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Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Supplemental Cash Flow Elements [Abstract]
Cash paid for interest	$ 196,622	$ 317,975	$ 210,918
Cash paid for income taxes (net of refunds)	$ 140,718	$ 163,778	$ 116,322

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Amounts due to third parties for reimbursable expenses	$ 369,200	$ 333,000
Change in unbilled services (unbilled revenue)	334,338
Change in unearned revenue (payments on account)	39,749
Decrease in net balance	374,087
Bad debt expense	28,400	24,600
Revenue, remaining performance obligation, amount	$ 15,900,000	$ 14,800,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
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
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation (in percent)	47.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months

Goodwill (Tables)

12 Months Ended

Dec. 31, 2024

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

The change in the carrying amount of goodwill for the years ended December 31, 2024 and 2023 is as follows:


	December 31, 2024		December 31, 2023
	(in thousands)
Opening balance	$	9,022,075	$	8,971,670
Current period acquisitions (note 6)	46,126		36,750
Foreign exchange movement	(16,791)		13,655
Closing balance	$	9,051,410	$	9,022,075

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 24
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482548/350-20-55-24

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

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Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
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Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-2

+ Details

Property, Plant and Equipment, net (Tables)

12 Months Ended

Dec. 31, 2024

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, 2024 and 2023 is as follows:


	December 31, 2024		December 31, 2023
Cost	(in thousands)
Land	$	3,724	$	3,724
Buildings	66,132		70,072
Computer equipment and software	689,979		550,119
Office furniture and fixtures	51,849		45,856
Laboratory equipment	55,111		56,217
Leasehold improvements	62,034		55,000
Motor vehicles	65		79

Total Cost	928,894		781,067
Less accumulated depreciation and asset write offs	(546,015)		(419,883)

Property, plant and equipment (net)	$	382,879	$	361,184

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities)

12 Months Ended

Dec. 31, 2024

Revenue from Contract with Customer [Abstract]

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities)

Disaggregation of Revenue

Revenue disaggregated by customer concentration is as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Top client	$	639,520	$	721,309	$	683,546
Clients 2-5	1,431,873		1,453,508		1,506,087
Clients 6-10	1,306,604		1,188,943		1,112,636
Clients 11-25	1,774,160		1,743,539		1,585,739
Other	3,129,519		3,012,877		2,853,378
Total	$	8,281,676	$8,120,176		$7,741,386

There was no revenue from individual customers greater than 10% of consolidated revenue in the respective years. Our customers have similar profiles and economic characteristics, and therefore have similar degrees of risk and growth opportunities.

Accounts receivable and unbilled revenue are as follows:


	December 31, 2024		December 31, 2023
	(in thousands)
Billed services (accounts receivable)	$	1,437,653	$	1,821,855
Allowance for credit losses (note 5)	(35,664)		(31,533)
Accounts receivable (net)	1,401,989		1,790,322
Unbilled services (unbilled revenue)	1,286,274		951,936
Accounts receivable and unbilled revenue, net	$	2,688,263	$	2,742,258

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


	December 31, 2024		December 31, 2023		$ Change		% Change
	(in thousands, except percentages)
Unbilled services (unbilled revenue)	$	1,286,274	$	951,936	$	334,338	35.1	%
Unearned revenue (payments on account)	(1,614,758)		(1,654,507)		39,749		(2.4)	%
Net balance	$	(328,484)	$	(702,571)	$	374,087	(53.2)	%

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, 2024 and December 31, 2023 were $369.2 million and $333.0 million (see note 12. Other liabilities).

Unbilled services as at December 31, 2024 increased by $334.3 million as compared to December 31, 2023. Unearned revenue decreased by $39.7 million over the same period resulting in a decrease of $374.1 million in the net balance of unbilled services and unearned revenue or payments on account between December 31, 2023 and December 31, 2024. These fluctuations are primarily due to the timing of payments and invoicing related to the Company's clinical trial management contracts. Billings and payments are established by contractual provisions on the delivery of units/milestones 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 Company's receivables and unbilled services was $28.4 million and $24.6 million for the years ended December 31, 2024 and 2023, respectively.

As of December 31, 2024, $15.9 billion (December 31, 2023: $14.8 billion) of revenue is expected to be recognized in the future in respect of unsatisfied performance obligations. The Company expects to recognize revenue on approximately 47% of the unsatisfied performance obligation over the next twelve months (December 31, 2023: 52%), 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
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-9

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org/606/tableOfContent

+ Details

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 538,785	$ 378,102
Available for sale investments (Note 8)	0	1,954
Accounts receivable, net of allowance for credit losses (Note 4)	1,401,989	1,790,322
Unbilled services (unbilled revenue)	1,286,274	951,936
Other receivables	79,487	65,797
Prepayments and other current assets	140,435	132,105
Income taxes receivable	83,523	91,254
Total current assets	3,530,493	3,411,470
Non-current assets:
Property, plant and equipment, net (Note 9)	382,879	361,184
Goodwill (Note 10)	9,051,410	9,022,075
Intangible assets, net (Note 11)	3,559,792	3,855,865
Operating right-of-use assets (Note 15)	147,602	140,333
Other receivables	72,796	78,470
Deferred tax asset (Note 20)	74,758	73,662
Investments in equity (Note 8)	57,948	46,804
Total Assets	16,877,678	16,989,863
Current liabilities:
Accounts payable	173,025	131,584
Unearned revenue (Note 4)	1,614,758	1,654,507
Other liabilities (Note 12)	923,603	915,399
Income taxes payable	55,258	13,968
Current bank credit lines, loan facilities and notes (Note 13)	29,762	110,150
Total current liabilities	2,796,406	2,825,608
Non-current liabilities:
Non-current bank credit lines, loan facilities and notes, net (Note 13)	3,396,398	3,665,439
Lease liabilities (Note 15)	140,085	126,321
Non-current other liabilities (Note 16)	83,470	45,998
Non-current income taxes payable	125,834	186,654
Deferred tax liability (Note 20)	812,486	899,100
Commitments and contingencies (Note 17)	0	0
Total Liabilities	7,354,679	7,749,120
Shareholders' Equity:
80,756,860 shares issued and outstanding at December 31, 2024 and 82,495,086 shares issued and outstanding at December 31, 2023.	6,586	6,699
Additional paid-in capital	7,020,231	6,942,669
Other undenominated capital (Note 18b)	1,304	1,162
Accumulated other comprehensive loss (Note 24)	(229,929)	(143,506)
Retained earnings	2,724,807	2,433,719
Total Shareholders' Equity	9,522,999	9,240,743
Total Liabilities and Shareholders’ Equity	$ 16,877,678	$ 16,989,863

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Ordinary Shares	Additional Paid-in Capital	Other Undenominated Capital	Accumulated Other Comprehensive Loss	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2021		81,554,683
Beginning balance at Dec. 31, 2021	$ 8,066,827	$ 6,640	$ 6,733,910	$ 1,134	$ (90,937)	$ 1,416,080
Comprehensive income (net of tax):
Net income	505,304					505,304
Currency translation adjustment	(89,530)				(89,530)
Remeasurement of retirement benefit obligations	12,657				12,657
Gain on cash flow hedge	(3,728)				(3,728)
Total comprehensive income	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 issuance costs	(17)		(17)
Share repurchase program, number of shares repurchased (in shares)		(420,530)
Repurchase of ordinary shares	(99,983)	$ (28)		28		(99,983)
Share repurchase costs	(17)
Ending balance (in shares) at Dec. 31, 2022		81,723,555
Ending balance at Dec. 31, 2022	8,497,963	$ 6,649	6,840,306	1,162	(171,538)	1,821,384
Comprehensive income (net of tax):
Net income	612,335					612,335
Currency translation adjustment	26,221				26,221
Remeasurement of retirement benefit obligations	244				244
Gain on cash flow hedge	1,567				1,567
Total comprehensive income	640,367
Exercise of share options (in shares)		535,705
Exercise of share options	50,958	$ 35	50,923
Issue of restricted share units / performance share units (in shares)		235,826
Issue of restricted share units / performance share units	15	$ 15
Share based compensation expense	51,456		51,456
Share issuance costs	$ (16)		(16)
Ending balance (in shares) at Dec. 31, 2023	82,495,086	82,495,086
Ending balance at Dec. 31, 2023	$ 9,240,743	$ 6,699	6,942,669	1,162	(143,506)	2,433,719
Comprehensive income (net of tax):
Net income	791,474					791,474
Currency translation adjustment	(84,927)				(84,927)
Remeasurement of retirement benefit obligations	(6,077)				(6,077)
Gain on cash flow hedge	4,581				4,581
Total comprehensive income	705,051
Exercise of share options (in shares)		311,040
Exercise of share options	36,178	$ 20	36,158
Issue of restricted share units / performance share units (in shares)		130,433
Issue of restricted share units / performance share units	9	$ 9
Share based compensation expense	41,426		41,426
Share issuance costs	(22)		(22)
Share repurchase program, number of shares repurchased (in shares)		(2,179,699)
Repurchase of ordinary shares	(499,998)	$ (142)		142		(499,998)
Share repurchase costs	$ (388)
Ending balance (in shares) at Dec. 31, 2024	80,756,860	80,756,860
Ending balance at Dec. 31, 2024	$ 9,522,999	$ 6,586	$ 7,020,231	$ 1,304	$ (229,929)	$ 2,724,807

Business Segment and Geographical Information

12 Months Ended

Dec. 31, 2024

Segment Reporting [Abstract]

Business Segment and Geographical Information

The Company is a CRO providing outsourced services on a global basis to pharmaceutical, biotechnology, medical device and government and public health organizations. It specializes 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. 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" or “blended-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 operates as one reportable segment, which is the provision of outsourced development services on a global basis to the pharmaceutical, biotechnology and medical devices industries. For each of the accounting periods presented herein, the Company determined that Chief Operating Decision Maker ('CODM') was comprised of the Chief Executive Officer and the Chief Financial Officer. As the Company is managed on a consolidated basis, the CODM evaluates performance and allocates resources based on consolidated net income. The CODM uses consolidated net income, as reported on the Consolidated Statement of Operations, to evaluate income generated from segment assets and for decisions related to the deployment of operating and capital resources. The measure of segment assets is reported on the Consolidated Balance Sheet as total consolidated assets.

The accounting policies of the reportable segment are the same as those described in Note 2. Summary of Significant Accounting Policies. In the context of considerations around significant segment expenses, as the expense information that is regularly provided to the CODM is aligned with the respective consolidated expenses for direct costs and selling, general, and administrative expenses, as presented on the Consolidated Statement of Operations, such expense disclosures are not replicated here. Furthermore, as the Company consists of a single reportable segment, other quantitative disclosures, as required by Topic 280, are as presented on the Consolidated Statement of Operations.

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 Group on the basis of an arm’s length return for the services they perform in each of their local territories. The arm’s length return 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 return having regard to their respective functions performed, assets owned, and risks assumed in these intercompany transactions. The arm’s length return is reviewed annually to ensure that it is market appropriate.

The geographic split of revenue disclosed for each region outside Ireland is the arm’s length 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 arm’s length revenues attributable to the activities performed outside Ireland.

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

Reportable geographic information at December 31, 2024 and December 31, 2023 and for the years ended December 31, 2024, December 31, 2023 and December 31, 2022 is as follows:

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


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022

	(in thousands)
Ireland	$	2,793,045	$	2,377,104	$	1,984,567
Rest of Europe	1,560,735		1,574,783		1,618,350
U.S.	2,985,256		3,283,790		3,574,610
Other	942,640		884,499		563,859
Total	$	8,281,676	$	8,120,176	$	7,741,386

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


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Ireland	$	919,126	$	885,886	$	673,804
Rest of Europe	216,768		154,626		254,955
U.S.	241,549		314,982		260,890
Other	70,661		60,512		68,675
Sub-total	$	1,448,104	$	1,416,006	$	1,258,324
Amortization on intangible assets	(350,292)		(459,854)		(463,087)
Total	$	1,097,812	$	956,152	$	795,237

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, 2024		December 31, 2023
	(in thousands)
Ireland	$	234,175	$	199,051
Rest of Europe	88,556		94,046
U.S.	145,391		159,245
Other	62,359		49,175
Total	$	530,481	$	501,517

- 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/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 48
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Business Combinations - Narrative, Oncacare Acquisition (Details) - USD ($) $ in Thousands		12 Months Ended
	Apr. 20, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Goodwill		$ 9,051,410	$ 9,022,075	$ 8,971,670
Acquisition related costs		$ 0	$ 6,160	$ 0
Oncacare
Business Acquisition [Line Items]
Percentage of share capital acquired	51.00%
Business combination, consideration transferred	$ 5,100
Goodwill	13,400
Acquisition related costs	$ 6,200

- Definition

Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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+ Details

Business Segment and Geographical Information - Distribution of Income from Operations, Excluding Restructuring, by Geographical Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Income from operations	$ 1,097,812	$ 956,152	$ 795,237
Amortization on intangible assets	(350,300)	(459,900)	(463,100)
Operating Segments
Segment Reporting Information [Line Items]
Income from operations	1,448,104	1,416,006	1,258,324
Amortization on intangible assets	(350,292)	(459,854)	(463,087)
Ireland
Segment Reporting Information [Line Items]
Income from operations	919,126	885,886	673,804
Rest of Europe
Segment Reporting Information [Line Items]
Income from operations	216,768	154,626	254,955
U.S.
Segment Reporting Information [Line Items]
Income from operations	241,549	314,982	260,890
Other
Segment Reporting Information [Line Items]
Income from operations	$ 70,661	$ 60,512	$ 68,675

Intangible Assets

12 Months Ended

Dec. 31, 2024

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

The carrying amount of Intangible Assets for the years ended December 31, 2024 and 2023 is as follows:


	December 31, 2024		December 31, 2023
Cost	(in thousands)
Customer relationships	$	4,129,501	$	4,090,393
Order backlog	543,933		541,302
Trade names & brands	204,588		204,653
Patient database	170,324		170,366
Technology assets	150,658		141,257
Total cost	5,199,004		5,147,971
Accumulated amortization	(1,639,212)		(1,292,106)
Net book value	$	3,559,792	$	3,855,865

The amortization expense recognized by the Company was $350.3 million, $459.9 million, and $463.1 million for the years ended December 31, 2024, 2023, and 2022, respectively. The decrease in amortization in the twelve months ended December 31, 2024 is due to the order backlog and trade name intangible assets recognized in connection with the PRA merger amounting to $500.0 million and $202.0 million respectively as of the date of acquisition, becoming fully amortized on July 1, 2024.

On August 19, 2024, the Company acquired KCR. The acquisition resulted in the recognition of intangible assets of $45.1 million, comprising customer relationships of $41.4 million and order backlog of $3.7 million. These assets will be amortized over their expected useful lives of 13 years and 5 years respectively. In total, $1.3 million has been amortized in the period since the date of acquisition. Refer to note 6. Business Combinations.

On January 9, 2024, the Company acquired HumanFirst. The acquisition resulted in the recognition of a developed technology intangible asset of $9.9 million which will be amortized over its expected useful life of 5 years. In total, $2.0 million has been amortized in the period since the date of acquisition. Refer to note 6. Business Combinations.

On October 2, 2023, the Company acquired BioTel Research LLC (“BioTel”). The acquisition resulted in the recognition of intangible assets of $36.4 million, comprising customer relationships of $12.5 million, order backlog of $3.9 million and developed technology assets of $20.0 million. These assets will be amortized over their expected useful lives of between 3 years and 16 years. $6.1 million has been amortized during the twelve months ended December 31, 2024 (December 31, 2023: $1.5 million). Refer to note 6. Business Combinations.

