ICON Public Limited (ICLR) 6-K 28 Jul 23 2023 Q2 Current report (foreign) Financial data

Cover

Cover	6 Months Ended
	Jun. 30, 2023
Cover [Abstract]
Document Type	6-K
Document Fiscal Year Focus	2023
Entity Registrant Name	ICON plc
Amendment Flag	false
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001060955
Current Fiscal Year End Date	--12-31
Document Period End Date	Jun. 30, 2023

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 270,176	$ 288,768
Available for sale investments	1,653	1,713
Accounts receivable, net of allowance for credit losses	1,759,111	1,731,388
Unbilled revenue	985,034	957,655
Other receivables	129,101	63,658
Prepayments and other current assets	152,774	137,094
Income taxes receivable	70,021	48,790
Total current assets	3,367,870	3,229,066
Non-current assets:
Property, plant and equipment, net	346,521	350,320
Goodwill	8,993,583	8,971,670
Intangible assets	4,049,793	4,278,659
Operating right-of-use assets	144,514	153,832
Other receivables	64,140	70,790
Income taxes receivable	25,169	21,380
Deferred tax asset	80,772	76,930
Equity method investments	0	0
Investments in equity- long term	35,298	32,631
Total Assets	17,107,660	17,185,278
Current Liabilities:
Accounts payable	46,920	81,194
Unearned revenue	1,573,311	1,507,449
Other liabilities	994,883	1,005,025
Income taxes payable	39,885	41,783
Current bank credit lines and loan facilities	105,150	55,150
Total current liabilities	2,760,149	2,690,601
Non-current liabilities:
Non-current bank credit lines and loan facilities	4,206,936	4,599,037
Lease liabilities	129,079	131,644
Non-current other liabilities	39,438	38,260
Non-current income taxes payable	241,410	239,188
Deferred tax liability	934,208	988,585
Commitments and contingencies	0	0
Total Liabilities	8,311,220	8,687,315
Shareholders' Equity:
Ordinary shares, par value 6 euro cents per share; 100,000,000 shares authorized, 81,928,422 shares issued and outstanding at June 30, 2023 and 81,723,555 shares issued and outstanding at December 31, 2022	6,676	6,649
Additional paid-in capital	6,891,494	6,840,306
Other undenominated capital	1,162	1,162
Accumulated other comprehensive loss	(156,528)	(171,538)
Retained earnings	2,053,636	1,821,384
Total Shareholders' Equity	8,796,440	8,497,963
Total Liabilities and Shareholders' Equity	$ 17,107,660	$ 17,185,278

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - € / shares	Jun. 30, 2023	Dec. 31, 2022
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)	82,151,049	81,723,555
Ordinary shares, shares outstanding (in shares)	82,151,049	81,723,555

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
Revenue	$ 2,020,251	$ 1,935,193	$ 3,998,829	$ 3,836,957
Costs and expenses:
Direct costs (excluding depreciation and amortization)	1,429,540	1,392,062	2,825,086	2,770,529
Selling, general and administrative expense	187,806	189,953	387,812	385,214
Depreciation and amortization	145,059	144,019	290,185	285,424
Transaction and integration-related expenses	12,701	8,884	24,083	20,969
Restructuring	35,661	22,486	45,390	26,693
Total costs and expenses	1,810,767	1,757,404	3,572,556	3,488,829
Income from operations	209,484	177,789	426,273	348,128
Interest income	949	166	2,021	293
Interest expense	(85,206)	(47,111)	(171,757)	(91,536)
Income before provision for income taxes	125,227	130,844	256,537	256,885
Provision for income taxes	(9,629)	(14,254)	(23,902)	(27,540)
Income before share of earnings from equity method investments	115,598	116,590	232,635	229,345
Share of losses in equity method investments	0	(856)	(383)	(1,641)
Net income attributable to the Group	$ 115,598	$ 115,734	$ 232,252	$ 227,704
Net income per Ordinary Share attributable to the Group (note 13):
Basic (in USD per share)	$ 1.41	$ 1.42	$ 2.84	$ 2.80
Diluted (in USD per share)	$ 1.40	$ 1.41	$ 2.81	$ 2.76
Weighted average number of Ordinary Shares outstanding (note 13):
Basic (in shares)	81,999,746	81,398,071	81,892,662	81,430,507
Diluted (in shares)	82,627,933	82,312,946	82,617,391	82,462,842

