricted share units / performance share units	16	$ 16
Share based compensation expense	70,606		70,606
Share issue costs	(17)		(17)
Repurchase of ordinary shares (in shares)		(420,530)
Repurchase of ordinary shares	(99,983)	$ (28)		28		(99,983)
Share repurchase costs	$ (17)					(17)
Ending balance (in shares) at Dec. 31, 2022	81,723,555	81,723,555
Ending balance at Dec. 31, 2022	$ 8,497,963	$ 6,649	$ 6,840,306	$ 1,162	$ (171,538)	$ 1,821,384

Summary of Significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Adjustments resulting from foreign currency translations

Amounts charged or credited to the Consolidated Statements of Operations for the years ended December 31, 2022, December 31, 2021 and December 31, 2020 were as follows:


	Year ended December 31,
	2022		2021		2020
	(in thousands)
Amounts (credited)/charged	$	(25,997)	$	(14,316)	$	5,979

Estimated useful lives of assets

Depreciation of property, plant and equipment is computed using the straight line method based on the estimated useful lives of the assets as listed below:


			Years
Building			40
Computer equipment and software			2-8
Office furniture and fixtures			8
Laboratory equipment			5
Motor vehicles			5

Schedule of Finite-Lived Intangible Assets

Intangible assets are amortized on a straight-line basis over the expected useful life, as set forth in the table below:


			Estimated Useful Life
Customer relationships			23 years
Order backlog			3 years
Trade names			3 years
Patient database			7 years
Technology assets			5 years

The carrying amount of Intangible Assets for the years ended December 31, 2022 and 2021 is as follows:


	December 31, 2022		December 31, 2021
Cost	(in thousands)
Customer relationships	$	4,076,435	$	4,056,642
Order backlog	536,934		528,022
Trade names & brands	204,621		204,685
Patient database	170,238		170,525
Technology assets	120,984		121,507
Total cost	5,109,212		5,081,381

Accumulated amortization	(830,553)		(370,538)
Net book value	$	4,278,659	$	4,710,843

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current Assets:
Cash and cash equivalents	$ 288,768	$ 752,213
Available for sale investments (Note 8a)	1,713	1,712
Accounts receivable, net of allowance for credit losses (Note 4)	1,731,388	1,342,770
Unbilled revenue (Note 4)	957,655	623,121
Other receivables	63,658	56,760
Prepayments and other current assets	137,094	114,323
Income taxes receivable	48,790	50,299
Total current assets	3,229,066	2,941,198
Non-current Assets:
Property, plant and equipment, net (Note 9)	350,320	336,444
Goodwill (Note 10)	8,971,670	9,037,931
Intangible assets, net (Note 11)	4,278,659	4,710,843
Operating right-of-use assets (Note 15)	153,832	198,123
Other receivables	70,790	70,557
Income taxes receivable	21,380	18,637
Deferred tax asset (Note 20)	76,930	48,392
Equity method investments	0	2,373
Investments in equity-long term (Note 8b)	32,631	22,592
Total Assets	17,185,278	17,387,090
Current Liabilities:
Accounts payable	81,194	90,764
Unearned revenue (Note 4)	1,507,449	1,323,961
Other liabilities (Note 12)	1,005,025	949,629
Income taxes payable	41,783	59,433
Current bank credit lines and loan facilities (Note 13)	55,150	55,150
Total current liabilities	2,690,601	2,478,937
Non-current Liabilities:
Non-current bank credit lines and loan facilities (Note 13)	4,599,037	5,381,162
Lease liabilities (Note 15)	131,644	159,483
Non-current other liabilities (Note 16)	38,260	42,596
Non-current income taxes payable	239,188	172,109
Deferred tax liability (Note 20)	988,585	1,085,976
Commitments and contingencies (Note 17)	0	0
Liabilities, Total	8,687,315	9,320,263
Shareholders' Equity:
Ordinary shares par value 6 euro cents per share; 100,000,000 shares authorized, (Note 18). 81,723,555 shares issued and outstanding at December 31, 2022 and 81,554,683 shares issued and outstanding at December 31, 2021.	6,649	6,640
Additional paid-in capital	6,840,306	6,733,910
Other undenominated capital (Note 18b)	1,162	1,134
Accumulated other comprehensive income (Note 25)	(171,538)	(90,937)
Retained earnings	1,821,384	1,416,080
Total Shareholders' Equity	8,497,963	8,066,827
Total Liabilities and Shareholders’ Equity	$ 17,185,278	$ 17,387,090

Restructuring charges - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 31,143	$ 31,105	$ 18,089
Restructuring reserve	6,022	$ 10,311	$ 4,675
2021 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring charges	31,100
Severance costs	2,700
Other restructuring costs	24,500
Fixed asset impairment	4,000
Lease Liability
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	1,400
Restructuring reserve, current	900
Restructuring reserve, noncurrent	500
Workforce reductions
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 4,600

Employee Benefits - Funded Status (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
United Kingdom \| ICON Development Solutions Limited pension plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ (19,558)	$ (41,813)
Fair value of plan assets	26,050	36,198	$ 34,612
Funded status	6,492	(5,615)
Switzerland \| Aptiv Solutions pension plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	(5,806)	(7,643)
Fair value of plan assets	5,681	6,964	7,601
Funded status	(125)	(679)
Switzerland \| PRA Switzerland AG pension plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	(5,345)	(4,990)
Fair value of plan assets	4,059	3,017	$ 2,849
Funded status	$ (1,286)	$ (1,973)

- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References + Details

Derivatives

12 Months Ended

Dec. 31, 2022

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivatives

The Company has entered into interest rate cap and swap agreements for purposes of managing its exposure to interest rate fluctuations. These financial derivative agreements are designated as Cash Flow Hedges.

On November 29, 2022, the Company entered into two interest rate cap agreements ("2022 Caps") with an initial total notional value of $2,101 million to limit its exposure to changes in the variable interest rate on its Senior Secured Credit Facilities. Interest on the 2022 Caps began accruing on December 30, 2022 and the interest rate cap expires on December 31, 2024. The Company pays a fixed rate of 0.42% and receives a variable rate equal to the amount that the three-month SOFR rate exceeds 4.75%.

On November 29, 2022, the Company entered into an interest rate swap agreement ("2022 Swap") with an initial notional value of $1,101 million to limit its exposure to changes in the variable interest rate on its Senior Secured Credit Facilities. Interest on the 2022 Swaps begins accruing on December 31, 2024 and the interest rate swap expires on December 31, 2026. The Company pays a fixed rate of 3.4% and receives a variable rate of interest equal to the three-month SOFR on the 2022 Swap.

The critical terms of the caps and swap are substantially the same as the underlying borrowings. The interest rate caps and swap are accounted for as cash flow hedges as these transactions were executed to hedge the Company's interest payments and for accounting purposes are considered highly effective. As such, the effective portion of the hedges is recorded as unrealized gains (losses) on derivatives in Accumulated Other Comprehensive Income.

The fair value of these cash flow hedges represents the present value of the anticipated net payments the Company will make to the counterparty, which, when they occur, are reflected as interest expense on the consolidate statement of income.

The fair value of the Company’s derivative financial instruments, on a gross basis, and the line items on the accompanying consolidate balance sheets to which they were recorded are summarized in the following table:


		December 31, 2022
		Asset	Liability	Notional
		(in thousands)
Derivatives designated as hedging instruments:

Interest Rate Caps	Other Assets and Liabilities	$12	$3,363	2,100,606
Interest Rate Swap	Other Assets and Liabilities	$—	$307	1,100,606

Total derivatives designated as hedging instruments		$12	$3,670	3,201,213

During 2023, the Company estimates that an additional $3.3 million will be reflected as interest expense in the consolidated statements.

At December 31, 2021 the fair value of the Company's derivative financial instruments was $nil as the Company had no outstanding derivative financial instruments.

The Company recognized $0.1 million of gain within OCI and reclassified $0.1 million of gain from OCI to the income statement for the year end December 31, 2022.

Business Combinations (Tables)

12 Months Ended

Dec. 31, 2022

Business Combinations [Abstract]

Schedule of Business Acquisitions, by Acquisition

The Merger Date fair value of the consideration transferred consisted of the following:


			(in thousands)
Fair value of cash consideration			5,308,646
Fair value of ordinary shares issued to acquiree stockholders			5,658,126
Fair value of replacement share-based awards issued to acquiree employees			209,399
Repayment of term loan obligations and accrued interest *			865,800
			12,041,971

* This represents the portion of PRA debt paid by ICON. PRA also paid $401.6 million from available cash to settle debt obligations that existed at the Merger Date.

Summary of Estimates of Fair Values of Assets Acquired and Liabilities Assumed

The following table summarizes the allocation of the consideration transferred based on the Merger Date fair values of assets acquired and liabilities assumed, with the excess of the purchase price over the estimated fair values of the identifiable net assets acquired recorded as goodwill:


	July 1,
	2021
	(in thousands)
Cash and cash equivalents	$	259,971
Accounts receivable and unbilled revenue	934,308
Other current assets	125,156
Fixed assets	156,851
Operating lease right-of-use assets	180,601
Goodwill *	8,084,314
Intangible assets	4,919,000
Deferred tax assets	25,190
Other assets	33,928
Accounts payable	(50,259)
Accrued expenses and other current liabilities	(380,048)
Current portion of operating lease liabilities	(36,506)
Unearned revenue	(739,278)
Non-current portion of operating lease liabilities	(147,204)
Deferred tax liabilities	(1,119,762)
Other non-current liabilities	(204,291)

Net assets acquired	$	12,041,971

* The goodwill in connection with the Merger is primarily attributable to the assembled workforce of PRA and the expected synergies of the Merger. None of the goodwill recognized is deductible for income tax purposes.

Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination

The following table summarizes the fair value of identified intangible assets and their respective useful lives as of the Merger Date (in thousands, except for estimated useful lives):


	Estimated Fair Value	Estimated Useful Life
Customer relationships	3,938,000	23 years
Order backlog	500,000	3 years
Trade names	202,000	3 years
Patient database	168,000	7 years
Technology assets	111,000	5 years
	4,919,000

Schedule of measurement period adjustments

In the period since the Merger Date, the Company recognized certain measurement period adjustments as shown in the table below:


	Measurement period adjustments

	(in thousands)
Cash and cash equivalents	$	—
Accounts receivable and unbilled revenue	—
Other current assets	14,465
Fixed assets	(6,137)
Operating lease right-of-use assets	(11,744)
Goodwill	70,436
Intangible assets *	44,000
Deferred tax assets	(147,039)
Other assets	(1,166)
Accounts payable	—
Accrued expenses and other current liabilities	(37,496)
Current portion of operating lease liabilities	1,865
Unearned revenue **	19,623
Non-current portion of operating lease liabilities	10,454
Non-current deferred tax liabilities	193,837
Other non-current liabilities	(151,098)

* In the year ended December 31, 2022, the Company incurred $2.2 million amortization which related to the year ended December 31, 2021 due to the timing of when the measurement period adjustment was identified.

** The unearned revenue measurement period adjustment also includes $16.0 million as a result of the early adoption of ASU 2021-08 'Business Combinations (Topic 805) - Accounting for Contract Assets and Contract Liabilities from Contracts with Customers' in Quarter 4 2021.

Description of business	12 Months Ended
Description of business	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of business	Description of Business ICON plc and its subsidiaries ("the Company" or "ICON") is a clinical research organization ("CRO"), providing outsourced development services on a global basis to the pharmaceutical, biotechnology and medical device industries. We specialize in the strategic development, management and analysis of programs that support all stages of the clinical development process from compound selection to Phase I-IV clinical studies. Our mission is to improve the lives of patients by accelerating the development of our customers' drugs and devices through innovative solutions. We believe that we are one of a select group of CROs with the expertise and capability to conduct clinical trials in most major therapeutic areas on a global basis and have the operational flexibility to provide development services on a stand-alone basis or as part of an integrated "full-service" solution. At December 31, 2022 we had approximately 41,100 employees, in 111 locations in 53 countries. During the year ended December 31, 2022, we derived approximately 46.2%, 46.5% and 7.3% of our revenue in the United States, Europe and Rest of World, respectively. ICON’s ordinary shares are traded on the NASDAQ Global Select Market under the symbol “ICLR”. We began operations in 1990 and have expanded our business through internal growth, together with a number of strategic acquisitions to enhance our capabilities and expertise in certain areas of the clinical development process. We are incorporated in Ireland and our principal executive office is located at: South County Business Park, Leopardstown, Dublin 18, Republic of Ireland. The contact telephone number of this office is +353 1 2912000.