Future intangible asset amortization expense for the years ended December 31, 2025 to December 31, 2029 is as follows:


(in thousands)
2025	$	235,011
2026	220,771
2027	208,448
2028	195,447
2029	180,201
Total	$	1,039,878

Income Taxes - Expected Expiry Dates of NOL's (Details) - United States $ in Thousands	Dec. 31, 2024 USD ($)
State NOL's
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, not subject to expiration	$ 9,601
Net operating loss carryforwards	277,828
State NOL's \| 2025-2038
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, subject to expiration	262,170
State NOL's \| 2039-2043
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, subject to expiration	6,057
Federal NOL's
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, not subject to expiration	0
Net operating loss carryforwards	8,035
Federal NOL's \| 2025-2038
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, subject to expiration	8,035
Federal NOL's \| 2039-2043
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, subject to expiration	$ 0

Business Segment and Geographical Information (Tables)

12 Months Ended

Dec. 31, 2024

Segment Reporting [Abstract]

Schedule of Distribution of Net Revenue by Geographical Area

The distribution of revenue by geographical area was as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022

	(in thousands)
Ireland	$	2,793,045	$	2,377,104	$	1,984,567
Rest of Europe	1,560,735		1,574,783		1,618,350
U.S.	2,985,256		3,283,790		3,574,610
Other	942,640		884,499		563,859
Total	$	8,281,676	$	8,120,176	$	7,741,386

Schedule of Distribution of Income from Operations by Geographical Area

The distribution of income from operations by geographical area was as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Ireland	$	919,126	$	885,886	$	673,804
Rest of Europe	216,768		154,626		254,955
U.S.	241,549		314,982		260,890
Other	70,661		60,512		68,675
Sub-total	$	1,448,104	$	1,416,006	$	1,258,324
Amortization on intangible assets	(350,292)		(459,854)		(463,087)
Total	$	1,097,812	$	956,152	$	795,237

Schedule of Distribution of Net Revenue 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, 2024		December 31, 2023
	(in thousands)
Ireland	$	234,175	$	199,051
Rest of Europe	88,556		94,046
U.S.	145,391		159,245
Other	62,359		49,175
Total	$	530,481	$	501,517

Operating Leases - Schedule of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Operating lease costs	$ 46,466	$ 46,820	$ 53,880
Income from sub-leases	(1,614)	(1,103)	(1,165)
Net operating lease costs	$ 44,852	$ 45,717	$ 52,715

Equity Incentive Schemes and Stock Compensation Charges - Schedule of Non-cash Stock Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	$ 45,870	$ 55,667	$ 70,523
Direct costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	26,046	26,595	22,854
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	$ 19,824	$ 29,072	$ 47,669

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Intangible Assets - Future Intangible Asset Amortization Expense (Details) $ in Thousands	Dec. 31, 2024 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2025	$ 235,011
2026	220,771
2027	208,448
2028	195,447
2029	180,201
Total	$ 1,039,878

Equity Incentive Schemes and Stock Compensation Charges

12 Months Ended

Dec. 31, 2024

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 four to 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"), and 2014 Omnibus Incentive Plan (the "2014 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 2.0 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.

The following table summarizes the transactions for the Company's share option plans for the years ended December 31, 2024, December 31, 2023 and December 31, 2022:


	Options Granted Under Plans	Weighted Average Exercise Price
Outstanding at December 31, 2021	1,695,460	$	110.38
Granted	108,643	$	229.94
Exercised	(348,286)	$	102.87
Forfeited/expired	(77,698)	$	143.08
Outstanding at December 31, 2022	1,378,119	$	119.86
Granted	82,472	$	232.48
Exercised	(535,705)	$	95.12
Forfeited/expired	(22,080)	$	196.20
Outstanding at December 31, 2023	902,806	$	142.96
Granted	68,380	$	325.51
Exercised	(311,040)	$	116.31
Forfeited/expired	(37,854)	$	238.51
Outstanding at December 31, 2024	622,292	$	170.52
Vested and exercisable at December 31, 2024	426,497	$	135.39

The weighted average remaining contractual life of options outstanding and options exercisable at December 31, 2024 was 3.91 years and 3.06 years respectively (2023: 4.42 years and 3.89 years respectively).

The intrinsic value of options outstanding and options exercisable as of December 31, 2024 was $34.0 million and $32.4 million, respectively.

The intrinsic value of options exercised during the years ended December 31, 2024, 2023, and 2022, was $57.4 million, $80.4 million, and $41.9 million, respectively.

Fair value of Stock Options Assumptions

The weighted average fair value of options granted during the years ended December 31, 2024, December 31, 2023 and December 31, 2022 was calculated using the Black-Scholes option pricing model. The weighted average fair values and assumptions were as follows:


	Year Ended
	December 31, 2024			December 31, 2023			December 31, 2022
Weighted average fair value	$	115.76		$	85.12		$	68.42
Assumptions:
Expected volatility	36		%	33		%	31		%
Dividend yield	—		%	—		%	—		%
Risk-free interest rate	4.20		%	4.18		%	1.86		%
Expected life	4.3 years			5.0 years			5.0 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 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. Further, on October 25, 2024, the 2013 RSU Plan was amended and restated effective as of November 6, 2024 in order to increase the number of shares that can be issued under the RSU Plan by a further 2.5 million shares. Accordingly, an aggregate of 6.6 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 November 6, 2034.

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 vest over twelve months. No awards may be granted under the 2019 Consultants RSU Plan after May 16, 2029.

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, 2024:


	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, 2023	105,256	$	226.29	621,011	$	218.27
Granted	48,626	$	325.51	258,345	$	313.41
Shares vested	(9,975)	$	177.38	(120,458)	$	223.29
Forfeited	(124,186)	$	260.42	(111,309)	$	241.13
Outstanding at December 31, 2024	19,721	$	280.76	647,589	$	251.36

The fair value of RSUs vested for the year ended December 31, 2024 totaled $26.9 million (2023: $35.4 million). The share price range for the year was $174.96 - $265.96 (2023: $159.33 - $265.96).

The fair value of PSUs vested for the year ended December 31, 2024 totaled $1.8 million (2023: $7.5 million). The share price range for the year was $174.96 - $231.08 (2023: $159.33 - $166.51).

The PSUs vest based on service and specified EPS targets over the period 2022 – 2024, 2023 – 2025, and 2024 - 2026. Depending on the actual amount of EPS from 2022 to 2026, up to an additional 80,051 PSUs may also be granted.

Stock compensation expense

Income from operations for the year ended December 31, 2024 is stated after charging $45.9 million in respect of stock compensation expense (inclusive of employer related taxes). Stock compensation expense has been allocated as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Direct costs	$	26,046	$	26,595	$	22,854
Selling, general and administrative	19,824		29,072		47,669
Total	$	45,870	$	55,667	$	70,523

As of December 31, 2024, total unrecognized stock-based compensation expense related to outstanding non-vested stock-based compensation arrangements amounted to $108.1 million, which the Company expects to recognize over a weighted average period of 2.29 years.

The income tax expense for the year ended December 31, 2024 reflects a net income tax benefit of $23.4 million in connection with stock compensation (including excess tax benefits) and the total tax benefit in connection with stock options exercised during 2024 was $10.1 million. The income tax expense for the year ended December 31, 2023 reflects a net income tax benefit of $20.0 million in connection with stock compensation (including excess tax benefits) and the total tax benefit in connection with stock options exercised during 2023 was $10.9 million. 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 realized in connection with stock options exercised during 2022 was $7.7 million.

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, 2024	Dec. 31, 2023	Dec. 31, 2022
Earnings Per Share [Abstract]
Weighted average number of ordinary shares outstanding for basic net income per ordinary share (in shares)	82,482,764	82,101,813	81,532,320
Effect of dilutive share options and other awards outstanding under share based compensation programs (in shares)	549,660	615,827	936,043
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share (in shares)	83,032,424	82,717,640	82,468,363

Property, Plant and Equipment, net - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Depreciation	$ 138.2	$ 126.1	$ 106.4

Commitments and Contingencies - Narrative (Details)	Dec. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Non-cancelable operating leases for facilities expiration period	16 years

Fair Value - Measurement of Fair Value of Major Asset and Liability classed (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
ASSETS
Available for sale investments (Note 8)	$ 0	$ 1,954
Investments in equity (Note 8)	57,948	46,804
Liabilities:
Equity securities, FV-NI, cost	3,500
Fair Value, Recurring
ASSETS
Available for sale investments (Note 8)		1,954
Investments in equity (Note 8)	54,448	46,804
Total assets	54,448	48,758
Liabilities:
Total liabilities		2,411
Total derivatives designated as hedging instruments \| Total derivatives designated as hedging instruments \| Fair Value, Recurring
Liabilities:
Derivative instruments		2,411
Level 1 \| Fair Value, Recurring
ASSETS
Available for sale investments (Note 8)		1,954
Investments in equity (Note 8)	0	0
Total assets	0	1,954
Liabilities:
Total liabilities		0
Level 1 \| Total derivatives designated as hedging instruments \| Total derivatives designated as hedging instruments \| Fair Value, Recurring
Liabilities:
Derivative instruments		0
Level 2 \| Fair Value, Recurring
ASSETS
Available for sale investments (Note 8)		0
Investments in equity (Note 8)	0	0
Total assets	0	0
Liabilities:
Total liabilities		2,411
Level 2 \| Total derivatives designated as hedging instruments \| Total derivatives designated as hedging instruments
Liabilities:
Derivative instruments	0	2,411
Level 2 \| Total derivatives designated as hedging instruments \| Total derivatives designated as hedging instruments \| Fair Value, Recurring
Liabilities:
Derivative instruments		2,411
Level 3 \| Fair Value, Recurring
ASSETS
Available for sale investments (Note 8)		0
Investments in equity (Note 8)	0	0
Total assets	0	0
Liabilities:
Total liabilities		0
Level 3 \| Total derivatives designated as hedging instruments \| Total derivatives designated as hedging instruments \| Fair Value, Recurring
Liabilities:
Derivative instruments		0
Other \| Fair Value, Recurring
ASSETS
Available for sale investments (Note 8)		0
Investments in equity (Note 8)	54,448	46,804
Total assets	$ 54,448	46,804
Liabilities:
Total liabilities		0
Other \| Total derivatives designated as hedging instruments \| Total derivatives designated as hedging instruments \| Fair Value, Recurring
Liabilities:
Derivative instruments		$ 0

Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2024

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Finite-Lived Intangible Assets


			Estimated Useful Life
Customer relationships			8 - 23 years
Order backlog			3 - 5 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, 2024 and 2023 is as follows:


	December 31, 2024		December 31, 2023
Cost	(in thousands)
Customer relationships	$	4,129,501	$	4,090,393
Order backlog	543,933		541,302
Trade names & brands	204,588		204,653
Patient database	170,324		170,366
Technology assets	150,658		141,257
Total cost	5,199,004		5,147,971
Accumulated amortization	(1,639,212)		(1,292,106)
Net book value	$	3,559,792	$	3,855,865

Schedule of Future Intangible Asset Amortization Expense

Future intangible asset amortization expense for the years ended December 31, 2025 to December 31, 2029 is as follows:


(in thousands)
2025	$	235,011
2026	220,771
2027	208,448
2028	195,447
2029	180,201
Total	$	1,039,878

Business Combinations - Narrative, KCR Acquisition (Details) - USD ($) $ in Thousands		4 Months Ended	12 Months Ended
	Aug. 19, 2024	Dec. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Purchase of subsidiary undertakings (net of cash acquired)			$ 84,159	$ 71,766	$ 0
Goodwill		$ 9,051,410	9,051,410	9,022,075	$ 8,971,670
KCR S.A Group
Business Acquisition [Line Items]
Business combination, consideration transferred	$ 92,500
Payments to acquire businesses, net of cash acquired	76,400
Purchase of subsidiary undertakings (net of cash acquired)	88,100
Cash acquired from acquisition	11,700
Fair value of contingent consideration	4,300	1,100	1,100
Goodwill	43,400
Intangible assets acquired	$ 45,100
Business combination, revenue of acquiree since acquisition date, actual		32,800
Business combination, net income (loss) of acquiree since acquisition date, actual		$ 1,800
Pro forma revenue			8,331,500	8,202,000
Pro forma net income (loss)			$ 792,500	$ 613,300

Summary of Significant accounting policies - Adjustments Resulting from Foreign Currency Translation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Foreign Currency [Abstract]
Amounts (credited) / charged	$ (18,085)	$ 12,916	$ (25,997)

Income Taxes - Consolidated Reported Provision for Income Taxes Differed from Statutory Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Taxes at Irish statutory rate of 12.5% (2023:12.5%; 2022:12.5%)	$ 108,648	$ 78,058	$ 70,980
Rate differential from amortization of intangible assets	(48,240)	(71,223)	(59,330)
Global Minimum Tax	16,719	0	0
Foreign and other income taxed at higher rates	49,703	35,778	52,464
Research & development tax incentives	(3,041)	(3,868)	(2,608)
Movement in valuation allowance	(5,279)	(1,068)	(777)
Effects of change in tax rates	25,691	3,154	(300)
(Decrease)/ increase in unrecognized tax benefits	(59,456)	(54,347)	8,392
Investor tax expense on foreign subsidiary earnings	(7,995)	39,165	0
Impact of stock compensation	(9,385)	(11,487)	(8,756)
Other and non-deductible expenses	10,345	(2,413)	(654)
Income tax expense	$ 77,710	$ 11,749	$ 59,411

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2024

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, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Ireland	$	736,374	$	624,642	$	432,963
United States	(304,546)		(352,532)		(270,440)
Other	437,356		352,357		405,328
Income before income tax expense	$	869,184	$	624,467	$	567,851

Summary of Components of Provision for Income Taxes

The components of income tax expense are as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
Income tax expense:	(in thousands)
Current tax (benefit)/expense:
Ireland	$	118,255	$	80,427	$	53,248
United States	(45,307)		(42,428)		60,753
Other	105,304		59,153		70,395
Total current tax expense	178,252		97,152		184,396

Deferred tax (benefit)/expense:
Ireland	(26,663)		45,253		(6,166)
United States	(69,493)		(143,323)		(118,475)
Other	(4,386)		12,667		(344)
Total deferred tax benefit	(100,542)		(85,403)		(124,985)

Income tax expense	77,710		11,749		59,411

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

Currency impact on long term funding	1,728		(3,903)		7,211

Retirement benefit obligations	(895)		—		—
Cash flow hedge	647		301		—
Total	$	79,190	$	8,147	$	66,622

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, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Taxes at Irish statutory rate of 12.5% (2023:12.5%; 2022:12.5%)	$	108,648	$	78,058	$	70,980
Rate differential from amortization of intangible assets	(48,240)		(71,223)		(59,330)
Global Minimum Tax	16,719		—		—
Foreign and other income taxed at higher rates	49,703		35,778		52,464
Research & development tax incentives	(3,041)		(3,868)		(2,608)
Movement in valuation allowance	(5,279)		(1,068)		(777)
Effects of change in tax rates	25,691		3,154		(300)
(Decrease)/ increase in unrecognized tax benefits	(59,456)		(54,347)		8,392
Investor tax expense on foreign subsidiary earnings	(7,995)		39,165		—
Impact of stock compensation	(9,385)		(11,487)		(8,756)

Other and non-deductible expenses	10,345		(2,413)		(654)
Income tax expense	$	77,710	$	11,749	$	59,411

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 and carryforwards that give rise to significant portions of deferred tax assets and deferred tax liabilities are presented below:


	December 31, 2024		December 31, 2023
Deferred tax liabilities:	(in thousands)
Property, plant and equipment	$	2,869	$	7,547
Operating right-of-use-assets	15,633		16,108
Goodwill	43,390		39,014
Intangible assets	901,731		950,055
Investments in foreign subsidiaries	34,983		52,408
Other	3,887		7,982
Total deferred tax liabilities recognized	1,002,493		1,073,114

Deferred tax assets:
Operating loss and tax credits carryforwards	164,904		124,150
Property, plant and equipment	7,869		9,082
Operating lease liabilities	21,503		20,190
Intangible assets	45		2,166
Stock compensation	14,309		17,605
Other liabilities	78,428		84,928
Unearned revenue	10,364		23,748
Other	6,298		8,774
Total deferred tax assets	303,720		290,643
Valuation allowance for deferred tax assets	(38,955)		(42,967)
Deferred tax assets recognized	264,765		247,676
Overall net deferred tax liability	$	(737,728)	$	(825,438)

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)
2025-2038	$	8,035	$	262,170
2039-2043	—		6,057
Indefinite	—		9,601
	$	8,035	$	277,828

Schedule of Unrecognized Tax Benefits Roll Forward

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


	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Unrecognized tax benefits at start of year	$	160,016	$	217,584	$	202,065
Increase related to prior year tax positions	7,374		1,161		16,098
Decrease related to prior year tax positions	(2,525)		(918)		(5,442)
Increase related to current year tax positions	2,171		4,552		5,701
Lapse of statute of limitations	(65,417)		(62,363)		(838)
Unrecognized tax benefits at end of year	$	101,619	$	160,016	$	217,584

Supplemental Disclosure of Cash Flow Information (Tables)

12 Months Ended

Dec. 31, 2024

Supplemental Cash Flow Elements [Abstract]

Schedule of Supplemental Disclosure of Cash Flow Information


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Cash paid for interest	$	196,622	$	317,975	$	210,918
Cash paid for income taxes (net of refunds)	$	140,718	$	163,778	$	116,322

Equity Incentive Schemes and Stock Compensation Charges - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended			24 Months Ended	252 Months Ended
	Oct. 25, 2024	Feb. 14, 2017	May 11, 2015	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2020	Dec. 31, 2017	May 18, 2020	May 16, 2019	May 31, 2018	Feb. 13, 2017
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Weighted average contractual term of options outstanding				3 years 10 months 28 days	4 years 5 months 1 day
Exercisable - weighted average remaining contractual life				3 years 21 days	3 years 10 months 20 days
Options outstanding, intrinsic value (in USD)				$ 34,000
Options exercisable, intrinsic value (in USD)				32,400
Options exercised during period, intrinsic value (in USD)				57,400	$ 80,400	$ 41,900
Total				45,870	55,667	70,523
Unrecognized share-based compensation cost				$ 108,100
Unrecognized share-based compensation cost, period of recognition				2 years 3 months 14 days
Income tax benefit related to stock compensation				$ 23,400	20,000	12,900
Cash tax benefit related to stock options exercised				10,100	10,900	$ 7,700
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
The 2018 Legacy PRA Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)											2,000,000
Consultants Stock Plan, 2008 Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)		400,000										1,000,000.0
Limit of shares issued or to be issued pursuant to options granted (in shares)		1,000,000.0
Employee Stock Plan, 2008 Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)		6,000,000.0
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 \| Award date, prior to 2018
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Shares expiration period								8 years
Employee Stock Option \| Award date, prior to 2018 \| Minimum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Shares vesting period								4 years
Employee Stock Option \| Award date, prior to 2018 \| Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
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)	6,600,000
Additional number of ordinary shares which have been reserved for issuance (in shares)	2,500,000		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				$ 26,900	$ 35,400
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)				$ 174.96	$ 159.33
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	$ 265.96
Performance Share Unit (PSUs)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Fair value of stock units vested				$ 1,800	$ 7,500
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)				$ 174.96	$ 159.33
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)				$ 231.08	$ 166.51
PSUs Based on Service and EPS Targets \| Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock units to be granted (in shares)				80,051

Summary of Significant accounting policies

12 Months Ended

Dec. 31, 2024

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

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

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, intangible assets acquired in a business combination, goodwill impairment and income taxation.

