Other receivables Nontrade Receivables, Current Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Summary of significant accounting policies Significant Accounting Policies [Text Block] Statistical Measurement [Domain] Statistical Measurement [Domain] Thereafter Lessee, Operating Lease, Liability, to be Paid, after Year Five PSUs based on service and EPS targets Performance Based Grants [Member] Performance Based Grants [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Additional Paid-in Capital Additional Paid-in Capital [Member] Interest and penalties recognized as an benefit Unrecognized Tax Benefits Income Tax Penalties And Interest Benefit Unrecognized Tax Benefits Income Tax Penalties And Interest Benefit Leases [Abstract] Leases [Abstract] Increase related to prior year tax positions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Standard & Poor's, BB Rating Standard & Poor's, BB Rating [Member] Change in unearned revenue (payments on account) Decrease in unearned revenue (payments on account) Increase (Decrease) In Contract With Customer, Liability, Gross, Current Increase (Decrease) In Contract With Customer, Liability, Gross, Current Variable Rate Component [Axis] Variable Rate Component [Axis] Variable Rate Component Type of Restructuring [Domain] Type of Restructuring [Domain] Goodwill [Line Items] Goodwill [Line Items] Basic (in USD per share) Earnings Per Share, Basic Revenue Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) Revenue from Contract with Customer [Text Block] Change in net balance Decrease in net balance Change In Advance Payments Netted Against Unbilled Contracts Receivable Change In Advance Payments Netted Against Unbilled Contracts Receivable Unrecognized tax benefits and related interest and penalties Unrecognized Tax Benefits And Related Interest And Penalties Unrecognized Tax Benefits And Related Interest And Penalties Cost Finite-Lived Intangible Assets, Gross [Abstract] Schedule of Indefinite-Lived Intangible Assets [Table] Intangible Asset, Indefinite-Lived [Table] Percentage change in net balance Change In Advance Payments Netted Against Unbilled Contracts Receivable, Percent Change In Advance Payments Netted Against Unbilled Contracts Receivable, Percent Revenue, remaining performance obligation Revenue, Remaining Performance Obligation, Amount Percentage change in unbilled services (unbilled revenue) Increase (Decrease) In Contract With Customer, Asset, Gross, Current, Percent Increase (Decrease) In Contract With Customer, Asset, Gross, Current, Percent Less debt issuance costs and debt discount Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Revenue, remaining performance obligation percentage Revenue, Remaining Performance Obligation, Percentage Stock compensation expense Share-Based Payment Arrangement, Noncash Expense Indefinite-Lived Intangible Assets [Line Items] Indefinite-Lived Intangible Assets [Line Items] Employee Stock Option Share-Based Payment Arrangement, Option [Member] Accelerated charge on repayments Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid Schedule of RSU and PSU Activity Summary Of Share Based Compensation Restricted Stock Units Performance Stock Units, Award, Activity [Table Text Block] Summary Of Share Based Compensation Restricted Stock Units Performance Stock Units Award Activity [Table Text Block] Total Shareholders' Equity Beginning balance Ending balance Equity, Attributable to Parent Measurement Frequency [Axis] Measurement Frequency [Axis] Other comprehensive income, net of tax: Comprehensive income (net of tax): Other Comprehensive Income (Loss), Net of Tax [Abstract] Total Share-Based Payment Arrangement, Expense Ordinary shares, shares authorized (in shares) Common Stock, Shares Authorized Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Current assets: Assets, Current [Abstract] Total Liabilities and Shareholders' Equity Liabilities and Equity Fair value, recurring Fair Value, Recurring [Member] Options Outstanding Number of Shares  Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] Stock repurchase program, additional amount authorized Share Repurchase Program, Authorized, Additional Amount Share Repurchase Program, Authorized, Additional Amount Senior Secured Term Loan Term Loan Facility [Member] Term Loan Facility LIABILITIES AND SHAREHOLDERS’ EQUITY Liabilities and Equity [Abstract] Schedule of Distribution of Income from Operations by Geographical Area Schedule Of Operating Income By Geography [Table Text Block] Schedule Of Operating Income By Geography Cover [Abstract] The New