Operating Leases (Tables)

12 Months Ended

Dec. 31, 2022

Leases [Abstract]

Lease Cost

Lease costs recorded under operating leases as of December 31, 2022 and 2021 were as follows:


	Year ended
	December 31, 2022		December 31, 2021
	(in thousands)

Operating lease costs	$	53,880	$	51,200
Income from sub-leases	(1,165)		(1,338)
Net operating lease costs	$	52,715	$	49,862

Schedule of Operating Lease Maturity

Future minimum lease payments under non-cancelable leases as of December 31, 2022 were as follows:


	Minimum rental
	payments
	(in thousands)
2023	$	47,479
2024	34,400
2025	25,045
2026	20,430
2027	17,249
Thereafter	45,065
Total future minimum lease payments	189,668
Lease imputed interest	(14,367)
Total	$	175,301

Cover	12 Months Ended
Cover	Dec. 31, 2022 shares
Document Information [Line Items]
Document Type	20-F
Document Registration Statement	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Document Shell Company Report	false
Entity File Number	333-08704
Entity Registrant Name	ICON PLC
Entity Incorporation, State or Country Code	L2
Entity Address, Address Line One	South County Business Park,
Entity Address, Address Line Two	Leopardstown,
Entity Address, City or Town	Dublin 18, D18 X5R3
Entity Address, Postal Zip Code	D18 X5R3
Entity Address, Country	IE
Title of 12(b) Security	ORDINARY SHARES, PAR VALUE €0.06 EACH
Trading Symbol	ICLR
Security Exchange Name	NASDAQ
Entity common stock, shares outstanding (in shares)	81,723,555
Entity Well Known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filler Category	Large Accelerated Filer
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Accounting Standard	U.S. GAAP
Entity Shell Company	false
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Central Index Key	0001060955
Business Contact
Document Information [Line Items]
Entity Address, Address Line One	South County Business Park
Entity Address, Address Line Two	Leopardstown
Entity Address, City or Town	Dublin 18
Entity Address, Postal Zip Code	D18 X5R3
Entity Address, Country	IE
Contact Personnel Name	Brendan Brennan
Contact Personnel Email Address	Brendan.Brennan@iconplc.com
Country Region	353
City Area Code	1
Local Phone Number	291-2000

Equity Incentive Schemes and Stock Compensation Charges (Tables)

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of Transactions for Company's Share Option Plans

The following table summarizes the transactions for the Company's share option plans for the years ended December 31, 2022, December 31, 2021 and December 31, 2020:


	Options Granted Under Plans	Weighted Average Exercise Price
Outstanding at December 31, 2019	656,107	$	87.80
Granted	107,737	$	159.83
Exercised	(193,417)	$	68.19
Canceled	(16,681)	$	92.21
Outstanding at December 31, 2020	553,746	$	108.53
Assumed through business combinations *	2,177,130	$	108.78
Granted	100,299	$	177.76
Exercised	(1,065,529)	$	111.29
Canceled/expired	(70,186)	$	128.46
Outstanding at December 31, 2021	1,695,460	$	110.38
Granted	108,643	$	229.94
Exercised	(348,286)	$	102.87
Canceled/expired	(77,698)	$	143.08
Outstanding at December 31, 2022	1,378,119	$	119.86
Vested and exercisable at December 31, 2022	1,047,803	$	102.29

*Represents stock options issued as replacement awards in connection with the Merger.

Summary of Information Concerning Outstanding and Exercisable Share Options

The following table summarizes information concerning outstanding and exercisable share options as of December 31, 2022:


Options Outstanding					Options Exercisable
Range Exercise Price	Number of Shares	Weighted Average Remaining Contractual Life	Weighted Average Exercise Price		Number of Shares	Weighted Average Exercise Price

14.88 - 96.15	494,565	2.70	—		494,565	—
103.81 - 124.00	226,489	5.58	—		203,605	—
125.74 - 147.26	386,518	5.65	—		303,054	—
159.33 - 231.68	270,547	6.24	—		46,579	—

14.88 - 231.68	1,378,119	4.69	$	119.86	1,047,803	$	102.29

Summary of Weighted Average Fair Values and Assumptions Used

The weighted average fair values and assumptions were as follows:


	Year Ended
	December 31, 2022			December 31, 2021			December 31, 2020
Weighted average fair value	$	68.42		$	49.15		$	42.43

Assumptions:
Expected volatility	31		%	30		%	30		%
Dividend yield	—		%	—		%	—		%
Risk-free interest rate	1.86		%	0.78		%	0.57		%
Expected life	5.0 years			5.0 years			5.0 years


	July 1, 2021
Weighted average grant date fair value	$	107.21
Assumptions:
Expected volatility	30		%
Dividend yield	—		%
Risk-free interest rate	0.56		%
Expected life	3.5 years

Summary of RSU and PSU Activity

The following table summarizes RSU and PSU activity for the year ended December 31, 2022:


	PSU Outstanding Number of Shares	PSU Weighted Average Grant Date Fair Value		RSU Outstanding Number of Shares	RSU Weighted Average Grant Date Fair Value
Outstanding at December 31, 2021	154,190	$	160.23	572,785	$	191.20

Granted	64,682	$	229.79	302,307	$	216.85
Shares vested	(46,087)	$	140.48	(195,029)	$	174.35
Forfeited	(20,365)	$	185.90	(97,451)	$	205.25

Outstanding at December 31, 2022	152,420	$	192.29	582,612	$	207.73

Schedule of Non-cash Stock Compensation Expense

Non-cash stock compensation expense has been allocated as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Direct costs	$	22,854	$	18,551	$	8,557
Selling, general and administrative	47,669		41,457		17,714
Transaction and integration related *	—		73,836		—
Total compensation costs	$	70,523	$	133,844	$	26,271

* Represents the post combination portion of the accelerated vesting of awards following the completion of the Merger

Equity Incentive Schemes and Stock Compensation Charges - Schedule of Weighted Average Fair Values and Assumptions Used (Details) - Employee Stock Option - $ / shares		12 Months Ended
	Jul. 01, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value (USD per share)	$ 107.21	$ 68.42	$ 49.15	$ 42.43
Assumptions:
Expected volatility (in percent)	30.00%	31.00%	30.00%	30.00%
Dividend yield (in percent)	0.00%	0.00%	0.00%	0.00%
Risk free interest rate (in percent)	0.56%	1.86%	0.78%	0.57%
Expected life	3 years 6 months	5 years	5 years	5 years

Restructuring charges - Summary of Restructuring Charges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Restructuring and Related Activities [Abstract]
Restructuring charges	$ 31,143	$ 31,105	$ 18,089

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenue:
Revenue	$ 7,741,386	$ 5,480,826	$ 2,797,288
Costs and expenses:
Direct costs (excluding depreciation and amortization)	5,527,045	3,972,612	1,979,883
Selling, general and administrative	778,753	585,330	342,449
Depreciation and amortization	569,513	314,987	66,126
Transaction and integration related (Note 6)	39,695	198,263	(759)
Restructuring (Note 19)	31,143	31,105	18,089
Total costs and expenses	6,946,149	5,102,297	2,405,788
Income from operations	795,237	378,529	391,500
Interest income	2,345	574	2,724
Interest expense (Note 13)	(229,731)	(182,423)	(13,019)
Income before income tax expense	567,851	196,680	381,205
Income tax expense (Note 20)	(59,411)	(41,334)	(47,875)
Income before share of earnings from equity method investments	508,440	155,346	333,330
Share of equity method investments	(3,136)	(2,161)	(366)
Net Income	505,304	153,185	332,964
Net income attributable to noncontrolling interest	0	0	(633)
Net income attributable to the Group	$ 505,304	$ 153,185	$ 332,331
Net income per Ordinary Share attributable to the Group (Note 24):
Basic (USD per share)	$ 6.20	$ 2.28	$ 6.20
Diluted (USD per share)	$ 6.13	$ 2.25	$ 6.15
Weighted average number of ordinary shares outstanding:
Basic (in shares)	81,532,320	67,110,186	52,859,911
Diluted (in shares)	82,468,363	68,068,311	53,283,585

Property, Plant and Equipment, net (Tables)

12 Months Ended

Dec. 31, 2022

Property, Plant and Equipment [Abstract]

Schedule of Property Plant and Equipment, Net

The carrying amount of Property, Plant and Equipment for the years ended December 31, 2022 and 2021 is as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Cost
Land	$	3,724	$	3,724
Building	70,880		82,017
Computer equipment and software	500,135		506,322
Office furniture and fixtures	50,600		107,507
Laboratory equipment	59,946		29,210
Leasehold improvements	65,167		70,123
Motor vehicles	41		65

	750,493		798,968
Less accumulated depreciation and asset write offs	(400,173)		(462,524)

Property, plant and equipment (net)	$	350,320	$	336,444

Property, Plant and Equipment depreciation expense is as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Depreciation expense	$	106,426	$	75,484

Non-current other liabilities

12 Months Ended

Dec. 31, 2022

Payables and Accruals [Abstract]

Non-current other liabilities

The carrying amount of Non-current other liabilities for the years ended December 31, 2022 and 2021 is as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Defined benefit pension obligations, net (note 21)	$	13,033	$	16,262
Other non-current liabilities	25,227		26,334
	$	38,260	$	42,596

Employee Benefits (Tables)

12 Months Ended

Dec. 31, 2022

Retirement Benefits [Abstract]

Schedule of Amounts Recognized in Balance Sheet

The balances recorded to the balance sheet are as follows:


	December 31, 2022		December 31, 2021
Other receivables	$	6,492	$	—
Non-current other liabilities (note 16)	(13,033)		(16,262)

Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan


Funded status	December 31, 2022		December 31, 2021
	(in thousands)
Projected benefit obligation	$	(19,558)	$	(41,813)
Fair value of plan assets	26,050		36,198
Funded status	$	6,492	$	(5,615)

The funded status as at December 31, 2022 is included in other long-term receivables on the Consolidated Balance Sheet. The funded status as at December 31, 2021 is included in non-current other liabilities on the Consolidated Balance Sheet.


Change in benefit obligation	December 31, 2022		December 31, 2021
	(in thousands)
Benefit obligation at beginning of year	$	41,813	$	43,988
Service cost	117		134
Interest cost	672		665
Plan participants' contributions	19		23

Benefits paid	(514)		(489)
Actuarial gain	(18,636)		(2,097)
Foreign currency exchange rate changes	(3,913)		(411)
Benefit obligation at end of year	$	19,558	$	41,813


Change in plan assets	December 31, 2022		December 31, 2021
	(in thousands)
Fair value of plan assets at beginning of year	$	36,198	$	34,612
Expected return on plan assets	1,258		1,171
Actual return on plan assets	(7,305)		1,176
Employer contributions	70		91
Plan participants' contributions	19		23
Benefits paid	(514)		(489)
Foreign currency exchange rate changes	(3,676)		(386)
Fair value of plan assets at end of year	$	26,050	$	36,198


Funded surplus/(deficit)	December 31, 2022		December 31, 2021
	(in thousands)
Projected benefit obligation	$	(5,806)	$	(7,643)
Fair value of plan assets	5,681		6,964
Funded deficit	$	(125)	$	(679)

The funded deficit at December 31, 2022 and December 31, 2021 are included in non-current other liabilities on the Consolidated Balance Sheet.

The change in benefit obligation is presented in the following table. The discount rates used in calculating the benefit obligation in years ended December 31, 2022 and December 31, 2021 were 2.3% and 0.4%, respectively.


Change in benefit obligation	December 31, 2022		December 31, 2021
	(in thousands)
Benefit obligation at beginning of year	$	7,643	$	8,620
Service cost	146		150
Interest cost	30		12
Plan participants' contributions	82		95
Settlement	(218)		(483)
Prior service cost	(23)		(82)
Benefits paid and transferred balances	(182)		76
Actuarial gain	(1,527)		(484)
Foreign currency exchange rate changes	(145)		(261)
Benefit obligation at end of year	$	5,806	$	7,643


Change in plan assets	December 31,		December 31,
	2022		2021
	(in thousands)
Fair value of plan assets at beginning of year	$	6,964	$	7,601
Expected return on plan assets	29		15
Actual return on plan assets	(987)		(238)
Scheme contributions	114		128
Plan participants' contributions	82		95
Benefits paid and transferred balances	(182)		76
Settlement	(218)		(483)
Foreign currency exchange rate changes	(121)		(230)
Fair value of plan assets at end of year	$	5,681	$	6,964

The pension costs of this plan are presented in the following tables in accordance with the requirements of ASC 715-60 'Defined Benefit Plans – Other Postretirement'.


