ICON Public Limited (ICLR) 6-K 4 Nov 22 2022 Q3 Current report (foreign) Financial data

Cover

Cover	9 Months Ended
	Sep. 30, 2022
Cover [Abstract]
Document Type	6-K
Document Fiscal Year Focus	2022
Entity Registrant Name	ICON plc
Amendment Flag	false
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001060955
Current Fiscal Year End Date	--12-31
Document Period End Date	Sep. 30, 2022

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Current Assets:
Cash and cash equivalents	$ 609,158	$ 752,213
Available for sale investments	1,712	1,712
Accounts receivable, net of allowance for credit losses	1,435,010	1,342,770
Unbilled revenue	894,291	623,121
Other receivables	60,251	56,760
Prepayments and other current assets	129,218	114,323
Income taxes receivable	41,935	50,299
Total current assets	3,171,575	2,941,198
Non-current Assets:
Property, plant and equipment, net	315,524	336,444
Goodwill	8,942,525	9,037,931
Intangible assets	4,391,699	4,710,843
Operating right-of-use assets	137,000	198,123
Other receivables	61,792	70,557
Income taxes receivable	15,468	18,637
Deferred tax asset	62,298	48,392
Equity method investments	0	2,373
Investments in equity- long term	27,932	22,592
Total Assets	17,125,813	17,387,090
Current Liabilities:
Accounts payable	60,851	90,764
Unearned revenue	1,395,160	1,323,961
Other liabilities	1,147,142	949,629
Income taxes payable	72,580	59,433
Current bank credit lines and loan facilities	55,150	55,150
Total current liabilities	2,730,883	2,478,937
Non-current Liabilities:
Non-current bank credit lines and loan facilities	4,794,856	5,381,162
Lease liabilities	126,482	159,483
Non-current other liabilities	41,888	42,596
Non-current income taxes payable	218,644	172,109
Deferred tax liability	974,339	1,085,976
Commitments and contingencies	0	0
Total Liabilities	8,887,092	9,320,263
Shareholders' Equity:
Ordinary shares, par value 6 euro cents per share; 100,000,000 shares authorized, 81,645,279 shares issued and outstanding at September 30, 2022 and 81,554,683 shares issued and outstanding at December 31, 2021	6,645	6,640
Additional paid-in capital	6,818,877	6,733,910
Other undenominated capital	1,162	1,134
Accumulated other comprehensive loss	(291,901)	(90,937)
Retained earnings	1,703,938	1,416,080
Total Shareholders' Equity	8,238,721	8,066,827
Total Liabilities and Shareholders' Equity	$ 17,125,813	$ 17,387,090

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - € / shares	Sep. 30, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Ordinary shares, par value (in EUR cents per share)	€ 0.06	€ 0.06
Ordinary shares, shares authorized (in shares)	100,000,000	100,000,000
Ordinary shares, shares issued (in shares)	81,645,279	81,554,683
Ordinary shares, shares outstanding (in shares)	81,645,279	81,554,683

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Statement [Abstract]
Revenue	$ 1,942,427	$ 1,866,352	$ 5,779,384	$ 3,595,705
Costs and expenses:
Direct costs (excluding depreciation and amortization)	1,375,837	1,357,942	4,146,366	2,615,309
Selling, general and administrative expense	166,787	206,713	552,000	382,614
Depreciation and amortization	141,861	140,636	427,285	175,317
Transaction and integration-related expenses	8,001	149,791	28,970	182,309
Restructuring	6,197	6,162	32,890	6,162
Total costs and expenses	1,698,683	1,861,244	5,187,511	3,361,711
Income from operations	243,744	5,108	591,873	233,994
Interest income	1,434	53	1,727	496
Interest expense	(63,010)	(102,306)	(154,546)	(129,584)
Income/(loss) before provision for income taxes	182,168	(97,145)	439,054	104,906
Benefit arising/(Provision) for income taxes	(21,012)	3,563	(48,552)	(26,718)
Income before share of earnings from equity method investments	161,156	(93,582)	390,502	78,188
Share of losses in equity method investments	(1,002)	(688)	(2,643)	(1,471)
Net income/(loss) attributable to the Group	$ 160,154	$ (94,270)	$ 387,859	$ 76,717
Net income/(loss) per Ordinary Share attributable to the Group (note 13):
Basic (in USD per share)	$ 1.96	$ (1.17)	$ 4.76	$ 1.23
Diluted (in USD per share)	$ 1.94	$ (1.17)	$ 4.70	$ 1.22
Weighted average number of Ordinary Shares outstanding (note 13):
Basic (in shares)	81,582,375	80,771,397	81,481,686	62,264,851
Diluted (in shares)	82,493,211	80,771,397	82,473,521	63,095,857

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Comprehensive income:
Net income/(loss) attributable to the group	$ 160,154	$ (94,270)	$ 387,859	$ 76,717
Currency translation adjustment	(98,140)	(35,300)	(199,763)	(44,209)
Currency impact of long term funding (net of tax)	(826)	(162)	(1,201)	(401)
Amortization of interest rate hedge	0	0	0	113
Write off of loss on interest rate hedge	0	0	0	778
Total comprehensive income attributable to the group	$ 61,188	$ (129,732)	$ 186,895	$ 32,998

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) - 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, 2020		52,788,093
Beginning balance at Dec. 31, 2020	$ 1,850,236	$ 4,580	$ 617,104	$ 1,134	$ (35,477)	$ 1,262,895
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	97,122					97,122
Issue of restricted share units / performance share units (in shares)		70,097
Issue of restricted share units / performance share units	5	$ 5
Non-cash stock compensation expense	6,310		6,310
Share issuance costs	(5)		(5)
Other comprehensive loss, net of tax	(19,497)				(19,497)
Ending balance (in shares) at Mar. 31, 2021		52,858,190
Ending balance at Mar. 31, 2021	1,934,171	$ 4,585	623,409	1,134	(54,974)	1,360,017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	73,865					73,865
Exercise of share options (in shares)		4,020
Exercise of share options	170		170
Issue of restricted share units / performance share units (in shares)		95,853
Issue of restricted share units / performance share units	7	$ 7
Non-cash stock compensation expense	8,495		8,495
Share issuance costs	(5)		(5)
Other comprehensive loss, net of tax	11,240				11,240
Ending balance (in shares) at Jun. 30, 2021		52,958,063
Ending balance at Jun. 30, 2021	2,027,943	$ 4,592	632,069	1,134	(43,734)	1,433,882
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	(94,270)					(94,270)
Exercise of share options (in shares)		909,723
Exercise of share options	103,865	$ 54	103,811
Issue of restricted share units / performance share units (in shares)		157,608
Issue of restricted share units / performance share units	23	$ 23
Issue of shares associated with a business combination (in shares)		27,372,427
Issue of shares associated with a business combination	5,658,126	$ 1,960	5,656,166
Replacement share-based awards issued to acquiree employees	209,399		209,399
Non-cash stock compensation expense	99,771		99,771
Share issuance costs	(809)		(809)
Other comprehensive loss, net of tax	(35,462)				(35,462)
Ending balance (in shares) at Sep. 30, 2021		81,397,821
Ending balance at Sep. 30, 2021	$ 7,968,586	$ 6,629	6,700,407	1,134	(79,196)	1,339,612
Beginning balance (in shares) at Dec. 31, 2021	81,554,683	81,554,683
Beginning balance at Dec. 31, 2021	$ 8,066,827	$ 6,640	6,733,910	1,134	(90,937)	1,416,080
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	111,970					111,970
Exercise of share options (in shares)		84,090
Exercise of share options	7,497	$ 6	7,491
Issue of restricted share units / performance share units (in shares)		74,769
Issue of restricted share units / performance share units	4	$ 4
Non-cash stock compensation expense	18,840		18,840
Share issuance costs	(3)		(3)
Share repurchase program (in shares)		(420,530)
Share repurchase program	(99,983)	$ (28)		28		(99,983)
Share repurchase costs	(17)					(17)
Other comprehensive loss, net of tax	(35,818)				(35,818)
Ending balance (in shares) at Mar. 31, 2022		81,293,012
Ending balance at Mar. 31, 2022	$ 8,069,317	$ 6,622	6,760,238	1,162	(126,755)	1,428,050
Beginning balance (in shares) at Dec. 31, 2021	81,554,683	81,554,683
Beginning balance at Dec. 31, 2021	$ 8,066,827	$ 6,640	6,733,910	1,134	(90,937)	1,416,080
Ending balance (in shares) at Sep. 30, 2022	81,645,279	81,645,279
Ending balance at Sep. 30, 2022	$ 8,238,721	$ 6,645	6,818,877	1,162	(291,901)	1,703,938
Beginning balance (in shares) at Mar. 31, 2022		81,293,012
Beginning balance at Mar. 31, 2022	8,069,317	$ 6,622	6,760,238	1,162	(126,755)	1,428,050
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	115,734					115,734
Exercise of share options (in shares)		75,671
Exercise of share options	7,653	$ 4	7,649
Issue of restricted share units / performance share units (in shares)		157,924
Issue of restricted share units / performance share units	11	$ 11
Non-cash stock compensation expense	19,478		19,478
Other comprehensive loss, net of tax	(66,180)				(66,180)
Ending balance (in shares) at Jun. 30, 2022		81,526,607
Ending balance at Jun. 30, 2022	8,146,013	$ 6,637	6,787,365	1,162	(192,935)	1,543,784
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	160,154					160,154
Exercise of share options (in shares)		117,140
Exercise of share options	13,831	$ 4	13,827
Issue of restricted share units / performance share units (in shares)		1,532
Issue of restricted share units / performance share units	4	$ 4
Non-cash stock compensation expense	17,686		17,686
Share issuance costs	(1)		(1)
Other comprehensive loss, net of tax	$ (98,966)				(98,966)
Ending balance (in shares) at Sep. 30, 2022	81,645,279	81,645,279
Ending balance at Sep. 30, 2022	$ 8,238,721	$ 6,645	$ 6,818,877	$ 1,162	$ (291,901)	$ 1,703,938