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Comprehensive income (net of tax):
Net income attributable to the Group	$ 115,598	$ 115,734	$ 232,252	$ 227,704
Currency translation adjustment	(10,638)	(66,180)	4,862	(101,998)
Gain on cash flow hedge	14,006	0	10,148	0
Total comprehensive income attributable to the Group	$ 118,966	$ 49,554	$ 247,262	$ 125,706

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, 2021		81,554,683
Beginning balance at Dec. 31, 2021	$ 8,066,827	$ 6,640	$ 6,733,910	$ 1,134	$ (90,937)	$ 1,416,080
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
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
Beginning balance (in shares) at Dec. 31, 2022	81,723,555	81,723,555
Beginning balance at Dec. 31, 2022	$ 8,497,963	$ 6,649	6,840,306	1,162	(171,538)	1,821,384
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	116,654					116,654
Exercise of share options (in shares)		136,649
Exercise of share options	12,936	$ 9	12,927
Issue of restricted share units / performance share units (in shares)		68,218
Issue of restricted share units / performance share units	4	$ 4
Non-cash stock compensation expense	14,658		14,658
Share issuance costs	(4)		(4)
Other comprehensive loss, net of tax	11,642				11,642
Ending balance (in shares) at Mar. 31, 2023		81,928,422
Ending balance at Mar. 31, 2023	$ 8,653,853	$ 6,662	6,867,887	1,162	(159,896)	1,938,038
Beginning balance (in shares) at Dec. 31, 2022	81,723,555	81,723,555
Beginning balance at Dec. 31, 2022	$ 8,497,963	$ 6,649	6,840,306	1,162	(171,538)	1,821,384
Ending balance (in shares) at Jun. 30, 2023	82,151,049	82,151,049
Ending balance at Jun. 30, 2023	$ 8,796,440	$ 6,676	6,891,494	1,162	(156,528)	2,053,636
Beginning balance (in shares) at Mar. 31, 2023		81,928,422
Beginning balance at Mar. 31, 2023	8,653,853	$ 6,662	6,867,887	1,162	(159,896)	1,938,038
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	115,598					115,598
Exercise of share options (in shares)		93,304
Exercise of share options	7,229	$ 6	7,223
Issue of restricted share units / performance share units (in shares)		129,323
Issue of restricted share units / performance share units	8	$ 8
Non-cash stock compensation expense	16,389		16,389
Share issuance costs	(5)		(5)
Other comprehensive loss, net of tax	$ 3,368				3,368
Ending balance (in shares) at Jun. 30, 2023	82,151,049	82,151,049
Ending balance at Jun. 30, 2023	$ 8,796,440	$ 6,676	$ 6,891,494	$ 1,162	$ (156,528)	$ 2,053,636