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 the net present value of estimated future cash flows. Debt is measured at amortized cost.

Financial instruments are measured 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.

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. Accounting for contingent consideration, after the acquisition, depends on the classification of the contingent consideration. Equity-classified contingent consideration is not remeasured after the acquisition date and subsequent settlement is accounted for within equity. Contingent consideration, which is classified as a liability or an asset, is remeasured to fair value at each reporting date until the contingency is resolved. The changes in fair value are recognized in earnings, unless the arrangement is a derivative which has been designated as a hedging instrument in a cash flow hedging relationship, in which case, the changes are initially recognized in other comprehensive income/loss.

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 any 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.

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/loss.

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/loss as currency translation adjustments. Amounts charged or credited to the Consolidated Statements of Operations for the years ended December 31, 2024, December 31, 2023 and December 31, 2022 were as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Amounts (credited) / charged	$	(18,085)	$	12,916	$	(25,997)

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

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 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

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, 2024 and December 31, 2023 meet the definition of equity securities without readily determinable fair values. The Company concluded that the interests held at December 31, 2024 and December 31, 2023 qualify for the Net Asset Value ("NAV") practical expedient in ASC Topic 820, Fair value Measurements ("ASC 820"). Any increases or decreases in fair value are recognized in earnings in the period.

Investments in equity which do not qualify for the NAV practical expedient are measured at cost, less impairment.

Equity method investments

The Company’s investments that are not consolidated are accounted for under the equity method if the Company exercises significant influence. These investments are classified as equity method investments on the Consolidated Balance Sheet. The Company records its pro rata share of the earnings/losses of these investments in Share of losses in equity investments in the Consolidated Statement of Operations. The Company reviews equity method investments 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 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, 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 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:


			Estimated Useful Life
Buildings			40 years
Computer equipment and software			2 - 8 years
Office furniture and fixtures			8 years
Laboratory equipment			5 years
Motor vehicles			5 years

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, 2024 and December 31, 2023, the Company did not account for any leases as finance leases.

Operating leases are included in operating right-of-use ("ROU") 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 the lease commencement date. 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 ASC 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 are measured at fair value at the date of acquisition and amortized on a straight-line basis over their respective estimated useful lives. The Company has no indefinite-lived intangible assets. The Company evaluates its intangible assets for impairment when indicators of impairment exist.

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


			Estimated Useful Life
Customer relationships			8 - 23 years
Order backlog			3 - 5 years
Trade names			3 years
Patient database			7 years
Technology assets			5 years

The Company periodically assesses the estimated 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. 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. Fair value is determined through various valuation techniques including discounted cash flow models and third-party independent appraisals, as considered necessary. 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 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

The Company has used derivative financial instruments to reduce exposures to interest rates. Derivatives are recorded on the Consolidated 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 criteria for designating a derivative as a hedge include 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.

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 the provision of income taxes 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 Global Intangible Low-Taxed Income ("GILTI") 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.

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 Topic 718, Compensation – Stock Compensation ("ASC 718").

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

Transaction and integration-related expenses are the incremental costs directly attributable to completion and integration activities associated with the Company’s recent acquisitions. The costs consist of investment banking fees, advisory costs, professional fees, legal costs, retention agreements with employees, and ongoing integration activities offset by the remeasurement of liability-classified contingent consideration. 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.

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. Asset related impairment charges are taken when the fair value 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.

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.

Impact of Recently Issued or Adopted Accounting Standards

Accounting pronouncements recently adopted

In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2023-07, Segment Reporting – Improvements to Reportable Segment Disclosures (“ASU 2023-07”), which amends the guidance in ASC Topic 280, Segment Reporting (“Topic 280”). The amended guidance requires disclosure of significant segment expenses and other segment items on an annual and interim basis, as well as additional qualitative disclosures. Furthermore, all disclosures about a reportable segment’s profit or loss, which are currently required annually, will be mandated for interim periods. The Company adopted ASU 2023-07 effective January 1, 2024, which resulted in additional segment reporting related disclosures. Refer to note 22. Business Segment and Geographical Information.

Accounting pronouncements issued but not adopted as of December 31, 2024

The following accounting pronouncements have been issued, but not yet adopted, as of December 31, 2024:

In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures, which requires disaggregated information about an entity’s effective tax rate reconciliation and additional discloses on income taxes paid. The new requirements are effective for annual periods beginning after December 15, 2024. The guidance is to be applied prospectively, with an option for retrospective application. The Company is currently evaluating the impact of this new guidance on disclosures within its consolidated financial statements.

In November 2024, the FASB issued ASU 2024-03, Disaggregation of Income Statement Expenses, which requires disaggregated disclosure of income statement expenses. The new standard requires disclosures about specific types of expenses included in the expense captions presented on the face of the income statement, as well as disclosures about selling expenses. The new requirements are effective for annual periods beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. Requirements are to be applied prospectively, with an option for retrospective application. The Company is currently evaluating the impact of this new guidance on disclosures within its consolidated financial statements.

Summary of Significant accounting policies - Estimated Useful Lives of Property Plant and Equipment (Details)	Dec. 31, 2024
Buildings
Property, Plant and Equipment [Line Items]
Estimated Useful Life	40 years
Office furniture and fixtures
Property, Plant and Equipment [Line Items]
Estimated Useful Life	8 years
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Motor vehicles
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Minimum \| Computer equipment and software
Property, Plant and Equipment [Line Items]
Estimated Useful Life	2 years
Maximum \| Computer equipment and software
Property, Plant and Equipment [Line Items]
Estimated Useful Life	8 years

Other Liabilities

12 Months Ended

Dec. 31, 2024

Other Liabilities Disclosure [Abstract]

Other Liabilities

The carrying amount of Other Liabilities for the years ended December 31, 2024 and 2023 is as follows:


	December 31, 2024		December 31, 2023
	(in thousands)
General trade and overhead liabilities*	$	531,560	$	463,882
Personnel related liabilities	225,822		385,499
Operating lease liabilities	36,783		36,414
Facility related liabilities	8,547		11,078
Other liabilities	91,730		13,532
Restructuring liabilities	29,120		4,951
Short term government grants	41		43
Total	$	923,603	$	915,399

*includes amounts due to third parties in respect of accrued reimbursable investigator expenses of $369.2 million at December 31, 2024 and $333.0 million at December 31, 2023.

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Net Income (Loss) Attributable to Parent [Abstract]
Net income	$ 791,474	$ 612,335	$ 505,304
Other comprehensive income, net of tax:
Currency translation adjustment	(84,927)	26,221	(89,530)
Remeasurement of retirement benefit obligations	(6,077)	244	12,657
Gain / (loss) on cash flow hedge	4,581	1,567	(3,728)
Total comprehensive income	$ 705,051	$ 640,367	$ 424,703

- Definition

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

+ References + Details

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

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+ Details

Goodwill - Schedule of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Goodwill [Roll Forward]
Opening balance	$ 9,022,075	$ 8,971,670
Current period acquisitions (note 6)	46,126	36,750
Foreign exchange movement	(16,791)	13,655
Closing balance	$ 9,051,410	$ 9,022,075

- Definition

+ References

+ Details

Business Segment and Geographical Information - Narrative (Details)	12 Months Ended
	Dec. 31, 2024 segment
Segment Reporting [Abstract]
Number of reporting segments	1

Non-current other liabilities

12 Months Ended

Dec. 31, 2024

Payables and Accruals [Abstract]

Non-current other liabilities

The carrying amount of Non-current other liabilities for the years ended December 31, 2024 and 2023 is as follows:


	December 31, 2024		December 31, 2023
	(in thousands)
Other non-current liabilities	83,470		45,998
Total	$	83,470	$	45,998

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Revenues [Abstract]
Revenue	$ 8,281,676	$ 8,120,176	$ 7,741,386
Costs and expenses:
Direct costs	5,845,319	5,719,949	5,527,045
Selling, general and administrative	728,348	768,559	778,753
Depreciation and amortization	488,500	585,950	569,513
Transaction and integration related (Note 6)	$ 29,574	44,176	39,695
Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration]	Restructuring (Note 19)
Restructuring (Note 19)	$ 92,123	45,390	31,143
Total costs and expenses	7,183,864	7,164,024	6,946,149
Income from operations	1,097,812	956,152	795,237
Interest income	8,609	5,014	2,345
Interest expense (Note 13)	(237,237)	(336,699)	(229,731)
Income before income tax expense	869,184	624,467	567,851
Income tax expense (Note 20)	(77,710)	(11,749)	(59,411)
Income before share of losses from equity method investments	791,474	612,718	508,440
Share of losses from equity method investments	0	(383)	(3,136)
Net income	$ 791,474	$ 612,335	$ 505,304
Net income per ordinary share (Note 23):
Basic (USD per share)	$ 9.60	$ 7.46	$ 6.20
Diluted (USD per share)	$ 9.53	$ 7.40	$ 6.13
Weighted average number of ordinary shares outstanding (Note 23):
Basic (in shares)	82,482,764	82,101,813	81,532,320
Diluted (in shares)	83,032,424	82,717,640	82,468,363

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) - $ / shares	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Net income per ordinary share:
Basic (USD per share)	$ 9.60	$ 7.46	$ 6.20
Diluted (USD per share)	$ 9.53	$ 7.40	$ 6.13

- Definition

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

+ References

+ 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

+ Details

Investments	12 Months Ended
Investments	Dec. 31, 2024
Investments, Debt and Equity Securities [Abstract]
Investments	Investments Investments in equity The Company entered into subscription agreements with a number of funds. During the year ended December 31, 2024, net capital totaling $13.1 million (December 31, 2023: $14.0 million) had been advanced under the terms of the subscription agreements. The Company determined that the interest in funds meets the definition of equity securities without readily determinable fair values. The Company therefore concluded that the interests held at December 31, 2024 and December 31, 2023 qualify for the NAV practical expedient in ASC 820. There was a decrease in fair value of $3.3 million (December 31, 2023: increase in fair value $0.2 million) recognized in net income during the year bringing the carrying value of the subscriptions to $54.4 million at December 31, 2024. At December 31, 2024, the Company had committed to future investments of $102.2 million in respect of these funds. Investments in equity also include equity investments of $3.5 million (of which $1.5 million was invested during the year ended December 31, 2024) which do not qualify for the NAV practical expedient, and for which the measurement alternative has been applied. Accordingly, these investments in equity are measured at cost, less impairment. Available for sale investments As at December 31, 2024, the Company held available for sale investments amounting to $nil (December 31, 2023: $2.0 million). Short-term investments comprise highly liquid investments with maturities of greater than three months and minimum "A-" rated fixed term deposits. The Company classifies its short- term investments as available for sale.

Net Income Per Ordinary Share (Tables)

12 Months Ended

Dec. 31, 2024

Earnings Per Share [Abstract]

Schedule of 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:


	Year ended
	December 31, 2024	December 31, 2023	December 31, 2022
Weighted average number of ordinary shares outstanding for basic net income per ordinary share	82,482,764	82,101,813	81,532,320
Effect of dilutive share options and other awards outstanding under share based compensation programs	549,660	615,827	936,043
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share	83,032,424	82,717,640	82,468,363








	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
Net income per ordinary share:
Basic	$	9.60	$	7.46	$	6.20
Diluted	$	9.53	$	7.40	$	6.13

Summary of Significant accounting policies - Estimated Useful Lives of Intangible Assets (Details)	Dec. 31, 2024
Customer relationships \| Minimum
Indefinite-lived Intangible Assets [Line Items]
Amortization period	8 years
Customer relationships \| Maximum
Indefinite-lived Intangible Assets [Line Items]
Amortization period	23 years
Order backlog \| Minimum
Indefinite-lived Intangible Assets [Line Items]
Amortization period	3 years
Order backlog \| Maximum
Indefinite-lived Intangible Assets [Line Items]
Amortization period	5 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

Allowances for Credit Losses (Tables)

12 Months Ended

Dec. 31, 2024

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, 2024 and December 31, 2023 comprises:


	December 31, 2024		December 31, 2023
	(in thousands)
Opening provision	$	31,533	$	20,562
Amounts used during the year	(24,887)		(13,358)
Amounts provided during the year	28,417		24,550
Foreign exchange	601		(221)
Closing provision	$	35,664	$	31,533

Operating Leases Operating Leases - Operating Lease Maturity (Details) $ in Thousands	Dec. 31, 2024 USD ($)
Leases [Abstract]
2025	$ 42,931
2026	38,445
2027	31,257
2028	24,156
2029	17,838
Thereafter	45,047
Total future minimum lease payments	199,674
Lease imputed interest	(22,806)
Total	$ 176,868

Derivatives - Effect of Derivative Financial Instruments on Statement of Financial Position (Details) - Total derivatives designated as hedging instruments - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Interest Rate Caps
Derivative [Line Items]
Asset		$ 0
Liability		1,871
Notional		1,600,606
Interest Rate Swap
Derivative [Line Items]
Asset		0
Liability		540
Notional		1,100,606
Total derivatives designated as hedging instruments
Derivative [Line Items]
Notional		2,701,212
Total derivatives designated as hedging instruments \| Level 2
Derivative [Line Items]
Asset		0
Liability	$ 0	$ 2,411

- Definition

Nominal or face amount used to calculate payments on the derivative asset.

+ References + Details

- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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+ Details

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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+ Details

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Schedule of Accounts Receivables and Unbilled Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Contract Assets [Abstract]
Billed services (accounts receivable)	$ 1,437,653	$ 1,821,855
Allowance for credit losses (note 5)	(35,664)	(31,533)	$ (20,562)
Accounts receivable (net)	1,401,989	1,790,322
Unbilled services (unbilled revenue)	1,286,274	951,936
Accounts receivable and unbilled revenue, net	$ 2,688,263	$ 2,742,258

Fair Value (Tables)

12 Months Ended

Dec. 31, 2024

Fair Value Disclosures [Abstract]

Fair Value, Liabilities Measured on Recurring Basis

he fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows:


	December 31, 2024
	Level 1		Level 2		Level 3		Other1		Total
	(in thousands)
Assets:
Investments in equity1,2	$	—	$	—	$	—	$	54,448	$	54,448
Total assets	$	—	$	—	$	—	$	54,448	$	54,448

1Excludes investments in equity securities recorded at cost of $3.5 million which do not qualify for the NAV practical expedient.

As at December 31, 2023, 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:


	December 31, 2023
	Level 1		Level 2		Level 3		Other1		Total
	(in thousands)
Assets:
Available for sale securities3	$	1,954	$	—	$	—	$	—	$	1,954
Investments in equity2	—		—		—		46,804		46,804
Total assets	$	1,954	$	—	$	—	$	46,804	$	48,758

Liabilities:
Derivative instruments4	—		2,411		—		—		2,411
Total liabilities	$	—	$	2,411	$	—	$	—	$	2,411

2Certain investments qualify for the NAV practical expedient in ASC 820. Investments in equity consist of interests in funds and equity securities without readily determinable fair values. To determine the classification of investments in equity, 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, 2024 and December 31, 2023 meet the definition of equity securities without readily determinable fair values. The Company concluded that the interests held at December 31, 2024 and December 31, 2023 qualify for the NAV practical expedient. Any increases or decreases in fair value are recognized in net income in the period.