Funded surplus/(deficit)	December 31, 2022		December 31, 2021
	(in thousands)
Projected benefit obligation	$	(5,345)	$	(4,990)
Fair value of plan assets	4,059		3,017
Funded deficit	$	(1,286)	$	(1,973)

The funded deficit at December 31, 2022 and December 31, 2021 are included in non-current other liabilities on the Consolidated Balance Sheet.

The change in benefit obligation is presented in the following table. The discount rate used in calculating the benefit obligation in years ended December 31, 2022 and December 31, 2021 was 2.3% and 0.4%, respectively.


Change in benefit obligation	December 31, 2022		December 31, 2021
	(in thousands)
Benefit obligation at beginning of period	$	4,990	$	4,890
Service cost	404		207
Interest cost	20		19
Plan participants’ contributions	2,396		135


Settlement	(844)		—
Benefits paid	(946)		(113)
Actuarial (gain)/loss	(627)		1
Foreign currency exchange rate changes	(48)		(149)
Benefit obligation at end of year	$	5,345	$	4,990


Change in plan assets	December 31, 2022		December 31, 2021
	(in thousands)
Fair value of plan assets at beginning of period	$	3,017	$	2,849
Expected return on plan assets	29		15

Actual return on plan assets	87		—
Scheme contributions	325		135
Plan participants’ contributions	2,396		135
Benefits paid	(946)		(113)

Settlement	(844)		—
Foreign currency exchange rate changes	(5)		(4)
Fair value of plan assets at end of year	$	4,059	$	3,017

Schedule of Components of Net Periodic Benefit Cost

The following amounts were recorded in the Consolidated Statement of Operations as components of the net periodic benefit cost:


	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Service cost	$	117	$	134	$	100
Interest cost	672		665		746
Expected return on plan assets	(1,258)		(1,171)		(1,214)
Amortization of net loss	228		625		160

Net periodic benefit cost	$	(241)	$	253	$	(208)

Summary of Assumptions Used in Calculating Pension Benefit Obligations

The following assumptions were used at the commencement of the year in determining the net periodic pension benefit cost for the years ended December 31, 2022, December 31, 2021 and December 31, 2020:


	December 31, 2022		December 31, 2021		December 31, 2020
Discount rate	1.8	%	1.5	%	2.1	%
Rate of compensation increase	3.7	%	3.4	%	3.3	%
Expected rate of return on plan assets	3.8	%	3.4	%	4.0	%

The following assumptions were used in determining the benefit obligation at December 31, 2022 and December 31, 2021:


	December 31, 2022		December 31, 2021
Discount rate	4.9	%	1.8	%
Rate of compensation increase	3.6	%	3.7	%

Schedule of Amounts Recognized in Other Comprehensive Income (Loss)


Other comprehensive income	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Actuarial (gain)/loss - benefit obligation	$	(18,636)	$	(2,097)	$	5,294
Actuarial loss/(gain) – plan assets	7,305		(1,176)		(878)
Actuarial loss recognized in net periodic benefit cost	(228)		(625)		(160)
Total	$	(11,559)	$	(3,898)	$	4,256

Schedule of Underlying Asset Split of Fund

The Company's pension plan asset allocation is as follows:


Asset Category	December 31, 2022		December 31, 2021
Government Bonds	88	%	—	%
Diversified Bonds	12	%	—	%
Equities	—	%	24	%
Corporate Bonds (including 50% high yield bonds)	—	%	37	%
Secured Loans and Multi Asset Credit	—	%	39	%


	100	%	100	%

Schedule of Plan Asset Fair Value Measurements


	December 31, 2022		December 31, 2021
	(in thousands)
Government Bonds	$	22,887	$	—
Diversified Bonds	$	3,163	$	—
Equities	$	—	$	8,782
Corporate Bonds (including 50% high yield bonds)	$	—	$	13,434
Secured Loans and Multi Asset Credit	$	—	$	13,982

	$	26,050	$	36,198

Schedule of Annual Benefit Payments which Reflect Expected Future Service

The following annual benefit payments, which reflect expected future service as appropriate, are expected to be paid.


	(in thousands)
2023	$	302
2024	371
2025	402
2026	703
2027	643
Years 2028 - 2032	3,614

Allowances for Credit Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Opening provision	$ 7,081	$ 7,149
Amounts used during the year	(3,913)	(116)
Amounts provided during the year	17,800	705
Amounts released during the year	0	(544)
Foreign exchange	(406)	(113)
Closing provision	$ 20,562	$ 7,081

Commitments and Contingencies - Narrative (Details)	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Non-cancelable operating leases for facilities expiration period	12 years

Accumulated Other Comprehensive Income (Tables)

12 Months Ended

Dec. 31, 2022

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Schedule of Accumulated Other Comprehensive Income


	Year ended
	December 31, 2022		December 31, 2021
	(in thousands)
Currency translation adjustments	$	(175,369)	$	(85,840)

Actuarial gain/(loss) on defined benefit pension plan (note 21)	7,559		(5,098)
Loss on cash flow hedge	(3,728)		—
Amortization of loss on cash flow hedge	—		1
Total	$	(171,538)	$	(90,937)

Derivatives - Narrative (Details) $ in Thousands	12 Months Ended
Derivatives - Narrative (Details) $ in Thousands	Dec. 31, 2022 USD ($)	Nov. 29, 2022 USD ($) instrument	Dec. 31, 2021 USD ($) tranche
Derivative [Line Items]
Interest rate cash flow hedge gain (loss) to be reclassified euring next 12 months, net	$ (3,300)
Other comprehensive income (loss), cash flow hedge, gain (loss), before reclassification and tax	100
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax	$ 100
Derivative, Fair Value, Net			$ 0
Derivative, number of instruments held \| tranche			0
Interest Rate Caps \| Total derivatives designated as hedging instruments
Derivative [Line Items]
Number of interest rate derivatives held \| instrument		2
Derivative, notional Amount		$ 2,101,000
Derivative, fixed interest rate		0.42%
Interest Rate Caps \| Total derivatives designated as hedging instruments \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Derivative [Line Items]
Derivative, variable interest rate, reference rate in excess of		4.75%
Interest Rate Swap
Derivative [Line Items]
Derivative, notional Amount		$ 1,101,000
Derivative, fixed interest rate		3.40%

Goodwill - Schedule of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Goodwill [Roll Forward]
Opening goodwill	$ 9,037,931	$ 936,257
Current year acquisitions (note 6)	0	8,120,006
Prior period acquisition (note 6)	(35,692)	0
Foreign exchange movement	(30,569)	(18,332)
Closing goodwill	$ 8,971,670	$ 9,037,931

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References + Details

Summary of Significant accounting policies - Adjustments Resulting from Foreign Currency Translation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Foreign Currency [Abstract]
Amounts (credited)/charged	$ (25,997)	$ (14,316)	$ 5,979

Net Income Per Ordinary Share (Tables)

12 Months Ended

Dec. 31, 2022

Earnings Per Share [Abstract]

Reconciliation of Number of Shares Used in Computation of Basic and Diluted Net Income Per Ordinary Share

The reconciliation of the number of shares used in the computation of basic and diluted net income per ordinary share is as follows:


	December 31, 2022	December 31, 2021	December 31, 2020
Weighted average number of ordinary shares outstanding for basic net income per ordinary share	81,532,320	67,110,186	52,859,911
Effect of dilutive share options outstanding	936,043	958,125	423,674
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share	82,468,363	68,068,311	53,283,585

Reconciliation of net income attributable to the group per the statement of operating income and net income used for net income per ordinary share

The reconciliation between net income attributable to the Group per the Consolidated Statement of Operations and the net income used to calculate net income per ordinary share attributable to the Group is as follows:


	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Net income attributable to the Group	$	505,304	153,185		$	332,331
Noncontrolling interest adjustment to redemption amount	—		—		(4,522)
Net income attributable to the Group (including NCI redemption adjustment)	505,304		153,185		327,809

	December 31, 2022		December 31, 2021		December 31, 2020
Net income per Ordinary Share attributable to the Group (including NCI redemption adjustment):
Basic	$	6.20	$	2.28	$	6.20
Diluted	$	6.13	$	2.25	$	6.15

Investments (Tables)

12 Months Ended

Dec. 31, 2022

Investments, Debt and Equity Securities [Abstract]

Equity Method Investments

The following table represents our equity method investments at December 31, 2022:


	Ownership Percentage		Carrying Value		Carrying Value

	December 31, 2022		December 31, 2022		December 31, 2021
			(in thousands)
Oncacare Limited	49	%	$	—	$	2,373

Related Parties	12 Months Ended
Related Parties	Dec. 31, 2022
Related Party Transactions [Abstract]
Related Parties	Related Parties Subsidiaries of the Company earned revenue of $2,000 (December 31, 2021: $30,000) from DS Biopharma Limited (formerly Dignity Sciences Limited) during the year. Dr. John Climax is Executive Chairman and a Director and shareholder of DS Biopharma Limited. $12,000 was recorded as due from DS Biopharma Limited at December 31, 2022 (December 31, 2021: $12,000). Subsidiaries of the Company earned revenue of $235,000 (December 31, 2021: $551,000) from Afimmune Limited during the year. Dr. John Climax is Chief Executive Officer and a Director and shareholder of Afimmune Limited. $263,000 was recorded as due from Afimmune Limited at December 31, 2022 (December 31, 2021: $197,000). Subsidiaries of the Company earned revenue of $428,000 from Corvus Pharmaceuticals during the year. Dr. Linda Grais serves as a Director and shareholder of Corvus Pharmaceuticals. $231,000 was recorded as due from Corvus Pharmaceuticals at December 31, 2022. On July 24, 2020, a subsidiary of the Company, ICON Clinical Research Limited, entered into an agreement to jointly establish a new company, Oncacare, with a third party. The Company has invested $4.9 million to obtain a 49% interest in the voting share capital of Oncacare. The Company provided corporate support services to Oncacare to the value of $451,000 during the year ended December 31, 2022 (December 31, 2021: $465,000). $715,000 was recorded as due from Oncacare at December 31, 2022 (December 31, 2021: $264,000). During the year ended December 31, 2021, the Company provided a loan of $10 million to Oncacare in order to fund the continued start up of the business' operations. The loan accrues annual interest at 1.6% and the loan is repayable on June 30, 2025. The Company has recorded losses of $3.1 million and $2.2 million representing its pro rata share of the losses in Oncacare during the year ended December 31, 2022 and December 31, 2021, respectively. The carrying value of the Company's investment in Oncacare was reduced by $2.3 million of pro rata losses. The remaining $0.8 million in pro rata losses served to reduce the carrying value of the Company's loan receivable from Oncacare. At December 31, 2022 accrued interest of $183,000 remained outstanding. The majority investor in Oncacare has the right to sell the 51% majority voting share capital exclusively to the Company in an eighteen month period, commencing January 1, 2023 and ICON also has the right to acquire the 51% majority voting share capital from August 1, 2025.

Business Combinations

12 Months Ended

Dec. 31, 2022

Business Combinations [Abstract]

Business Combinations

PRA Health Sciences, Inc. Acquisition

On July 1, 2021 (the "Merger Date"), the Company completed the Acquisition of PRA by means of a merger whereby Indigo Merger Sub, Inc., a Delaware corporation and subsidiary of ICON, merged with and into PRA Health Sciences, Inc., the parent of the PRA Health Sciences ("the Acquisition" and "the Merger"). The combined Group has retained the name ICON and brought together approximately 38,000 (as at the Merger date) employees across the globe, creating the world's largest clinical research organization with a singular focus on clinical research and commercialization. The Merger was accounted for as a business combination using the acquisition method of accounting in accordance with ASC Topic 805, Business Combinations.

The combined Company leverages its enhanced operations to transform clinical trials and accelerate biopharma customers’ commercial success through the development of much needed medicines and medical devices. The new ICON has a renewed focus on leveraging data, applying technology and accessing diverse patient populations to speed up drug development.

Upon completion of the Merger, pursuant to the terms of the Merger Agreement, PRA became a wholly owned subsidiary of the ICON Group. Under the terms of the Merger, PRA shareholders received per share $80 in cash and 0.4125 shares of ICON stock. The trading of PRA common stock on NASDAQ was suspended prior to market open on July 1, 2021.