Notes The New Notes [Member] The New Notes Maximum Maximum [Member] Exercisable at end of period (in USD per share) Weighted average exercise price of options exercisble (USD per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price Estimated Useful Life Finite-Lived Intangible Asset, Useful Life Share repurchase costs Stock Repurchased During Period, Cost, Equity Stock Repurchased During Period, Cost, Equity Accounting Policies [Abstract] Accounting Policies [Abstract] Intangible assets, net  Net book value Finite-Lived Intangible Assets, Net Schedule of Operating Lease Maturity Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block] Senior Secured Notes (the "2026 Notes") Senior Secured Notes Due July 2026 [Member] Senior Secured Notes Due July 2026 Debt Instrument [Line Items] Debt Instrument [Line Items] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Fair value of stock units vested Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Less current portion of debt Long-term Debt, Current Maturities, Gross Long-term Debt, Current Maturities, Gross Total Operating Lease, Liability Share Repurchase Program [Line Items] Share Repurchase Program [Line Items] External Credit Rating, Standard & Poor's [Domain] External Credit Rating, Standard & Poor's [Domain] Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Debt instrument, redemption price, percentage of principal amount redeemed Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed Non-current other liabilities Other Liabilities, Noncurrent Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Senior Secured Notes Senior Secured Notes [Member] Senior Secured Notes Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Goodwill impairment Goodwill impairment Impairment Goodwill impairment Goodwill, Impairment Loss Operating Segments Operating Segments [Member] (Gain) / loss on cash flow hedge Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Year 3 Lessee, Operating Lease, Liability, to be Paid, Year Three Total comprehensive (loss) / income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Restructuring reserve Opening provision Closing provision Restructuring Reserve Non-current income taxes payable Accrued Income Taxes, Noncurrent Senior Secured Term Loan Secured Debt [Member] Operating lease liabilities, current Operating Lease, Liability, Current Deferred tax liability Deferred Income Tax Liabilities, Net Document Fiscal Period Focus Document Fiscal Period Focus Award Type [Axis] Award Type [Axis] Closing Balance Long-Term Debt Total Assets Assets Cash flows used in investing activities: Cash Provided by (Used in) Investing Activity, Continuing Operation [Abstract] Year 4 Lessee, Operating Lease, Liability, to be Paid, Year Four Shares vested (in USD per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Geographical [Domain] Geographical [Domain] Income taxes Income Tax, Policy [Policy Text Block] Issue of restricted share units / performance share units (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Compensation Related Costs Share Based Payments Disclosure [Table] Compensation Related Costs Share Based Payments Disclosure [Table] Compensation Related Costs Share Based Payments Disclosure [Table] Intangible assets Intangible Assets Disclosure [Text Block] Effect of exchange rate movements on cash Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Restricted Stock Units (RSUs) Restricted Stock Units (RSUs) [Member] Income Statement Location [Domain] Statement of Income Location, Balance [Domain] Severance costs Severance Costs Business combination, consideration transferred Business Combination, Consideration Transferred Assets: Assets, Fair Value Disclosure [Abstract] Order backlog Order or Production Backlog [Member] Restructuring Restructuring charges Restructuring Costs 2028 Long-Term Debt, Maturity, Year Three Restructuring reserve, current Restructuring Reserve, Current Right-of-use assets obtained in exchange for lease obligations Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Outstanding at beginning of period (in shares) Outstanding at end of period (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Billed services (accounts receivable) Billed Contracts Receivable Repayment of credit lines and loan facilities Repayment Repayments of Lines of Credit Level 2 Fair Value, Inputs, Level 2 [Member] Restructuring Reserve [Roll Forward] Restructuring Reserve [Roll Forward] Business Combination [Domain] Business Combination [Domain] Ordinary shares, shares outstanding (in shares) Common Stock, Shares, Outstanding