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities:
Net income	$ 387,859	$ 76,717
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	427,285	175,317
Impairment of long lived assets	27,727	5,731
Reduction in carrying value of operating right-of-use assets	35,238	30,607
Loss on equity method investments	2,643	1,471
Charge on interest rate hedge	0	891
Amortization of financing costs and debt discount	13,544	4,448
Stock compensation expense	55,703	114,791
Loss on extinguishment of debt	0	14,434
Deferred taxes	(126,620)	(26,532)
Unrealized foreign exchange gain	(52,334)	(7,374)
Loss on issuance of debt	0	59,460
Other non-cash items	18,595	(1,592)
Changes in operating assets and liabilities:
Accounts receivable	(140,760)	123,413
Unbilled revenue	(221,104)	49,203
Unearned revenue	28,352	(60,514)
Other net assets	166,613	(21,147)
Net cash provided by operating activities	622,741	539,324
Cash flows from investing activities:
Purchase of property, plant and equipment	(85,145)	(46,067)
Purchase of subsidiary undertakings, net of cash acquired	0	(5,914,475)
Purchase of equity method investment	0	(2,450)
Purchase of available for sale investments	0	17
Purchase of investments in equity - long term	(1,840)	(2,243)
Net cash used in investing activities	(86,985)	(5,965,218)
Cash flows from financing activities:
Financing related costs	0	(30,349)
Proceeds from exercise of equity compensation	28,967	104,070
Share issue costs	(3)	(848)
Repurchase of ordinary shares	(99,983)	0
Share repurchase costs	(17)	0
Drawdown of bank credit lines and loan facilities	25,000	5,905,100
Repayment of bank credit lines and loan facilities	(625,000)	(377,780)
Net cash used in financing activities	(671,036)	5,600,193
Effect of exchange rate movements on cash	(7,775)	(6,080)
Net (decrease)/ increase in cash and cash equivalents	(143,055)	168,219
Cash and cash equivalents at beginning of period	752,213	840,305
Cash and cash equivalents at end of period	$ 609,158	$ 1,008,524

Basis of presentation

Basis of presentation	9 Months Ended
	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	Basis of presentation These condensed consolidated financial statements which have been prepared in accordance with United States Generally Accepted Accounting Principles (“US GAAP”) have not been audited. The condensed consolidated financial statements reflect all adjustments, which are, in the opinion of management, necessary to present a fair statement of the operating results and financial position for the periods presented. The preparation of the condensed consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect reported amounts and disclosures in the condensed consolidated financial statements. Actual results could differ from those estimates. The condensed consolidated financial statements should be read in conjunction with the accounting policies and notes to the consolidated financial statements included in ICON’s Form 20-F for the year ended December 31, 2021 (see note 2 - Significant accounting policies ). Operating results for the nine months ended September 30, 2022 are not necessarily indicative of the results that may be expected for the fiscal period ending December 31, 2022.

Significant accounting policies

Significant accounting policies	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Significant accounting policies	Significant accounting policies 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 in detail 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 several 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 itself 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. Business Combinations The cost of a business combination is measured as the aggregate of the fair values at the date of exchange of assets given, liabilities incurred or assumed and equity instruments issued in exchange for control. Where a business combination agreement provides for an adjustment to the cost of the acquisition which is contingent upon future events, the amount of the estimated adjustment is recognized at the acquisition date at the fair value of the contingent consideration. Any changes to this estimate outside the measurement period will depend on the classification of the contingent consideration. If the contingent consideration is classified as equity it shall not be re-measured and the settlement shall be accounted for within equity. If the contingent consideration is classified as a liability any adjustments will be accounted for through the Consolidated Statement of Operations or Other Comprehensive Income depending on whether the liability is considered a financial instrument. The assets, liabilities and contingent liabilities of businesses acquired are measured at their fair values at the date of acquisition. In the case of a business combination which is completed in stages, the fair values of the identifiable assets, liabilities and contingent liabilities are determined at the date of each exchange transaction. When the initial accounting for a business combination is determined provisionally, any subsequent adjustments to the provisional values allocated to the identifiable assets, liabilities and contingent liabilities are made within twelve months of the acquisition date and presented as adjustments to goodwill in the reporting period in which the adjustments are determined. The Company allocates a share of net income to the noncontrolling interest holders based on percentage ownership. Intangible Assets Intangible assets are amortized on a straight line basis over their estimated useful life. The carrying values of intangible assets are reviewed for recoverability to determine if the facts and circumstances suggest that a potential impairment may have occurred. If this review indicates that carrying values will not be recoverable the Company will record an impairment charge to reduce carrying values to estimated fair value.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2022
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Revenue disaggregated by customer concentration is as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Clients 1-5 539,907 525,806 1,595,007 1,242,446 Clients 6-10 270,073 283,003 831,660 472,788 Clients 11-25 405,171 398,816 1,100,118 704,312 Other 727,276 658,727 2,252,599 1,176,159 Total $ 1,942,427 $ 1,866,352 $ 5,779,384 $ 3,595,705 There was no revenue from individual customers greater than 10% of consolidated revenue in the respective periods. Accounts receivables and unbilled revenue are as follows: September 30, 2022 December 31, 2021 (in thousands) Contract assets: Billed services (accounts receivable) $ 1,458,753 $ 1,349,851 Unbilled services (unbilled revenue) 894,291 623,121 Accounts receivable and unbilled revenue, gross 2,353,044 1,972,972 Allowance for credit losses (23,743) (7,081) Accounts receivable and unbilled revenue, net $ 2,329,301 $ 1,965,891 Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows: (in thousands, except percentages) September 30, 2022 December 31, 2021 $ Change % Change Unbilled services (unbilled revenue) $ 894,291 $ 623,121 $ 271,170 43.5 % Unearned revenue (payments on account) (1,395,160) (1,323,961) (71,199) 5.4 % Net balance $ (500,869) $ (700,840) $ 199,971 (28.5) % 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 services and therefore contract assets rather than accounts receivables 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 to set-off between unbilled services (contract assets) and unearned revenue (contract liabilities), each are separately presented gross on the Condensed Consolidated Balance Sheet. Unbilled services as at September 30, 2022 increased by $271.2 million compared to December 31, 2021. Unearned revenue increased by $71.2 million over the same period resulting in an increase of $200.0 million in the net balance of unbilled services and unearned revenue or payments on account between December 31, 2021 and September 30, 2022. These fluctuations are primarily due to timing of payments and invoicing related to the Group's clinical trial management contracts. Billings and payments are established by contractual provisions including predetermined payment schedules which may or may not correspond to the timing of the transfer of control of the Company's services under the contract. Unbilled services arise from long-term contracts when a cost-based input method of revenue recognition is applied and revenue recognized exceeds the amount billed to the customer.

Accounts receivable, unbilled r

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities)	9 Months Ended
	Sep. 30, 2022
Revenue from Contract with Customer [Abstract]
Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities)	Revenue Revenue disaggregated by customer concentration is as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Clients 1-5 539,907 525,806 1,595,007 1,242,446 Clients 6-10 270,073 283,003 831,660 472,788 Clients 11-25 405,171 398,816 1,100,118 704,312 Other 727,276 658,727 2,252,599 1,176,159 Total $ 1,942,427 $ 1,866,352 $ 5,779,384 $ 3,595,705 There was no revenue from individual customers greater than 10% of consolidated revenue in the respective periods. Accounts receivables and unbilled revenue are as follows: September 30, 2022 December 31, 2021 (in thousands) Contract assets: Billed services (accounts receivable) $ 1,458,753 $ 1,349,851 Unbilled services (unbilled revenue) 894,291 623,121 Accounts receivable and unbilled revenue, gross 2,353,044 1,972,972 Allowance for credit losses (23,743) (7,081) Accounts receivable and unbilled revenue, net $ 2,329,301 $ 1,965,891 Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows: (in thousands, except percentages) September 30, 2022 December 31, 2021 $ Change % Change Unbilled services (unbilled revenue) $ 894,291 $ 623,121 $ 271,170 43.5 % Unearned revenue (payments on account) (1,395,160) (1,323,961) (71,199) 5.4 % Net balance $ (500,869) $ (700,840) $ 199,971 (28.5) % 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 services and therefore contract assets rather than accounts receivables 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 to set-off between unbilled services (contract assets) and unearned revenue (contract liabilities), each are separately presented gross on the Condensed Consolidated Balance Sheet. Unbilled services as at September 30, 2022 increased by $271.2 million compared to December 31, 2021. Unearned revenue increased by $71.2 million over the same period resulting in an increase of $200.0 million in the net balance of unbilled services and unearned revenue or payments on account between December 31, 2021 and September 30, 2022. These fluctuations are primarily due to timing of payments and invoicing related to the Group's clinical trial management contracts. Billings and payments are established by contractual provisions including predetermined payment schedules which may or may not correspond to the timing of the transfer of control of the Company's services under the contract. Unbilled services arise from long-term contracts when a cost-based input method of revenue recognition is applied and revenue recognized exceeds the amount billed to the customer.

Goodwill

Goodwill	9 Months Ended
	Sep. 30, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill Nine Months Ended Year Ended September 30, 2022 December 31, 2021 (in thousands) Opening balance $ 9,037,931 $ 936,257 Current period acquisitions (Note 7) — 8,120,006 Prior period acquisitions (Note 7) (35,692) — Foreign exchange movement (59,714) (18,332) Closing balance $ 8,942,525 $ 9,037,931

Intangible assets

Intangible assets	9 Months Ended
	Sep. 30, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets	Intangible assets Intangible assets, net consisted of the following: Nine Months Ended Year Ended September 30, 2022 December 31, 2021 Cost (in thousands) Customer relationships $ 4,072,988 $ 4,056,642 Order backlog 535,557 528,022 Trade names & brands 204,536 204,685 Patient database 170,049 170,525 Technology assets 120,283 121,507 Total cost 5,103,413 5,081,381 Accumulated amortization (711,714) (370,538) Net book value $ 4,391,699 $ 4,710,843