In the years ended December 31, 2022 and 2021, the Company incurred Merger-related expenses of $39.7 million and $198.3 million, respectively, which were accounted for separately from the business combination and expensed as incurred within the “Transaction and integration related” line item of the Consolidated Statement of Operations. These costs consist primarily of investment banker fees, advisory fees, legal costs, accounting and consulting fees, share-based compensation expense, and employee retention bonuses. Included in transaction and integration costs in the years ended December 31, 2022 and 2021 are acquisition related costs (as defined by ASC 805) of $0.8 million and $57.1 million, respectively.

The Company also incurred approximately $86.7 million of Merger-related financing fees which are included in the “Interest expense” line item in the Consolidated Statement of Operations for the year ended December 31, 2021. During the year ended December 31, 2021, the Company deferred $76.2 million of financing costs incurred as a result of the Senior Secured Credit Facility and Senior Secured Notes. These costs will be amortized over the term of the related debt.

The Merger Date fair value of the consideration transferred consisted of the following:


			(in thousands)
Fair value of cash consideration			5,308,646
Fair value of ordinary shares issued to acquiree stockholders			5,658,126
Fair value of replacement share-based awards issued to acquiree employees			209,399
Repayment of term loan obligations and accrued interest *			865,800
			12,041,971

* This represents the portion of PRA debt paid by ICON. PRA also paid $401.6 million from available cash to settle debt obligations that existed at the Merger Date.


	July 1,
	2021
	(in thousands)
Cash and cash equivalents	$	259,971
Accounts receivable and unbilled revenue	934,308
Other current assets	125,156
Fixed assets	156,851
Operating lease right-of-use assets	180,601
Goodwill *	8,084,314
Intangible assets	4,919,000
Deferred tax assets	25,190
Other assets	33,928
Accounts payable	(50,259)
Accrued expenses and other current liabilities	(380,048)
Current portion of operating lease liabilities	(36,506)
Unearned revenue	(739,278)
Non-current portion of operating lease liabilities	(147,204)
Deferred tax liabilities	(1,119,762)
Other non-current liabilities	(204,291)

Net assets acquired	$	12,041,971

The following table summarizes the fair value of identified intangible assets and their respective useful lives as of the Merger Date (in thousands, except for estimated useful lives):


	Estimated Fair Value	Estimated Useful Life
Customer relationships	3,938,000	23 years
Order backlog	500,000	3 years
Trade names	202,000	3 years
Patient database	168,000	7 years
Technology assets	111,000	5 years
	4,919,000

At June 30, 2022, the Company completed its review of the July 1, 2021 acquisition balance sheet of PRA and completed the final valuation associated with certain assets acquired and liabilities assumed. In the period since the Merger Date, the Company recognized certain measurement period adjustments as shown in the table below:


	Measurement period adjustments

	(in thousands)
Cash and cash equivalents	$	—
Accounts receivable and unbilled revenue	—
Other current assets	14,465
Fixed assets	(6,137)
Operating lease right-of-use assets	(11,744)
Goodwill	70,436
Intangible assets *	44,000
Deferred tax assets	(147,039)
Other assets	(1,166)
Accounts payable	—
Accrued expenses and other current liabilities	(37,496)
Current portion of operating lease liabilities	1,865
Unearned revenue **	19,623
Non-current portion of operating lease liabilities	10,454
Non-current deferred tax liabilities	193,837
Other non-current liabilities	(151,098)

Description of business (Details)	12 Months Ended
Description of business (Details)	Dec. 31, 2022 Employee Location Country	Jul. 01, 2021 Employee
Product Information [Line Items]
Number of employees \| Employee	41,100	38,000
Number of locations in which company operates \| Location	111
Number of countries in which company operates \| Country	53
Geographic Concentration Risk \| United States \| Net Revenue
Product Information [Line Items]
Percentage of company revenue (in percent)	46.20%
Geographic Concentration Risk \| Europe \| Net Revenue
Product Information [Line Items]
Percentage of company revenue (in percent)	46.50%
Geographic Concentration Risk \| Rest of World \| Net Revenue
Product Information [Line Items]
Percentage of company revenue (in percent)	7.30%

Net Income Per Ordinary Share - Reconciliation of Number of Shares Used in Computation of Basic and Diluted Net Income Per Ordinary Share (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Earnings Per Share [Abstract]
Weighted average number of ordinary shares outstanding for basic net income per ordinary share (in shares)	81,532,320	67,110,186	52,859,911
Effect of dilutive share options outstanding (in shares)	936,043	958,125	423,674
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share (in shares)	82,468,363	68,068,311	53,283,585

Intangible Assets - Summary of Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	$ 5,109,212	$ 5,081,381
Accumulated amortization	(830,553)	(370,538)
Net book value	4,278,659	4,710,843
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	4,076,435	4,056,642
Order backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	536,934	528,022
Trade names & brands
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	204,621	204,685
Patient database
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	170,238	170,525
Technology assets
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	$ 120,984	$ 121,507

Operating Leases Operating Leases - Operating Lease Maturity (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Leases [Abstract]
2023	$ 47,479
2024	34,400
2025	25,045
2026	20,430
2027	17,249
Thereafter	45,065
Total future minimum lease payments	189,668
Lease imputed interest	(14,367)
Total	$ 175,301

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
Income Taxes - Narrative (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Valuation allowance for deferred tax assets	$ 43,379,000	$ 45,495,000	$ 32,800,000
Net change in the total valuation allowance	2,100,000	(12,800,000)
Deferred tax liabilities, undistributed foreign earnings	1,600,000	800,000
Unrecognized tax benefit, potentially expire in 2021	37,900,000
Total unrecognized tax benefits net of potential benefits	217,600,000	202,100,000	19,100,000
Interest and penalties recognized as an expense	7,100,000	1,900,000	$ 600,000
Total accrued interest and penalties	22,600,000	15,500,000
Acquired entity
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Net change in the total valuation allowance		(9,300,000)
Provision for income taxes
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Net change in the total valuation allowance	800,000	(4,400,000)
Other Comprehensive Income
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Net change in the total valuation allowance	1,300,000	$ (900,000)
Foreign Country
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Other non-U.S subsidiaries operating loss carryforwards for income tax	37,900,000
Foreign Country \| Tax Year 2022 to 2028
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Additional operating loss carryforward	14,800,000
Foreign Country \| Tax Year 2029 to 2038
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Additional operating loss carryforward	18,200,000
Ireland \| Foreign Country
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Ireland subsidiaries additional tax credit carryforward for income tax	16,600,000
United States
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
U.S. Federal net operating loss carry forwards currently available for offset	3,500,000
Alternative minimum tax credit carry forwards	800,000
United States \| Federal NOL's
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Net operating loss carryforwards	5,363,000
U.S. federal net operating loss carry forwards	5,300,000
Tax credit carry forward	93,000,000
Other non-U.S subsidiaries operating loss carryforwards for income tax	95,000
United States \| State NOL's
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Net operating loss carryforwards	401,898,000
Other non-U.S subsidiaries operating loss carryforwards for income tax	6,736,000
Other \| Foreign Country
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Ireland subsidiaries additional tax credit carryforward for income tax	$ 4,700,000

Business Combinations - Fair Value of Consideration Transferred, PRA Acquisition (Details) - USD ($) $ in Thousands		12 Months Ended
	Jul. 01, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Fair value of cash consideration		$ 0	$ 5,914,475	$ 47,931
PRA Health Sciences, Inc
Business Acquisition [Line Items]
Fair value of cash consideration	$ 5,308,646
Fair value of ordinary shares issued to acquiree stockholders	5,658,126
Fair value of replacement share-based awards issued to acquiree employees	209,399
Repayment of term loan obligations and accrued interest	865,800
Consideration transferred	12,041,971
Payments to settle debt obligations that existed prior to acquisition date	$ 401,600

Income Taxes - Consolidated Reported Provision for Income Taxes Differed from Statutory Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Taxes at Irish statutory rate of 12.5% (2021:12.5%; 2020:12.5%)	$ 70,980	$ 24,586	$ 47,651
Rate differential from amortization of intangible assets	(59,330)	(31,228)	(2,298)
Foreign and other income taxed at higher rates	52,464	51,273	10,241
Research & development tax incentives	(2,608)	(3,120)	(1,243)
Movement in valuation allowance	(777)	3,101	3,581
Effects of change in tax rates	(300)	(128)	108
Change in unrecognized tax benefits	8,392	5,246	(1,672)
Impact of stock compensation	(8,756)	(9,083)	(5,150)
Other	(654)	687	(3,343)
Income tax expense allocated to continuing operations	$ 59,411	$ 41,334	$ 47,875

Business Segment and Geographical Information - Distribution of Net Revenue by Geographical Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenue	$ 7,741,386	$ 5,480,826	$ 2,797,288
Ireland
Segment Reporting Information [Line Items]
Revenue	1,984,567	1,365,909	1,181,292
Rest of Europe
Segment Reporting Information [Line Items]
Revenue	1,618,350	1,175,515	416,884
U.S.
Segment Reporting Information [Line Items]
Revenue	3,574,610	2,581,007	925,563
Other
Segment Reporting Information [Line Items]
Revenue	$ 563,859	$ 358,395	$ 273,549

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8906-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9031-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9038-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130543-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9054-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130545-203045

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI https://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

Non-current Bank Credit Lines and Loan Facilities - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Jul. 01, 2021
Debt Instrument [Line Items]
Total debt	$ 4,701,213	$ 5,501,213
Less current portion of long-term debt and debt issuance costs	(55,150)	(55,150)
Total long-term debt	4,646,063	5,446,063
Less long-term portion of debt issuance costs and debt discount	(47,026)	(64,901)
Total long-term debt, net	$ 4,599,037	$ 5,381,162
Credit Facilities: \| Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	7.092%	2.75%	1.00%
Total debt	$ 4,201,213	$ 5,001,213
Senior Secured Notes \| Senior Secured Notes
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	2.875%	2.875%	2.875%
Total debt	$ 500,000	$ 500,000

Employee Benefits

12 Months Ended

Dec. 31, 2022

Retirement Benefits [Abstract]

Employee Benefits

Defined Contribution Plans

Defined contribution or profit sharing style plans ("the Plans") are offered in a number of countries. In some cases, these plans are required by local laws or regulations. Certain employees are eligible to participate in the Plans and participants in the Plans may elect to defer a portion of their pre-tax earnings into a pension plan, which is run by an independent party. The Company matches participant's contributions up to certain levels of the participant's annual compensation.

The Company's United States operations maintain retirement plans (the "U.S. Plans") that qualify as a deferred salary arrangement under Section 401(k) of the Internal Revenue Code. Participants in the U.S. Plans may elect to defer a portion of their earnings, up to the Internal Revenue Service annual contribution limit. The Company matches participant's contributions at varying amounts, subject to a maximum of 4.5% of the participant's annual compensation. Contributions to this U.S. Plan are recorded, in the year contributed, as an expense in the Consolidated Statement of Operations. Contributions for the years ended December 31, 2022, December 31, 2021 and December 31, 2020 were $30.2 million, $23.7 million and $17.0 million respectively.

Pension and Postretirement Benefit Plans

The Company maintains various retirement plans across the Group, many of which are required by local employment laws. The balances recorded to the balance sheet are as follows:


	December 31, 2022		December 31, 2021
Other receivables	$	6,492	$	—
Non-current other liabilities (note 16)	(13,033)		(16,262)

In addition to the specific defined-benefit schemes shown separately below, the Company maintains several other retirement plans which have a cumulative total net obligation of $11.6 million and $8.0 million recorded to non-current liabilities as of December 31, 2022 and December 31, 2021, respectively.

ICON Development Solutions Limited pension plan

One of the Company's subsidiaries, ICON Development Solutions Limited, operates a defined benefit pension plan in the United Kingdom for its employees. The plan is managed externally and the related pension costs and liabilities are assessed in accordance with the advice of a professionally qualified actuary. Plan assets at December 31, 2022, December 31, 2021 and December 31, 2020, consist of units held in independently administered funds. The pension costs of this plan are presented in the following tables in accordance with the requirements of ASC 715-60 'Defined Benefit Plans – Other Postretirement'. The plan has been closed to new entrants with effect from July 1, 2003.