3Represents the fair value of highly liquid investments with maturities greater than three months, a minimum "A-" rated fixed term deposit and are based on quoted market prices.

4Represents the fair value of the interest rate caps and the interest rate swap.

Fair Value, Assets Measured on Recurring Basis

he fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows:


	December 31, 2024
	Level 1		Level 2		Level 3		Other1		Total
	(in thousands)
Assets:
Investments in equity1,2	$	—	$	—	$	—	$	54,448	$	54,448
Total assets	$	—	$	—	$	—	$	54,448	$	54,448

1Excludes investments in equity securities recorded at cost of $3.5 million which do not qualify for the NAV practical expedient.

As at December 31, 2023, 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:


	December 31, 2023
	Level 1		Level 2		Level 3		Other1		Total
	(in thousands)
Assets:
Available for sale securities3	$	1,954	$	—	$	—	$	—	$	1,954
Investments in equity2	—		—		—		46,804		46,804
Total assets	$	1,954	$	—	$	—	$	46,804	$	48,758

Liabilities:
Derivative instruments4	—		2,411		—		—		2,411
Total liabilities	$	—	$	2,411	$	—	$	—	$	2,411

3Represents the fair value of highly liquid investments with maturities greater than three months, a minimum "A-" rated fixed term deposit and are based on quoted market prices.

4Represents the fair value of the interest rate caps and the interest rate swap.

Cover	12 Months Ended
Cover	Dec. 31, 2024 shares
Document Information [Line Items]
Document Type	20-F
Document Registration Statement	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2024
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
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)	80,756,860
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 Financial Statement Error Correction [Flag]	false
Document Accounting Standard	U.S. GAAP
Entity Shell Company	false
Amendment Flag	false
Document Fiscal Year Focus	2024
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	Nigel Clerkin
Contact Personnel Email Address	Nigel.Clerkin@iconplc.com
Country Region	353
City Area Code	1
Local Phone Number	291-2000

Operating Leases

12 Months Ended

Dec. 31, 2024

Leases [Abstract]

Operating Leases

Lease costs recorded under operating leases for the years ended December 31, 2024, 2023 and 2022 were as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Operating lease costs	$	46,466	$	46,820	$	53,880
Income from sub-leases	(1,614)		(1,103)		(1,165)
Net operating lease costs	$	44,852	$	45,717	$	52,715

Of the total cost of $44.9 million incurred in the year ended December 31, 2024 (December 31, 2023, $45.7 million; December 31, 2022, $52.7 million), $37.2 million (December 31, 2023, $37.9 million; December 31, 2022, $48.3 million) is recorded within selling, general and administration costs and $7.7 million (December 31, 2023, $7.8 million; December 31, 2022, $4.4 million) is recorded within direct costs.

Right-of-use assets obtained, in exchange for lease obligations, during the years ended December 31, 2024 and December 31, 2023 totaled $64.8 million and $37.7 million, respectively.

During the years ended December 31, 2024, 2023 and 2022, impairments of operating right-of-use assets were recognized within restructuring charges for $13.8 million, $8.7 million, and $28.4 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, 2024 were 6.56 years and 4.01%, respectively. The weighted average remaining lease term and weighted-average discount rate at December 31, 2023 were 6.72 years and 3.29%, respectively.

Future minimum lease payments under non-cancelable leases as of December 31, 2024 were as follows:


Minimum rental payments	(in thousands)
2025	$	42,931
2026	38,445
2027	31,257
2028	24,156
2029	17,838
Thereafter	45,047
Total future minimum lease payments	199,674
Lease imputed interest	(22,806)
Total	$	176,868

Operating lease liabilities are presented as current and non-current. As at December 31, 2024, operating lease liabilities of $36.8 million have been included in Other liabilities (December 31, 2023: $36.4 million) and $140.1 million million have been classified as Non-current Lease Liabilities (December 31, 2023: $126.3 million).

Summary of Significant accounting policies (Policies)

12 Months Ended

Dec. 31, 2024

Accounting Policies [Abstract]

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

Transaction and integration-related expenses

Foreign currencies and translation of subsidiaries


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Amounts (credited) / charged	$	(18,085)	$	12,916	$	(25,997)

Revenue recognition

Clinical trial service revenue

Laboratory services revenue

Contracting services revenue

Consulting services revenue

Data services revenue

Commissions

Reimbursable expenses and Direct costs

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.

Investment in debt, equity and other

Investments in debt, equity and other

Available for sale investments

Long term investments

Investments in equity which do not qualify for the NAV practical expedient are measured at cost, less impairment.

Equity method investments

Accounts receivable, net and unbilled revenue

Accounts receivable early payment discounting

Property, plant and equipment


			Estimated Useful Life
Buildings			40 years
Computer equipment and software			2 - 8 years
Office furniture and fixtures			8 years
Laboratory equipment			5 years
Motor vehicles			5 years

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 their estimated useful lives, as set forth in the table below:


			Estimated Useful Life
Customer relationships			8 - 23 years
Order backlog			3 - 5 years
Trade names			3 years
Patient database			7 years
Technology assets			5 years

The Company periodically assesses the estimated 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

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

Business combinations

Transaction and integration-related expenses

Restructuring

Net income per ordinary share

Impact of recently issued or adopted accounting standards

Impact of Recently Issued or Adopted Accounting Standards

Accounting pronouncements recently adopted

Accounting pronouncements issued but not adopted as of December 31, 2024

The following accounting pronouncements have been issued, but not yet adopted, as of December 31, 2024:

Accumulated Other Comprehensive Loss (Tables)

12 Months Ended

Dec. 31, 2024

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

Schedule of Accumulated Other Comprehensive Income


	Year ended
	December 31, 2024		December 31, 2023
	(in thousands)
Currency translation adjustments	$	(234,075)	$	(149,148)
Remeasurement of retirement benefit obligations	1,726		7,803
Gain / (loss) on cash flow hedge	2,420		(2,161)
Total	$	(229,929)	$	(143,506)

Bank Credit Lines, Loan Facilities and Notes (Tables)

12 Months Ended

Dec. 31, 2024

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

The Company had the following debt outstanding as of December 31, 2024 and December 31, 2023:


		Interest rate as of				Principal amount as of
	Maturity Date	December 31, 2024		December 31, 2023		December 31, 2024		December 31, 2023
						(in thousands)
Senior Secured Term Loan	July 2028	6.329	%	7.860	%	$	946,450	$	3,251,213
Senior Secured Notes (the "2026 Notes")	July 2026	2.875	%	2.875	%	500,000		500,000
Senior Secured Revolving Loan		—		6.720	%	—		55,000
Senior Secured Notes (the "2027 Notes")*	May 2027	5.809	%	—		750,000		—
Senior Secured Notes (the "2029 Notes")*	May 2029	5.849	%	—		750,000		—
Senior Secured Notes (the "2034 Notes")*	May 2034	6.000	%	—		500,000		—
Total debt						3,446,450		3,806,213
Less current portion of debt						(29,762)		(110,150)
Total long-term debt						3,416,688		3,696,063
Less debt issuance costs and debt discount						(20,290)		(30,624)
Total long-term debt, net						$	3,396,398	$	3,665,439

*Issued May 8, 2024


	Drawdown		Repayment		Closing Balance
	(in thousands)
Quarter 1, 2023	$	180,000	$	(100,000)	$	80,000
Quarter 2, 2023	50,000		(80,000)		50,000
Quarter 3, 2023	75,000		(50,000)		75,000
Quarter 4, 2023	65,000		(85,000)		55,000
Total drawdown / (repayments) in 2023	370,000		(315,000)
Quarter 1, 2024	50,000		(55,000)		50,000
Quarter 2, 2024	143,000		(193,000)		—
Quarter 3, 2024	50,000		(50,000)		—
Quarter 4, 2024	75,000		(75,000)		—
Total drawdown / (repayments) in 2024	$	318,000	$	(373,000)

Schedule of Financing Cost


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Interest expense on drawn facilities	$	206,198	$	311,019	$	209,189
Amortization of merger related financing fees	23,533		16,402		17,749

Other financing costs*	7,506		9,278		2,793
Total financing costs	$	237,237	$	336,699	$	229,731

*Includes costs associated with the senior secured revolving loan facility.

Schedule of Maturities of Long-term Debt

As of December 31, 2024, the contractual maturities of the Company's debt obligations were as follows:


Maturities of debt:	(in thousands)
2025		$	29,762
2026		529,762
2027		779,762
2028		857,164
2029 and thereafter		1,250,000
Total		$	3,446,450

Schedule of Principal Payments on Debt Instrument

Principal repayments, comprising mandatory and voluntary repayments, during the year ended December 31, 2024 and December 31, 2023 were as follows:


Principal repayments	December 31, 2024		December 31, 2023
	(in thousands)
Quarter 1	$	(275,000)	$	(250,000)
Quarter 2	(2,014,882)		(150,000)
Quarter 3	(7,441)		(300,000)
Quarter 4	(7,440)		(250,000)
Total repayments	$	(2,304,763)	$	(950,000)

- 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

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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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+ Details

Income Taxes

12 Months Ended

Dec. 31, 2024

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, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Ireland	$	736,374	$	624,642	$	432,963
United States	(304,546)		(352,532)		(270,440)
Other	437,356		352,357		405,328
Income before income tax expense	$	869,184	$	624,467	$	567,851

The components of income tax expense are as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
Income tax expense:	(in thousands)
Current tax (benefit)/expense:
Ireland	$	118,255	$	80,427	$	53,248
United States	(45,307)		(42,428)		60,753
Other	105,304		59,153		70,395
Total current tax expense	178,252		97,152		184,396

Deferred tax (benefit)/expense:
Ireland	(26,663)		45,253		(6,166)
United States	(69,493)		(143,323)		(118,475)
Other	(4,386)		12,667		(344)
Total deferred tax benefit	(100,542)		(85,403)		(124,985)

Income tax expense	77,710		11,749		59,411

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

Currency impact on long term funding	1,728		(3,903)		7,211

Retirement benefit obligations	(895)		—		—
Cash flow hedge	647		301		—
Total	$	79,190	$	8,147	$	66,622

Ireland's statutory trading income tax rate, the rate of our country of domicile, 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, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Taxes at Irish statutory rate of 12.5% (2023:12.5%; 2022:12.5%)	$	108,648	$	78,058	$	70,980
Rate differential from amortization of intangible assets	(48,240)		(71,223)		(59,330)
Global Minimum Tax	16,719		—		—
Foreign and other income taxed at higher rates	49,703		35,778		52,464
Research & development tax incentives	(3,041)		(3,868)		(2,608)
Movement in valuation allowance	(5,279)		(1,068)		(777)
Effects of change in tax rates	25,691		3,154		(300)
(Decrease)/ increase in unrecognized tax benefits	(59,456)		(54,347)		8,392
Investor tax expense on foreign subsidiary earnings	(7,995)		39,165		—
Impact of stock compensation	(9,385)		(11,487)		(8,756)

Other and non-deductible expenses	10,345		(2,413)		(654)
Income tax expense	$	77,710	$	11,749	$	59,411

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


	December 31, 2024		December 31, 2023
Deferred tax liabilities:	(in thousands)
Property, plant and equipment	$	2,869	$	7,547
Operating right-of-use-assets	15,633		16,108
Goodwill	43,390		39,014
Intangible assets	901,731		950,055
Investments in foreign subsidiaries	34,983		52,408
Other	3,887		7,982
Total deferred tax liabilities recognized	1,002,493		1,073,114

Deferred tax assets:
Operating loss and tax credits carryforwards	164,904		124,150
Property, plant and equipment	7,869		9,082
Operating lease liabilities	21,503		20,190
Intangible assets	45		2,166
Stock compensation	14,309		17,605
Other liabilities	78,428		84,928
Unearned revenue	10,364		23,748
Other	6,298		8,774
Total deferred tax assets	303,720		290,643
Valuation allowance for deferred tax assets	(38,955)		(42,967)
Deferred tax assets recognized	264,765		247,676
Overall net deferred tax liability	$	(737,728)	$	(825,438)

At December 31, 2024 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 $15.6 million.

At December 31, 2024 U.S. subsidiaries had U.S. federal and state net operating loss ("NOL") carryforwards of approximately $8.0 million and $277.8 million, respectively. These NOLs are available for offset against future taxable income and the expiry dates are shown in the table below. The subsidiaries' ability to use the U.S. federal NOL carryforwards is limited on an annual basis due to change of ownership in 2014, 2017, 2019 and 2024 as defined by Section 382 of the Internal Revenue Code of 1986, as amended and expire between 2025 - 2037. The U.S. state NOL carryforwards are restricted by the state/entity in which they arose. As of December 31, 2024, U.S subsidiaries also had disallowed interest carried forward of $317.0 million (December 31, 2023: $204.0 million) that can be carried forward indefinitely. The increase of $113.0 million was recognized within the income tax expense. 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)
2025-2038	$	8,035	$	262,170
2039-2043	—		6,057
Indefinite	—		9,601
	$	8,035	$	277,828

In addition, we also have general business tax credit carryforwards of approximately $1.0 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, 2024 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 $42.4 million. In addition, at December 31, 2024 those subsidiaries had tax credit carryforwards for income tax purposes that may be carried forward for up to 30 years, available to offset against future tax liabilities, if any, of $2.7 million.

The valuation allowance at December 31, 2024 was $39.0 million (December 31, 2023; $43.0 million). The net change in the total valuation allowance was a decrease of $4.0 million during 2024 and a decrease of $0.4 million during 2023. Of the total decrease of $4.0 million in 2024, an increase of $2.0 million was in respect of an acquired entity, $5.3 million decrease was recognized within income tax expense and a decrease of $0.7 million was recognized in Other Comprehensive Income. Of the total decrease of $0.4 million in 2023, $1.1 million was recognized within income tax expenses and an increase of $0.7 million was recognized in Other Comprehensive Income.

The valuation allowances at December 31, 2024 and December 31, 2023 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 tax planning 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 $35.0 million (2023: $52.4 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 recently implemented a participation exemption in respect of distributions from foreign subsidiaries in EEA/treaty countries, in addition to the foreign tax credit regime 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, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Unrecognized tax benefits at start of year	$	160,016	$	217,584	$	202,065
Increase related to prior year tax positions	7,374		1,161		16,098
Decrease related to prior year tax positions	(2,525)		(918)		(5,442)
Increase related to current year tax positions	2,171		4,552		5,701
Lapse of statute of limitations	(65,417)		(62,363)		(838)
Unrecognized tax benefits at end of year	$	101,619	$	160,016	$	217,584

The relevant statute of limitations for unrecognized tax benefits totaling $61.6 million could potentially expire during 2025.

Included in the balance of total unrecognized tax benefits at December 31, 2024 were potential benefits of $101.6 million, which if recognized, would affect the effective rate on income from continuing operations. The balance of total unrecognized tax benefits at December 31, 2023 and December 31, 2022 included potential benefits which, if recognized, would affect the effective rate of income tax from continuing operations of $160.0 million and $217.6 million respectively.

Interest and penalties recognized during the year ended December 31, 2024 amounted to a net charge of $1.9 million (2023: $4.2 million, 2022: $7.1 million) and are included within the income tax expense. Total accrued interest and penalties as of December 31, 2024 and December 31, 2023 were $24.2 million and $27.1 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, 2020, December 31, 2021, December 31, 2022, December 31, 2023 and December 31, 2024. In the United States, tax periods open to audit include the years ended December 31, 2021, December 31, 2022, December 31, 2023 and December 31, 2024. During such audits, local tax authorities may challenge the positions taken by us in our tax returns.

- Definition

The entire disclosure for income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

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+ Details

Restructuring charges - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 92,123	$ 45,390	$ 31,143
Severance costs	74,500	34,100	2,700
Other restructuring costs	17,600	11,300	28,400
Impairment of operating right-of-use assets and related property, plant and equipment	15,731	8,686	28,767
Restructuring reserve	31,474	6,999	6,022
Workforce reduction and onerous contract cost
Restructuring Cost and Reserve [Line Items]
Impairment of operating right-of-use assets and related property, plant and equipment	15,700	8,700	28,400
Onerous contract provision	1,900	2,600	$ 0
Personnel related liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	27,700	4,000
Facility liability
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	3,800	3,000
Restructuring reserve, current	1,400	1,000
Restructuring reserve, noncurrent	$ 2,400	$ 2,000

Derivatives - Narrative (Details) $ in Millions	12 Months Ended
Derivatives - Narrative (Details) $ in Millions	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Nov. 29, 2022 USD ($) instrument
Derivative [Line Items]
Percentage of debt hedged by interest rate derivatives	73.00%	13.00%
Other comprehensive income (loss), cash flow hedge, gain (loss), before reclassification and tax	$ 5.0	$ 1.6
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, before tax	$ 13.9	$ 2.4
Interest Rate Caps \| Total derivatives designated as hedging instruments
Derivative [Line Items]
Number of interest rate derivatives held \| instrument			2
Derivative, notional amount			$ 2,101.0
Derivative, fixed interest rate			0.42%
Derivative, variable interest rate, reference rate in excess of			4.75%
Interest Rate Swap
Derivative [Line Items]
Derivative, notional amount			$ 1,101.0
Derivative, fixed interest rate			3.40%

Related Parties	12 Months Ended
Related Parties	Dec. 31, 2024
Related Party Transactions [Abstract]
Related Parties	Related Parties During the year, subsidiaries of the Company earned revenue of $0.3 million (December 31, 2023: $0.2 million) from Corvus Pharmaceuticals. Dr. Linda Grais serves as a Director and shareholder of Corvus Pharmaceuticals. At December 31, 2024, $0.1 million (December 31, 2023: $0.1 million) was noted as due from Corvus Pharmaceuticals . During the year, subsidiaries of the Company earned revenue of $nil (December 31, 2023: $0.05 million) from Afimmune Limited. Dr. John Climax is Chief Executive Officer and a Director and shareholder of Afimmune Limited. At December 31, 2024, $0.1 million was noted as due from Afimmune Limited (December 31, 2023: $0.05 million).