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash flows from operating activities:
Net income	$ 232,252	$ 227,704
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	290,185	285,424
Impairment of long lived assets	8,613	20,749
Reduction in carrying value of operating right-of-use assets	23,607	23,570
Loss on equity method investments	383	1,641
Acquisition-related gain	(6,160)	0
Charge on cash flow hedge	3,646	0
Amortization of financing costs and debt discount	7,899	9,188
Stock compensation expense	31,357	38,186
Deferred taxes	(59,177)	(75,265)
Foreign exchange movements	(3,345)	(37,421)
Other non-cash items	18,202	9,159
Changes in operating assets and liabilities:
Accounts receivable	(40,675)	(41,032)
Unbilled revenue	(27,210)	(33,187)
Unearned revenue	65,266	(176,904)
Other net assets	(165,462)	157,154
Net cash provided by operating activities	379,381	408,966
Cash flows from investing activities:
Purchase of property, plant and equipment	(58,880)	(47,840)
Purchase of subsidiary undertakings	(5,100)	0
Sale of available for sale investments	482	0
Purchase of available for sale investments	(422)	0
Purchase of investments in equity - long term	(4,733)	(799)
Net cash used in investing activities	(68,653)	(48,639)
Cash flows from financing activities:
Drawdown of bank credit lines and loan facilities	230,000	25,000
Repayment of bank credit lines and loan facilities	(580,000)	(425,000)
Proceeds from exercise of equity compensation	20,177	15,140
Share issue costs	(9)	(3)
Repurchase of ordinary shares	0	(99,983)
Share repurchase costs	0	(17)
Net cash used in financing activities	(329,832)	(484,863)
Effect of exchange rate movements on cash	512	(12,759)
Net decrease in cash and cash equivalents	(18,592)	(137,295)
Cash and cash equivalents at beginning of period	288,768	752,213
Cash and cash equivalents at end of period	$ 270,176	$ 614,918

Basis of presentation

Basis of presentation	6 Months Ended
	Jun. 30, 2023
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, 2022 (see note 2 - Summary of significant accounting policies ). Operating results for the six months ended June 30, 2023 are not necessarily indicative of the results that may be expected for the fiscal period ending December 31, 2023.