Funded status	December 31, 2022		December 31, 2021
	(in thousands)
Projected benefit obligation	$	(19,558)	$	(41,813)
Fair value of plan assets	26,050		36,198
Funded status	$	6,492	$	(5,615)


Change in benefit obligation	December 31, 2022		December 31, 2021
	(in thousands)
Benefit obligation at beginning of year	$	41,813	$	43,988
Service cost	117		134
Interest cost	672		665
Plan participants' contributions	19		23

Benefits paid	(514)		(489)
Actuarial gain	(18,636)		(2,097)
Foreign currency exchange rate changes	(3,913)		(411)
Benefit obligation at end of year	$	19,558	$	41,813


Change in plan assets	December 31, 2022		December 31, 2021
	(in thousands)
Fair value of plan assets at beginning of year	$	36,198	$	34,612
Expected return on plan assets	1,258		1,171
Actual return on plan assets	(7,305)		1,176
Employer contributions	70		91
Plan participants' contributions	19		23
Benefits paid	(514)		(489)
Foreign currency exchange rate changes	(3,676)		(386)
Fair value of plan assets at end of year	$	26,050	$	36,198

The fair values of the assets above do not include any of the Company's own financial instruments, property occupied by, or other assets used by, the Company.

The following amounts were recorded in the Consolidated Statement of Operations as components of the net periodic benefit cost:


	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Service cost	$	117	$	134	$	100
Interest cost	672		665		746
Expected return on plan assets	(1,258)		(1,171)		(1,214)
Amortization of net loss	228		625		160

Net periodic benefit cost	$	(241)	$	253	$	(208)


	December 31, 2022		December 31, 2021		December 31, 2020
Discount rate	1.8	%	1.5	%	2.1	%
Rate of compensation increase	3.7	%	3.4	%	3.3	%
Expected rate of return on plan assets	3.8	%	3.4	%	4.0	%


Other comprehensive income	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Actuarial (gain)/loss - benefit obligation	$	(18,636)	$	(2,097)	$	5,294
Actuarial loss/(gain) – plan assets	7,305		(1,176)		(878)
Actuarial loss recognized in net periodic benefit cost	(228)		(625)		(160)
Total	$	(11,559)	$	(3,898)	$	4,256

The estimated net loss and prior service cost for the defined benefit pension plan that will be amortized from accumulated other comprehensive income into net periodic benefit cost over the next year are $0.3 million and $Nil respectively.

Benefit Obligation

The following assumptions were used in determining the benefit obligation at December 31, 2022 and December 31, 2021:


	December 31, 2022		December 31, 2021
Discount rate	4.9	%	1.8	%
Rate of compensation increase	3.6	%	3.7	%

A single discount rate is used which, when used to discount the projected benefit cash flows underlying a pension scheme with a 19 year duration, gives the same result as a full AA corporate bond yield curve.

Actuarial gains on the benefit obligation during 2022 resulted from changes in the assumptions compared to those adopted at December 2021. Changes in the assumptions reflect the changes in market conditions from December 2021 to December 2022 and the actuarial gain is primarily due to the change in the discount rate.

Plan Assets

The Company's pension plan asset allocation is as follows:


Asset Category	December 31, 2022		December 31, 2021
Government Bonds	88	%	—	%
Diversified Bonds	12	%	—	%
Equities	—	%	24	%
Corporate Bonds (including 50% high yield bonds)	—	%	37	%
Secured Loans and Multi Asset Credit	—	%	39	%


	100	%	100	%

During 2022, the scheme's asset strategy changed to align the plan assets more closely with government and diversified bonds. There is no self-investment in employer related assets. The Company’s assumption for the expected return on plan assets was determined by the weighted average of the long-term expected rate of return on each of the asset classes invested as of the balance sheet date. The expected long-term rate of return on assets is 3.8% at December 31, 2022 and December 31, 2021, respectively.

Plan Asset Fair Value Measurements


	December 31, 2022		December 31, 2021
	(in thousands)
Government Bonds	$	22,887	$	—
Diversified Bonds	$	3,163	$	—
Equities	$	—	$	8,782
Corporate Bonds (including 50% high yield bonds)	$	—	$	13,434
Secured Loans and Multi Asset Credit	$	—	$	13,982

	$	26,050	$	36,198

The value of assets held by the plan are represented by quoted prices in active markets for identical assets and are therefore classified as level 1 investments.

Cash Flows

The Company expects to contribute $0.1 million to the pension fund in the year ending December 31, 2023.

The following annual benefit payments, which reflect expected future service as appropriate, are expected to be paid.


	(in thousands)
2023	$	302
2024	371
2025	402
2026	703
2027	643
Years 2028 - 2032	3,614

The expected cash flows are estimated figures based on the members expected to retire over the next 10 years assuming no early retirements, withdrawals or commutation of pension for cash. At the present time it is not clear whether annuities will be purchased when members reach retirement or whether pensions will be paid each month out of scheme assets. The cash flows above have been estimated on the assumption that pensions will be paid monthly out of scheme assets. If annuities are purchased, then the expected benefit payments will be significantly different from those shown above.

Aptiv Solutions pension plan

On May 7, 2014 the Company acquired 100% of the common stock of Aptiv Solutions ("Aptiv"). The Company has a defined benefit plan covering its employees in Switzerland as mandated by the Swiss government. Benefits are based on the employee's years of service and compensation. Benefits are paid directly by the Company when they become due, in conformity with the funding requirements of applicable government regulations. The plan is managed externally and the related pension costs and liabilities are assessed in accordance with the advice of a professionally qualified actuary. Plan assets at December 31, 2022 and December 31, 2021 consist of units held in independently administered funds. The pension costs of this plan are presented in the following tables in accordance with the requirements of ASC 715-60 'Defined Benefit Plans – Other Postretirement'.


Funded surplus/(deficit)	December 31, 2022		December 31, 2021
	(in thousands)
Projected benefit obligation	$	(5,806)	$	(7,643)
Fair value of plan assets	5,681		6,964
Funded deficit	$	(125)	$	(679)

The funded deficit at December 31, 2022 and December 31, 2021 are included in non-current other liabilities on the Consolidated Balance Sheet.


Change in benefit obligation	December 31, 2022		December 31, 2021
	(in thousands)
Benefit obligation at beginning of year	$	7,643	$	8,620
Service cost	146		150
Interest cost	30		12
Plan participants' contributions	82		95
Settlement	(218)		(483)
Prior service cost	(23)		(82)
Benefits paid and transferred balances	(182)		76
Actuarial gain	(1,527)		(484)
Foreign currency exchange rate changes	(145)		(261)
Benefit obligation at end of year	$	5,806	$	7,643


Change in plan assets	December 31,		December 31,
	2022		2021
	(in thousands)
Fair value of plan assets at beginning of year	$	6,964	$	7,601
Expected return on plan assets	29		15
Actual return on plan assets	(987)		(238)
Scheme contributions	114		128
Plan participants' contributions	82		95
Benefits paid and transferred balances	(182)		76
Settlement	(218)		(483)
Foreign currency exchange rate changes	(121)		(230)
Fair value of plan assets at end of year	$	5,681	$	6,964

The fair values of the assets above do not include any of the Company's own financial instruments, property occupied by, or other assets used by, the Company.

PRA Switzerland AG pension plan

On July 1, 2021, the Company completed the Acquisition of PRA. PRA Switzerland AG, a subsidiary of the Company has a defined benefit plan covering its employees in Switzerland as mandated by the Swiss government. Benefits are based on the employee's years of service and compensation. Benefits are paid directly by the Company when they become due, in conformity with the funding requirements of applicable government regulations. The plan is managed externally and the related pension costs and liabilities are assessed in accordance with the advice of a professionally qualified actuary. Plan assets at December 31, 2022 consist of units held in independently administered funds. The pension costs of this plan are presented in the following tables in accordance with the requirements of ASC 715-60 'Defined Benefit Plans – Other Postretirement'.


Funded surplus/(deficit)	December 31, 2022		December 31, 2021
	(in thousands)
Projected benefit obligation	$	(5,345)	$	(4,990)
Fair value of plan assets	4,059		3,017
Funded deficit	$	(1,286)	$	(1,973)

The funded deficit at December 31, 2022 and December 31, 2021 are included in non-current other liabilities on the Consolidated Balance Sheet.


Change in benefit obligation	December 31, 2022		December 31, 2021
	(in thousands)
Benefit obligation at beginning of period	$	4,990	$	4,890
Service cost	404		207
Interest cost	20		19
Plan participants’ contributions	2,396		135


Settlement	(844)		—
Benefits paid	(946)		(113)
Actuarial (gain)/loss	(627)		1
Foreign currency exchange rate changes	(48)		(149)
Benefit obligation at end of year	$	5,345	$	4,990


Change in plan assets	December 31, 2022		December 31, 2021
	(in thousands)
Fair value of plan assets at beginning of period	$	3,017	$	2,849
Expected return on plan assets	29		15

Actual return on plan assets	87		—
Scheme contributions	325		135
Plan participants’ contributions	2,396		135
Benefits paid	(946)		(113)

Settlement	(844)		—
Foreign currency exchange rate changes	(5)		(4)
Fair value of plan assets at end of year	$	4,059	$	3,017

The fair values of the assets above do not include any of the Company's own financial instruments, property occupied by, or other assets used by, the Company.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI https://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section S99
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=21916913&loc=d3e273930-122802

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (o)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (p)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-URI https://asc.fasb.org/topic&trid=2235017

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 60
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=6414203&loc=d3e39689-114964

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(03)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (q)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (r)(1)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iii)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (l)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (r)(2)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

+ Details

Contract Balances (Tables)

12 Months Ended

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

Schedule of Contracts with Customers, Asset and Liabilities

Accounts receivable and unbilled revenue are as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Billed services (accounts receivable)	$	1,751,950	$	1,349,851
Allowance for credit losses (note 5)	(20,562)		(7,081)
Accounts receivable (net)	1,731,388		1,342,770
Unbilled services (unbilled revenue)	$	957,655	$	623,121
Accounts receivable and unbilled revenue, net	$	2,689,043	$	1,965,891

Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows:


(in thousands, except percentages)	December 31, 2022		December 31, 2021		$ Change		% Change

Unbilled services (unbilled revenue)	$	957,655	$	623,121	$	334,534	53.7	%
Unearned revenue (payments on account)	(1,507,449)		(1,323,961)		(183,488)		13.9	%
Net balance	$	(549,794)	$	(700,840)	$	151,046	21.6	%

Restructuring charges (Tables)

12 Months Ended

Dec. 31, 2022

Restructuring and Related Activities [Abstract]

Schedule of Restructuring Charges


	Year Ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Restructuring charges	$	31,143	$	31,105	$	18,089
Net charge	$	31,143	$	31,105	$	18,089

Schedule of Restructuring Reserve by Type of Cost


	Year Ended
	December 31, 2022		December 31, 2021
	(in thousands)

Opening provision	$	10,311	$	4,675
Additional provision in the year	4,364		11,273
Utilization	(8,653)		(5,637)
Ending provision	$	6,022	$	10,311

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 505,304	$ 153,185	$ 332,964
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	569,513	314,987	66,126
Impairment of long lived assets	28,767	20,037	5,411
Reduction in carrying value of operating right-of-use assets	45,215	45,339	28,480
Loss on equity method investments	3,136	2,161	366
Amortization of financing costs and debt discount	17,749	12,890	523
Stock compensation expense	70,523	133,844	26,271
Loss on extinguishment of debt	0	14,434	0
Loss on issuance of debt	0	59,460	0
Deferred tax (benefit)/expense	(124,985)	(60,616)	927
Unrealized foreign exchange (gain)/loss	(13,009)	(6,054)	5,979
Other non-cash items	11,324	4,480	(7,859)
Changes in operating assets and liabilities:
Accounts receivable	(420,695)	113,513	(175,040)
Unbilled revenue	(332,592)	(17,656)	(5,748)
Unearned revenue	192,944	(69,121)	291,844
Other net assets	10,121	108,259	(2,209)
Net cash provided by operating activities	563,315	829,142	568,035
Cash flows from investing activities:
Purchase of property, plant and equipment	(142,160)	(93,750)	(40,885)
Purchase of subsidiary undertakings (net of cash acquired)	0	(5,914,475)	(47,931)
Investment in equity method investments	0	(2,450)	(2,450)
Loan to equity method investment	0	(10,000)	0
Sale of available for sale investments	481	497	47,902
Purchase of available for sale investments	(482)	(480)	0
Proceeds from investments in equity - long term	1,906	500	87
Purchase of investments in equity - long term	(5,612)	(4,077)	(3,299)
Net cash used in investing activities	(145,867)	(6,024,235)	(46,576)
Cash flows from financing activities:
Financing costs	0	(30,328)	(1,554)
Drawdown of credit lines and facilities	75,000	5,905,100	350,000
Repayment of credit lines and facilities	(875,000)	(877,780)	(350,000)
Purchase of noncontrolling interest	0	0	(43,923)
Proceeds from the exercise of equity compensation	35,844	118,589	13,203
Share issue costs	(17)	(853)	(14)
Repurchase of ordinary shares	(99,983)	0	(175,000)
Share repurchase costs	(17)	0	(140)
Settlement of cash flow hedge	0	0	(905)
Net cash (used in)/provided by financing activities	(864,173)	5,114,728	(208,333)
Effect of exchange rate movements on cash	(16,720)	(7,727)	6,870
Net (decrease)/increase in cash and cash equivalents	(463,445)	(88,092)	319,996
Cash and cash equivalents at beginning of year	752,213	840,305	520,309
Cash and cash equivalents at end of year	$ 288,768	$ 752,213	$ 840,305