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/850/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-6

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

+ Details

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive income (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Currency translation adjustments	$ (234,075)	$ (149,148)
Remeasurement of retirement benefit obligations	1,726	7,803
Gain / (loss) on cash flow hedge	2,420	(2,161)
Total	$ (229,929)	$ (143,506)

- Definition

Amount, after tax, of accumulated increase (decrease) in equity from transaction and other event and circumstance from nonowner source.

+ References + Details

Bank Credit Lines, Loan Facilities and Notes - Schedule of Long-term Debt Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2024	May 08, 2024	Dec. 31, 2023	Jul. 01, 2021
Debt Instrument [Line Items]
Total debt	$ 3,446,450		$ 3,806,213
Less current portion of debt	(29,762)		(110,150)
Total long-term debt	3,416,688		3,696,063
Less debt issuance costs and debt discount	(20,290)		(30,624)
Total long-term debt, net	$ 3,396,398		$ 3,665,439
Senior Secured Term Loan \| Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	6.329%		7.86%	1.00%
Total debt	$ 946,450		$ 3,251,213
Senior Secured Notes (the "2026 Notes") \| Senior Secured Notes (the "2026 Notes")
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	2.875%		2.875%	2.875%
Total debt	$ 500,000		$ 500,000
Senior Secured Notes (the "2026 Notes") \| Senior Secured Notes (the "2027 Notes")*
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	5.809%	5.809%	0.00%
Total debt	$ 750,000		$ 0
Senior Secured Notes (the "2026 Notes") \| Senior Secured Notes (the "2029 Notes")*
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	5.849%	5.849%	0.00%
Total debt	$ 750,000		$ 0
Senior Secured Notes (the "2026 Notes") \| Senior Secured Notes (the "2034 Notes")*
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	6.00%	6.00%	0.00%
Total debt	$ 500,000		$ 0
Senior Secured Revolving Loan \| Senior Secured Revolving Loan
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	0.00%		6.72%
Senior Secured Revolving Loan \| Senior Secured Revolving Loan \| Senior Secured Revolving Loan
Debt Instrument [Line Items]
Total debt	$ 0		$ 55,000

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flows provided by operating activities:
Net income	$ 791,474	$ 612,335	$ 505,304
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	488,500	585,950	569,513
Impairment of operating right-of-use assets and related property, plant and equipment	15,731	8,686	28,767
Reduction in carrying value of operating right-of-use assets	39,787	41,546	45,215
Loss on equity method investments	0	383	3,136
Acquisition-related gain	0	(6,160)	0
Amortization of financing costs and debt discount	23,533	16,402	17,749
Stock compensation expense	45,870	55,667	70,523
Deferred tax benefit	(100,542)	(85,403)	(124,985)
Unrealized foreign exchange movements	6,911	19,706	(13,009)
Other non-cash items	31,900	24,332	11,324
Changes in operating assets and liabilities:
Accounts receivable	349,309	(83,296)	(420,695)
Unbilled revenue	(339,921)	4,716	(332,592)
Unearned revenue	(37,743)	134,566	192,944
Other net assets	(28,157)	(168,403)	10,121
Net cash provided by operating activities	1,286,652	1,161,027	563,315
Cash flows used in investing activities:
Purchase of property, plant and equipment	(168,060)	(140,692)	(142,160)
Purchase of subsidiary undertakings (net of cash acquired)	(84,159)	(71,766)	0
Movement of available for sale investments	0	(241)	(1)
Proceeds from investments in equity	2,690	0	1,906
Purchase of investments in equity	(17,261)	(13,954)	(5,612)
Net cash used in investing activities	(266,790)	(226,653)	(145,867)
Cash flows used in financing activities:
New Notes issue costs	(12,679)	0	0
Drawdown of credit lines and loan facilities	2,317,480	370,000	75,000
Repayment of credit lines and loan facilities	(2,677,763)	(1,265,000)	(875,000)
Proceeds from exercise of equity compensation	36,187	50,973	35,844
Share issue costs	(22)	(16)	(17)
Repurchase of ordinary shares	(499,998)	0	(99,983)
Share repurchase costs	(388)	0	(17)
Net cash used in financing activities	(837,183)	(844,043)	(864,173)
Effect of exchange rate movements on cash	(21,996)	(997)	(16,720)
Net increase/(decrease) in cash and cash equivalents	160,683	89,334	(463,445)
Cash and cash equivalents at beginning of year	378,102	288,768	752,213
Cash and cash equivalents at end of year	$ 538,785	$ 378,102	$ 288,768

Income Taxes - Reconciliation of Beginning and Ending Amount of Total Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Unrecognized Tax Benefits [Roll Forward]
Unrecognized tax benefits at start of year	$ 160,016	$ 217,584	$ 202,065
Increase related to prior year tax positions	7,374	1,161	16,098
Decrease related to prior year tax positions	(2,525)	(918)	(5,442)
Increase related to current year tax positions	2,171	4,552	5,701
Lapse of statute of limitations	(65,417)	(62,363)	(838)
Unrecognized tax benefits at end of year	$ 101,619	$ 160,016	$ 217,584

Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	4 Months Ended	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2024	Dec. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Aug. 19, 2024	Jan. 09, 2024	Oct. 02, 2023
Indefinite-lived Intangible Assets [Line Items]
Amortization of intangible assets			$ 350.3		$ 459.9	$ 463.1
Customer relationships \| Minimum
Indefinite-lived Intangible Assets [Line Items]
Amortization period		8 years	8 years	8 years
Customer relationships \| Maximum
Indefinite-lived Intangible Assets [Line Items]
Amortization period		23 years	23 years	23 years
Order backlog
Indefinite-lived Intangible Assets [Line Items]
Decrease in amortisation			$ 500.0
Order backlog \| Minimum
Indefinite-lived Intangible Assets [Line Items]
Amortization period		3 years	3 years	3 years
Order backlog \| Maximum
Indefinite-lived Intangible Assets [Line Items]
Amortization period		5 years	5 years	5 years
Technology assets
Indefinite-lived Intangible Assets [Line Items]
Amortization period		5 years	5 years	5 years
Trade names & brands
Indefinite-lived Intangible Assets [Line Items]
Decrease in amortisation			$ 202.0
Amortization period		3 years	3 years	3 years
HumanFirst Inc
Indefinite-lived Intangible Assets [Line Items]
Amortization of intangible assets				$ 2.0
Value of intangible assets acquired								$ 9.9
Amortization period								5 years
KCR S.A Group
Indefinite-lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 1.3
Value of intangible assets acquired							$ 45.1
KCR S.A Group \| Customer relationships
Indefinite-lived Intangible Assets [Line Items]
Value of intangible assets acquired							$ 41.4
Amortization period							13 years
KCR S.A Group \| Order backlog
Indefinite-lived Intangible Assets [Line Items]
Value of intangible assets acquired							$ 3.7
Amortization period							5 years
Biotel Research LLC
Indefinite-lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 1.5		$ 6.1
Value of intangible assets acquired									$ 36.4
Biotel Research LLC \| Minimum
Indefinite-lived Intangible Assets [Line Items]
Amortization period									3 years
Biotel Research LLC \| Maximum
Indefinite-lived Intangible Assets [Line Items]
Amortization period									16 years
Biotel Research LLC \| Customer relationships
Indefinite-lived Intangible Assets [Line Items]
Value of intangible assets acquired									$ 12.5
Biotel Research LLC \| Order backlog
Indefinite-lived Intangible Assets [Line Items]
Value of intangible assets acquired									3.9
Biotel Research LLC \| Technology assets
Indefinite-lived Intangible Assets [Line Items]
Value of intangible assets acquired									$ 20.0

Accumulated Other Comprehensive Loss

12 Months Ended

Dec. 31, 2024

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

Accumulated Other Comprehensive Loss


	Year ended
	December 31, 2024		December 31, 2023
	(in thousands)
Currency translation adjustments	$	(234,075)	$	(149,148)
Remeasurement of retirement benefit obligations	1,726		7,803
Gain / (loss) on cash flow hedge	2,420		(2,161)
Total	$	(229,929)	$	(143,506)

Property, Plant and Equipment, net

12 Months Ended

Dec. 31, 2024

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment, net

The carrying amount of Property, Plant and Equipment for the years ended December 31, 2024 and 2023 is as follows:


	December 31, 2024		December 31, 2023
Cost	(in thousands)
Land	$	3,724	$	3,724
Buildings	66,132		70,072
Computer equipment and software	689,979		550,119
Office furniture and fixtures	51,849		45,856
Laboratory equipment	55,111		56,217
Leasehold improvements	62,034		55,000
Motor vehicles	65		79

Total Cost	928,894		781,067
Less accumulated depreciation and asset write offs	(546,015)		(419,883)

Property, plant and equipment (net)	$	382,879	$	361,184

The depreciation expense recognized by the Company was $138.2 million, $126.1 million, and $106.4 million for the years ended December 31, 2024, 2023, and 2022, respectively.

The Company regularly updates its register of property, plant and equipment and during the year ended December 31, 2024 and the year ended December 31, 2023, certain fully depreciated assets were written off as they were no longer used by the Company.

Goodwill

12 Months Ended

Dec. 31, 2024

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill

The change in the carrying amount of goodwill for the years ended December 31, 2024 and 2023 is as follows:


	December 31, 2024		December 31, 2023
	(in thousands)
Opening balance	$	9,022,075	$	8,971,670
Current period acquisitions (note 6)	46,126		36,750
Foreign exchange movement	(16,791)		13,655
Closing balance	$	9,051,410	$	9,022,075

There were no impairment charges for the year ended December 31, 2024 or the year ended December 31, 2023.

Business Combinations - Narrative, Biotel Acquisition (Details) - USD ($) $ in Thousands		12 Months Ended
	Oct. 02, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Fair value of cash consideration		$ 84,159	$ 71,766	$ 0
Goodwill		$ 9,051,410	$ 9,022,075	$ 8,971,670
Biotel Research LLC
Business Acquisition [Line Items]
Fair value of cash consideration	$ 68,100
Cash acquired from acquisition	1,400
Intangible assets acquired	36,400
Goodwill	$ 23,400

- Definition

+ References

+ Details

Allowances for Credit Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Opening provision	$ 31,533	$ 20,562
Amounts used during the year	(24,887)	(13,358)
Amounts provided during the year	28,417	24,550
Foreign exchange	601	(221)
Closing provision	$ 35,664	$ 31,533

Business Segment and Geographical Information - Distribution of Net Revenue by Geographical Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Revenue	$ 8,281,676	$ 8,120,176	$ 7,741,386
Ireland
Segment Reporting Information [Line Items]
Revenue	2,793,045	2,377,104	1,984,567
Rest of Europe
Segment Reporting Information [Line Items]
Revenue	1,560,735	1,574,783	1,618,350
U.S.
Segment Reporting Information [Line Items]
Revenue	2,985,256	3,283,790	3,574,610
Other
Segment Reporting Information [Line Items]
Revenue	$ 942,640	$ 884,499	$ 563,859

- 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
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-41

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 4: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 5: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479941/924-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-5

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-30

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-40

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-4

+ Details

Business Combinations - Narrative, HumanFirst Acquisition (Details) - USD ($) $ in Thousands		12 Months Ended
	Jan. 09, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Purchase of subsidiary undertakings (net of cash acquired)		$ 84,159	$ 71,766	$ 0
Goodwill		9,051,410	$ 9,022,075	$ 8,971,670
HumanFirst Inc
Business Acquisition [Line Items]
Business combination, consideration transferred	$ 13,300
Payments to acquire businesses, net of cash acquired	7,800
Purchase of subsidiary undertakings (net of cash acquired)	11,800
Cash acquired from acquisition	4,000
Contingent consideration		$ 1,400
Goodwill	2,700
Intangible assets acquired	$ 9,900

- Definition

+ References

+ Details

Subsequent Events (Details) - Subsequent event $ in Millions	Feb. 18, 2025 USD ($)
Subsequent Event [Line Items]
Stock repurchase program, authorized amount	$ 1,000.0
February 2025
Subsequent Event [Line Items]
Stock repurchase program, authorized amount	$ 750.0

Income Taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Current tax (benefit)/expense:
Current tax expense	$ 178,252	$ 97,152	$ 184,396
Deferred tax (benefit)/expense:
Deferred tax (benefit)/expense	(100,542)	(85,403)	(124,985)
Income tax expense	77,710	11,749	59,411
Income tax expense was allocated to the following components of other comprehensive income:
Currency impact on long term funding	1,728	(3,903)	7,211
Retirement benefit obligations	(895)	0	0
Cash flow hedge	647	301	0
Total	79,190	8,147	66,622
Ireland
Current tax (benefit)/expense:
Current tax expense	118,255	80,427	53,248
Deferred tax (benefit)/expense:
Deferred tax (benefit)/expense	(26,663)	45,253	(6,166)
United States
Current tax (benefit)/expense:
Current tax expense	(45,307)	(42,428)	60,753
Deferred tax (benefit)/expense:
Deferred tax (benefit)/expense	(69,493)	(143,323)	(118,475)
Other
Current tax (benefit)/expense:
Current tax expense	105,304	59,153	70,395
Deferred tax (benefit)/expense:
Deferred tax (benefit)/expense	$ (4,386)	$ 12,667	$ (344)

Bank Credit Lines, Loan Facilities and Notes

12 Months Ended

Dec. 31, 2024

Debt Disclosure [Abstract]

Bank credit lines, loan facilities and notes

The Company had the following debt outstanding as of December 31, 2024 and December 31, 2023:


		Interest rate as of				Principal amount as of
	Maturity Date	December 31, 2024		December 31, 2023		December 31, 2024		December 31, 2023
						(in thousands)
Senior Secured Term Loan	July 2028	6.329	%	7.860	%	$	946,450	$	3,251,213
Senior Secured Notes (the "2026 Notes")	July 2026	2.875	%	2.875	%	500,000		500,000
Senior Secured Revolving Loan		—		6.720	%	—		55,000
Senior Secured Notes (the "2027 Notes")*	May 2027	5.809	%	—		750,000		—
Senior Secured Notes (the "2029 Notes")*	May 2029	5.849	%	—		750,000		—
Senior Secured Notes (the "2034 Notes")*	May 2034	6.000	%	—		500,000		—
Total debt						3,446,450		3,806,213
Less current portion of debt						(29,762)		(110,150)
Total long-term debt						3,416,688		3,696,063
Less debt issuance costs and debt discount						(20,290)		(30,624)
Total long-term debt, net						$	3,396,398	$	3,665,439

*Issued May 8, 2024

The Company incurred interest costs from various financing arrangements during the years ended December 31, 2024, December 31, 2023 and December 31, 2022 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, 2024, December 31, 2023 and December 31, 2022, the Company expensed $23.5 million, $16.4 million and $17.7 million of transaction related financing costs, inclusive of the amortization of financing fees which were previously capitalized.


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Interest expense on drawn facilities	$	206,198	$	311,019	$	209,189
Amortization of merger related financing fees	23,533		16,402		17,749

Other financing costs*	7,506		9,278		2,793
Total financing costs	$	237,237	$	336,699	$	229,731

*Includes costs associated with the senior secured revolving loan facility.

As of December 31, 2024, the contractual maturities of the Company's debt obligations were as follows:


Maturities of debt:	(in thousands)
2025		$	29,762
2026		529,762
2027		779,762
2028		857,164
2029 and thereafter		1,250,000
Total		$	3,446,450

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; the 2026 Notes and the New Notes.