Schedule of Components of Income Tax Expense Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Standard & Poor's, BB+ Rating Standard & Poor's, BB+ Rating [Member] Interest income Investment Income, Interest Unrealized foreign exchange movements Unrealized Gain (Loss), Foreign Currency Transaction, before Tax Income taxes payable Accrued Income Taxes, Current U.S. UNITED STATES Changes in operating assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Exercise of share options Stock Issued During Period, Value, Stock Options Exercised Expected volatility Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate Retained Earnings Retained Earnings [Member] Prepayments and other current assets Prepaid Expense and Other Assets, Current Outstanding Number of Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Accounts receivable and unbilled revenue, net Contracts Receivable, Net Contracts Receivable, Net Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Income Statement [Abstract] Income Statement [Abstract] Income tax expense Income tax expense Income Tax Expense (Benefit) Basis spread on variable rate (in percent) Debt Instrument, Basis Spread on Variable Rate Clients 6-10 Clients 6-10 [Member] Clients 6-10 [Member] Credit Rating, Standard & Poor's [Axis] Credit Rating, Standard & Poor's [Axis] Fair value, nonrecurring Fair Value, Nonrecurring [Member] Other Undenominated Capital Other Undenominated Capital [Member] Other undenominated capital. Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Purchase of investments in equity Payments to Acquire Long-Term Investments Net income Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Organization, Consolidation and Presentation of Financial Statements [Abstract] Net intangible assets at fair value Finite-Lived Intangible Assets, Fair Value Disclosure Restructuring Restructuring and Related Activities Disclosure [Text Block] Reduction in carrying value of operating right-of-use assets Operating Lease, Right-of-Use Asset, Periodic Reduction Current period acquisitions Goodwill, Acquired During Period Proceeds from exercise of equity compensation Proceeds from Stock Options Exercised Outstanding at beginning of period (in shares) Outstanding at end of period (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Commitments and Contingencies Disclosure [Abstract] Schedule of Accounts Receivables and Unbilled Revenue, and Unbilled Services and Unearned Revenue Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Long-lived assets Long-Lived Assets Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration] Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration] Subsequent Event Subsequent Event [Member] Schedule of Weighted Average Fair Values and Assumptions Used Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Selling, general and administration costs Selling, general and administrative Selling, General and Administrative Expenses [Member] Net operating lease costs Total lease cost Lease, Cost Direct costs Cost of Sales [Member] Goodwill Opening balance Closing balance Goodwill Schedule of Lease Costs Lease, Cost [Table Text Block] Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Clients 1-5 Clients 1-5 [Member] Clients 2-5 [Member] Equity Components [Axis] Equity Components [Axis] Unrecognized Tax Benefits [Roll Forward] Unrecognized Tax Benefits [Roll Forward] Income from sub-leases Sublease Income Share repurchase costs Payments For Broker Commission Share Repurchase Costs Payments For Broker Commission Share Repurchase Costs Number of reportable segments Number of Reportable Segments Assumptions: Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions and Methodology [Abstract] Decrease in deferred tax benefit, amortization of intangible assets Income Tax Benefit, Adjustment Of Deferred Tax Asset, Amortization of Intangible Assets Income Tax Benefit, Adjustment Of Deferred Tax Asset, Amortization of Intangible Assets Impairment of operating right-of-use assets and related property, plant and equipment Impairment, Operating Right-Of-Use Assets And Related Property, Plant And Equipment Impairment, Operating Right-Of-Use Assets And Related Property, Plant And Equipment Other restructuring costs Other Restructuring Costs Restructuring Cost and Reserve [Line Items] Restructuring Cost and Reserve [Line Items] Weighted Average Exercise Price Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] New Notes issue costs Payments of Debt Issuance Costs Total current liabilities Liabilities, Current Net balance Advance Payments Netted