Summary of significant accounti

Summary of significant accounting policies	6 Months Ended
	Jun. 30, 2023
Accounting Policies [Abstract]
Summary of significant accounting policies	Summary of 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 below, can be purchased collectively or individually as part of a clinical trial contract. There is not significant variability in how economic factors affect these services. Contracts range in duration from a number of months to several years. ASC 606 requires application of five steps: (1) identify the contract(s) with a customer; (2) identify the performance obligation in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the entity satisfies the performance obligation(s), which have been applied to revenue recognized from each service described below. Clinical trial service revenue A clinical trial service is a single performance obligation satisfied over time, i.e. the full-service obligation in respect of a clinical trial (including those services performed by investigators and other parties) is considered a single performance obligation. Promises offered to the customer are not distinct within the context of the contract. ICON is the contract principal in respect of both direct services and in the use of third parties (principally investigator services) that support the clinical research projects. The transaction price is determined by reference to the contract or change order value (total service revenue and pass-through/ reimbursable expenses) adjusted to reflect a realizable contract value. Revenue is recognized over time as the single performance obligation is satisfied. The progress towards completion for clinical service contracts is measured based on an input measure being total project costs incurred (inclusive of pass-through/ reimbursable expenses) at each reporting period as a percentage of forecasted total project costs. Laboratory services revenue Revenue is recognized when, or as, obligations under the terms of a contract are satisfied, which occurs when control of the products or services are transferred to the customer. Revenue for laboratory services is measured as the amount of consideration we expect to receive in exchange for transferring products or services. Where contracts with customers contain multiple performance obligations, the transaction price is allocated to each performance obligation based on the estimated relative selling price of the promised good or service. Service revenue is recognized over time as the services are delivered to the customer based on the extent of progress towards completion of the performance obligation. The determination of the methodology to measure progress requires judgment and is based on the nature of services provided. This requires an assessment of the transfer of value to the customer. The right to invoice measure of progress is generally related to rate per unit contracts, as the extent of progress towards completion is measured based on discrete service or time-based increments, such as samples tested or labor hours incurred. Revenue is recorded in the amount invoiced since that amount corresponds to the value of the Company's performance and the transfer of value to the customer. Contracting services revenue The Company has availed of the practical expedient which results in recognition of revenue on a right to invoice basis. Application of the practical expedient reflects the right to consideration from the customer in an amount that corresponds directly with the value to the customer of the performance completion to date. This reflects hours performed by contract staff. Consulting services revenue Our consulting services contracts represent a single performance obligation satisfied over time. The transaction price is determined by reference to contract or change order value. Revenue is recognized over time as the performance obligation is satisfied. The progress towards completion for consulting contracts is measured based on total project inputs (time) at each reporting period as a percentage of forecasted total project inputs. Data services revenue The Company provides data reports and analytics to customers based on agreed-upon specifications, including the timing of delivery, which is typically either weekly, monthly, or quarterly. If a customer requests more than one type of data report or series of data reports within a contract, each distinct type of data report is a separate performance obligation. The contracts provide for the Company to be compensated for the value of each deliverable. The transaction price is determined using list prices, discount agreements, if any, and negotiations with the customers, and generally includes any out-of-pocket expenses. Typically, the Company bills in advance of services being provided with the amount being recorded as unearned revenue. When multiple performance obligations exist, the transaction price is allocated to performance obligations on a relative standalone selling price basis. In cases where the Company contracts to provide a series of data reports, or in some cases data, the Company recognizes revenue over time using the “units delivered” output method as the data or reports are delivered. Expense reimbursements are recorded to revenue as the expenses are incurred as they relate directly to the services performed. Certain arrangements include upfront customization or consultative services for customers. These arrangements often include payments based on the achievement of certain contractual milestones. Under these arrangements, the Company contracts with a customer to carry out a specific study, ultimately resulting in delivery of a custom report or data product. These arrangements are a single performance obligation given the integrated nature of the service being provided. The Company typically recognizes revenue under these contracts over time, using an output-based measure, generally time elapsed, to measure progress and transfer of control of the performance obligation to the customer. Expense reimbursements are recorded to revenue as the expenses are incurred as they relate directly to the service performed. The Company enters into contracts with some of its larger data suppliers that involve non-monetary terms. The Company issues purchase credits to be used toward the data supplier's purchase of the Company's services based on the fair value of the data obtained. In exchange, the Company receives monetary discounts on the data received from the data suppliers. The fair value of the revenue earned from the customer purchases is recognized as services are delivered as described above. At the end of the contract year, any unused customer purchase credits may be forfeited or carried over to the next contract year based on the terms of the data supplier contract. Commissions Incremental costs of obtaining a contract are recognized as an asset on the Consolidated Balance Sheet in respect of those contracts that exceed one year. Where commission costs relate to contracts that are less than one year, the practical expedient is applied as the amortization period of the asset which would arise on deferral would be one year or less. Business Combinations The cost of a business combination is measured as the aggregate of the fair value of assets received, liabilities assumed and equity instruments issued in exchange for control. The Company records and allocates to its reporting units the excess of the cost over the fair value of the net assets acquired, known as goodwill. Where a business combination agreement provides for an adjustment to the cost of the acquisition which is contingent upon future events, the amount of the estimated adjustment is recognized at the acquisition date at the fair value of the contingent consideration. Any changes to this estimate outside the measurement period will depend on the classification of the contingent consideration. If the contingent consideration is classified as equity it shall not be re-measured and the settlement shall be accounted for within equity. If the contingent consideration is classified as a liability any adjustments will be accounted for through the Consolidated Statement of Operations or Other Comprehensive Income depending on whether the liability is considered a financial instrument. The assets, liabilities and contingent liabilities of businesses acquired are measured at their fair values at the date of acquisition. In the case of a business combination which is completed in stages, the fair values of the identifiable assets, liabilities and contingent liabilities are determined at the date of each exchange transaction. When the initial accounting for a business combination is determined provisionally, any subsequent adjustments to the provisional values allocated to the identifiable assets, liabilities and contingent liabilities are made within twelve months of the acquisition date and presented as adjustments to goodwill in the reporting period in which the adjustments are determined. The Company allocates a share of net income to the noncontrolling interest holders based on percentage ownership. Intangible Assets Intangible assets are measured at their fair value when acquired and amortized on the straight line basis over their respective useful lives. The Company has no indefinite life intangibles other than goodwill. The Company evaluates its intangibles for impairment when indicators of impairment exist. Intangible assets are amortized on a straight-line basis over the expected useful life, as set forth in the table below: Estimated Useful Life Customer relationships 23 years Order backlog 3 years Trade names 3 years Patient database 7 years Technology assets 5 years The Company periodically assesses the useful lives of intangible assets to evaluate whether what was established at acquisition continues to be appropriate. Income taxes The Company applies the asset and liability method of accounting for income taxes. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amount of existing assets and liabilities and their respective tax bases and for operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which these temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Deferred tax assets are reduced by a valuation allowance to the amount that is more likely than not to be realized. The Company recognizes the effect of income tax positions only if those positions will more likely than not be sustained. Recognized income tax positions are measured at the largest amount of tax benefit that is greater than 50 percent likely of being realized upon settlement. Interest and penalties related to income taxes are included in income tax expense and classified with the related liability on the Consolidated Balance Sheet. The Company accounts for the impact of GILTI (“global intangible low-taxed income”) in the period it arises and has therefore not provided for deferred taxes in respect of this item.