Business combinations

Business combinations	9 Months Ended
	Sep. 30, 2022
Business Combinations [Abstract]
Business combinations	Business combinations PRA Health Sciences, Inc. - Merger Completion 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, the parent of the PRA Health Sciences Group. The combined Group has retained the name ICON and brought together approximately 38,000 (as at the Merger date) employees across the globe, creating one of the world’s most advanced healthcare intelligence and clinical research organizations. The Merger was accounted for as a business combination using the acquisition method of accounting in accordance with ASC Topic 805, Business Combinations. The combined Company leverages its enhanced operations to transform clinical trials and accelerate biopharma customers’ commercial success through the development of much needed medicines and medical devices. The new ICON has a renewed focus on leveraging data, applying technology and accessing diverse patient populations to speed up drug development. Upon completion of the Merger, pursuant to the terms of the merger agreement, PRA became a wholly owned subsidiary of ICON plc. Under the terms of the Merger, PRA shareholders received per share $80 in cash and 0.4125 shares of ICON stock. The trading of PRA common stock on NASDAQ was suspended prior to market open on July 1, 2021. In the nine months ended September 30, 2022, the Company incurred $29.0 million of Merger-related expenses which were accounted for separately from the business combination and expensed as incurred within the “Transaction and integration related expenses” line item of the condensed consolidated statements of operations. These costs consisted primarily of integration costs including severance arrangements, retention agreements and advisory fees. The Merger Date fair value of the consideration transferred consisted of the following: (in thousands) Fair value of cash consideration $ 5,308,646 Fair value of ordinary shares issued to acquiree stockholders 5,658,126 Fair value of replacement share-based awards issued to acquiree employees 209,399 Repayment of term loan obligations and accrued interest * 865,800 $ 12,041,971 * This represents the portion of PRA debt paid by ICON. PRA also paid $401.6 million from available cash to settle debt obligations that existed at the Merger Date. The following table summarizes the allocation of the consideration transferred based on the Merger Date fair values of assets acquired and liabilities assumed, with the excess of the purchase price over the estimated fair values of the identifiable net assets acquired recorded as goodwill: July 1 2021 (in thousands) Cash and cash equivalents $ 259,971 Accounts receivable and unbilled revenue 934,308 Other current assets 125,156 Fixed assets 156,851 Operating lease right-of-use assets 180,601 Goodwill * 8,084,314 Intangible assets 4,919,000 Deferred tax assets 25,190 Other assets 33,928 Accounts payable (50,259) Accrued expenses and other current liabilities (380,048) Current portion of operating lease liabilities (36,506) Unearned revenue (739,278) Non-current portion of operating lease liabilities (147,204) Non-current deferred tax liabilities (1,119,762) Other non-current liabilities (204,291) Net assets acquired $ 12,041,971 * The goodwill in connection with the Merger is primarily attributable to the assembled workforce of PRA and the expected synergies of the Merger. None of the goodwill recognized is expected to be deductible for income tax purposes. The following table summarizes the fair value of identified intangible assets and their respective useful lives as of the Merger Date (in thousands, except for estimated useful lives): Estimated Fair Value Estimated Useful Life Customer relationship 3,938,000 23 years Order backlog 500,000 3 years Trade names 202,000 3 years Patient database 168,000 7 years Technology 111,000 5 years 4,919,000 At June 30, 2022, the Company completed its review of the July 1, 2021 acquisition balance sheet of PRA and completed final valuation reports associated with certain assets acquired and liabilities assumed. In the period since the Merger Date, the Company recognized certain measurement period adjustments as shown in the table below: Measurement period adjustments (in thousands) Cash and cash equivalents $ — Accounts receivable and unbilled revenue — Other current assets 14,465 Fixed assets (6,137) Operating lease right-of-use assets (11,744) Goodwill 70,436 Intangible assets * 44,000 Deferred tax assets (147,039) Other assets (1,166) Accounts payable — Accrued expenses and other current liabilities (37,496) Current portion of operating lease liabilities 1,865 Unearned revenue ** 19,623 Non-current portion of operating lease liabilities 10,454 Non-current deferred tax liabilities 193,837 Other non-current liabilities (151,098) * In the nine months ended September 30, 2022, the Company incurred $2.2 million amortization which related to the year ended December 31, 2021 due to the timing of when the measurement period adjustment was identified. ** The unearned revenue measurement period adjustment also includes $16.0 million as a result of the early adoption of ASU 2021-08 'Business Combinations (Topic 805) - Accounting for Contract Assets and Contract Liabilities from Contracts with Customers' in Quarter 4 2021. Pro forma financial information The following pro forma financial information was derived from the historical financial statements of the Company and PRA and presents the combined results of operations as if the Merger had occurred on January 1, 2021. The pro forma financial information is presented for comparative purposes only and is not necessarily indicative of the results that would have actually occurred had the Merger been completed on January 1, 2021. In addition, the pro forma financial information presented for the comparative period does not give effect to any anticipated cost savings, operating efficiencies or other synergies that may result from the Merger, or any estimated costs that have been or will be incurred by the Company to integrate the assets and operations of PRA. Nine Months Ended Nine Months Ended September 30, 2022 September 30, 2021 (in thousands, except per share data) Revenue $ 5,779,384 $ 5,580,879 Net income (loss) $ 387,859 $ 231,442 The pro forma financial information presented above for the nine months ended September 30, 2021 reflect certain pro forma adjustments to the financial performance of the Company had the Merger date been completed on January 1, 2021. The pro forma adjustments primarily relate to the amortization of acquired intangible assets, interest expense, amortization of deferred financing costs related to the new financing arrangements, transaction costs, share-based compensation expense related to the acceleration of share-based compensation awards and replacement share-based awards, and financing fees. The pro forma adjustments were tax effected using the tax rate relevant in the appropriate jurisdiction. The results presented above for the nine months ended September 30, 2022 are as reported in the Condensed Consolidated Statement of Operations.

Fair value measurements

Fair value measurements	9 Months Ended
	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Fair value measurements	Fair value measurements The Company records certain assets and liabilities at fair value. Fair value is defined as the price that would be received to sell an asset, or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. A three-level fair value hierarchy that prioritizes the inputs used to measure fair value is described below. This hierarchy requires entities to maximize the use of observable inputs and minimize the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows: • Level 1 — Quoted prices in active markets for identical assets or liabilities. • Level 2 — Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data. • Level 3 — Unobservable inputs that are supported by little or no market activity. This includes certain pricing models, discounted cash flow methodologies, and similar techniques that use significant unobservable inputs. The carrying amounts of financial instruments, including cash and cash equivalents, accounts receivable, unbilled services, contract assets, accounts payable, and unearned revenue approximate fair value due to the short maturities of these instruments. Recurring Fair Value Measurements The Company classifies its interests in investments in equity-long term 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 September 30, 2022 and December 31, 2021 meet the definition of equity securities without readily determinable fair values. The Company concluded that the interests held at September 30, 2022 and December 31, 2021 qualify for the Net Asset Value (NAV) practical expedient in ASC 820 'Fair value measurements and disclosures'. There was an increase in fair value of $3.5 million (December 31, 2021: $3.2 million) recognized in net income during the year bringing the carrying value of the subscriptions to $27.9 million at September 30, 2022 (December 31, 2021: $22.6 million). Non-recurring Fair Value Measurements

Restructuring

Restructuring	9 Months Ended
	Sep. 30, 2022
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring In the nine months ended September 30, 2022, a restructuring charge of $32.9 million was recorded in the Condensed Consolidated Statement of Operations under a restructuring plan adopted following a review of operations. The restructuring plan reflected resource rationalization across the business to improve employee utilization and an office consolidation program to optimize the Company's office footprint. Nine Months Ended September 30, 2022 September 30, 2021 (in thousands) Restructuring charges $ 32,890 $ 6,162 Net charge $ 32,890 $ 6,162 At September 30, 2022, a total liability of $11.3 million was recorded on the Consolidated Balance Sheet relating to restructuring activities. The total liability included $4.0 million of facilities related liabilities of which $1.7 million is included within other liabilities and $2.3 million is included within non-current other liabilities. The remaining provision of $7.3 million relates to workforce reduction and is included within other liabilities. Nine Months Ended Year ended September 30, 2022 December 31, 2021 (in thousands) Opening provision $ 10,311 $ 4,676 Additional provisions 5,066 11,272 Utilization (4,087) (5,637) Ending provision $ 11,290 $ 10,311

Operating leases

Operating leases	9 Months Ended
	Sep. 30, 2022
Leases [Abstract]
Operating leases	Operating leases Lease costs recorded under operating leases for the nine months ended September 30, 2022 and September 30, 2021 were as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Operating lease costs $ 12,164 $ 18,905 $ 40,976 $ 34,243 Income from sub-leases (268) (312) (898) (743) Net operating lease costs $ 11,896 $ 18,593 $ 40,078 $ 33,500 Of the total cost of $40.1 million incurred in the nine months ended September 30, 2022 (September 30, 2021: $33.5 million), $38.1 million (September 30, 2021: $31.9 million) is recorded within selling, general and administration costs and $2.0 million (September 30, 2021: $1.6 million) is recorded within direct costs. During the nine months ended September 30, 2022 and September 30, 2021, costs incurred by the Group related to variable lease payments was de minimis. Right-of-use assets obtained during the three months ended September 30, 2022, excluding early termination options, now reasonably certain to be exercised of $Nil (September 30, 2021: $Nil), totaled $1.7 million (September 30, 2021: $1.1 million). Right-of-use assets obtained during the nine months ended September 30, 2022, excluding early termination options, now reasonably certain to be exercised of $Nil (September 30, 2021: $4.2 million), totaled $37.6 million (September 30, 2021: $4.9 million). The weighted average remaining lease term and weighted-average discount rate at September 30, 2022 were 6.77 years and 2.48%, respectively. Future minimum lease payments under non-cancelable leases as of September 30, 2022 were as follows: Minimum rental payments (in thousands) September 30, 2022 Year 1 $ 45,854 Year 2 33,861 Year 3 23,134 Year 4 18,684 Year 5 15,497 Thereafter 45,708 Total future minimum lease payments 182,738 Lease imputed interest (14,030) Total $ 168,708 other liabilities