Against Unbilled Contracts Receivable Advance Payments Netted Against Unbilled Contracts Receivable Vesting [Axis] Vesting [Axis] Other net assets and liabilities Increase (Decrease) in Other Current Assets and Liabilities, Net Release of deferred tax liability, undistributed earnings of foreign subsidiaries Income Tax Benefit (Expense), Adjustment Of Deferred Tax Liability, Undistributed Earnings Of Foreign Subsidiaries Income Tax Benefit (Expense), Adjustment Of Deferred Tax Liability, Undistributed Earnings Of Foreign Subsidiaries Additional paid-in capital Additional Paid in Capital, Common Stock Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Revenue, remaining performance obligation, expected timing of satisfaction, period Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Document Fiscal Year Focus Document Fiscal Year Focus Proceeds from investments in equity Proceeds from Sale of Long-Term Investments Operating right-of-use assets Operating Lease, Right-of-Use Asset Decrease related to prior year tax positions Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Operating lease costs Operating Lease, Cost Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] Total long-term debt Long-term Debt, Excluding Current Maturities, Gross Long-term Debt, Excluding Current Maturities, Gross Cash flows provided by operating activities: Cash Provided by (Used in) Operating Activity, Continuing Operation [Abstract] Transaction and integration related Business Combination, Acquisition-Related Cost, Expense Exercise of share options (in shares) Exercised (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Equity [Abstract] Equity [Abstract] Revenue recognition Revenue from Contract with Customer [Policy Text Block] Restricted stock units 2013 Restricted Stock Units Twenty Thirteen [Member] Restricted Stock Units Twenty Thirteen [Member] Business Segment and Geographical Information Segment Reporting Disclosure [Text Block] Periodic principal payment Debt Instrument, Periodic Payment, Principal Goodwill [Table] Goodwill [Table] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Amortization of intangible assets Amortization of intangible assets Amortization of Intangible Assets Impairment of goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Selling, general and administrative Selling, General and Administrative Expense Deferred tax asset Deferred Income Tax Assets, Net Depreciation and amortization expense Depreciation, Depletion and Amortization Other receivables Other Assets, Noncurrent Customer [Domain] Customer [Domain] Entity Central Index Key Entity Central Index Key Schedule of Segment Reporting Information, by Segment [Table] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Schedule of Contractual Maturities of Debt Schedule of Maturities of Long-Term Debt [Table Text Block] Senior Secured Revolving Loan Revolving Credit Facility [Member] Variable rate component two Variable Rate Component Two [Member] Variable Rate Component Two Goodwill at fair value Goodwill, Fair Value Disclosure Unearned revenue Unearned revenue (payments on account) Contract with Customer, Liability, Current Other undenominated capital Other Undenominated Capital Other undenominated capital. Subsequent Event Type [Axis] Subsequent Event Type [Axis] Share-based awards Share-Based Payment Arrangement [Text Block] Repurchase of ordinary shares (in shares) Total number of shares purchased (in shares) Stock Repurchased and Retired During Period, Shares Onerous contract provision Loss Contingency Accrual, Provision ASSETS Assets [Abstract] Non-executive directors Non-Executive Director [Member] Non-executive Director [Member] Total long-term debt, net Long-Term Debt, Excluding Current Maturities Credit Facility [Axis] Credit Facility [Axis] Vesting [Domain] Vesting [Domain] Debt Instrument [Axis] Debt Instrument [Axis] Annual principal payment Debt Instrument, Annual Principal Payment Forfeited (in USD per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Fair value measurements Fair Value Disclosures [Text Block] Credit Facility [Domain] Credit Facility [Domain] Total cost Finite-Lived Intangible Assets, Gross Shareholders' Equity: Equity, Attributable to Parent [Abstract] Debt instrument, discount rate on underwriting (in percent) Debt Instrument, Discount Rate Debt Instrument, Discount Rate Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Fair value of stock units granted Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value Debt instrument, interest rate (in percent) Debt Instrument, Interest Rate, Stated