Non-current Bank Credit Lines and Loan Facilities - Schedule of Finance Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Interest expense on drawn facilities	$ 209,189	$ 93,809	$ 13,406
Amortization of financing costs and debt discount	17,749	12,890	523
Transaction and one time financing costs	0	75,391	0
Other financing costs/(credits)	2,793	333	(910)
Total financing costs	$ 229,731	$ 182,423	$ 13,019

Non-current other liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Defined benefit pension obligations, net (note 21)	$ 13,033	$ 16,262
Other non-current liabilities	25,227	26,334
Other Liabilities, Noncurrent	$ 38,260	$ 42,596

Business Combinations - Narrative, PRA Acquisition (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Jul. 01, 2021 Employee $ / shares shares	Dec. 31, 2022 USD ($) Employee	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Business Acquisition [Line Items]
Number of employees \| Employee	38,000	41,100
Transaction and one time financing costs		$ 0	$ 75,391	$ 0
PRA Health Sciences, Inc
Business Acquisition [Line Items]
Business acquisition, share price (in USD per share) \| $ / shares	$ 80
Business acquisition, number of shares issued (in shares) \| shares	0.4125
Transaction and integration related (Note 6)		39,700	198,300
Acquisition related costs		800	57,100
Transaction and one time financing costs			$ 86,700
Gross debt issuance costs		$ 76,200

Income Taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current tax expense:
Current tax expense	$ 184,396	$ 101,950	$ 46,948
Deferred tax (benefit)/expense:
Deferred tax (benefit)/expense	(124,985)	(60,616)	927
Income tax expense allocated to continuing operations	59,411	41,334	47,875
Income tax expense was allocated to the following components of other comprehensive income:
Currency impact on long term funding	7,211	1,776	68
Total	66,622	43,110	47,943
Ireland
Current tax expense:
Current tax expense	53,248	18,469	28,963
Deferred tax (benefit)/expense:
Deferred tax (benefit)/expense	(6,166)	553	1,654
United States
Current tax expense:
Current tax expense	60,753	35,478	3,022
Deferred tax (benefit)/expense:
Deferred tax (benefit)/expense	(118,475)	(52,717)	4,577
Other
Current tax expense:
Current tax expense	70,395	48,003	14,963
Deferred tax (benefit)/expense:
Deferred tax (benefit)/expense	$ (344)	$ (8,452)	$ (5,304)

Employee Benefits - Expected Rate of Return and Actual Plan Asset Allocation (Details) - ICON Development Solutions Limited pension plan	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocations	100.00%	100.00%
Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocations	88.00%	0.00%
Diversified Bonds
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocations	12.00%	0.00%
Corporate Bonds (including 50% high yield bonds)
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocations	0.00%	37.00%
Equities
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocations	0.00%	24.00%
Secured Loans and Multi Asset Credit
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocations	0.00%	39.00%

Restructuring charges - Restructuring Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Restructuring Reserve [Roll Forward]
Opening provision	$ 10,311	$ 4,675
Additional provision in the year	4,364	11,273
Utilization	(8,653)	(5,637)
Ending provision	$ 6,022	$ 10,311

Income Taxes

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Income Taxes

The Company's United States and Irish based subsidiaries file income tax returns in the United States and Ireland respectively. Other foreign subsidiaries are taxed separately under the laws of their respective countries.

The components of income before income tax expense are as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Ireland	$	432,963	$	231,893	$	280,310
United States	(270,440)		(278,413)		41,950
Other	405,328		243,200		58,945
Income before income tax expense	$	567,851	$	196,680	$	381,205

The components of income tax expense are as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Income tax expense:
Current tax expense:
Ireland	$	53,248	$	18,469	$	28,963
United States	60,753		35,478		3,022
Other	70,395		48,003		14,963
Total current tax expense	184,396		101,950		46,948

Deferred tax (benefit)/expense:
Ireland	(6,166)		553		1,654
United States	(118,475)		(52,717)		4,577
Other	(344)		(8,452)		(5,304)
Total deferred tax (benefit)/expense	(124,985)		(60,616)		927

Income tax expense allocated to continuing operations	59,411		41,334		47,875

Income tax expense was allocated to the following components of other comprehensive income:

Currency impact on long term funding	7,211		1,776		68


Total	$	66,622	$	43,110	$	47,943

Ireland's statutory income tax rate is 12.5%. The Company's consolidated reported income tax expense differed from the amount that would result from applying the Irish statutory rate as set forth below:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Taxes at Irish statutory rate of 12.5% (2021:12.5%; 2020:12.5%)	$	70,980	$	24,586	$	47,651
Rate differential from amortization of intangible assets	(59,330)		(31,228)		(2,298)
Foreign and other income taxed at higher rates	52,464		51,273		10,241
Research & development tax incentives	(2,608)		(3,120)		(1,243)
Movement in valuation allowance	(777)		3,101		3,581
Effects of change in tax rates	(300)		(128)		108
Change in unrecognized tax benefits	8,392		5,246		(1,672)
Impact of stock compensation	(8,756)		(9,083)		(5,150)

Other	(654)		687		(3,343)
Income tax expense	$	59,411	$	41,334	$	47,875

The tax effects of temporary differences that give rise to significant portions of deferred tax assets and deferred tax liabilities are presented below:


	December 31, 2022		December 31, 2021
	(in thousands)
Deferred tax liabilities:
Property, plant and equipment	$	10,927	$	19,606
Operating right-of-use-assets	23,260		33,449
Goodwill	37,150		33,354
Intangible assets	1,078,302		1,201,086
Other	9,054		1,761
Total deferred tax liabilities recognized	1,158,693		1,289,256

Deferred tax assets:
Operating loss and tax credits carryforwards	88,697		86,893
Property, plant and equipment	6,010		5,846
Operating lease liabilities	27,593		36,106
Intangible assets	3,602		4,596
Accrued expenses and unbilled revenue	64,016		69,198
Stock compensation	21,862		25,557
Deferred compensation	2,917		3,445
Unearned revenue	66,565		64,924
Other	9,155		602
Total deferred tax assets	290,417		297,167
Valuation allowance for deferred tax assets	(43,379)		(45,495)
Deferred tax assets recognized	247,038		251,672
Overall net deferred tax asset/(liability)	$	(911,655)	$	(1,037,584)

At December 31, 2022 Ireland subsidiaries had tax credit carryforwards for income tax purposes that may be carried forward indefinitely, available for offset against future tax liabilities, if any, of $16.6 million.

At December 31, 2022 U.S. subsidiaries had U.S. federal and state net operating loss ("NOL") carryforwards of approximately $5.4 million and $401.9 million, respectively. These NOLs are available for offset against future taxable income and the expiry dates are shown in the table below. Of the $5.4 million U.S. federal NOLs, approximately $3.5 million is available for offset against future U.S. federal taxable income in 2023. The subsidiaries' ability to use the remaining U.S. federal and state NOL carryforwards is limited on an annual basis due to change of ownership in 2014, 2017, and 2019, as defined by Section 382 of the Internal Revenue Code of 1986, as amended. Of the U.S. federal NOLs, $5.3 million are limited by Section 382 for the years 2023 - 2036. As of December 31, 2022, U.S subsidiaries also had disallowed interest carryforwards of $93.0 million that can be carried forward indefinitely. These carryforwards are available for offset against future taxable income in the event that the U.S subsidiaries have excess capacity for interest deductions in future years.

The expected expiry dates of the US NOLs are as follows:


	Federal NOL's		State NOL's
	(in thousands)
2023-2036	$	5,268	$	249,530
2033-2041	—		145,632
Indefinite	95		6,736

	$	5,363	$	401,898

In addition, we also have general business tax credit carryforwards of approximately $0.8 million that are available to reduce future U.S. federal and state income taxes. The general business tax credits are non-refundable and are due to expire between the years 2026-2038.

At December 31, 2022 other than those in the U.S. and Ireland, we had operating loss carryforwards for income tax purposes that may be carried forward indefinitely, available to offset against future taxable income, if any, of approximately $37.9 million. At December 31, 2022 those subsidiaries also had additional operating loss carryforwards of $14.8 million which are due to expire between 2023 and 2029 and operating loss carryforwards of $18.2 million which are due to expire between 2030 and 2039. In addition, at December 31, 2022 those subsidiaries had tax credit carryforwards for income tax purposes that may be carried forward indefinitely, available to offset against future tax liabilities, if any, of $4.7 million.

The valuation allowance at December 31, 2022 was approximately $43.4 million. The valuation allowance for deferred tax assets as of December 31, 2021 and December 31, 2020 was $45.5 million and $32.8 million respectively. The net change in the total valuation allowance was a decrease of $2.1 million during 2022 and an increase of $12.8 million during 2021. Of the total decrease of $2.1 million in 2022, $0.8 million was recognized within income tax expense and a decrease of $1.3 million was recognized in Other Comprehensive Income. Of the total increase of $12.8 million in 2021, $9.3 million was in respect of an acquired entity, $4.4 million was recognized within income tax expenses, and $0.9 million was recognized in Other Comprehensive Income.

The valuation allowances at December 31, 2022 and December 31, 2021 were primarily related to operating losses and tax credits carried forward that, in the judgment of management, are not more likely than not to be realized. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities, loss utilization, projected future taxable income and mitigation strategies in making this assessment. In respect of deferred tax assets not subject to a valuation allowance, management considers that it is more likely than not that these deferred tax assets will be realized on the basis that there will be sufficient reversals of deferred tax liabilities and taxable income in future periods.

The Company has recognized a deferred tax liability of $1.6 million (2021: $0.8 million) for investments in foreign subsidiaries where the Company does not consider the earnings to be indefinitely reinvested. For the deferred tax liability not recognized in respect of temporary differences related to investments in foreign subsidiaries which are considered to be indefinitely reinvested, it is not practicable to calculate the exact unrecognized deferred tax liability, however it is not expected to be material as Ireland allows a tax credit in respect of distributions from foreign subsidiaries at the statutory tax rate in the jurisdiction of the subsidiary so that no material tax liability would be expected to arise in Ireland in the event these earnings were ever remitted. In addition, withholding taxes applicable to remittances from foreign subsidiaries would not be expected to be material given Ireland’s tax treaty network and the EU parent subsidiary directive.

A reconciliation of the beginning and ending amount of total unrecognized tax benefits is as follows:


	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Unrecognized tax benefits at start of year	$	202,065	$	19,078	$	20,156
Increase related to acquired tax positions			170,047		—
Increase related to prior year tax positions	16,098		204		401
Decrease related to prior year tax positions	(5,442)		(1,695)		(1,271)
Increase related to current year tax positions	5,701		18,613		2,931
Settlements	—		(844)		(369)
Lapse of statute of limitations	(838)		(3,338)		(2,770)
Unrecognized tax benefits at end of year	$	217,584	$	202,065	$	19,078

The relevant statute of limitations for unrecognized tax benefits totaling $37.9 million could potentially expire during 2023.

Included in the balance of total unrecognized tax benefits at December 31, 2022 were potential benefits of $217.6 million, which if recognized, would affect the effective rate on income tax from continuing operations. The balance of total unrecognized tax benefits at December 31, 2021 and December 31, 2020 included potential benefits which, if recognized, would affect the effective rate of income tax from continuing operations of $202.1 million and $19.1 million respectively.

Interest and penalties recognized during the year ended December 31, 2022 amounted to a net charge of $7.1 million (2021: $1.9 million, 2020: ($0.6 million)) and are included within the income tax expense. Total accrued interest and penalties as of December 31, 2022 and December 31, 2021 were $22.6 million and $15.5 million respectively and are included in closing income taxes payable at those dates.