Revenue

Revenue	6 Months Ended
	Jun. 30, 2023
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Revenue disaggregated by customer concentration is as follows: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Clients 1-5 $ 529,792 $ 525,938 $ 1,092,220 $ 1,065,641 Clients 6-10 $ 284,382 $ 260,689 $ 563,908 $ 553,350 Clients 11-25 $ 420,880 $ 368,675 $ 829,047 $ 726,985 Other $ 785,197 $ 779,891 $ 1,513,654 $ 1,490,981 Total $ 2,020,251 $ 1,935,193 $ 3,998,829 $ 3,836,957 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: June 30, 2023 December 31, 2022 (in thousands) Contract assets: Billed services (accounts receivable) $ 1,788,140 $ 1,751,950 Unbilled services (unbilled revenue) 985,034 957,655 Accounts receivable and unbilled revenue, gross 2,773,174 2,709,605 Allowance for credit losses (29,029) (20,562) Accounts receivable and unbilled revenue, net $ 2,744,145 $ 2,689,043 Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows: (in thousands, except percentages) June 30, 2023 December 31, 2022 $ Change % Change Unbilled services (unbilled revenue) $ 985,034 $ 957,655 $ 27,379 2.9 % Unearned revenue (payments on account) (1,573,311) (1,507,449) (65,862) 4.4 % Net balance $ (588,277) $ (549,794) $ (38,483) 7.0 % 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 June 30, 2023 increased by $27.4 million compared to December 31, 2022. Unearned revenue increased by $65.9 million over the same period resulting in a decrease of $38.5 million in the net balance of unbilled services and unearned revenue or payments on account between December 31, 2022 and June 30, 2023. 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)	6 Months Ended
	Jun. 30, 2023
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 Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Clients 1-5 $ 529,792 $ 525,938 $ 1,092,220 $ 1,065,641 Clients 6-10 $ 284,382 $ 260,689 $ 563,908 $ 553,350 Clients 11-25 $ 420,880 $ 368,675 $ 829,047 $ 726,985 Other $ 785,197 $ 779,891 $ 1,513,654 $ 1,490,981 Total $ 2,020,251 $ 1,935,193 $ 3,998,829 $ 3,836,957 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: June 30, 2023 December 31, 2022 (in thousands) Contract assets: Billed services (accounts receivable) $ 1,788,140 $ 1,751,950 Unbilled services (unbilled revenue) 985,034 957,655 Accounts receivable and unbilled revenue, gross 2,773,174 2,709,605 Allowance for credit losses (29,029) (20,562) Accounts receivable and unbilled revenue, net $ 2,744,145 $ 2,689,043 Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows: (in thousands, except percentages) June 30, 2023 December 31, 2022 $ Change % Change Unbilled services (unbilled revenue) $ 985,034 $ 957,655 $ 27,379 2.9 % Unearned revenue (payments on account) (1,573,311) (1,507,449) (65,862) 4.4 % Net balance $ (588,277) $ (549,794) $ (38,483) 7.0 % 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 June 30, 2023 increased by $27.4 million compared to December 31, 2022. Unearned revenue increased by $65.9 million over the same period resulting in a decrease of $38.5 million in the net balance of unbilled services and unearned revenue or payments on account between December 31, 2022 and June 30, 2023. 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	6 Months Ended
	Jun. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill Six Months Ended Year Ended June 30, 2023 December 31, 2022 (in thousands) Opening balance $ 8,971,670 $ 9,037,931 Current period acquisition 13,379 — Prior period acquisition — (35,692) Foreign exchange movement 8,534 (30,569) Closing balance $ 8,993,583 $ 8,971,670 On April 20, 2023, the Company completed the purchase of the majority investor's 51% majority voting share capital of Oncacare Limited ("Oncacare"), such that Oncacare and its subsidiaries became wholly-owned subsidiaries of the ICON Group. The Oncacare acquisition resulted in goodwill of $13.4 million and also gave rise to an acquisition-related gain of $6.2 million. There were no impairment charges for the six months ended June 30, 2023 or for the year ended December 31, 2022.