The New Notes

On May 8, 2024, ICON Investments Six Designated Activity Company (the "Issuer"), a wholly-owned subsidiary of ICON plc, issued $2 billion senior secured notes ("the New Notes"). The New Notes were issued in aggregate principal amounts of: $750 million 5.809% Senior Secured Notes due 2027 (the "2027 Notes"), $750 million 5.849% Senior Secured Notes due 2029 (the "2029 Notes") and $500 million 6.000% Senior Secured Notes due 2034 (the "2034 Notes").

The Company paid an underwriting discount of $6.8 million on the New Notes being: 0.250% of the principal amount of the 2027 Notes, 0.350% of the principal amount of the 2029 Notes and 0.450% of the 2034 Notes. Further, the 2034 Notes were issued at a discount of $0.5 million (issued at 99.896% of par).

The proceeds from the issuance were used to repay a portion of the senior secured term loan outstanding under the Senior Secured Credit Facilities and to pay fees, costs and expenses related to the offering.

Interest on the New Notes is payable on May 8 and November 8 of each year, having commenced on November 8, 2024. Unless previously redeemed, the 2027 Notes will mature on May 8, 2027, the 2029 Notes will mature on May 8, 2029 and the 2034 Notes will mature on May 8, 2034.

The New Notes are guaranteed on a senior secured basis by ICON and its existing and future wholly owned subsidiaries, in each case that guarantee the obligations under our Senior Secured Credit Facilities and the 2026 Notes. The New Notes are the senior secured obligation of the Issuer and the Guarantors and rank equally in right of payment to all of the Issuer’s and Guarantors’ existing and future senior debt and senior in right of payment to all of the Issuer's and Guarantors' existing and future subordinated debt. The New Notes and the guarantees are secured on a first-lien basis by substantially all of the existing and future assets of the Issuer and the Guarantors that also secure the Issuer’s and the Guarantors’ obligations under the Senior Secured Credit Facilities and the 2026 Notes on a pari passu basis, subject to permitted liens, and the liens on the collateral securing the New Notes rank equally in priority with the liens on the collateral securing borrowings and guarantees under the Senior Secured Credit Facilities, the 2026 Notes and any other future pari passu first lien indebtedness.

Senior Secured Credit Facilities

On July 1, 2021, the Company completed the acquisition of PRA Health Sciences, Inc. ("PRA") by means of a merger whereby Indigo Merger Sub, Inc., a Delaware corporation and subsidiary of ICON, merged with and into PRA, the parent of the PRA Health Sciences ("the Merger"). In conjunction with the completion of the Merger, 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"). On May 2, 2023, the Company agreed with its lenders to increase the aggregate principal amount of the senior secured revolving loan facility from $300 million to $500 million. The Senior Secured Credit Facilities and the 2026 Notes were issued at a discount of $27.6 million.

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 plus an applicable margin which is dependent on the Company's net leverage ratio. At December 31, 2024, the applicable margin is 2.0% (which reflects the Third Amendment). The senior secured term loan facility is subject to a floor of 0.50%.

Reflecting the Third Amendment, 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 0.45%, 0.10% or –% based on the Company’s current corporate family rating assigned by S&P of BB (or lower), BB+ or BBB- (or higher), respectively, or (ii) Term SOFR plus an applicable margin of 1.45%, 1.10%, 0.85%, 0.65%, or 0.50% based on the Company’s current corporate family rating assigned by S&P of BB (or lower), BB+, BBB-, BBB or BBB+ (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.

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 2026 Notes and the New Notes subject to other permitted liens. The Company is permitted to make prepayments on the senior secured term loan without penalty.

Principal repayments, comprising mandatory and voluntary repayments, during the year ended December 31, 2024 and December 31, 2023 were as follows:


Principal repayments	December 31, 2024		December 31, 2023
	(in thousands)
Quarter 1	$	(275,000)	$	(250,000)
Quarter 2	(2,014,882)		(150,000)
Quarter 3	(7,441)		(300,000)
Quarter 4	(7,440)		(250,000)
Total repayments	$	(2,304,763)	$	(950,000)

The voluntary repayments made during the year resulted in an accelerated charge associated with previously capitalized fees of $16.9 million (December 31, 2023: $7.9 million).

During the year ended December 31, 2024, the Company drew down $318.0 million (December 31, 2023: $370.0 million) of the senior secured revolving loan facility and repaid $373.0 million (December 31, 2023: $315.0 million) as shown below. As at December 31, 2024, $nil (December 31, 2023: $55.0 million) was drawn under the senior secured revolving loan facility.


	Drawdown		Repayment		Closing Balance
	(in thousands)
Quarter 1, 2023	$	180,000	$	(100,000)	$	80,000
Quarter 2, 2023	50,000		(80,000)		50,000
Quarter 3, 2023	75,000		(50,000)		75,000
Quarter 4, 2023	65,000		(85,000)		55,000
Total drawdown / (repayments) in 2023	370,000		(315,000)
Quarter 1, 2024	50,000		(55,000)		50,000
Quarter 2, 2024	143,000		(193,000)		—
Quarter 3, 2024	50,000		(50,000)		—
Quarter 4, 2024	75,000		(75,000)		—
Total drawdown / (repayments) in 2024	$	318,000	$	(373,000)

2026 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 (the "2026 Notes") in a private offering (the “Offering”). The 2026 Notes will mature on July 15, 2026.

Fair Value of Debt

The estimated fair value of the Company’s debt was $3,469.2 million at December 31, 2024 and (December 31, 2023: $3,793.5 million). The fair values of the senior secured term loan facility, the 2026 Notes and the New Notes were determined based on Level 2 inputs, which are based on rates at which the debt is traded among financial institutions. The fair value of the senior secured revolving loan facility approximates its carrying value due to the short term duration.

Business Combinations	12 Months Ended
Business Combinations	Dec. 31, 2024
Business Combinations [Abstract]
Business Combinations	Business Combinations KCR S.A. Group Acquisition On August 19, 2024, the Company acquired the KCR S.A. Group ("KCR"), a CRO offering full service and functional services partnership ("FSP") clinical trial services, in exchange for consideration of $92.5 million. The acquisition of KCR has been accounted for as a business combination in accordance with ASC 805 'Business Combinations' ('ASC 805'). The net cash outflow was $76.4 million comprising cash payments of $88.1 million, net of cash acquired of $11.7 million. The fair value of contingent consideration was initially measured at the date of acquisition at $4.3 million and subsequently remeasured at $1.1 million. The final purchase price allocation resulted in the recognition of goodwill of $43.4 million and intangible assets of $45.1 million. Goodwill arising in connection with the acquisition is primarily attributable to the assembled workforce of KCR and the expected synergies of the acquisition. The goodwill recognized is not deductible for income tax purposes. Since August 19, 2024, KCR has earned revenue of $32.8 million and net income of $1.8 million which are included in the Group's Consolidated Statement of Operations for the year ended December 31, 2024. The pro-forma effect of the KCR acquisition if completed on January 1, 2023 would have resulted in revenue and net income for the fiscal year ended December 31, 2024 of $8,331.5 million and $792.5 million respectively and in revenue and net income for the fiscal year ended December 31, 2023 of $8,202.0 million and $613.3 million respectively. HumanFirst Inc. On January 9, 2024, the Company acquired HumanFirst Inc. ("HumanFirst"), a life sciences technology company in exchange for consideration of $13.3 million. The acquisition of HumanFirst has been accounted for as a business combination in accordance with ASC 805. The net cash outflow was $7.8 million comprising initial cash payments of $11.8 million, net of cash acquired of $4.0 million. Deferred consideration of $1.4 million remains unpaid as of December 31, 2024. The final purchase price allocation resulted in the recognition of goodwill of $2.7 million and a developed technology intangible asset of $9.9 million. Goodwill arising in connection with the acquisition is primarily attributable to the assembled workforce of HumanFirst. The goodwill recognized is not deductible for income tax purposes. BioTel Research LLC Acquisition On October 2, 2023, the Company acquired the entire outstanding equity interests of BioTel Research LLC (“BioTel”), a leading provider of medical imaging and cardiac safety monitoring services, from BioTelemetry Inc. in exchange for initial cash consideration of $68.1 million. Cash acquired amounted to $1.4 million. The final purchase price allocation resulted in the recognition of intangible assets of $36.4 million and goodwill of $23.4 million. Goodwill arising in connection with the acquisition is primarily attributable to the assembled workforce of BioTel and the expected synergies of the acquisition. The goodwill recognized is deductible for income tax purposes. 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 PRA Health Sciences ("the Acquisition" and "the Merger"). The Merger was accounted for as a business combination using the acquisition method of accounting in accordance with ASC 805. In the years ended December 31, 2024, December 31, 2023 and December 31, 2022, the Company incurred approximately $23.5 million, $16.4 million and $17.7 million of Merger-related financing fees which are included in the “Interest expense” line item in the Consolidated Statement of Operations. Oncacare Limited Acquisition On April 20, 2023, the Company completed the purchase of the majority investor's 51% majority voting share capital of Oncacare Limited ("Oncacare") for $5.1 million, such that Oncacare and its subsidiaries became wholly-owned subsidiaries of the ICON Group. The Oncacare acquisition resulted in goodwill of $13.4 million and also gave rise to an acquisition-related gain of $6.2 million. Transaction and Integration Costs In the years ended December 31, 2024, December 31, 2023, and December 31, 2022, the Company incurred net Merger, transaction and integration related expenses of $29.6 million, $44.2 million and $39.7 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. The costs consist of investment banking fees, advisory costs, professional fees, legal costs, retention agreements with employees, ongoing business combination and integration activities offset by the remeasurement of liability-classified contingent consideration.

Goodwill - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Goodwill - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill impairment charge	$ 0.0	$ 0.0

Derivatives (Tables)

12 Months Ended

Dec. 31, 2024

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivative Instruments in Statement of Financial Position, Fair Value

The fair value of the Company’s derivative financial instruments at December 31, 2024 amount to $nil. The fair value of the Company’s derivative financial instruments at December 31, 2023 on a gross basis, are summarized in the following table:


	December 31, 2023
		Asset		Liability		Notional
	(in thousands)
Interest Rate Caps		$	—	$	1,871	$	1,600,606
Interest Rate Swap		—		540		1,100,606
Total derivatives designated as hedging instruments		$	—	$	2,411	$	2,701,212

Investments - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Investments - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, cumulative amount advanced under subscription agreements	$ 13,100	$ 14,000
Increase (decrease) in equity securities, FV-NI	(3,300)	200
Carrying value of long-term investments in equity	54,400
Commitment to acquire future long-term investments	102,200
Equity securities, FV-NI, cost	3,500
Payments to acquire equity securities, FV-NI	1,500
Available for sale investments	$ 0	$ 1,954

Restructuring charges (Tables)

12 Months Ended

Dec. 31, 2024

Restructuring and Related Activities [Abstract]

Schedule of Restructuring Charges


	Year Ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Restructuring charges	$	92,123	$	45,390	$	31,143
Total	$	92,123	$	45,390	$	31,143

Schedule of Restructuring Reserve by Type of Cost


	Year Ended
	December 31, 2024		December 31, 2023
	(in thousands)
Opening provision	$	6,999	$	6,022
Charge during the year*	76,392		36,704
Utilization	(51,917)		(35,727)
Ending provision	$	31,474	$	6,999

*The charge for the year ended December 31, 2024 reflects the workforce reduction of $74.5 million (December 31, 2023: $34.1 million) and onerous contract costs of $1.9 million (December 31, 2023: $2.6 million).

Allowances for Credit Losses

12 Months Ended

Dec. 31, 2024

Accounts Receivable, after Allowance for Credit Loss [Abstract]

Allowance for Credit Losses

The Company does business with most major international pharmaceutical companies. Provision for credit losses at December 31, 2024 and December 31, 2023 comprises:


	December 31, 2024		December 31, 2023
	(in thousands)
Opening provision	$	31,533	$	20,562
Amounts used during the year	(24,887)		(13,358)
Amounts provided during the year	28,417		24,550
Foreign exchange	601		(221)
Closing provision	$	35,664	$	31,533

Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue	$ 8,281,676	$ 8,120,176	$ 7,741,386
Top client
Disaggregation of Revenue [Line Items]
Revenue	639,520	721,309	683,546
Clients 2-5
Disaggregation of Revenue [Line Items]
Revenue	1,431,873	1,453,508	1,506,087
Clients 6-10
Disaggregation of Revenue [Line Items]
Revenue	1,306,604	1,188,943	1,112,636
Clients 11-25
Disaggregation of Revenue [Line Items]
Revenue	1,774,160	1,743,539	1,585,739
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 3,129,519	$ 3,012,877	$ 2,853,378

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

- Definition

+ References

+ Details

Restructuring charges - Schedule of Restructuring Reserve by Type of Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Restructuring Reserve [Roll Forward]
Opening provision	$ 6,999	$ 6,022
Charge during the year*	76,392	36,704
Utilization	(51,917)	(35,727)
Ending provision	$ 31,474	$ 6,999

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2024
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 sixteen 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, 2024, 2023 and 2022 and future minimum rental commitments as of December 31, 2024.

Equity Incentive Schemes and Stock Compensation Charges - Schedule of Weighted Average Fair Values and Assumptions Used (Details) - Employee Stock Option - $ / shares	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value (USD per share)	$ 115.76	$ 85.12	$ 68.42
Assumptions:
Expected volatility (in percent)	36.00%	33.00%	31.00%
Dividend yield (in percent)	0.00%	0.00%	0.00%
Risk free interest rate (in percent)	4.20%	4.18%	1.86%
Expected life	4 years 3 months 18 days	5 years	5 years

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Property, Plant and Equipment, net (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Land	$ 3,724	$ 3,724
Buildings	66,132	70,072
Computer equipment and software	689,979	550,119
Office furniture and fixtures	51,849	45,856
Laboratory equipment	55,111	56,217
Leasehold improvements	62,034	55,000
Motor vehicles	65	79
Total Cost	928,894	781,067
Less accumulated depreciation and asset write offs	(546,015)	(419,883)
Property, plant and equipment (net)	$ 382,879	$ 361,184

Bank Credit Lines, Loan Facilities and Notes - Schedule of Movement on Debt Instrument (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Drawdown of credit lines and loan facilities									$ 2,317,480	$ 370,000	$ 75,000
Repayment of credit lines and loan facilities									(2,677,763)	(1,265,000)	$ (875,000)
Senior Secured Revolving Loan \| Senior Secured Revolving Loan \| Senior Secured Revolving Loan
Debt Instrument [Line Items]
Drawdown of credit lines and loan facilities	$ 75,000	$ 50,000	$ 143,000	$ 50,000	$ 65,000	$ 75,000	$ 50,000	$ 180,000	318,000	370,000
Repayment of credit lines and loan facilities	(75,000)	(50,000)	(193,000)	(55,000)	(85,000)	(50,000)	(80,000)	(100,000)	(373,000)	(315,000)
Total long-term debt, net	$ 0	$ 0	$ 0	$ 50,000	$ 55,000	$ 75,000	$ 50,000	$ 80,000	$ 0	$ 55,000

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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+ Details

- Definition

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

+ References + Details

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Schedule of Unbilled Services and Unearned Revenue or Payments on Account (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Unbilled services (unbilled revenue)	$ 1,286,274	$ 951,936
Change in unbilled services (unbilled revenue)	$ 334,338
Percentage change in unbilled services (unbilled revenue)	35.10%
Unearned revenue (payments on account)	$ (1,614,758)	(1,654,507)
Change in unearned revenue (payments on account)	$ 39,749
Percentage change in unearned revenue (payments on account)	(2.40%)
Net balance	$ (328,484)	$ (702,571)
Change in net balance	$ 374,087
Percentage change in net balance	(53.20%)

Share Capital	12 Months Ended
Share Capital	Dec. 31, 2024
Equity [Abstract]
Share Capital	Share Capital Holders 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)Share based payments During the year ended December 31, 2024, 311,040 options were exercised at an average exercise price of $116.31 per share for total proceeds of $36.2 million. During the year ended December 31, 2024, 120,458 ordinary shares were issued in respect of certain RSUs and 9,975 ordinary shares were issued in respect of PSUs previously awarded by the Company. During the year ended December 31, 2023, 535,705 options were exercised at an average exercise price of $95.12 per share for total proceeds of $51.0 million. During the year ended December 31, 2023, 188,800 ordinary shares were issued in respect of certain RSUs and 47,026 ordinary shares were issued in respect of PSUs previously awarded by the Company. During the year ended December 31, 2022, 348,286 options were exercised 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. (b)Share Repurchase Program The Company can acquire up to 10% of its outstanding ordinary shares (by way of redemption), in accordance with Irish law and the Company’s constitutional documents through open market share acquisitions. A resolution was passed at the Company’s Annual General Meeting (“AGM”) on July 23, 2024, which renewed the authorization for the Directors to purchase (buyback) up to 10% of the outstanding shares in the Company. On February 20, 2024, the Company's Board of Directors authorized a new buyback program of up to $500.0 million of the outstanding ordinary shares of the Company. On October 22, 2024, the Company's Board of Directors authorized an additional buyback program of up to $250.0 million of the outstanding ordinary shares of the Company. All ordinary shares that are redeemed under the buyback program will be canceled in accordance with the constitutional documents of the Company and the nominal value of these shares transferred to an undenominated capital fund as required under Irish Company law. During the year ended December 31, 2024, 2,179,699 ordinary shares were redeemed by the Company under this buyback program for a total consideration of $500.0 million. No ordinary shares were redeemed by the Company during the year ended December 31, 2023. During the year ended December 31, 2022, 420,530 ordinary shares were redeemed by the Company for total consideration of $100.0 million. 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 equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Paragraph 2
-Subparagraph (d)
-Publisher FASB
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147478448/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147480237/815-40-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
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-Paragraph 1
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
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Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Subparagraph (b)
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-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