Bank credit lines and loan faci

Bank credit lines and loan facilities	9 Months Ended
	Sep. 30, 2022
Debt Disclosure [Abstract]
Bank credit lines and loan facilities	Bank credit lines and loan facilities The Company had the following debt outstanding as of September 30, 2022 and December 31, 2021: Principal amount Interest rate as of Interest rate as of September 30, December 31, (in thousands) September 30, 2022 December 31, 2021 2022 2021 Maturity Date Credit Facilities: Senior Secured Term Loan 5.938 % 2.750 % $ 4,401,213 $ 5,001,213 July 2028 Senior Secured Notes 2.875 % 2.875 % 500,000 500,000 July 2026 Total debt 4,901,213 5,501,213 Less current portion of long-term debt and debt issuance costs (55,150) (55,150) Total long-term debt 4,846,063 5,446,063 Less long-term portion of debt issuance costs and debt discount (51,207) (64,901) Total long-term debt, net $ 4,794,856 $ 5,381,162 The Company paid a $27.6 million debt discount in connection with the Senior Secured Credit Facility and Senior Secured Notes on July 1, 2021. As of September 30, 2022, the contractual maturities of the Company's debt obligations were as follows: Current maturities of long-term debt: (in thousands) 2022 (remaining) $ 13,788 2023 55,150 2024 55,150 2025 55,150 2026 and thereafter 4,721,975 Total $ 4,901,213 The Company's primary financing arrangements are its senior secured credit facilities (the "Senior Secured Credit Facilities"), which consists of a senior secured term loan and a revolving credit facility, and the senior secured notes (the "Senior Secured Notes"). Senior Secured Credit Facilities In conjunction with the completion of the Merger agreement, on July 1, 2021, ICON entered into a credit agreement providing for a senior secured term loan facility of $5,515 million and a senior secured revolving loan facility in an initial aggregate principal amount of $300 million (the "Senior Secured Credit Facilities"). 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 LIBOR plus an applicable margin of 2.50%, in each case, with a step down of 0.25% if the first lien net leverage ratio is equal to or less than 4.00 to 1.00. On November 10, 2021, the Company achieved a net leverage ratio of less than 4 times and the margin applicable to the senior secured term loan was reduced by 0.25%. The senior secured term loan facility is subject to a LIBOR floor of 0.50%. The interest rate margin applicable to borrowings under the revolving loan facility will be, at the option of the borrower, either (i) the applicable base rate plus an applicable margin of 1.00%, 0.60% or 0.25% based on ICON’s current corporate family rating assigned by S&P of BB- (or lower), BB or BB+ (or higher), respectively, or (ii) LIBOR (or an alternative reference rate) plus an applicable margin of 2.00%, 1.60% or 1.25% based on ICON’s current corporate family rating assigned by S&P of BB- (or lower), BB or BB+ (or higher), respectively. In addition, lenders under the revolving loan facility are entitled to commitment fees as a percentage of the applicable margin at the time of drawing and utilization fees dependent on the proportion of the facility drawn. On April 11, 2022, $25 million of the senior secured revolving loan facility was drawn down at an interest rate of 1.75%, representing one month LIBOR plus a margin of 1.25%. This was repaid in full on May 9, 2022. At September 30, 2022 $300.0 million remained available for borrowing under the senior secured revolving loan facility. On October 11, 2022, $50 million of the senior secured revolving loan facility was drawn down at an interest rate of 4.56%, representing 1 month LIBOR plus a margin of 1.25%. The Borrowers’ (as defined in the credit agreement) 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 have a first-priority lien on such assets, which will rank pari passu with the lien securing the Senior Secured Notes (see below), subject to other permitted liens. Our long-term debt arrangements contain customary restrictive covenants and, as of September 30, 2022, we were in compliance with our restrictive covenants in all material respects. On September 30, 2022 the Company repaid $200.0 million of the senior secured term loan facility and made a quarterly interest payment of $53.6 million. This repayments resulted in an additional charge associated with previously capitalized fees of $1.9 million. On June 30, 2022 the Company repaid $100.0 million of the senior secured term loan facility and made a quarterly interest payment of $39.4 million. This repayments resulted in an additional charge associated with previously capitalized fees of $0.9 million. On March 31, 2022 the Company repaid $300.0 million of the senior secured term loan facility and made a quarterly interest payment of $35.1 million. This repayment resulted in an additional charge associated with previously capitalized fees of $3.2 million. On December 29, 2021, the Company repaid $500.0 million of the senior secured term loan facility and made a quarterly interest payment of $40.8 million. These repayments resulted in an additional charge associated with previously capitalized fees of $5.6 million. The Company is permitted to make repayments on the senior secured term loan without penalty. Senior Secured Notes In addition to the Senior Secured Credit Facilities, on July 1, 2021, a subsidiary of the Company issued $500 million in aggregate principal amount of 2.875% senior secured notes due 2026 (the "Senior Secured Notes") in a private offering (the “Offering”). The Senior Secured Notes will mature on July 15, 2026. Fair Value of Debt The estimated fair value of the Company’s debt was $4,751.7 million at September 30, 2022. The fair values of the Senior Secured Credit Facilities and Senior Secured Notes were determined based on Level 2 inputs, which are based on rates at which the debt is traded among financial institutions.

Income taxes

Income taxes	9 Months Ended
	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Income taxes	Income taxes Income taxes recognized during the nine months ended September 30, 2022 and September 30, 2021, comprise: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Provision for income taxes $ 21,012 $ (3,563) $ 48,552 $ 26,718 As at September 30, 2022 the Company maintains a $223.8 million liability (December 31, 2021: $217.6 million) for unrecognized tax benefit, which is comprised of $201.7 million (December 31, 2021: $202.1 million) related to items generating unrecognized tax benefits and $22.1 million (December 31, 2021: $15.5 million) for interest and penalties related to such items. The Company recognizes interest accrued on unrecognized tax benefits as an additional income tax expense. The Company has analyzed the filing positions in all of the significant federal, state and foreign jurisdictions where it is required to file income tax returns, as well as open tax years in these jurisdictions. The only periods subject to audit by the major tax jurisdictions where the Company does business are the 2016 through 2021 tax years. During such audits, local tax authorities may challenge the positions taken by us in our tax returns.

Net income_(loss) per ordinary

Net income/(loss) per ordinary share	9 Months Ended
	Sep. 30, 2022
Earnings Per Share [Abstract]
Net income/(loss) per ordinary share	Net income/(loss) per ordinary share Basic net income/(loss) per ordinary share attributable to the Group has been computed by dividing net income/(loss) available to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period. Diluted net income/(loss) 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/(loss) 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/(loss) used for basic and diluted net income/(loss) per ordinary share. The reconciliation of the number of shares used in the computation of basic and diluted net income/(loss) per ordinary share is as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 Weighted average number of ordinary shares outstanding for basic net income/(loss) per ordinary share 81,582,375 80,771,397 81,481,686 62,264,851 Effect of dilutive share options and other awards outstanding under share based compensation programs 910,836 — 991,835 831,006 Weighted average number of ordinary shares outstanding for diluted net income/(loss) per ordinary share 82,493,211 80,771,397 82,473,521 63,095,857 Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 Net income/(loss) per Ordinary Share attributable to the Group: Basic $ 1.96 $ (1.17) $ 4.76 $ 1.23 Diluted $ 1.94 $ (1.17) $ 4.70 $ 1.22

Share-based awards

Share-based awards	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Share-based awards	Share-based awards Share Options The following table summarizes option activity for the nine months ended September 30, 2022: Options Weighted Weighted Outstanding at December 31, 2021 1,695,460 $ 104.79 5.39 Granted 108,643 $ 229.94 Exercised (276,901) $ 104.70 Canceled/expired (56,143) $ 141.35 Outstanding at September 30, 2022 1,471,059 $ 119.10 4.85 Exercisable at September 30, 2022 1,100,950 $ 101.29 4.31 The Company issues ordinary shares for all options exercised. The total amount of fully vested share options which remained outstanding at September 30, 2022 was 1,100,950. Fully vested share options at September 30, 2022 have an average remaining contractual term of 4.31 years and an average exercise price of $101.29. Fair value of Stock Options Assumptions The weighted average fair value of options granted during the nine months ended September 30, 2022 and September 30, 2021 was calculated using the Black-Scholes option pricing model. The weighted average grant date fair values and assumptions used were as follows: Nine Months Ended September 30, 2022 September 30, 2021 Weighted average grant date fair value $ 68.40 $ 49.15 Assumptions: Expected volatility 31 % 30 % Dividend yield — % — % Risk-free interest rate 1.85 % 0.78 % Expected life 5 years 5 years Expected volatility is based on the historical volatility of our common stock over a period equal to the expected term of the options; the expected life represents the weighted average period of time that options granted are expected to be outstanding given consideration to vesting schedules and our historical experience of past vesting and termination patterns. The risk-free rate is based on the U.S. government zero-coupon bonds yield curve in effect at time of the grant for periods corresponding with the expected life of the option. Restricted Share Units and Performance Share Units On April 30 2019, the Company approved the 2019 Consultants and Directors Restricted Share Unit Plan (the “2019 Consultants RSU Plan”), which was effective as of May 16, 2019, pursuant to which the Compensation and Organization Committee of the Company’s Board of Directors may select any consultant, adviser or non-executive Director retained by the Company, or a Subsidiary to receive an award under the plan. 250,000 ordinary shares have been reserved for issuance under the 2019 Consultants RSU Plan. The awards are at par value and vest over a service period. Awards granted to non-executive directors during 2020, 2021 and 2022 vest in twelve months. The Company has awarded RSUs and PSUs to certain key individuals of the Group. The following table summarizes RSU and PSU activity for the nine months ended September 30, 2022: Outstanding at December 31, 2021 154,190 $ 160.23 572,785 $ 191.20 Granted 64,682 $ 214.25 291,043 $ 217.51 Shares vested (45,567) $ 140.18 (188,658) $ 174.17 Forfeited (14,542) $ 182.33 (68,261) $ 203.82 Outstanding at September 30, 2022 158,763 $ 189.13 606,909 $ 207.94 The fair value of PSUs vested for the nine months ended September 30, 2022 totaled $6.4 million (full year 2021: $5.1 million). The fair value of RSUs vested for the nine months ended September 30, 2022 totaled $32.9 million (full year 2021: $83.5 million). The PSUs vest based on service and specified EPS targets over the periods 2020 – 2022, 2021 - 2023 and 2022 - 2024. Depending on the amount of EPS from 2021 to 2024, up to an additional 79,381 PSUs may also be granted. Non-cash stock compensation expense Non-cash stock compensation expense for the nine months ended September 30, 2022 and September 30, 2021 has been allocated as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Direct costs $ 6,285 $ 8,787 $ 17,117 $ 13,822 Selling, general and administrative 11,232 17,568 38,586 27,133 Transaction and integration-related expenses — 73,836 0 73,836 $ 17,517 $ 100,191 $ 55,703 $ 114,791

Share capital

Share capital	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Share capital	Share capital On July 1, 2021, the Company completed its Merger with PRA. In accordance with the terms of the Merger Agreement, the Company issued 27,372,427 shares of the Company’s ordinary share capital at par value in exchange for all outstanding PRA shares of common stock. The Company can acquire up to 10% of its outstanding ordinary shares (by way of redemption), in accordance with Irish law, the United States securities laws, and the Company’s constitutional documents through open market share acquisitions. On February 18, 2022, the Company commenced a share buyback program which was fully complete at March 31, 2022. Under this buyback program, 420,530 ordinary shares were redeemed by the Company for total consideration of $100.0 million. The buyback program gives a broker authority to acquire the Company’s ordinary shares from time to time on the open market in accordance with agreed terms and limitations. All ordinary shares that were redeemed under the buyback program were canceled in accordance with the Constitution of the Company and the nominal value of these shares transferred to other undenominated capital reserve as required under Irish Company Law.