Our major tax jurisdictions are Ireland and the United States. We may potentially be subjected to tax audits in both our major jurisdictions. In Ireland, tax periods open to audit include the years ended December 31, 2018, December 31, 2019, December 31, 2020, December 31, 2021 and December 31, 2022. In the United States, tax periods open to audit include the years ended December 31, 2016, December 31, 2017, December 31, 2018, December 31, 2019, December 31, 2020, December 31, 2021 and December 31, 2022. During such audits, local tax authorities may challenge the positions taken by us in our tax returns.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI https://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Investments - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Investments - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jul. 24, 2020
Related Party Transaction [Line Items]
Available for sale investments	$ 1,713	$ 1,712
Short term investments average maturity period	2 years 9 months 18 days	2 years 8 months 12 days
Debt securities, available for sale, cumulative amount advanced under subscription agreements	$ 20,600	$ 16,900
Increase (decrease) in equity securities, FV-NI	6,300	3,200
Carrying value of long-term investments in equity	32,600	22,600
Commitment to acquire future long-term investments	23,300
Equity method investments	$ 0	2,373		$ 4,900
Majority investor, ownership percentage	51.00%
Period majority voting share capital can be sold to the company	18 months
Loss on equity method investments	$ 3,136	2,161	$ 366
Oncacare
Related Party Transaction [Line Items]
Ownership Percentage	49.00%
Loss on equity method investments	$ 3,100	2,200
Increase (decrease) in equity method investments	(2,300)
Oncacare
Related Party Transaction [Line Items]
Loan granted tp related party		$ 10,000
Related party, loan interest rate		1.60%
Equity method investment, decrease in loan receivable	800
Loans and Leases Receivable, Related Parties	$ 9,200

Non-current Bank Credit Lines and Loan Facilities (Tables)

12 Months Ended

Dec. 31, 2022

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

The Company had the following debt outstanding as of December 31, 2022 and 2021:


					Principal amount
	Interest rate as of		Interest rate as of		December 31,		December 31,
(in thousands)	December 31, 2022		December 31, 2021		2022		2021		Maturity Date
Credit Facilities:
Senior Secured Term Loan	7.092	%	2.750	%	$	4,201,213	$	5,001,213	July 2028

Senior Secured Notes	2.875	%	2.875	%	500,000		500,000		July 2026



Total debt					4,701,213		5,501,213

Less current portion of long-term debt and debt issuance costs					(55,150)		(55,150)
Total long-term debt					4,646,063		5,446,063
Less long-term portion of debt issuance costs and debt discount					(47,026)		(64,901)
Total long-term debt, net					$	4,599,037	$	5,381,162

Schedule of Financing Cost


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)

Interest expense on drawn facilities	$	209,189	$	93,809	$	13,406
Amortization of financing costs	17,749		12,890		523
Transaction and one time financing costs	—		75,391		—
Other financing costs/(credits)	2,793		333		(910)
Total financing costs	$	229,731	$	182,423	$	13,019

Schedule of Maturities of Long-term Debt

As of December 31, 2022, the contractual maturities of the Company's debt obligations were as follows:


Current maturities of long-term debt:	(in thousands)
2023	55,150
2024	55,150
2025	55,150
2026	55,150
2027 and thereafter	4,480,613
Total	$	4,701,213

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(a))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e24072-122690

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI https://asc.fasb.org/extlink&oid=124435984&loc=d3e28541-108399

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21506-112644

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69B
-URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69E
-URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495743-112612

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21521-112644

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21538-112644

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=123599511&loc=d3e64711-112823

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21475-112644

+ Details

Net Income Per Ordinary Share

12 Months Ended

Dec. 31, 2022

Earnings Per Share [Abstract]

Net Income Per Ordinary Share

Basic net income per ordinary share attributable to the Group has been computed by dividing net income available to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period.

Diluted net income per ordinary share is computed by adjusting the weighted average number of ordinary shares outstanding during the period for all potentially dilutive ordinary shares outstanding during the period and adjusting net income for any changes in income or loss that would result from the conversion of such potential ordinary shares.

There is no difference in net income used for basic and diluted net income per ordinary share.

Basic and diluted net income per ordinary share attributable to the Group for the year ended December 31, 2020 includes an adjustment to reflect the accretion of the noncontrolling interest in MeDiNova to its redemption value. The noncontrolling interest was acquired in the year ended December 31, 2020 and therefore no adjustment has been required in the years ended December 31, 2022 and December 31, 2021.

The reconciliation of the number of shares used in the computation of basic and diluted net income per ordinary share is as follows:


	December 31, 2022	December 31, 2021	December 31, 2020
Weighted average number of ordinary shares outstanding for basic net income per ordinary share	81,532,320	67,110,186	52,859,911
Effect of dilutive share options outstanding	936,043	958,125	423,674
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share	82,468,363	68,068,311	53,283,585


	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Net income attributable to the Group	$	505,304	153,185		$	332,331
Noncontrolling interest adjustment to redemption amount	—		—		(4,522)
Net income attributable to the Group (including NCI redemption adjustment)	505,304		153,185		327,809

	December 31, 2022		December 31, 2021		December 31, 2020
Net income per Ordinary Share attributable to the Group (including NCI redemption adjustment):
Basic	$	6.20	$	2.28	$	6.20
Diluted	$	6.13	$	2.25	$	6.15

Contract Balances (Details) - USD ($) $ in Thousands	12 Months Ended
Contract Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Billed services (accounts receivable)	$ 1,751,950	$ 1,349,851
Allowance for credit losses (note 5)	(20,562)	(7,081)	$ (7,149)
Accounts receivable (net)	1,731,388	1,342,770
Unbilled services (unbilled revenue)	957,655	623,121
Accounts receivable and unbilled revenue, net	2,689,043	1,965,891
Unearned revenue (payments on account)	(1,507,449)	(1,323,961)
Net balance	(549,794)	$ (700,840)
Change in unbilled receivables	334,534
Change in unearned revenue (payments on account)	(183,488)
Change in advance payments netted against unbilled contracts receivable	$ 151,046
Change in unbilled receivables (in percent)	53.70%
Change in unearned revenue (payments on account) (in percent)	13.90%
Change in advance payments netted against unbilled contracts receivable (in percent)	21.60%

Net Income Per Ordinary Share - Reconciliation of Net Income Attributable to the Group Per the Statement of Operating Income and Net Income Used For Net Income Per Ordinary Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Earnings Per Share [Abstract]
Net income attributable to the Group	$ 505,304	$ 153,185	$ 332,331
Noncontrolling interest adjustment to redemption amount	0	0	(4,522)
Net income attributable to the Group (including NCI redemption adjustment)	$ 505,304	$ 153,185	$ 327,809
Net income per Ordinary Share attributable to the Group (Note 24):
Basic (USD per share)	$ 6.20	$ 2.28	$ 6.20
Diluted (USD per share)	$ 6.13	$ 2.25	$ 6.15

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-URI https://asc.fasb.org/extlink&oid=126732423&loc=SL123482106-238011

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1448-109256

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1337-109256

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126732423&loc=SL123482106-238011

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 52
-URI https://asc.fasb.org/extlink&oid=128363288&loc=d3e4984-109258

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 15
-URI https://asc.fasb.org/extlink&oid=128363288&loc=d3e3842-109258

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22644-107794

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1252-109256

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126958026&loc=SL5780133-109256

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 52
-URI https://asc.fasb.org/extlink&oid=128363288&loc=d3e4984-109258

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22644-107794

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 15
-URI https://asc.fasb.org/extlink&oid=128363288&loc=d3e3842-109258

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1252-109256

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126958026&loc=SL5780133-109256

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126732423&loc=SL123482106-238011

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1337-109256

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-URI https://asc.fasb.org/extlink&oid=126732423&loc=SL123482106-238011

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126732423&loc=SL123482106-238011

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 50
-Paragraph 6
-URI https://asc.fasb.org/extlink&oid=124431353&loc=SL124452729-227067

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22499-107794

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22663-107794

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 17: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126958026&loc=SL5780133-109256

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22658-107794

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669619-108580

Reference 25: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8924-108599

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669625-108580

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8906-108599

Reference 35: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1448-109256

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 11
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1377-109256

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126958026&loc=SL5780133-109256

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8924-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8906-108599

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

+ Details

Intangible Assets

12 Months Ended

Dec. 31, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

The carrying amount of Intangible Assets for the years ended December 31, 2022 and 2021 is as follows:


	December 31, 2022		December 31, 2021
Cost	(in thousands)
Customer relationships	$	4,076,435	$	4,056,642
Order backlog	536,934		528,022
Trade names & brands	204,621		204,685
Patient database	170,238		170,525
Technology assets	120,984		121,507
Total cost	5,109,212		5,081,381

Accumulated amortization	(830,553)		(370,538)
Net book value	$	4,278,659	$	4,710,843

On July 1, 2021, ICON plc announced the completion of its Merger with PRA Health Sciences, Inc. The Merger resulted in the recognition of Customer relationships of $3,938.0 million, Order backlog of $500.0 million, Trade names of $202.0 million, Patient database of $168.0 million and Technology assets of $111.0 million. These assets will be amortized over their expected useful lives of between 3 and 23 years. The valuation of these assets were finalized in June 30, 2022. In total, $677.1 million has been amortized in the period since the date of acquisition, $453.6 million has been amortized in the year ended December 31, 2022.

Future intangible asset amortization expense for the years ended December 31, 2023 to December 31, 2027 is as follows:


	Year Ended December 31, 2022
	(in thousands)
2023	$	460,711
2024	339,940
2025	223,674
2026	209,681
2027	198,300
	$	1,432,306

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2022
Audit Information [Abstract]
Auditor firm ID	1116
Auditor name	KPMG
Auditor location	Dublin, Ireland

Business Segment and Geographical Information - Narrative (Details)	12 Months Ended
	Dec. 31, 2022 segment
Segment Reporting [Abstract]
Number of reporting segments	1

Summary of Significant accounting policies - Narrative (Details)	Mar. 09, 2020
MeDiNova
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Business combination acquisition percentage (in percent)	100.00%

Business Combinations - Schedule of Pro-Forma Information, PRA Acquisition (Details) - PRA Health Sciences, Inc - USD ($) $ in Thousands	12 Months Ended	18 Months Ended
	Dec. 31, 2022	Dec. 31, 2022
Business Acquisition [Line Items]
Cash and cash equivalents		$ 0
Accounts receivable and unbilled revenue		0
Other current assets		14,465
Fixed assets		(6,137)
Operating lease right-of-use assets		(11,744)
Goodwill		70,436
Intangible assets		44,000
Deferred tax assets		(147,039)
Other assets		(1,166)
Accounts payable		0
Accrued expenses and other current liabilities		(37,496)
Current portion of operating lease liabilities		1,865
Unearned revenue		19,623
Non-current portion of operating lease liabilities		10,454
Non-current deferred tax liabilities		193,837
Other non-current liabilities		$ (151,098)
Amortization adjustment	$ 2,200
Accounting Standards Update 2021-08
Business Acquisition [Line Items]
Unearned revenue	$ 16,000

Business Segment and Geographical Information

12 Months Ended

Dec. 31, 2022

Segment Reporting [Abstract]

Business Segment and Geographical Information

The Company has the expertise and capability to conduct clinical trials in most major therapeutic areas on a global basis and has the operational flexibility to provide development services on a stand-alone basis or as part of an integrated "full-service" solution. The Company has expanded through internal growth, together with a number of strategic acquisitions to enhance its expertise and capabilities in certain areas of the clinical development process.

The Company determines and presents operating segments based on the information that is internally provided to the chief operating decision maker, the (‘CODM’) in accordance with ASC 280 'Segment Reporting'. The Company determined that the CODM was comprised of the Chief Executive Officer and the Chief Financial Officer.

The Company operates as one reporting segment, which is the provision of outsourced development services on a global basis to the pharmaceutical, biotechnology and medical devices industries.

Revenues are allocated to individual entities based on where the work is performed in accordance with the Company's global transfer pricing model. Revenues and income from operations in Ireland are a function of our global contracting model and the Group’s transfer pricing model.

ICON Ireland acts as the Group entrepreneur under the Company’s global transfer pricing model given its role in the development and management of the Group, its ownership of key intellectual property and customer relationships, its key role in the mitigation of risks faced by the Group and its responsibility for maintaining the Company’s global network. ICON Ireland enters into the majority of the Company’s customer contracts.

ICON Ireland remunerates other operating entities in the ICON Group on the basis of a guaranteed cost plus mark-up for the services they perform in each of their local territories. The cost plus mark-up for each ICON entity is established to ensure that each of ICON Ireland and the ICON entities that are involved in the conduct of services for customers, earn an appropriate arms-length return having regard to the assets owned, risks borne, and functions performed by each entity from these intercompany transactions. The cost plus mark-up policy is reviewed annually to ensure that it is market appropriate. The integration of entities acquired through the Merger into this global network and global transfer pricing model remains ongoing.