+ Details

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) (Tables)

12 Months Ended

Dec. 31, 2024

Revenue from Contract with Customer [Abstract]

Schedule of Accounts Receivables and Unbilled Revenue, and Unbilled Services and Unearned Revenue

Accounts receivable and unbilled revenue are as follows:


	December 31, 2024		December 31, 2023
	(in thousands)
Billed services (accounts receivable)	$	1,437,653	$	1,821,855
Allowance for credit losses (note 5)	(35,664)		(31,533)
Accounts receivable (net)	1,401,989		1,790,322
Unbilled services (unbilled revenue)	1,286,274		951,936
Accounts receivable and unbilled revenue, net	$	2,688,263	$	2,742,258

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


	December 31, 2024		December 31, 2023		$ Change		% Change
	(in thousands, except percentages)
Unbilled services (unbilled revenue)	$	1,286,274	$	951,936	$	334,338	35.1	%
Unearned revenue (payments on account)	(1,614,758)		(1,654,507)		39,749		(2.4)	%
Net balance	$	(328,484)	$	(702,571)	$	374,087	(53.2)	%

Disaggregation of Revenue (Tables)

12 Months Ended

Dec. 31, 2024

Revenue from Contract with Customer [Abstract]

Schedule of Disaggregation of Revenue

Revenue disaggregated by customer concentration is as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Top client	$	639,520	$	721,309	$	683,546
Clients 2-5	1,431,873		1,453,508		1,506,087
Clients 6-10	1,306,604		1,188,943		1,112,636
Clients 11-25	1,774,160		1,743,539		1,585,739
Other	3,129,519		3,012,877		2,853,378
Total	$	8,281,676	$8,120,176		$7,741,386

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2024
Audit Information [Abstract]
Auditor firm ID	1116
Auditor name	KPMG
Auditor location	Dublin, Ireland

Equity Incentive Schemes and Stock Compensation Charges (Tables)

12 Months Ended

Dec. 31, 2024

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, 2024, December 31, 2023 and December 31, 2022:


	Options Granted Under Plans	Weighted Average Exercise Price
Outstanding at December 31, 2021	1,695,460	$	110.38
Granted	108,643	$	229.94
Exercised	(348,286)	$	102.87
Forfeited/expired	(77,698)	$	143.08
Outstanding at December 31, 2022	1,378,119	$	119.86
Granted	82,472	$	232.48
Exercised	(535,705)	$	95.12
Forfeited/expired	(22,080)	$	196.20
Outstanding at December 31, 2023	902,806	$	142.96
Granted	68,380	$	325.51
Exercised	(311,040)	$	116.31
Forfeited/expired	(37,854)	$	238.51
Outstanding at December 31, 2024	622,292	$	170.52
Vested and exercisable at December 31, 2024	426,497	$	135.39

Summary of Weighted Average Fair Values and Assumptions Used

The weighted average fair values and assumptions were as follows:


	Year Ended
	December 31, 2024			December 31, 2023			December 31, 2022
Weighted average fair value	$	115.76		$	85.12		$	68.42
Assumptions:
Expected volatility	36		%	33		%	31		%
Dividend yield	—		%	—		%	—		%
Risk-free interest rate	4.20		%	4.18		%	1.86		%
Expected life	4.3 years			5.0 years			5.0 years

Summary of RSU and PSU Activity

The following table summarizes RSU and PSU activity for the year ended December 31, 2024:


	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, 2023	105,256	$	226.29	621,011	$	218.27
Granted	48,626	$	325.51	258,345	$	313.41
Shares vested	(9,975)	$	177.38	(120,458)	$	223.29
Forfeited	(124,186)	$	260.42	(111,309)	$	241.13
Outstanding at December 31, 2024	19,721	$	280.76	647,589	$	251.36

Schedule of Non-cash Stock Compensation Expense

Stock compensation expense has been allocated as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Direct costs	$	26,046	$	26,595	$	22,854
Selling, general and administrative	19,824		29,072		47,669
Total	$	45,870	$	55,667	$	70,523

Bank Credit Lines, Loan Facilities and Notes - Schedule of Maturities of Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Debt Disclosure [Abstract]
2025	$ 29,762
2026	529,762
2027	779,762
2028	857,164
2029 and thereafter	1,250,000
Total debt	$ 3,446,450	$ 3,806,213

Restructuring charges - Schedule of Restructuring Charges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Restructuring and Related Activities [Abstract]
Restructuring charges	$ 92,123	$ 45,390	$ 31,143

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, 2024	Dec. 31, 2023
Deferred tax liabilities:
Property, plant and equipment	$ 2,869	$ 7,547
Operating right-of-use-assets	15,633	16,108
Goodwill	43,390	39,014
Intangible assets	901,731	950,055
Investments in foreign subsidiaries	34,983	52,408
Other	3,887	7,982
Total deferred tax liabilities recognized	1,002,493	1,073,114
Deferred tax assets:
Operating loss and tax credits carryforwards	164,904	124,150
Property, plant and equipment	7,869	9,082
Operating lease liabilities	21,503	20,190
Intangible assets	45	2,166
Stock compensation	14,309	17,605
Other liabilities	78,428	84,928
Unearned revenue	10,364	23,748
Other	6,298	8,774
Total deferred tax assets	303,720	290,643
Valuation allowance for deferred tax assets	(38,955)	(42,967)
Deferred tax assets recognized	264,765	247,676
Overall net deferred tax liability	$ (737,728)	$ (825,438)

Business Combinations - Narrative, PRA Acquisition (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Interest expense	$ 237,237	$ 336,699	$ 229,731
PRA Health Sciences, Inc
Business Acquisition [Line Items]
Interest expense	$ 23,500	$ 16,400	$ 17,700

Restructuring Charges

12 Months Ended

Dec. 31, 2024

Restructuring and Related Activities [Abstract]

Restructuring Charges

In the years ended December 31, 2024, December 31, 2023 and December 31, 2022, the Company incurred approximately $92.1 million, $45.4 million and $31.1 million of restructuring charge in the Consolidated Statements of Operations under a restructuring plan adopted following a review of operations.

The restructuring plan reflected a workforce reduction of $74.5 million (December 31, 2023: $34.1 million, December 31, 2022: $2.7 million) and an office consolidation program to optimize the Company's office footprint of $17.6 million (December 31, 2023: $11.3 million, December 31, 2022: $28.4 million), being the impairment of operating right-off-use assets and related property plant and equipment of $15.7 million (December 31, 2023: $8.7 million, December 31, 2022: $28.4 million) and onerous contract costs of $1.9 million (December 31, 2023: $2.6 million, December 31, 2022: $nil ).


	Year Ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Restructuring charges	$	92,123	$	45,390	$	31,143
Total	$	92,123	$	45,390	$	31,143

At December 31, 2024, a total liability of $31.5 million (December 31, 2023: $7.0 million) was recorded on the Consolidated Balance Sheet relating to restructuring activities.


	Year Ended
	December 31, 2024		December 31, 2023
	(in thousands)
Opening provision	$	6,999	$	6,022
Charge during the year*	76,392		36,704
Utilization	(51,917)		(35,727)
Ending provision	$	31,474	$	6,999

The closing provision of $31.5 million (December 31, 2023: $7.0 million) reflects:

(1) $27.7 million (December 31, 2023: $4.0 million) of personnel related liabilities as a result of the workforce reduction; all of which have been classified as short-term within Other Liabilities, and

(2) $3.8 million (December 31, 2023: $3.0 million) of facilities related liabilities of which $1.4 million (December 31, 2023: $1.0 million) is included within Other Liabilities and $2.4 million (December 31, 2023: $2.0 million) is included within Non-Current Other Liabilities.

Fair Value

12 Months Ended

Dec. 31, 2024

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 and accounts payable approximate fair value due to the short maturities of these instruments.

As of December 31, 2024, 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:


	December 31, 2024
	Level 1		Level 2		Level 3		Other1		Total
	(in thousands)
Assets:
Investments in equity1,2	$	—	$	—	$	—	$	54,448	$	54,448
Total assets	$	—	$	—	$	—	$	54,448	$	54,448

1Excludes investments in equity securities recorded at cost of $3.5 million which do not qualify for the NAV practical expedient.

As at December 31, 2023, 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:


	December 31, 2023
	Level 1		Level 2		Level 3		Other1		Total
	(in thousands)
Assets:
Available for sale securities3	$	1,954	$	—	$	—	$	—	$	1,954
Investments in equity2	—		—		—		46,804		46,804
Total assets	$	1,954	$	—	$	—	$	46,804	$	48,758

Liabilities:
Derivative instruments4	—		2,411		—		—		2,411
Total liabilities	$	—	$	2,411	$	—	$	—	$	2,411

3Represents the fair value of highly liquid investments with maturities greater than three months, a minimum "A-" rated fixed term deposit and are based on quoted market prices.

4Represents the fair value of the interest rate caps and the interest rate swap.

Non-recurring Fair Value Measurements

Certain assets and liabilities are carried on the 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, 2024, assets carried on the balance sheet and not re-measured to fair value on a recurring basis totaled approximately $12,614.7 million (December 31, 2023: $12,878.0 million) and are identified as Level 3 assets. These assets are comprised of goodwill of $9,051.4 million (December 31, 2023: $9,022.1 million), intangible assets of $3,559.8 million (December 31, 2023: $3,855.9 million) and investments in equity recorded at cost of $3.5 million.

The estimated fair value of the Company’s debt was $3,469.2 million at December 31, 2024 (December 31, 2023: $3,793.5 million). The fair values of the senior secured term loan facility, the 2026 Notes and the New Notes were determined based on Level 2 inputs, which are based on rates at which the debt is traded among financial institutions. The fair value of the senior secured revolving loan facility approximates its carrying value, due to the short term duration.

- 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

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 107
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-107

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
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-Paragraph 100
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (f)
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-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
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-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 940
-SubTopic 820
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478119/940-820-50-1

+ Details

Bank Credit Lines, Loan Facilities and Notes - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	May 08, 2024	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	May 02, 2023	Jul. 01, 2021
Debt Instrument [Line Items]
Amortization of financing costs and debt discount										$ 23,533	$ 16,402	$ 17,749
Drawdown of credit lines and loan facilities										2,317,480	370,000	$ 75,000
Repayments of senior debt										373,000	315,000
Line of credit facility, remaining borrowing capacity						$ 55,000					55,000
Long-term debt at fair value		$ 3,469,200				$ 3,793,500				$ 3,469,200	$ 3,793,500
Senior Secured Term Loan \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)										0.50%
Senior Secured Term Loan \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)										2.00%
Senior Secured Revolving Loan \| Variable rate component one \| Base rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)										0.10%
Senior Secured Revolving Loan \| Variable rate component one \| Base rate \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)										0.45%
Senior Secured Revolving Loan \| Variable rate component one \| Base rate \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)										0.00%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BB Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)										1.45%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BB+ Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)										1.10%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BBB- Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)										0.85%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BBB Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)										0.65%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BBB+ Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)										0.50%
Senior Secured Term Loan \| Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, principal amount														$ 5,515,000
Debt instrument, interest rate (in percent)		6.329%				7.86%				6.329%	7.86%			1.00%
Accelerated charge on repayments		$ 16,900				$ 7,900				$ 16,900	$ 7,900
Senior Secured Term Loan \| Senior secured credit facility and senior secured notes
Debt Instrument [Line Items]
Debt discount paid														$ 27,600
Senior Secured Notes (the "2026 Notes")
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 2,000,000
Debt discount paid	6,800
Senior Secured Notes (the "2026 Notes") \| Senior Secured Notes (the "2026 Notes")
Debt Instrument [Line Items]
Debt instrument, principal amount														$ 500,000
Debt instrument, interest rate (in percent)		2.875%				2.875%				2.875%	2.875%			2.875%
Senior Secured Notes (the "2026 Notes") \| Senior Secured Notes (the "2027 Notes")*
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 750,000
Debt instrument, interest rate (in percent)	5.809%	5.809%				0.00%				5.809%	0.00%
Debt instrument, discount rate on underwriting (in percent)	0.00250
Senior Secured Notes (the "2026 Notes") \| Senior Secured Notes (the "2029 Notes")*
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 750,000
Debt instrument, interest rate (in percent)	5.849%	5.849%				0.00%				5.849%	0.00%
Debt instrument, discount rate on underwriting (in percent)	0.00350
Senior Secured Notes (the "2026 Notes") \| Senior Secured Notes (the "2034 Notes")*
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 500,000
Debt instrument, interest rate (in percent)	6.00%	6.00%				0.00%				6.00%	0.00%
Debt discount paid	$ 500
Debt instrument, discount rate on underwriting (in percent)	0.00450
Debt instrument, redemption price, percentage of principal amount redeemed	99.896%
Senior Secured Revolving Loan \| Senior Secured Revolving Loan
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)		0.00%				6.72%				0.00%	6.72%
Senior Secured Revolving Loan \| Senior Secured Revolving Loan \| Senior Secured Revolving Loan
Debt Instrument [Line Items]
Maximum borrowing capacity													$ 500,000	$ 300,000
Drawdown of credit lines and loan facilities		$ 75,000	$ 50,000	$ 143,000	$ 50,000	$ 65,000	$ 75,000	$ 50,000	$ 180,000	$ 318,000	$ 370,000

Intangible Assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	$ 5,199,004	$ 5,147,971
Accumulated amortization	(1,639,212)	(1,292,106)
Net book value	3,559,792	3,855,865
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	4,129,501	4,090,393
Order backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	543,933	541,302
Trade names & brands
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	204,588	204,653
Patient database
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	170,324	170,366
Technology assets
Acquired Finite-Lived Intangible Assets [Line Items]
Total cost	$ 150,658	$ 141,257

Disaggregation of Revenue

12 Months Ended

Dec. 31, 2024

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

Revenue disaggregated by customer concentration is as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Top client	$	639,520	$	721,309	$	683,546
Clients 2-5	1,431,873		1,453,508		1,506,087
Clients 6-10	1,306,604		1,188,943		1,112,636
Clients 11-25	1,774,160		1,743,539		1,585,739
Other	3,129,519		3,012,877		2,853,378
Total	$	8,281,676	$8,120,176		$7,741,386

Accounts receivable and unbilled revenue are as follows:


	December 31, 2024		December 31, 2023
	(in thousands)
Billed services (accounts receivable)	$	1,437,653	$	1,821,855
Allowance for credit losses (note 5)	(35,664)		(31,533)
Accounts receivable (net)	1,401,989		1,790,322
Unbilled services (unbilled revenue)	1,286,274		951,936
Accounts receivable and unbilled revenue, net	$	2,688,263	$	2,742,258

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


	December 31, 2024		December 31, 2023		$ Change		% Change
	(in thousands, except percentages)
Unbilled services (unbilled revenue)	$	1,286,274	$	951,936	$	334,338	35.1	%
Unearned revenue (payments on account)	(1,614,758)		(1,654,507)		39,749		(2.4)	%
Net balance	$	(328,484)	$	(702,571)	$	374,087	(53.2)	%

The credit loss expense recognized on the Company's receivables and unbilled services was $28.4 million and $24.6 million for the years ended December 31, 2024 and 2023, respectively.

- Definition

+ References

+ Details

Equity Incentive Schemes and Stock Compensation Charges - Summary of RSU and PSU Activity (Details)	12 Months Ended
	Dec. 31, 2024 $ / shares shares
Performance Share Unit (PSUs)
Outstanding number of shares [Roll Forward]
Outstanding at beginning of period (in shares) \| shares	105,256
Granted (in shares) \| shares	48,626
Shares vested (in shares) \| shares	(9,975)
Forfeited (in shares) \| shares	(124,186)
Outstanding at ending of period (in shares) \| shares	19,721
Weighted Average Fair Value
Outstanding at beginning of period (USD per share) \| $ / shares	$ 226.29
Granted (USD per share) \| $ / shares	325.51
Shares vested (USD per share) \| $ / shares	177.38
Forfeited (USD per share) \| $ / shares	260.42
Outstanding at end of period (USD per share) \| $ / shares	$ 280.76
Restricted Stock Units (RSUs)
Outstanding number of shares [Roll Forward]
Outstanding at beginning of period (in shares) \| shares	621,011
Granted (in shares) \| shares	258,345
Shares vested (in shares) \| shares	(120,458)
Forfeited (in shares) \| shares	(111,309)
Outstanding at ending of period (in shares) \| shares	647,589
Weighted Average Fair Value
Outstanding at beginning of period (USD per share) \| $ / shares	$ 218.27
Granted (USD per share) \| $ / shares	313.41
Shares vested (USD per share) \| $ / shares	223.29
Forfeited (USD per share) \| $ / shares	241.13
Outstanding at end of period (USD per share) \| $ / shares	$ 251.36

Derivatives

12 Months Ended

Dec. 31, 2024

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivatives

The Company previously entered into interest rate cap and swap agreements for purposes of managing its exposure to interest rate fluctuations.