Business Segment and Geographic

Business Segment and Geographical Information	9 Months Ended
	Sep. 30, 2022
Segment Reporting [Abstract]
Business Segment and Geographical Information	Business Segment and Geographical Information The Company is a clinical research organization ("CRO"), providing outsourced development services on a global basis to the pharmaceutical, biotechnology and medical device industries. 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" solution. The Company has expanded through internal growth, together with a number of strategic acquisitions to enhance its expertise and capabilities in certain areas of the clinical development process. The Company determines and presents operating segments based on the information that is internally provided to the chief operating decision maker, the (‘CODM’) in accordance with ASC 280 'Segment Reporting' . The Company determined that the CODM was comprised of the Chief Executive Officer and the Chief Financial Officer. The Company operates as one reporting segment, which is the provision of outsourced development services on a global basis to the pharmaceutical, biotechnology and medical devices industries. Revenues are allocated to individual entities based on where the work is performed in accordance with the Company's global transfer pricing model. Revenues and income from operations in Ireland are a function of our global contracting model and the Group’s transfer pricing model. ICON Ireland (Ireland Segment) 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 a guaranteed cost plus mark-up for the services they perform in each of their local territories. The cost plus mark-up for each ICON entity is established to ensure that each of ICON Ireland and the ICON entities that are involved in the conduct of services for customers, earn an appropriate arms-length return having regard to the assets owned, risks borne, and functions performed by each entity from these intercompany transactions. The cost plus mark-up policy is reviewed annually to ensure that it is market appropriate. The integration of entities acquired through the Merger into this global network and global transfer pricing model remains ongoing. The geographic split of revenue disclosed for each region outside Ireland is the cost plus revenue attributable to these entities. The residual revenues of the Group, once each ICON entity has been paid its respective intercompany service fee, generally fall to be retained by ICON Ireland. As such, revenues and income from operations in Ireland are a function of this global transfer pricing model and comprise revenues of the Group after deducting the cost plus revenues attributable to the activities performed outside Ireland. The integration of entities acquired through the Merger into the global transfer pricing model remains ongoing and these entities were not substantially part of the Group's cost plus arrangement in the period ended September 30, 2022. The geographical distribution of the Company’s segment measures as at September 30, 2022 and December 31, 2021 and for the nine months ended September 30, 2022 and September 30, 2021 is as follows: a) The distribution of revenue by geographical area was as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Ireland $ 526,867 $ 358,026 $ 1,395,198 $ 1,029,877 Rest of Europe 397,538 471,110 1,281,996 710,043 U.S. 903,200 934,014 2,767,844 1,599,623 Rest of World 114,822 103,202 334,346 256,162 Total $ 1,942,427 $ 1,866,352 $ 5,779,384 $ 3,595,705 b) The distribution of income from operations by geographical area was as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Ireland $ 93,640 $ 95,478 $ 159,059 $ 270,126 Rest of Europe 76,178 92,605 194,860 109,009 U.S. 63,356 (159,704) 177,145 (133,997) Rest of World 10,570 (23,271) 60,809 (11,144) Total $ 243,744 $ 5,108 $ 591,873 $ 233,994 c) The distribution of long-lived assets (property, plant and equipment and operating right-of-use assets), net, by geographical area was as follows: September 30, 2022 December 31, 2021 (in thousands) Ireland $ 127,577 $ 118,253 Rest of Europe 89,412 121,174 U.S. 197,650 239,828 Rest of World 37,885 55,312 Total $ 452,524 $ 534,567

Significant accounting polici_2

Significant accounting policies (Policies)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Revenue recognition	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 in detail 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 several 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 itself 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.
Business Combinations	Business Combinations The cost of a business combination is measured as the aggregate of the fair values at the date of exchange of assets given, liabilities incurred or assumed and equity instruments issued in exchange for control. Where a business combination agreement provides for an adjustment to the cost of the acquisition which is contingent upon future events, the amount of the estimated adjustment is recognized at the acquisition date at the fair value of the contingent consideration. Any changes to this estimate outside the measurement period will depend on the classification of the contingent consideration. If the contingent consideration is classified as equity it shall not be re-measured and the settlement shall be accounted for within equity. If the contingent consideration is classified as a liability any adjustments will be accounted for through the Consolidated Statement of Operations or Other Comprehensive Income depending on whether the liability is considered a financial instrument. The assets, liabilities and contingent liabilities of businesses acquired are measured at their fair values at the date of acquisition. In the case of a business combination which is completed in stages, the fair values of the identifiable assets, liabilities and contingent liabilities are determined at the date of each exchange transaction. When the initial accounting for a business combination is determined provisionally, any subsequent adjustments to the provisional values allocated to the identifiable assets, liabilities and contingent liabilities are made within twelve months of the acquisition date and presented as adjustments to goodwill in the reporting period in which the adjustments are determined.
Intangible Assets	Intangible Assets Intangible assets are amortized on a straight line basis over their estimated useful life. The carrying values of intangible assets are reviewed for recoverability to determine if the facts and circumstances suggest that a potential impairment may have occurred. If this review indicates that carrying values will not be recoverable the Company will record an impairment charge to reduce carrying values to estimated fair value.

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2022
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	Revenue disaggregated by customer concentration is as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Clients 1-5 539,907 525,806 1,595,007 1,242,446 Clients 6-10 270,073 283,003 831,660 472,788 Clients 11-25 405,171 398,816 1,100,118 704,312 Other 727,276 658,727 2,252,599 1,176,159 Total $ 1,942,427 $ 1,866,352 $ 5,779,384 $ 3,595,705 There was no revenue from individual customers greater than 10% of consolidated revenue in the respective periods.

Accounts receivable, unbilled_2

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) (Tables)	9 Months Ended
	Sep. 30, 2022
Revenue from Contract with Customer [Abstract]
Schedule of accounts receivables and unbilled revenue, and unbilled services and unearned revenue	Accounts receivables and unbilled revenue are as follows: September 30, 2022 December 31, 2021 (in thousands) Contract assets: Billed services (accounts receivable) $ 1,458,753 $ 1,349,851 Unbilled services (unbilled revenue) 894,291 623,121 Accounts receivable and unbilled revenue, gross 2,353,044 1,972,972 Allowance for credit losses (23,743) (7,081) Accounts receivable and unbilled revenue, net $ 2,329,301 $ 1,965,891 Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows: (in thousands, except percentages) September 30, 2022 December 31, 2021 $ Change % Change Unbilled services (unbilled revenue) $ 894,291 $ 623,121 $ 271,170 43.5 % Unearned revenue (payments on account) (1,395,160) (1,323,961) (71,199) 5.4 % Net balance $ (500,869) $ (700,840) $ 199,971 (28.5) %

Goodwill (Tables)

Goodwill (Tables)	9 Months Ended
	Sep. 30, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	Nine Months Ended Year Ended September 30, 2022 December 31, 2021 (in thousands) Opening balance $ 9,037,931 $ 936,257 Current period acquisitions (Note 7) — 8,120,006 Prior period acquisitions (Note 7) (35,692) — Foreign exchange movement (59,714) (18,332) Closing balance $ 8,942,525 $ 9,037,931

Intangible assets (Tables)

Intangible assets (Tables)	9 Months Ended
	Sep. 30, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	Intangible assets, net consisted of the following: Nine Months Ended Year Ended September 30, 2022 December 31, 2021 Cost (in thousands) Customer relationships $ 4,072,988 $ 4,056,642 Order backlog 535,557 528,022 Trade names & brands 204,536 204,685 Patient database 170,049 170,525 Technology assets 120,283 121,507 Total cost 5,103,413 5,081,381 Accumulated amortization (711,714) (370,538) Net book value $ 4,391,699 $ 4,710,843

Business combinations (Tables)

Business combinations (Tables)	9 Months Ended
	Sep. 30, 2022
Business Combinations [Abstract]
Schedule of Fair Value of PRA Health Sciences Inc Acquisition Consideration	The Merger Date fair value of the consideration transferred consisted of the following: (in thousands) Fair value of cash consideration $ 5,308,646 Fair value of ordinary shares issued to acquiree stockholders 5,658,126 Fair value of replacement share-based awards issued to acquiree employees 209,399 Repayment of term loan obligations and accrued interest * 865,800 $ 12,041,971 * This represents the portion of PRA debt paid by ICON. PRA also paid $401.6 million from available cash to settle debt obligations that existed at the Merger Date.
Schedule of PRA Health Sciences Inc Acquisition	The following table summarizes the allocation of the consideration transferred based on the Merger Date fair values of assets acquired and liabilities assumed, with the excess of the purchase price over the estimated fair values of the identifiable net assets acquired recorded as goodwill: July 1 2021 (in thousands) Cash and cash equivalents $ 259,971 Accounts receivable and unbilled revenue 934,308 Other current assets 125,156 Fixed assets 156,851 Operating lease right-of-use assets 180,601 Goodwill * 8,084,314 Intangible assets 4,919,000 Deferred tax assets 25,190 Other assets 33,928 Accounts payable (50,259) Accrued expenses and other current liabilities (380,048) Current portion of operating lease liabilities (36,506) Unearned revenue (739,278) Non-current portion of operating lease liabilities (147,204) Non-current deferred tax liabilities (1,119,762) Other non-current liabilities (204,291) Net assets acquired $ 12,041,971
Schedule of Fair Value of Intangible Assets PRA Health Sciences Inc Acquisition	The following table summarizes the fair value of identified intangible assets and their respective useful lives as of the Merger Date (in thousands, except for estimated useful lives): Estimated Fair Value Estimated Useful Life Customer relationship 3,938,000 23 years Order backlog 500,000 3 years Trade names 202,000 3 years Patient database 168,000 7 years Technology 111,000 5 years 4,919,000
Schedule of Measurement period adjustments of PRA Health Sciences Inc Acquisition	In the period since the Merger Date, the Company recognized certain measurement period adjustments as shown in the table below: Measurement period adjustments (in thousands) Cash and cash equivalents $ — Accounts receivable and unbilled revenue — Other current assets 14,465 Fixed assets (6,137) Operating lease right-of-use assets (11,744) Goodwill 70,436 Intangible assets * 44,000 Deferred tax assets (147,039) Other assets (1,166) Accounts payable — Accrued expenses and other current liabilities (37,496) Current portion of operating lease liabilities 1,865 Unearned revenue ** 19,623 Non-current portion of operating lease liabilities 10,454 Non-current deferred tax liabilities 193,837 Other non-current liabilities (151,098) * In the nine months ended September 30, 2022, the Company incurred $2.2 million amortization which related to the year ended December 31, 2021 due to the timing of when the measurement period adjustment was identified. ** The unearned revenue measurement period adjustment also includes $16.0 million as a result of the early adoption of ASU 2021-08 'Business Combinations (Topic 805) - Accounting for Contract Assets and Contract Liabilities from Contracts with Customers' in Quarter 4 2021.
Schedule of Proforma Information of PRA Health Sciences Inc Acquisition	Nine Months Ended Nine Months Ended September 30, 2022 September 30, 2021 (in thousands, except per share data) Revenue $ 5,779,384 $ 5,580,879 Net income (loss) $ 387,859 $ 231,442