Percentage Lease liabilities Operating lease liabilities, non-current Operating Lease, Liability, Noncurrent Net release of provisions for uncertain tax positions Unrecognized Tax Benefits, Period Increase (Decrease) Net income per Ordinary Share: Earnings Per Share, Basic and Diluted EPS [Abstract] Earnings Per Share, Basic and Diluted EPS KCR S.A Group KCR S.A Group [Member] KCR S.A Group Entity Registrant Name Entity Registrant Name Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Title of Individual [Domain] Title and Position [Domain] Total costs and expenses Costs and Expenses Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Share issuance costs Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs Total assets Total assets Assets, Fair Value Disclosure Deferred tax benefit Deferred Income Taxes and Tax Credits Long-term debt at fair value Long-Term Debt, Fair Value Number of operating segments Number of Operating Segments Year 2 Lessee, Operating Lease, Liability, to be Paid, Year Two Weighted average contractual term of options outstanding Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Schedule of Long-term Debt Instruments Schedule of Debt [Table Text Block] Granted (in USD per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Senior Secured Notes Senior Subordinated Notes [Member] Schedule of Finite-Lived Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Purchase of subsidiary undertakings (net of cash acquired) Purchase of subsidiary undertakings (net of cash acquired) Payments to Acquire Businesses, Gross Issue of restricted share units / performance share units Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Clients 11-25 Clients 11-25 [Member] Clients 11-25 [Member] Schedule of Restructuring Charges Restructuring and Related Costs [Table Text Block] Movement of available for sale investments Payments for (Proceeds from) Short-Term Investments Accounts receivable net Contracts Receivable, Gross Contracts Receivable Schedule of Fair Value, Liabilities Measured on Recurring Basis Fair Value, Liabilities Measured on Recurring Basis [Table Text Block] Award Type [Domain] Award Type [Domain] Year 1 Lessee, Operating Lease, Liability, to be Paid, Year One Goodwill Goodwill Disclosure [Text Block] Other non-cash items Other Noncash Income (Expense) Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Debt instrument, principal amount Debt Instrument, Face Amount Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Dividend yield Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Dividend Rate Statement of Comprehensive Income [Abstract] Outstanding at beginning of period (in USD per share) Outstanding at end of period (in USD per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Utilization Payments for Restructuring Restructuring Type [Axis] Restructuring Type [Axis] Share based compensation expense APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Standard & Poor's, BBB Rating Standard & Poor's, BBB Rating [Member] 2026 Long-Term Debt, Maturity, Year One Income Statement Location [Axis] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs, by Report Line Statement of Income Location, Balance [Axis] Senior Secured Revolving Loan Senior Secured Revolving Loan Facility [Member] Senior Secured Revolving Loan Facility Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Current bank credit lines, loan facilities and notes Line of Credit, Current Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Minimum Minimum [Member] Non-current assets: Assets, Noncurrent [Abstract] Decrease in amortization Decrease In Amortisation Decrease In Amortisation Costs and expenses: Cost of Revenue [Abstract] Prior period acquisitions Goodwill, Measurement Period Adjustment Accounts payable Accounts Payable, Current Ordinary shares, issued and outstanding Common Stock, Value, Issued Goodwill [Roll Forward] Goodwill [Roll Forward] Contract Assets [Abstract] Contract Assets [Abstract] Contract Assets Commitments and contingencies Commitments and Contingencies Disclosure [Text Block] Title of Individual [Axis] Title and Position [Axis] Diluted (in shares) Weighted average number of ordinary shares outstanding for diluted net income per ordinary share (in shares) Weighted Average Number of Shares Outstanding, Diluted Commitments and contingencies Commitments and Contingencies Intangible assets acquired Business Combination, Recognized Asset Acquired, Identifiable Intangible Asset, Finite-Lived Investments Measured at Net Asset Value Fair Value Measured at Net Asset Value Per Share [Member] Business Combination [Axis] Business Combination [Axis] Variable rate component one Variable Rate Component One [Member] Variable Rate Component One Schedule of Distribution of Revenue by Geographical Area Revenue from External Customers by Geographic Areas [Table Text Block] Share issue costs Payments of Stock Issuance Costs Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Interest and penalties recognized as an expense Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense Patient database Database Rights [Member] Bank credit lines, loan facilities and notes Long-Term Debt [Text Block] Equity Component [Domain] Equity Component [Domain] Document Period End Date Document Period End Date Schedule of Distribution of Depreciation and Amortization by Geographical Area Long-Lived Assets by Geographic Areas [Table Text Block] Non-current bank credit lines, loan facilities and notes, net Long-Term Line of Credit, Noncurrent Forfeited/Expired (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures and Expirations in Period Income taxes Income Tax Disclosure [Text Block] Standard & Poor's, BBB+ Rating Standard & Poor's, BBB+ Rating [Member] Allowance for credit losses Accounts Receivable, Allowance for Credit Loss Drawdown of credit lines and loan facilities Drawdown Proceeds from Lines of Credit Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Income before income tax expense Income (Loss), Including Portion Attributable to Noncontrolling Interest, before Tax Weighted average contractual term of options exercisable Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Schedule of Unrecognized Tax Benefits Roll Forward Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Average price paid per share (in USD per share) Shares Acquired, Average Cost Per Share Document Type Document Type Level 3 Fair Value, Inputs, Level 3 [Member] Net income per ordinary share Earnings Per Share [Text Block] Revenue Revenue from Contract with Customer, Excluding Assessed Tax Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Fair Value Disclosures [Abstract] Purchase of property, plant and equipment Payments to Acquire Property, Plant, and Equipment Restructuring reserve, noncurrent Restructuring Reserve, Noncurrent Total current assets Assets, Current Additions to intangible assets Finite-Lived Intangible Assets Acquired Statistical Measurement [Axis] Statistical Measurement [Axis] Stock repurchase program, authorized amount Share Repurchase Program, Authorized, Amount Forfeited/Expired (in USD per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price Foreign exchange movement Goodwill, Foreign Currency Translation, Gain (Loss) Within next 12 months Within Next Twelve Months [Member] Within Next Twelve Months Schedule of Finite-Lived Intangible Assets [Table] Intangible Asset, Finite-Lived [Table] Current liabilities: Liabilities, Current [Abstract] Geographical [Axis] Geographical [Axis] Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] Level 1 Fair Value, Inputs, Level 1 [Member] Consultants Restricted Stock Units 2019 Consultants Restricted Stock Units Twenty Nineteen [Member] Consultants Restricted Stock Units Twenty Nineteen [Member] Workforce reduction and onerous contract cost Workforce Reduction And Office Consolidation Program [Member] Workforce Reduction And Office Consolidation Program Diluted (in USD per share) Earnings Per Share, Diluted Accounts receivable, net of allowance for credit losses Accounts Receivable, after Allowance for Credit Loss, Current Performance Share Unit (PSUs) Performance Share Unit [Member] Performance Share Unit [Member] Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Investments in equity Equity Securities, FV-NI and without Readily Determinable Fair Value Net income per ordinary share: Earnings Per Share [Abstract] Year 5 Lessee, Operating Lease, Liability, to be Paid, Year Five Investments in equity securities recorded at cost Other Investments and Securities, at Cost Consolidation Items [Domain] Consolidation Items [Domain] Standard & Poor's, BBB- Rating Standard & Poor's, BBB- Rating [Member] Repurchase of ordinary shares Share repurchase program, value of shares repurchased Stock Repurchased and Retired During Period, Value Unearned revenue Increase (Decrease) in Contract with Customer, Liability Schedule of Non-Cash Stock Compensation Expense Schedule of Non Cash Stock Compensation Expense [Table Text Block] Schedule of Non Cash Stock Compensation Expense. Schedule of Principal Payments on Debt Instrument Schedule of Principal Payments on Debt