Intangible assets

Intangible assets	6 Months Ended
	Jun. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets	Intangible assets Intangible assets, net consisted of the following: Six Months Ended Year Ended June 30, 2023 December 31, 2022 Cost (in thousands) Customer relationships $ 4,077,225 $ 4,076,435 Order backlog 537,182 536,934 Trade names & brands 204,636 204,621 Patient database 170,342 170,238 Technology assets 121,110 120,984 Total cost 5,110,495 5,109,212 Accumulated amortization (1,060,702) (830,553) Net book value $ 4,049,793 $ 4,278,659

Fair value measurements

Fair value measurements	6 Months Ended
	Jun. 30, 2023
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. As of June 30, 2023, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows (in thousands): Level 1 Level 2 Level 3 Investments Measured at Net Asset Value Total (in thousands) Assets: Available for sale securities (short-term) (a) 1,653 — — — 1,653 Available for sale investments (long-term) (b) — — — 35,298 35,298 Derivative instruments (c) — 7,433 — — 7,433 Total assets $ 1,653 $ 7,433 $ — $ 35,298 $ 44,384 Liabilities: Derivative instruments (c) — — — — — Total liabilities $ — $ — $ — $ — $ — As of December 31, 2022, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows (in thousands): Level 1 Level 2 Level 3 Investments Measured at Net Asset Value Total (in thousands) Assets: Available for sale securities (short-term) (a) 1,713 — — — 1,713 Available for sale investments (long-term) (b) — — — 32,631 32,631 Derivative instruments (c) — 12 — — 12 Total assets $ 1,713 $ 12 $ — $ 32,631 $ 34,356 Liabilities: Derivative instruments (c) — 3,670 — — 3,670 Total liabilities $ — $ 3,670 $ — $ — $ 3,670 (a) Represents the fair value of investments in highly liquid investments with maturities of greater than three months and a minimum "A-" rated fixed term deposits and are based on quoted market prices. (b) To determine the classification of its interests in long-term investments, the Company considered the nature of its investment, the extent of influence over operating and financial decisions and the availability of readily determinable fair values. The Company determined that the interests in funds meet the definition of equity securities without readily determinable fair values, which qualify for the Net Asset Value (NAV) practical expedient in ASC 820 'Fair value measurements and disclosures'. Any increases or decreases in fair value are recognized in net income in the period. (c) Represents the fair value of interest rate cap and interest rate swap agreements. The fair value of the agreements are the estimated amount that the Company would receive or pay to terminate such agreements, taking into account market interest rates and the remaining time to maturities or using market inputs with mid-market pricing as a practical expedient for bid-ask spread. Non-recurring Fair Value Measurements Certain assets and liabilities are carried on the accompanying Condensed Consolidated Balance Sheet at cost and are not re-measured to fair value on a recurring basis. These assets include finite-lived intangible assets that are tested for