Restructuring (Tables)

Restructuring (Tables)	9 Months Ended
	Sep. 30, 2022
Restructuring and Related Activities [Abstract]
Summary of Restructuring Charges	Nine Months Ended September 30, 2022 September 30, 2021 (in thousands) Restructuring charges $ 32,890 $ 6,162 Net charge $ 32,890 $ 6,162
Summary of details of movement in restructuring charges	Nine Months Ended Year ended September 30, 2022 December 31, 2021 (in thousands) Opening provision $ 10,311 $ 4,676 Additional provisions 5,066 11,272 Utilization (4,087) (5,637) Ending provision $ 11,290 $ 10,311

Operating leases (Tables)

Operating leases (Tables)	9 Months Ended
	Sep. 30, 2022
Leases [Abstract]
Schedule of Lease Costs	Lease costs recorded under operating leases for the nine months ended September 30, 2022 and September 30, 2021 were as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Operating lease costs $ 12,164 $ 18,905 $ 40,976 $ 34,243 Income from sub-leases (268) (312) (898) (743) Net operating lease costs $ 11,896 $ 18,593 $ 40,078 $ 33,500
Schedule of Operating Lease Maturity	Future minimum lease payments under non-cancelable leases as of September 30, 2022 were as follows: Minimum rental payments (in thousands) September 30, 2022 Year 1 $ 45,854 Year 2 33,861 Year 3 23,134 Year 4 18,684 Year 5 15,497 Thereafter 45,708 Total future minimum lease payments 182,738 Lease imputed interest (14,030) Total $ 168,708

Bank credit lines and loan fa_2

Bank credit lines and loan facilities (Tables)	9 Months Ended
	Sep. 30, 2022
Debt Disclosure [Abstract]
Schedule of Outstanding Debt	The Company had the following debt outstanding as of September 30, 2022 and December 31, 2021: Principal amount Interest rate as of Interest rate as of September 30, December 31, (in thousands) September 30, 2022 December 31, 2021 2022 2021 Maturity Date Credit Facilities: Senior Secured Term Loan 5.938 % 2.750 % $ 4,401,213 $ 5,001,213 July 2028 Senior Secured Notes 2.875 % 2.875 % 500,000 500,000 July 2026 Total debt 4,901,213 5,501,213 Less current portion of long-term debt and debt issuance costs (55,150) (55,150) Total long-term debt 4,846,063 5,446,063 Less long-term portion of debt issuance costs and debt discount (51,207) (64,901) Total long-term debt, net $ 4,794,856 $ 5,381,162
Schedule of Contractual Maturities of Debt	As of September 30, 2022, the contractual maturities of the Company's debt obligations were as follows: Current maturities of long-term debt: (in thousands) 2022 (remaining) $ 13,788 2023 55,150 2024 55,150 2025 55,150 2026 and thereafter 4,721,975 Total $ 4,901,213

Income taxes (Tables)

Income taxes (Tables)	9 Months Ended
	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense	Income taxes recognized during the nine months ended September 30, 2022 and September 30, 2021, comprise: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Provision for income taxes $ 21,012 $ (3,563) $ 48,552 $ 26,718

Net income_(loss) per ordinar_2

Net income/(loss) per ordinary share (Tables)	9 Months Ended
	Sep. 30, 2022
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/(loss) per ordinary share is as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 Weighted average number of ordinary shares outstanding for basic net income/(loss) per ordinary share 81,582,375 80,771,397 81,481,686 62,264,851 Effect of dilutive share options and other awards outstanding under share based compensation programs 910,836 — 991,835 831,006 Weighted average number of ordinary shares outstanding for diluted net income/(loss) per ordinary share 82,493,211 80,771,397 82,473,521 63,095,857 Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 Net income/(loss) per Ordinary Share attributable to the Group: Basic $ 1.96 $ (1.17) $ 4.76 $ 1.23 Diluted $ 1.94 $ (1.17) $ 4.70 $ 1.22

Share-based awards (Tables)

Share-based awards (Tables)	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Summary of stock option activity	The following table summarizes option activity for the nine months ended September 30, 2022: Options Weighted Weighted Outstanding at December 31, 2021 1,695,460 $ 104.79 5.39 Granted 108,643 $ 229.94 Exercised (276,901) $ 104.70 Canceled/expired (56,143) $ 141.35 Outstanding at September 30, 2022 1,471,059 $ 119.10 4.85 Exercisable at September 30, 2022 1,100,950 $ 101.29 4.31
Schedule of weighted average fair values and assumptions used	The weighted average grant date fair values and assumptions used were as follows: Nine Months Ended September 30, 2022 September 30, 2021 Weighted average grant date fair value $ 68.40 $ 49.15 Assumptions: Expected volatility 31 % 30 % Dividend yield — % — % Risk-free interest rate 1.85 % 0.78 % Expected life 5 years 5 years
Summary of RSU and PSU activity	The following table summarizes RSU and PSU activity for the nine months ended September 30, 2022: Outstanding at December 31, 2021 154,190 $ 160.23 572,785 $ 191.20 Granted 64,682 $ 214.25 291,043 $ 217.51 Shares vested (45,567) $ 140.18 (188,658) $ 174.17 Forfeited (14,542) $ 182.33 (68,261) $ 203.82 Outstanding at September 30, 2022 158,763 $ 189.13 606,909 $ 207.94
Schedule of non-cash stock compensation expense	Non-cash stock compensation expense for the nine months ended September 30, 2022 and September 30, 2021 has been allocated as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Direct costs $ 6,285 $ 8,787 $ 17,117 $ 13,822 Selling, general and administrative 11,232 17,568 38,586 27,133 Transaction and integration-related expenses — 73,836 0 73,836 $ 17,517 $ 100,191 $ 55,703 $ 114,791

Business Segment and Geograph_2

Business Segment and Geographical Information (Tables)	9 Months Ended
	Sep. 30, 2022
Segment Reporting [Abstract]
Schedule of Distribution of Revenue by Geographical Area	The distribution of revenue by geographical area was as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Ireland $ 526,867 $ 358,026 $ 1,395,198 $ 1,029,877 Rest of Europe 397,538 471,110 1,281,996 710,043 U.S. 903,200 934,014 2,767,844 1,599,623 Rest of World 114,822 103,202 334,346 256,162 Total $ 1,942,427 $ 1,866,352 $ 5,779,384 $ 3,595,705
Schedule of Distribution of Income from Operations by Geographical Area	The distribution of income from operations by geographical area was as follows: Three Months Ended Nine Months Ended September 30, 2022 September 30, 2021 September 30, 2022 September 30, 2021 (in thousands) (in thousands) Ireland $ 93,640 $ 95,478 $ 159,059 $ 270,126 Rest of Europe 76,178 92,605 194,860 109,009 U.S. 63,356 (159,704) 177,145 (133,997) Rest of World 10,570 (23,271) 60,809 (11,144) Total $ 243,744 $ 5,108 $ 591,873 $ 233,994
Schedule of Distribution of Depreciation and Amortization 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: September 30, 2022 December 31, 2021 (in thousands) Ireland $ 127,577 $ 118,253 Rest of Europe 89,412 121,174 U.S. 197,650 239,828 Rest of World 37,885 55,312 Total $ 452,524 $ 534,567

Revenue (Details)

Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Revenue	$ 1,942,427	$ 1,866,352	$ 5,779,384	$ 3,595,705
Clients 1-5
Disaggregation of Revenue [Line Items]
Revenue	539,907	525,806	1,595,007	1,242,446
Clients 6-10
Disaggregation of Revenue [Line Items]
Revenue	270,073	283,003	831,660	472,788
Clients 11-25
Disaggregation of Revenue [Line Items]
Revenue	405,171	398,816	1,100,118	704,312
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 727,276	$ 658,727	$ 2,252,599	$ 1,176,159

Accounts receivable, unbilled_3

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	Sep. 30, 2022	Dec. 31, 2021
Contract Assets [Abstract]
Billed services (accounts receivable)	$ 1,458,753	$ 1,349,851
Unbilled services (unbilled revenue)	894,291	623,121
Accounts receivable and unbilled revenue, gross	2,353,044	1,972,972
Allowance for credit losses	(23,743)	(7,081)
Accounts receivable and unbilled revenue, net	$ 2,329,301	$ 1,965,891

Accounts receivable, unbilled_4

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	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Unbilled services (unbilled revenue)	$ 894,291	$ 623,121
Change in unbilled services (unbilled revenue)	$ 271,170
Percentage change in unbilled services (unbilled revenue)	43.50%
Unearned revenue (payments on account)	$ (1,395,160)	(1,323,961)
Change in unearned revenue (payments on account)	$ (71,199)
Percentage change in unearned revenue (payments on account)	5.40%
Net balance	$ (500,869)	$ (700,840)
Change in net balance	$ 199,971
Percentage change in net balance	(28.50%)

Accounts receivable, unbilled_5

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Increase in unbilled services (unbilled revenue)	$ 271,170
Decrease in unearned revenue (payments on account)	(71,199)
Increase in net balance	199,971
Revenue, remaining performance obligation	$ 13,500,000	$ 13,000,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation percentage	49%
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months