Instrument [Table Text Block] Schedule of Principal Payments on Debt Instrument Lease imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Exercised (in USD per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Other Other Customers [Member] Other Customers [Member] Rest of Europe Rest Of Europe [Member] Rest Of Europe [Member] Total debt Long-Term Debt, Gross Granted (in USD per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Senior Secured Credit Facility And Senior Secured Notes Senior Secured Credit Facility And Senior Secured Notes [Member] Senior Secured Credit Facility And Senior Secured Notes Measurement Frequency [Domain] Measurement Frequency [Domain] Total future minimum lease payments Lessee, Operating Lease, Liability, to be Paid Share capital Equity [Text Block] Trade names & brands Trade Names [Member] Net income Net Income (Loss) Attributable to Parent Non-current liabilities: Liabilities, Noncurrent [Abstract] HumanFirst Inc HumanFirst Inc [Member] HumanFirst Inc Shares vesting period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Property, plant and equipment, net Property, Plant and Equipment, Net Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Charge during the period Restructuring Charges Repurchase of ordinary shares Payments for Repurchase of Common Stock Net Income (Loss) Attributable to Parent [Abstract] Net Income (Loss) Attributable to Parent [Abstract] Base rate Base Rate [Member] Accounts receivable Increase (Decrease) in Accounts Receivable Rest of World Rest of World [Member] Rest of World [Member] Schedule of Restructuring and Related Costs [Table] Restructuring Cost [Table] Customer [Axis] Customer [Axis] Cash flows used in financing activities: Cash Provided by (Used in) Financing Activity, Continuing Operation [Abstract] Customer relationships Customer Relationships [Member] Income from operations Income from operations Operating Income (Loss) Senior Secured Revolving Loan Line of Credit [Member] Retained earnings Retained Earnings (Accumulated Deficit) Schedule of Shares Redeemed Under Buyback Program Class of Treasury Stock [Table Text Block] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] 2029 and thereafter Long-Term Debt, Maturity, Year Four And Thereafter Long-Term Debt, Maturity, Year Four And Thereafter Personnel related liabilities Personnel Related Liabilities [Member] Personnel Related Liabilities Senior Secured Notes (the "2029 Notes") Senior Secured Notes Due May 2029 [Member] Senior Secured Notes Due May 2029 Current Fiscal Year End Date Current Fiscal Year End Date Technology assets Technology-Based Intangible Assets [Member] Ireland IRELAND Subsequent Event Type [Domain] Subsequent Event Type [Domain] Expected life Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Term Senior Secured Notes (the "2034 Notes") Senior Secured Notes Due May 2034 [Member] Senior Secured Notes - 2034 Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Weighted Average Grant Date Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Stock units to be granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Facility liability Facility Liability [Member] Facility Liability Statement [Table] Statement [Table] Adjustments to reconcile net income to net cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Lapse of statute of limitations Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations Weighted average grant date fair value Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Compensation Related Costs Share Based Payments Disclosure [Line Items] Compensation Related Costs Share Based Payments Disclosure [Line Items] Compensation Related Costs Share Based Payments Disclosure [Line Items] Variable Rate [Domain] Variable Rate [Domain] Basis of presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Unrecognized tax benefits Unrecognized tax benefits at start of period Unrecognized tax benefits at end of period Unrecognized Tax Benefits Weighted average number of ordinary shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Amendment Flag Amendment Flag Ordinary shares which have been reserved for issuance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized 2027 Long-Term Debt, Maturity, Year Two Operating leases Lessee, Operating Leases [Text Block] Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Unbilled revenue Increase (Decrease) in Contract with Customer, Asset Weighted average discount rate Operating Lease, Weighted Average Discount Rate, Percent Schedule of Stock Option Activity Share-Based Payment Arrangement, Option, Activity [Table Text Block] Interest and related penalties Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued Schedule of Fair Value, Assets Measured on Recurring Basis Fair Value, Assets Measured on Recurring Basis [Table Text Block] Basic (in shares) Weighted average number of ordinary shares outstanding for basic net income per ordinary share (in shares) Weighted Average Number of Shares Outstanding, Basic Approximate dollar value of shares that may yet be purchased under the program (in millions) Share Repurchase Program, Remaining Authorized, Amount Weighted Average Remaining Contractual Life Share-based Compensation Arrangement by Share-based Payment Award, Options, Weighted Average Remaining Contractual Term [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Options, Weighted Average Remaining Contractual Term [Abstract] Direct costs Cost of Goods and Service, Excluding Depreciation, Depletion, and Amortization Schedule of Reconciliation of Number of Shares Used in Computation of Basic and Diluted Net Income per Ordinary Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Share Repurchase Program [Table] Share Repurchase Program [Table] Exercisable at end of period (in shares) Number of shares exercisable (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number Subsequent Events [Abstract] Segment Reporting [Abstract] Segment Reporting [Abstract] Debt Disclosure [Abstract] Risk-free interest rate Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Amortization of financing costs and debt discount Amortization of Debt Issuance Costs Debt discount paid Debt Instrument, Unamortized Discount Outstanding at beginning of period (in USD per share) Outstanding at end of period (in USD per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price Restructuring and Related Activities [Abstract] Restructuring and Related Activities [Abstract] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Senior Secured Notes (the "2027 Notes") Senior Secured Notes Due May 2027 [Member] Senior Secured Notes Due May 2027 Ordinary shares, par value (in EUR cents per share) Common Stock, Par or Stated Value Per Share Ordinary shares, shares issued (in shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Issued Income taxes receivable Income Taxes Receivable, Current Weighted average remaining lease term Operating Lease, Weighted Average Remaining Lease Term Unbilled revenue Unbilled services (unbilled revenue) Contract with Customer, Asset, before Allowance for Credit Loss, Current Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Variable Rate Component [Domain] Variable Rate Component [Domain] Variable Rate Component [Domain] Percentage change in unearned revenue (payments on account) Increase (Decrease) In Contract With Customer, Liability, Gross, Current, Percent Increase (Decrease) In Contract with Customer, Liability, Gross, Current, Percent Schedule of Goodwill Schedule of Goodwill [Table Text Block] Interest expense Interest Expense, Nonoperating Subsequent events Subsequent Events [Text Block] Currency translation adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax 2025 (remaining) Long-Term Debt, Maturity, Remainder of Fiscal Year Total Liabilities Liabilities Debt instrument, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Increase related to current period tax positions Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Other liabilities Other Liabilities, Current Statement [Line Items] Statement [Line Items] Consolidation Items [Axis] Consolidation Items [Axis] Variable Rate [Axis] Variable Rate [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Schedule of Details of Movement in Restructuring Charges Schedule of Restructuring Reserve by Type of Cost [Table Text Block] Cash and cash equivalents Cash and Cash Equivalent Change in unbilled services (unbilled revenue) Increase (Decrease) In Contract With Customer, Asset, Gross, Current Increase (Decrease) In Contract With Customer, Asset, Gross, Current Additional ordinary shares which have been reserved for issuance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized Ordinary Shares Common Stock [Member] Shares vested (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Intangible assets Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block] Net (decrease) / increase in cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Effect of dilutive share options and other awards outstanding under share based compensation programs (in shares) Weighted Average Number of Shares Outstanding, Diluted, Adjustment Other Liabilities