The geographic split of revenue disclosed for each region outside Ireland is the cost plus revenue attributable to these entities. The residual revenues of the Group, once each ICON entity has been paid its respective intercompany service fee, generally fall to be retained by ICON Ireland. As such, revenues and income from operations in Ireland are a function of this global transfer pricing model and comprise revenues of the Group after deducting the cost plus revenues attributable to the activities performed outside Ireland.

There have been no changes to the basis of segmentation or the measurement basis for the segment results since the prior year.

Reportable geographic information at December 31, 2022 and December 31, 2021 and for the years ended December 31, 2022, December 31, 2021 and December 31, 2020 is as follows:

a) The distribution of revenue by geographical area was as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020

	(in thousands)
Ireland	$	1,984,567	$	1,365,909	$	1,181,292
Rest of Europe	1,618,350		1,175,515		416,884
U.S.	3,574,610		2,581,007		925,563
Other	563,859		358,395		273,549
Total	$	7,741,386	$	5,480,826	$	2,797,288

b) The distribution of income from operations (including Restructuring) by geographical area was as follows:


	Year ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Ireland *	$	218,088	$	131,961	$	276,478
Rest of Europe	253,799		177,863		35,765
U.S.	254,849		39,132		58,018
Other	68,501		29,573		21,239
Total	$	795,237	$	378,529	$	391,500

* Includes the full amount of the amortization charge associated with the intangible asset acquired in the Merger.

c) The distribution of long-lived assets (property, plant and equipment and operating right-of-use assets), net, by geographical area was as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Ireland	$	143,025	$	118,253
Rest of Europe	99,721		121,174
U.S.	213,311		239,828
Other	48,095		55,312
Total	$	504,152	$	534,567

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8924-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8981-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8721-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9031-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 26
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9038-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9054-108599

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 15
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8657-108599

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8721-108599

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-URI https://asc.fasb.org/topic&trid=2134510

+ Details

Summary of Significant accounting policies - Estimated Useful Lives of Property Plant and Equipment (Details)	12 Months Ended
	Dec. 31, 2022
Building
Property, Plant and Equipment [Line Items]
Estimated useful lives	40 years
Computer equipment and software \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	2 years
Computer equipment and software \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	8 years
Office furniture and fixtures
Property, Plant and Equipment [Line Items]
Estimated useful lives	8 years
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Motor vehicles
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years

Employee Benefits - Plan Asset Fair Value Measurements (Details) - Level 1 - ICON Development Solutions Limited pension plan - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 26,050	$ 36,198
Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22,887	0
Diversified Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,163	0
Equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	8,782
Corporate Bonds (including 50% high yield bonds)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	13,434
Secured Loans and Multi Asset Credit
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 13,982

- Definition

+ References + Details

Other Liabilities (Tables)

12 Months Ended

Dec. 31, 2022

Other Liabilities Disclosure [Abstract]

Schedule of Other Liabilities

The carrying amount of Other Liabilities for the years ended December 31, 2022 and 2021 is as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
General trade and overhead liabilities*	$	530,204	$	459,814
Personnel related liabilities	395,862		413,185
Operating lease liabilities	43,657		49,949
Facility related liabilities	16,896		12,055
Other liabilities	12,852		7,204
Restructuring liabilities	5,512		7,377
Short term government grants	42		45
	$	1,005,025	$	949,629

*includes amounts due to third parties in respect of accrued reimbursable investigator expenses of $406.3 million at December 31, 2022 and $323.6 million at December 31, 2021.

Related Parties (Details) - USD ($) $ in Thousands	12 Months Ended
Related Parties (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Majority investor, ownership percentage	51.00%
Oncacare
Related Party Transaction [Line Items]
Ownership Percentage	49.00%
DS Biopharma Limited \| Subsidiaries
Related Party Transaction [Line Items]
Revenue earned from related parties	$ 2	$ 30
Amounts due from related parties	12	12
Afimmune Limited \| Subsidiaries
Related Party Transaction [Line Items]
Revenue earned from related parties	235	551
Amounts due from related parties	263	197
Corvus Pharmaceuticals \| Subsidiaries
Related Party Transaction [Line Items]
Revenue earned from related parties	428
Amounts due from related parties	231
Oncacare
Related Party Transaction [Line Items]
Expenses incurred from related party transactions	451	465
Loan granted tp related party		$ 10,000
Related party, loan interest rate		1.60%
Interest receivable, related party loans	183
Oncacare \| Subsidiaries
Related Party Transaction [Line Items]
Amounts due from related parties	$ 715	$ 264

Other Liabilities

12 Months Ended

Dec. 31, 2022

Other Liabilities Disclosure [Abstract]

Other Liabilities

The carrying amount of Other Liabilities for the years ended December 31, 2022 and 2021 is as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
General trade and overhead liabilities*	$	530,204	$	459,814
Personnel related liabilities	395,862		413,185
Operating lease liabilities	43,657		49,949
Facility related liabilities	16,896		12,055
Other liabilities	12,852		7,204
Restructuring liabilities	5,512		7,377
Short term government grants	42		45
	$	1,005,025	$	949,629

*includes amounts due to third parties in respect of accrued reimbursable investigator expenses of $406.3 million at December 31, 2022 and $323.6 million at December 31, 2021.

Employee Benefits - Assumptions Used in Determining Benefit Obligation (Details) - United Kingdom - ICON Development Solutions Limited pension plan	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.90%	1.80%
Rate of compensation increase	3.60%	3.70%

Fair Value (Tables)

12 Months Ended

Dec. 31, 2022

Fair Value Disclosures [Abstract]

Fair Value, Liabilities Measured on Recurring Basis

As of December 31, 2022, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows (in thousands):


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
Assets:
Available for sale securities (short-term) (a)	1,713		—		—		—		1,713
Available for sale investments (long-term) (b)	—		—		—		32,663		32,663
Derivative instruments (c)	—		12		—		—		12
Total assets	$	1,713	$	12	$	—	$	32,663	$	34,388

Liabilities:
Derivative instruments (c)	—		3,670		—		—		3,670
Total Liabilities	$	—	$	3,670	$	—	$	—	3,670

As of December 31, 2021, the fair value of the major classes of the Company's assets measured at fair value on a recurring basis were as follows (in thousands):


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
Assets:
Available for sale securities (short-term) (a)	1,712		$	—	$	—	—		1,712
Available for sale investments (long-term) (b)	—		$	—	$	—	20,579		20,579
Total assets	$	1,712	$	—	$	—	$	20,579	$	22,291

Fair Value, Assets Measured on Recurring Basis

As of December 31, 2022, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows (in thousands):


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
Assets:
Available for sale securities (short-term) (a)	1,713		—		—		—		1,713
Available for sale investments (long-term) (b)	—		—		—		32,663		32,663
Derivative instruments (c)	—		12		—		—		12
Total assets	$	1,713	$	12	$	—	$	32,663	$	34,388

Liabilities:
Derivative instruments (c)	—		3,670		—		—		3,670
Total Liabilities	$	—	$	3,670	$	—	$	—	3,670

As of December 31, 2021, the fair value of the major classes of the Company's assets measured at fair value on a recurring basis were as follows (in thousands):


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
Assets:
Available for sale securities (short-term) (a)	1,712		$	—	$	—	—		1,712
Available for sale investments (long-term) (b)	—		$	—	$	—	20,579		20,579
Total assets	$	1,712	$	—	$	—	$	20,579	$	22,291

Property, Plant and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Land	$ 3,724	$ 3,724
Building	70,880	82,017
Computer equipment and software	500,135	506,322
Office furniture and fixtures	50,600	107,507
Laboratory equipment	59,946	29,210
Leasehold improvements	65,167	70,123
Motor vehicles	41	65
Property, plant and equipment, gross	750,493	798,968
Less accumulated depreciation and asset write offs	(400,173)	(462,524)
Property, plant and equipment (net)	350,320	336,444
Depreciation expense	$ 106,426	$ 75,484

Restructuring Charges

12 Months Ended

Dec. 31, 2022

Restructuring and Related Activities [Abstract]

Restructuring Charges

A restructuring charge of $31.1 million was recognized during the year ended December 31, 2022 under a restructuring plan adopted following a review of operations. The restructuring plan reflected resource rationalization across the business to improve employee utilization and an office consolidation program to optimize the Company's office footprint. The restructuring plan resulted in a charge of $2.7 million relating to workforce reductions, an impairment of right-of-use assets and associated unavoidable costs totaling $24.5 million and fixed asset impairment of $4.0 million. It is company policy to disclose operating right-of-use asset impairment as a restructuring charge when it is part of a coordinated program to decommission space.


	Year Ended
	December 31, 2022		December 31, 2021		December 31, 2020
	(in thousands)
Restructuring charges	$	31,143	$	31,105	$	18,089
Net charge	$	31,143	$	31,105	$	18,089

At December 31, 2022, a total liability of $6.0 million was recorded on the Consolidated Balance Sheet relating to restructuring activities. The total liability included $1.4 million of facilities related liabilities of which $0.9 million is included within other liabilities and $0.5 million is included within non-current other liabilities. The remaining provision of $4.6 million relates to workforce reduction and is included within other liabilities.


	Year Ended
	December 31, 2022		December 31, 2021
	(in thousands)

Opening provision	$	10,311	$	4,675
Additional provision in the year	4,364		11,273
Utilization	(8,653)		(5,637)
Ending provision	$	6,022	$	10,311

CONSOLIDATED BALANCE SHEETS (Parenthetical) - € / shares	Dec. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Ordinary shares, par value (in EUR per share)	€ 6	€ 6
Ordinary shares, shares authorized (in shares)	100,000,000	100,000,000
Ordinary shares, shares issued (in shares)	81,723,555	81,554,683
Ordinary shares, shares outstanding (in shares)	81,723,555	81,554,683

Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 7,741,386	$ 5,480,826	$ 2,797,288
Top client
Disaggregation of Revenue [Line Items]
Revenue	683,546	441,173	337,904
Clients 2-5
Disaggregation of Revenue [Line Items]
Revenue	1,506,087	1,291,946	754,906
Clients 6-10
Disaggregation of Revenue [Line Items]
Revenue	1,112,636	752,325	350,865
Clients 11-25
Disaggregation of Revenue [Line Items]
Revenue	1,585,739	1,077,073	501,643
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 2,853,378	$ 1,918,309	$ 851,970

- Definition

+ References

+ Details

Derivatives (Tables)

12 Months Ended

Dec. 31, 2022

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivative Instruments in Statement of Financial Position, Fair Value


		December 31, 2022
		Asset	Liability	Notional
		(in thousands)
Derivatives designated as hedging instruments:

Interest Rate Caps	Other Assets and Liabilities	$12	$3,363	2,100,606
Interest Rate Swap	Other Assets and Liabilities	$—	$307	1,100,606

Total derivatives designated as hedging instruments		$12	$3,670	3,201,213

Allowances for Credit Losses (Tables)

12 Months Ended

Dec. 31, 2022

Accounts Receivable, after Allowance for Credit Loss [Abstract]

Schedule of Provision for Credit Losses

The Company does business with most major international pharmaceutical companies. Provision for credit losses at December 31, 2022 and December 31, 2021 comprises:


	December 31, 2022		December 31, 2021
	(in thousands)
Opening provision	$	7,081	$	7,149
Amounts used during the year	(3,913)		(116)
Amounts provided during the year	17,800		705
Amounts released during the year	—		(544)
Foreign exchange	(406)		(113)
Closing provision	$	20,562	$	7,081

Non-current other liabilities (Tables)

12 Months Ended

Dec. 31, 2022

Payables and Accruals [Abstract]

Non-current other liabilities

The carrying amount of Non-current other liabilities for the years ended December 31, 2022 and 2021 is as follows:


	December 31, 2022		December 31, 2021
	(in thousands)
Defined benefit pension obligations, net (note 21)	$	13,033	$	16,262
Other non-current liabilities	25,227		26,334
	$	38,260	$	42,596

Business Segment and Geographical Information - Distribution of Long-lived Assets, Net, by Geographical Area (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Long-lived assets	$ 504,152	$ 534,567
Ireland
Segment Reporting Information [Line Items]
Long-lived assets	143,025	118,253
Rest of Europe
Segment Reporting Information [Line Items]
Long-lived assets	99,721	121,174
U.S.
Segment Reporting Information [Line Items]
Long-lived assets	213,311	239,828
Other
Segment Reporting Information [Line Items]
Long-lived assets	$ 48,095	$ 55,312