Goodwill - Schedule of Goodwill

Goodwill - Schedule of Goodwill (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Goodwill [Roll Forward]
Opening balance	$ 9,037,931	$ 936,257
Current period acquisitions (Note 7)	0	8,120,006
Prior period acquisitions (Note 7)	(35,692)	0
Foreign exchange movement	(59,714)	(18,332)
Closing balance	$ 8,942,525	$ 9,037,931

Goodwill - Narrative (Details)

Goodwill - Narrative (Details) - USD ($)	Sep. 30, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Accumulated impairment loss	$ 0	$ 0

Intangible assets (Details)

Intangible assets (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Total cost	$ 5,103,413	$ 5,081,381
Accumulated amortization	(711,714)	(370,538)
Net book value	4,391,699	4,710,843
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Total cost	4,072,988	4,056,642
Order backlog
Finite-Lived Intangible Assets [Line Items]
Total cost	535,557	528,022
Trade names & brands
Finite-Lived Intangible Assets [Line Items]
Total cost	204,536	204,685
Patient database
Finite-Lived Intangible Assets [Line Items]
Total cost	170,049	170,525
Technology assets
Finite-Lived Intangible Assets [Line Items]
Total cost	$ 120,283	$ 121,507

Business combinations - Narrati

Business combinations - Narrative (Details) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	Jul. 01, 2021 Employee $ / shares shares	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)
Business Acquisition [Line Items]
Entity number of employees | Employee	38,000
Acquisition-related costs		$ 8,001	$ 149,791	$ 28,970	$ 182,309
PRA Health Sciences, Inc
Business Acquisition [Line Items]
Business acquisition, share price (in USD per share) | $ / shares	$ 80
Business acquisition, number of shares issued (in shares) | shares	0.4125
Integration-related costs				$ 29,000

Business combinations - Schedul

Business combinations - Schedule of Fair Value of PRA Health Sciences Inc Acquisition Consideration (Details) - USD ($) $ in Thousands		9 Months Ended
	Jul. 01, 2021	Sep. 30, 2022	Sep. 30, 2021
Business Acquisition [Line Items]
Fair value of cash consideration		$ 0	$ 5,914,475
PRA Health Sciences, Inc
Business Acquisition [Line Items]
Fair value of cash consideration	$ 5,308,646
Fair value of ordinary shares issued to acquiree stockholders	5,658,126
Fair value of replacement share-based awards issued to acquiree employees	209,399
Repayment of term loan obligations and accrued interest	865,800
Total consideration transferred	12,041,971
Payments to settle debt obligations that existed prior to acquisition date	$ 401,600

Business combinations - Sched_2

Business combinations - Schedule of PRA Health Sciences Inc Acquisition (Details) - USD ($)	Sep. 30, 2022	Dec. 31, 2021	Jul. 01, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill	$ 8,942,525,000	$ 9,037,931,000		$ 936,257,000
PRA Health Sciences, Inc
Business Acquisition [Line Items]
Cash and cash equivalents			$ 259,971,000
Accounts receivable and unbilled revenue			934,308,000
Other current assets			125,156,000
Fixed assets			156,851,000
Operating lease right-of-use assets			180,601,000
Goodwill			8,084,314,000
Intangible assets			4,919,000,000
Deferred tax assets			25,190,000
Other assets			33,928,000
Accounts payable			(50,259,000)
Accrued expenses and other current liabilities			(380,048,000)
Current portion of operating lease liabilities			(36,506,000)
Unearned revenue			(739,278,000)
Non-current portion of operating lease liabilities			(147,204,000)
Non-current deferred tax liabilities			(1,119,762,000)
Other non-current liabilities			(204,291,000)
Net assets acquired			12,041,971,000
Goodwill expected to be tax deductible			$ 0

Business combinations - Sched_3

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

Schedule of Measurement Period

Schedule of Measurement Period Adjustments of PRA Health Sciences Inc Acquisition (Details) - PRA Health Sciences, Inc - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Jun. 30, 2022
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Cash and cash equivalents		$ 0
Accounts receivable and unbilled revenue		0
Other current assets		14,465
Fixed assets		(6,137)
Operating lease right-of-use assets		(11,744)
Goodwill		70,436
Intangible assets		44,000
Deferred tax assets		(147,039)
Other assets		(1,166)
Accounts payable		0
Accrued expenses and other current liabilities		(37,496)
Current portion of operating lease liabilities		1,865
Unearned Revenue		19,623
Non-current portion of operating lease liabilities		10,454
Non-current deferred tax liabilities		193,837
Other non-current liabilities		$ (151,098)
Amortization adjustment	$ 2,200
Accounting Standards Update 2021-08
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Unearned Revenue	$ 16,000

Business combinations - Sched_4

Business combinations - Schedule of Proforma Information of PRA Health Sciences Inc Acquisition (Details) - PRA Health Sciences, Inc - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Business Acquisition [Line Items]
Revenue	$ 5,779,384	$ 5,580,879
Net income (loss)	$ 387,859	$ 231,442

Fair value measurements (Detail

Fair value measurements (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase (decrease) in equity securities, FV-NI	$ 3.5	$ 3.2
Carrying value of long-term investments in equity	27.9	$ 22.6
Fair value, nonrecurring | Fair value, inputs, level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	13,334.2
Goodwill at fair value	8,942.5
Net intangible assets at fair value	$ 4,391.7

Restructuring - Narrative (Deta

Restructuring - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 6,197	$ 6,162	$ 32,890	$ 6,162
Provision balance	11,290		11,290		$ 10,311	$ 4,676
Employee severance
Restructuring Cost and Reserve [Line Items]
Provision balance	7,300		7,300
Other liability | Other liabilities
Restructuring Cost and Reserve [Line Items]
Provision balance	1,700		1,700
Other liability | Non-current other liabilities
Restructuring Cost and Reserve [Line Items]
Provision balance	2,300		2,300
Facility liability
Restructuring Cost and Reserve [Line Items]
Provision balance	$ 4,000		$ 4,000

Restructuring - Summary of Rest

Restructuring - Summary of Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Restructuring and Related Activities [Abstract]
Restructuring charges	$ 6,197	$ 6,162	$ 32,890	$ 6,162

Restructuring - Summary of Deta

Restructuring - Summary of Details of Movement in Restructuring Charges (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Restructuring Reserve [Roll Forward]
Opening provision	$ 10,311	$ 4,676
Additional provisions	5,066	11,272
Utilization	(4,087)	(5,637)
Ending provision	$ 11,290	$ 10,311

Operating leases - Schedule of

Operating leases - Schedule of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Leases [Abstract]
Operating lease costs	$ 12,164	$ 18,905	$ 40,976	$ 34,243
Income from sub-leases	(268)	(312)	(898)	(743)
Net operating lease costs	$ 11,896	$ 18,593	$ 40,078	$ 33,500

Operating leases - Narrative (D

Operating leases - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Lessee, Lease, Description [Line Items]
Total lease cost	$ 11,896	$ 18,593	$ 40,078	$ 33,500
Early termination options reasonably certain to be exercised	0	0	0	4,200
Right-of-use assets obtained in exchange for lease obligations	$ 1,700	$ 1,100	$ 37,600	$ 4,900
Weighted average remaining lease term	6 years 9 months 7 days		6 years 9 months 7 days
Weighted average discount rate	2.48%		2.48%
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities	Other Liabilities	Other Liabilities	Other Liabilities
Other liabilities
Lessee, Lease, Description [Line Items]
Operating lease liabilities	$ 42,200	$ 61,900	$ 42,200	$ 61,900
Selling, general and administration costs
Lessee, Lease, Description [Line Items]
Total lease cost			38,100	31,900
Direct costs
Lessee, Lease, Description [Line Items]
Total lease cost			$ 2,000	$ 1,600

Operating leases - Schedule o_2

Operating leases - Schedule of Operating Lease Maturity (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Leases [Abstract]
Year 1	$ 45,854
Year 2	33,861
Year 3	23,134
Year 4	18,684
Year 5	15,497
Thereafter	45,708
Total future minimum lease payments	182,738
Lease imputed interest	(14,030)
Total	$ 168,708

Bank credit lines and loan fa_3

Bank credit lines and loan facilities - Schedule of Outstanding Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021	Jul. 01, 2021
Debt Instrument [Line Items]
Total debt	$ 4,901,213	$ 5,501,213
Less current portion of long-term debt and debt issuance costs	(55,150)	(55,150)
Total long-term debt	4,846,063	5,446,063
Less long-term portion of debt issuance costs and debt discount	(51,207)	(64,901)
Total long-term debt, net	$ 4,794,856	$ 5,381,162
Senior Secured Term Loan | Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, interest rate	5.938%	2.75%	1%
Total debt	$ 4,401,213	$ 5,001,213
Senior Secured Notes | Senior Secured Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	2.875%	2.875%	2.875%
Total debt	$ 500,000	$ 500,000

Bank credit lines and loan fa_4

Bank credit lines and loan facilities - Narrative (Details) $ in Thousands									9 Months Ended
	Oct. 11, 2022 USD ($)	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Apr. 11, 2022 USD ($)	Mar. 31, 2022 USD ($)	Dec. 29, 2021 USD ($)	Nov. 10, 2021	Jul. 01, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
Long-term debt		$ 4,794,856							$ 4,794,856		$ 5,381,162
Drawdown of bank credit lines and loan facilities									25,000	$ 5,905,100
Long-term debt at fair value		$ 4,751,700							$ 4,751,700
Senior Secured Credit Facility and Senior Secured Notes | Senior Secured Term Loan
Debt Instrument [Line Items]
Debt discount paid								$ 27,600
Senior Secured Term Loan | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								2.50%
Variable rate, step down percentage (in percent)								0.25%
First lien net leverage ratio							4
Decrease in basis spread on variable rate							0.25%
Senior Secured Term Loan | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
First lien net leverage ratio								4
Senior Secured Term Loan | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								0.50%
First lien net leverage ratio								1
Senior Secured Term Loan | Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, principal amount								$ 5,515,000
Debt instrument, interest rate		5.938%						1%	5.938%		2.75%
Repayments of senior debt		$ 200,000	$ 100,000		$ 300,000	$ 500,000
Interest paid		53,600	39,400		35,100	40,800
Payments of debt restructuring costs		1,900	$ 900		$ 3,200	$ 5,600
Senior secured revolving loan facility | London Interbank Offered Rate (LIBOR) | Variable rate component two
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								1.60%
Senior secured revolving loan facility | London Interbank Offered Rate (LIBOR) | Maximum | Variable rate component two
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								2%
Senior secured revolving loan facility | London Interbank Offered Rate (LIBOR) | Minimum | Subsequent event
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)	1.25%
Senior secured revolving loan facility | London Interbank Offered Rate (LIBOR) | Minimum | Variable rate component two
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)				1.25%				1.25%
Senior secured revolving loan facility | Base rate | Variable rate component one
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								0.60%
Senior secured revolving loan facility | Base rate | Maximum | Variable rate component one
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								1%
Senior secured revolving loan facility | Base rate | Minimum | Variable rate component one
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)								0.25%
Senior secured revolving loan facility | Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, interest rate				1.75%
Long-term debt				$ 25,000
Line of credit facility, remaining borrowing capacity		$ 300,000							$ 300,000
Senior secured revolving loan facility | Senior Secured Term Loan | Subsequent event
Debt Instrument [Line Items]
Drawdown of bank credit lines and loan facilities	$ 50,000
Line of credit facility, interest rate during period	4.56%
Senior secured revolving loan facility | Senior Secured Term Loan | London Interbank Offered Rate (LIBOR) | Subsequent event
Debt Instrument [Line Items]
Long-term debt, floating rate, duration	1 month
Senior secured revolving loan facility | Senior Secured Term Loan | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Long-term debt, floating rate, duration				1 month
Senior secured revolving loan facility | Line of credit | Senior secured revolving loan facility
Debt Instrument [Line Items]
Debt instrument, maximum borrowing capacity								$ 300,000
Senior Secured Notes | Senior Secured Notes
Debt Instrument [Line Items]
Debt instrument, principal amount								$ 500,000
Debt instrument, interest rate		2.875%						2.875%	2.875%		2.875%