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 caps were due to expire on December 31, 2024. Under the terms of the interest rate caps, the Company had paid a fixed rate of 0.42% and received 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 Swap was due to begin accruing on December 31, 2024 and the interest rate swap was due to expire on September 30, 2026. Under the terms of the interest rate swap, the Company would have paid a fixed rate of 3.4% and would have received a variable rate of interest equal to the three-month SOFR on the 2022 Swap.

The 2022 Caps and the 2022 Swap were designated as cash flow hedges. Gains and losses were initially reported as a component of other comprehensive income/loss and subsequently recognized in net income.

During the year, the Company’s exposure to interest rate fluctuations significantly reduced with the voluntary and mandatory repayments of the senior secured term loan facility (refer to note 13. Bank credit lines, loan facilities and notes). Given this reduction and the repricing of the Senior Secured Credit facilities, the Company closed the 2022 Caps and 2022 Swap agreements.

At December 31, 2024, 73% of the Company's outstanding debt is at a fixed interest rate (December 31, 2023: 13%).

During the year ended December 31, 2024, the Company recognized a gain of $5.0 million (December 31, 2023: $1.6 million) within other comprehensive income/loss after a reclassification of $13.9 million (December 31, 2023: $2.4 million) from other comprehensive income/loss to the income statement.


	December 31, 2023
		Asset		Liability		Notional
	(in thousands)
Interest Rate Caps		$	—	$	1,871	$	1,600,606
Interest Rate Swap		—		540		1,100,606
Total derivatives designated as hedging instruments		$	—	$	2,411	$	2,701,212

Supplemental Disclosure of Cash Flow Information

12 Months Ended

Dec. 31, 2024

Supplemental Cash Flow Elements [Abstract]

Supplemental Disclosure of Cash Flow Information


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Cash paid for interest	$	196,622	$	317,975	$	210,918
Cash paid for income taxes (net of refunds)	$	140,718	$	163,778	$	116,322

Non-current other liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Other non-current liabilities	$ 83,470	$ 45,998
Total	$ 83,470	$ 45,998

Description of business (Details)	12 Months Ended
Description of business (Details)	Dec. 31, 2024 Employee Location Country
Product Information [Line Items]
Number of employees \| Employee	41,900
Number of locations in which company operates \| Location	106
Number of countries in which company operates \| Country	55
Geographic Concentration Risk \| United States \| Net Revenue
Product Information [Line Items]
Percentage of company revenue (in percent)	36.00%
Geographic Concentration Risk \| Europe \| Net Revenue
Product Information [Line Items]
Percentage of company revenue (in percent)	52.60%
Geographic Concentration Risk \| Rest of World \| Net Revenue
Product Information [Line Items]
Percentage of company revenue (in percent)	11.40%

Related Parties (Details) - Subsidiaries - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Corvus Pharmaceuticals
Related Party Transaction [Line Items]
Revenues	$ 300	$ 200
Other receivables	100	100
Afimmune Limited
Related Party Transaction [Line Items]
Revenues	0	50
Other receivables	$ 100	$ 50

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 48
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-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Business Segment and Geographical Information - Distribution of Long-lived Assets, Net, by Geographical Area (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Long-lived assets	$ 530,481	$ 501,517
Ireland
Segment Reporting Information [Line Items]
Long-lived assets	234,175	199,051
Rest of Europe
Segment Reporting Information [Line Items]
Long-lived assets	88,556	94,046
U.S.
Segment Reporting Information [Line Items]
Long-lived assets	145,391	159,245
Other
Segment Reporting Information [Line Items]
Long-lived assets	$ 62,359	$ 49,175

Operating Leases (Tables)

12 Months Ended

Dec. 31, 2024

Leases [Abstract]

Schedule of Lease Costs

Lease costs recorded under operating leases for the years ended December 31, 2024, 2023 and 2022 were as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Operating lease costs	$	46,466	$	46,820	$	53,880
Income from sub-leases	(1,614)		(1,103)		(1,165)
Net operating lease costs	$	44,852	$	45,717	$	52,715

Schedule of Operating Lease Maturity

Future minimum lease payments under non-cancelable leases as of December 31, 2024 were as follows:


Minimum rental payments	(in thousands)
2025	$	42,931
2026	38,445
2027	31,257
2028	24,156
2029	17,838
Thereafter	45,047
Total future minimum lease payments	199,674
Lease imputed interest	(22,806)
Total	$	176,868

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Tax credit carry forward, expiration period	30 years
Valuation allowance for deferred tax assets	$ 38,955	$ 42,967
Net change in the total valuation allowance	(4,000)	(400)
Investments in foreign subsidiaries	34,983	52,408
Unrecognized tax benefit, potentially expire in 2021	61,600
Total unrecognized tax benefits net of potential benefits	101,600	160,000	$ 217,600
Interest and penalties recognized as an expense	1,900	4,200	$ 7,100
Total accrued interest and penalties	24,200	27,100
Provision for income taxes
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Net change in the total valuation allowance	(5,300)	(1,100)
Tax of business acquired
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Net change in the total valuation allowance	2,000
Other Comprehensive Income
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Net change in the total valuation allowance	(700)	700
Foreign Country
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Other non-U.S subsidiaries operating loss carryforwards for income tax	42,400
Ireland \| Foreign Country
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Ireland subsidiaries additional tax credit carryforward for income tax	15,600
United States
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Alternative minimum tax credit carry forwards	1,000
United States \| Federal NOL's
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Net operating loss carryforwards	8,035
Tax credit carry forward	317,000	$ 204,000
Increase (decrease) tax credit carry forward	113,000
Other non-U.S subsidiaries operating loss carryforwards for income tax	0
United States \| State NOL's
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Net operating loss carryforwards	277,828
Other non-U.S subsidiaries operating loss carryforwards for income tax	9,601
Other \| Foreign Country
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Ireland subsidiaries additional tax credit carryforward for income tax	$ 2,700

Income Taxes - Components of Income Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]
Income before income tax expense	$ 869,184	$ 624,467	$ 567,851
Ireland
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]
Income before income tax expense	736,374	624,642	432,963
United States
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]
Income before income tax expense	(304,546)	(352,532)	(270,440)
Other
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]
Income before income tax expense	$ 437,356	$ 352,357	$ 405,328

- Definition

Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

+ References + Details

Equity Incentive Schemes and Stock Compensation Charges - Summary of Stock Option Activity (Details) - Stock Option and Award Plans - $ / shares	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Options Granted Under Plans
Beginning balance (in shares)	902,806	1,378,119	1,695,460
Granted (in shares)	68,380	82,472	108,643
Exercised (in shares)	(311,040)	(535,705)	(348,286)
Canceled/expired (in shares)	(37,854)	(22,080)	(77,698)
Ending balance (in shares)	622,292	902,806	1,378,119
Vested and exercisable at end of period (in shares)	426,497
Weighted Average Exercise Price
Beginning balance (USD per share)	$ 142.96	$ 119.86	$ 110.38
Granted (USD per share)	325.51	232.48	229.94
Exercised (USD per share)	116.31	95.12	102.87
Canceled/expired (USD per share)	238.51	196.20	143.08
Ending balance (USD per share)	170.52	$ 142.96	$ 119.86
Vested and exercisable at end of period (USD per share)	$ 135.39

Net Income Per Ordinary Share

12 Months Ended

Dec. 31, 2024

Earnings Per Share [Abstract]

Net Income Per Ordinary Share

Basic net income per ordinary share 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.

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


	Year ended
	December 31, 2024	December 31, 2023	December 31, 2022
Weighted average number of ordinary shares outstanding for basic net income per ordinary share	82,482,764	82,101,813	81,532,320
Effect of dilutive share options and other awards outstanding under share based compensation programs	549,660	615,827	936,043
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share	83,032,424	82,717,640	82,468,363








	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
Net income per ordinary share:
Basic	$	9.60	$	7.46	$	6.20
Diluted	$	9.53	$	7.40	$	6.13

Fair value - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, FV-NI, cost	$ 3.5
Long-term debt at fair value	3,469.2	$ 3,793.5
Fair value, nonrecurring \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	12,614.7	12,878.0
Goodwill	9,051.4	9,022.1
Identifiable intangible assets, net	$ 3,559.8	$ 3,855.9

Operating Leases Operating Leases - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Lessee, Lease, Description [Line Items]
Net operating lease costs	$ 44,852	$ 45,717	$ 52,715
Right-of-use assets obtained in exchange for lease obligations	64,800	37,700
Impairment of operating right-of-use assets and related property, plant and equipment	$ 13,800	$ 8,700	28,400
Weighted average remaining lease term	6 years 6 months 21 days	6 years 8 months 19 days
Weighted average discount rate (in percent)	4.01%	3.29%
Operating lease liabilities, current	$ 36,783	$ 36,414
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other liabilities (Note 12)	Other liabilities (Note 12)
Operating lease, liability, noncurrent	$ 140,085	$ 126,321
Selling, general and administrative
Lessee, Lease, Description [Line Items]
Net operating lease costs	37,200	37,900	48,300
Direct costs
Lessee, Lease, Description [Line Items]
Net operating lease costs	$ 7,700	$ 7,800	$ 4,400

Description of business	12 Months Ended
Description of business	Dec. 31, 2024
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 contract 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" or a “blended-service” solution. At December 31, 2024 we had approximately 41,900 employees, in 106 locations in 55 countries. During the year ended December 31, 2024, we derived 36.0%, 52.6% and 11.4% 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.

Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Other Liabilities Disclosure [Abstract]
General trade and overhead liabilities	$ 531,560	$ 463,882
Personnel related liabilities	225,822	385,499
Operating lease liabilities	36,783	36,414
Facility related liabilities	$ 8,547	11,078
Government Assistance, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other liabilities
Other liabilities	$ 91,730	13,532
Restructuring liabilities	29,120	4,951
Short term government grants	41	43
Other liabilities	923,603	915,399
Amounts due to third parties for reimbursable expenses	$ 369,200	$ 333,000

CONSOLIDATED BALANCE SHEETS (Parenthetical) - € / shares	Dec. 31, 2024	Dec. 31, 2023
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)	80,756,860	82,495,086
Ordinary shares, shares outstanding (in shares)	80,756,860	82,495,086

Summary of Significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2024

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, 2024, December 31, 2023 and December 31, 2022 were as follows:


	Year ended
	December 31, 2024		December 31, 2023		December 31, 2022
	(in thousands)
Amounts (credited) / charged	$	(18,085)	$	12,916	$	(25,997)

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:


			Estimated Useful Life
Buildings			40 years
Computer equipment and software			2 - 8 years
Office furniture and fixtures			8 years
Laboratory equipment			5 years
Motor vehicles			5 years

Schedule of Finite-Lived Intangible Assets


			Estimated Useful Life
Customer relationships			8 - 23 years
Order backlog			3 - 5 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, 2024 and 2023 is as follows:


	December 31, 2024		December 31, 2023
Cost	(in thousands)
Customer relationships	$	4,129,501	$	4,090,393
Order backlog	543,933		541,302
Trade names & brands	204,588		204,653
Patient database	170,324		170,366
Technology assets	150,658		141,257
Total cost	5,199,004		5,147,971
Accumulated amortization	(1,639,212)		(1,292,106)
Net book value	$	3,559,792	$	3,855,865

Insider Trading Policies and Procedures	12 Months Ended
Insider Trading Policies and Procedures	Dec. 31, 2024
Insider Trading Policies and Procedures [Line Items]
Insider Trading Policies and Procedures Adopted	true

Share Capital (Details) $ / shares in Units, $ in Thousands		12 Months Ended
Share Capital (Details) $ / shares in Units, $ in Thousands	Jul. 23, 2024	Dec. 31, 2024 USD ($) vote $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Oct. 22, 2024 USD ($)	Feb. 20, 2024 USD ($)
Equity, Class of Treasury Stock [Line Items]
Number of votes \| vote		1
Total proceeds from exercise of stock options by employees		$ 36,187	$ 50,973	$ 35,844
Ordinary shares redeemed, value		$ 499,998		$ 99,983
Buyback program
Equity, Class of Treasury Stock [Line Items]
Ordinary shares redeemed (in shares) \| shares		2,179,699	0	420,530
Ordinary shares redeemed, value		$ 500,000		$ 100,000
Buyback program \| Maximum
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized percentage (in percent)	10.00%	10.00%
February 2024
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount						$ 500,000
October 2024
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount					$ 250,000
Employee Stock Option
Equity, Class of Treasury Stock [Line Items]
Options exercised by employees (in shares) \| shares		311,040	535,705	348,286
Average exercise price of option per share (USD per share) \| $ / shares		$ 116.31	$ 95.12	$ 102.87
Total proceeds from exercise of stock options by employees		$ 36,200	$ 51,000	$ 35,800
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) \| shares		120,458	188,800	195,029
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) \| shares		9,975	47,026	46,087

Other Liabilities (Tables)

12 Months Ended

Dec. 31, 2024

Other Liabilities Disclosure [Abstract]

Schedule of Other Liabilities

The carrying amount of Other Liabilities for the years ended December 31, 2024 and 2023 is as follows:


	December 31, 2024		December 31, 2023
	(in thousands)
General trade and overhead liabilities*	$	531,560	$	463,882
Personnel related liabilities	225,822		385,499
Operating lease liabilities	36,783		36,414
Facility related liabilities	8,547		11,078
Other liabilities	91,730		13,532
Restructuring liabilities	29,120		4,951
Short term government grants	41		43
Total	$	923,603	$	915,399

*includes amounts due to third parties in respect of accrued reimbursable investigator expenses of $369.2 million at December 31, 2024 and $333.0 million at December 31, 2023.

Bank Credit Lines, Loan Facilities and Notes - Schedule of Finance Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Debt Disclosure [Abstract]
Interest expense on drawn facilities	$ 206,198	$ 311,019	$ 209,189
Amortization of merger related financing fees	23,533	16,402	17,749
Other financing costs	7,506	9,278	2,793
Total financing costs	$ 237,237	$ 336,699	$ 229,731

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2024
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company has evaluated subsequent events from the Balance Sheet date through February 21, 2025, the date at which the consolidated financial statements were available to be issued. On February 18, 2025, the Company's Board of Directors authorized an additional buyback program of up to $750.0 million of the outstanding ordinary shares of the Company. Along with unutilized amounts under the previous authorizations, this permits the Company to repurchase up to $1 billion worth of ordinary shares. All ordinary shares that are redeemed under the buyback program will be canceled in accordance with the constitutional documents of the Company and the nominal value of these shares transferred to an undenominated capital fund as required under Irish Company law. Repurchases under the share buyback program may be effected from time to time in open market or privately negotiated transactions in accordance with agreed terms and limitations. The timing and amount of the repurchase transactions under this program will depend on a variety of factors, including market conditions and corporate and regulatory considerations. Depending upon results of operations, market conditions and the development of the economy, as well as other factors, generally we will consider share repurchases on an opportunistic basis from time to time. The Company has determined that there are no other items to disclose.

Business Combinations - Transaction and Integration Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Business Combinations [Abstract]
Integration related costs	$ 29,574	$ 44,176	$ 39,695

Bank Credit Lines, Loan Facilities and Notes - Schedule of Principal payments (Details) - Senior Secured Term Loan - Senior Secured Term Loan - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023
Debt Instrument [Line Items]
Principal repayments	$ (7,440)	$ (7,441)	$ (2,014,882)	$ (275,000)	$ (250,000)	$ (300,000)	$ (150,000)	$ (250,000)
Total repayments	$ (2,304,763)				$ (950,000)

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pay vs Performance Disclosure
Net income	$ 791,474	$ 612,335	$ 505,304

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Non-current other liabilities (Tables)

12 Months Ended

Dec. 31, 2024

Payables and Accruals [Abstract]

Non-current other liabilities

The carrying amount of Non-current other liabilities for the years ended December 31, 2024 and 2023 is as follows:


	December 31, 2024		December 31, 2023
	(in thousands)
Other non-current liabilities	83,470		45,998
Total	$	83,470	$	45,998