Bank credit lines and loan fa_5

Bank credit lines and loan facilities - Schedule of Contractual Maturities of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Disclosure [Abstract]
2022 (remaining)	$ 13,788
2023	55,150
2024	55,150
2025	55,150
2026 and thereafter	4,721,975
Total debt	$ 4,901,213	$ 5,501,213

Income taxes - Schedule of Comp

Income taxes - Schedule of Components of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 21,012	$ (3,563)	$ 48,552	$ 26,718

Income taxes - Narrative (Detai

Income taxes - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Liability for unrecognized tax benefit	$ 223.8	$ 217.6
Items generating unrecognized tax benefits	201.7	202.1
Interest and related penalties	$ 22.1	$ 15.5

Net income_(loss) per ordinar_3

Net income/(loss) per ordinary share - Schedule of Reconciliation of Number of Shares Used in Computation of Basic and Diluted Net Income Per Ordinary Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share [Abstract]
Weighted average number of ordinary shares outstanding for basic net income per ordinary share (in shares)	81,582,375	80,771,397	81,481,686	62,264,851
Effect of dilutive share options and other awards outstanding under share based compensation programs (in shares)	910,836	0	991,835	831,006
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share (in shares)	82,493,211	80,771,397	82,473,521	63,095,857

Net income_(loss) per ordinar_4

Net income/(loss) per ordinary share - Schedule of Reconciliation of Net Income Attributable to the Group (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Net income/(loss) per Ordinary Share attributable to the Group:
Basic (in USD per share)	$ 1.96	$ (1.17)	$ 4.76	$ 1.23
Diluted (in USD per share)	$ 1.94	$ (1.17)	$ 4.70	$ 1.22

Share-based awards - Summary of

Share-based awards - Summary of Stock Option Activity (Details) - Employee Stock Option			9 Months Ended
	Sep. 30, 2022 $ / shares shares	Dec. 31, 2021 $ / shares shares	Sep. 30, 2022 $ / shares shares
Options Outstanding Number of Shares
Outstanding at beginning of period (in shares) | shares			1,695,460
Granted (in shares) | shares			108,643
Exercised (in shares) | shares			(276,901)
Canceled/expired (in shares) | shares			(56,143)
Outstanding at end of period (in shares) | shares	1,471,059	1,695,460	1,471,059
Exercisable at end of period (in shares) | shares	1,100,950		1,100,950
Weighted Average Exercise Price
Outstanding at beginning of period (in USD per share) | $ / shares			$ 104.79
Granted (in USD per share) | $ / shares			229.94
Exercised (in USD per share) | $ / shares			104.70
Canceled/expired (in USD per share) | $ / shares			141.35
Outstanding at end of period (in USD per share) | $ / shares	$ 119.10	$ 104.79	119.10
Exercisable at end of period (in USD per share) | $ / shares	$ 101.29		$ 101.29
Weighted Average Remaining Contractual Life
Weighted average contractual term of options outstanding	4 years 10 months 6 days	5 years 4 months 20 days
Weighted average contractual term of options exercisable	4 years 3 months 21 days

Share-based awards - Narrative

Share-based awards - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions		9 Months Ended	12 Months Ended	41 Months Ended
	Sep. 30, 2022	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2022	May 16, 2019
Employee Stock Option
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Number of shares exercisable (in shares)	1,100,950	1,100,950		1,100,950
Weighted average contractual term of options exercisable	4 years 3 months 21 days
Weighted average exercise price of options exercisble (USD per share)	$ 101.29	$ 101.29		$ 101.29
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 directors
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Shares vesting period				12 months
Performance Share Unit (PSUs)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Fair value of stock units vested		$ 6.4	$ 5.1
Restricted Stock Units (RSUs)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Fair value of stock units vested		$ 32.9	$ 83.5
PSUs based on service and EPS targets | Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock units to be granted (in shares)	79,381	79,381		79,381

Share-based awards - Schedule o

Share-based awards - Schedule of Weighted Average Fair Values and Assumptions Used (Details) - Employee Stock Option - $ / shares	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value	$ 68.40	$ 49.15
Assumptions:
Expected volatility	31%	30%
Dividend yield	0%	0%
Risk-free interest rate	1.85%	0.78%
Expected life	5 years	5 years

Share-based awards - Summary _2

Share-based awards - Summary of RSU and PSU Activity (Details)	9 Months Ended
	Sep. 30, 2022 $ / shares shares
Performance Share Unit (PSUs)
Outstanding Number of Shares
Outstanding at beginning of period (in shares) | shares	154,190
Granted (in shares) | shares	64,682
Shares vested (in shares) | shares	(45,567)
Forfeited (in shares) | shares	(14,542)
Outstanding at end of period (in shares) | shares	158,763
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in USD per share) | $ / shares	$ 160.23
Granted (in USD per share) | $ / shares	214.25
Shares vested (in USD per share) | $ / shares	140.18
Forfeited (in USD per share) | $ / shares	182.33
Outstanding at end of period (in USD per share) | $ / shares	$ 189.13
Restricted Stock Units (RSUs)
Outstanding Number of Shares
Outstanding at beginning of period (in shares) | shares	572,785
Granted (in shares) | shares	291,043
Shares vested (in shares) | shares	(188,658)
Forfeited (in shares) | shares	(68,261)
Outstanding at end of period (in shares) | shares	606,909
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in USD per share) | $ / shares	$ 191.20
Granted (in USD per share) | $ / shares	217.51
Shares vested (in USD per share) | $ / shares	174.17
Forfeited (in USD per share) | $ / shares	203.82
Outstanding at end of period (in USD per share) | $ / shares	$ 207.94

Share-based awards - Schedule_2

Share-based awards - Schedule of Non-cash Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 17,517	$ 100,191	$ 55,703	$ 114,791
Direct costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	6,285	8,787	17,117	13,822
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	11,232	17,568	38,586	27,133
Transaction and integration-related expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 0	$ 73,836	$ 0	$ 73,836

Share capital (Details)

Share capital (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 01, 2021	Mar. 31, 2022	Mar. 31, 2022	Sep. 30, 2021	Sep. 30, 2022
Equity, Class of Treasury Stock [Line Items]
Share repurchase program, value of shares repurchased			$ 99,983
Ordinary shares
Equity, Class of Treasury Stock [Line Items]
Issue of shares associated with a business combination (in shares)	27,372,427			27,372,427
Share repurchase program, number of shares repurchased (in shares)			420,530
Share repurchase program, value of shares repurchased			$ 28
Buyback Program
Equity, Class of Treasury Stock [Line Items]
Share repurchase program, number of shares repurchased (in shares)		420,530
Share repurchase program, value of shares repurchased		$ 100,000
Buyback Program | Maximum
Equity, Class of Treasury Stock [Line Items]
Share repurchase program, authorized percentage					10%

Business Segment and Geograph_3

Business Segment and Geographical Information - Narrative (Details)	9 Months Ended
	Sep. 30, 2022 segment
Segment Reporting [Abstract]
Number of operating segments	1

Business Segment and Geograph_4

Business Segment and Geographical Information - Schedule of Distribution of Revenue by Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Revenue	$ 1,942,427	$ 1,866,352	$ 5,779,384	$ 3,595,705
Ireland
Segment Reporting Information [Line Items]
Revenue	526,867	358,026	1,395,198	1,029,877
Rest of Europe
Segment Reporting Information [Line Items]
Revenue	397,538	471,110	1,281,996	710,043
U.S.
Segment Reporting Information [Line Items]
Revenue	903,200	934,014	2,767,844	1,599,623
Rest of World
Segment Reporting Information [Line Items]
Revenue	$ 114,822	$ 103,202	$ 334,346	$ 256,162

Business Segment and Geograph_5

Business Segment and Geographical Information - Schedule of Distribution of Income from Operations by Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Income from operations	$ 243,744	$ 5,108	$ 591,873	$ 233,994
Ireland
Segment Reporting Information [Line Items]
Income from operations	93,640	95,478	159,059	270,126
Rest of Europe
Segment Reporting Information [Line Items]
Income from operations	76,178	92,605	194,860	109,009
U.S.
Segment Reporting Information [Line Items]
Income from operations	63,356	(159,704)	177,145	(133,997)
Rest of World
Segment Reporting Information [Line Items]
Income from operations	$ 10,570	$ (23,271)	$ 60,809	$ (11,144)

Business Segment and Geograph_6

Business Segment and Geographical Information - Schedule of Distribution of Depreciation and Amortization by Geographical Area (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Long-lived assets	$ 452,524	$ 534,567
Ireland
Segment Reporting Information [Line Items]
Long-lived assets	127,577	118,253
Rest of Europe
Segment Reporting Information [Line Items]
Long-lived assets	89,412	121,174
U.S.
Segment Reporting Information [Line Items]
Long-lived assets	197,650	239,828
Rest of World
Segment Reporting Information [Line Items]
Long-lived assets	$ 37,885	$ 55,312