Restructuring

Restructuring	6 Months Ended
	Jun. 30, 2023
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring In the six months ended June 30, 2023, a restructuring charge of $45.4 million was recorde d in the Condensed Consolidated Statement of Operations under a restructuring plan adopted following a review of operations. The restructuring plan reflected a workforce reduction of $34.1 million and an office consolidation program to optimize the Company's office footprint of $11.3 million . Six Months Ended June 30, 2023 June 30, 2022 (in thousands) Restructuring charges $ 45,390 $ 26,693 Net charge $ 45,390 $ 26,693 At June 30, 2023, a total liability of $35.2 million was recorded on the Consolidated Balance Sheet relating to restructuring activities. The total liability included $29.4 million of personnel related liabilities as a result of the workforce reduction; all of which have been classified as short-term. The total liability also included $5.8 million of facilities related liabilities of which $3.2 million is included within other liabilities and $2.6 million is included within non-current other liabilities. Six Months Ended Year ended June 30, 2023 December 31, 2022 (in thousands) Opening provision $ 6,022 $ 10,311 Additional provisions 39,338 4,364 Utilization (10,188) (8,653) Ending provision $ 35,172 $ 6,022

Operating leases

Operating leases	6 Months Ended
	Jun. 30, 2023
Leases [Abstract]
Operating leases	Operating leases Lease costs recorded under operating leases for the six months ended June 30, 2023 and June 30, 2022 were as follows: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Operating lease costs 12,818 13,548 $ 25,689 $ 28,812 Income from sub-leases (283) (303) (561) (630) Net operating lease costs 12,535 13,245 $ 25,128 $ 28,182 Of the total cost of $25.1 million incurred in the six months ended June 30, 2023 (June 30, 2022: $28.2 million), $19.3 million (June 30, 2022: $27.1 million) is recorded within selling, general and administration costs and $5.8 million (June 30, 2022: $1.1 million) is recorded within direct costs. During the six months ended June 30, 2023 and June 30, 2022, costs incurred by the Group related to variable lease payments was de minimis. Right-of-use assets obtained, in exchange for lease obligations during the three months ended June 30, 2023, totaled $10.2 million (June 30, 2022: $29.0 million). Right-of-use assets obtained, in exchange for lease obligations during the six months ended June 30, 2023, totaled $22.5 million (June 30, 2022: $35.8 million). The weighted average remaining lease term and weighted-average discount rate at June 30, 2023 were 7.01 years and 2.66%, respectively. Future minimum lease payments under non-cancelable leases as of June 30, 2023 were as follows: Minimum rental payments (in thousands) June 30, 2023 Year 1 $ 44,466 Year 2 33,902 Year 3 26,909 Year 4 22,801 Year 5 16,924 Thereafter 38,952 Total future minimum lease payments 183,954 Lease imputed interest (14,729) Total $ 169,225 other liabilities

Bank credit lines and loan faci

Bank credit lines and loan facilities	6 Months Ended
	Jun. 30, 2023
Debt Disclosure [Abstract]
Bank credit lines and loan facilities	Bank credit lines and loan facilities The Company had the following debt outstanding as of June 30, 2023 and December 31, 2022: Principal amount Interest rate as of Interest rate as of June 30, December 31, (in thousands) June 30, 2023 December 31, 2022 2023 2022 Maturity Date Credit Facilities: Senior Secured Term Loan 7.41 % 7.09 % $ 3,801,213 $ 4,201,213 July 2028 Senior Secured Notes 2.88 % 2.88 % $ 500,000 $ 500,000 July 2026 Senior Secured Revolving Loan Facility 6.51 % — 50,000 — July 2023 Total debt 4,351,213 4,701,213 Less current portion of long-term debt (105,150) (55,150) Total long-term debt 4,246,063 4,646,063 Less debt issuance costs and debt discount (39,127) (47,026) Total long-term debt, net $ 4,206,936 $ 4,599,037 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 June 30, 2023, the contractual maturities of the Company's debt obligations were as follows: Contractual maturities of long-term debt: (in thousands) 2023 (remaining) $ 77,575 2024 55,150 2025 55,150 2026 55,150 2027 and thereafter 4,108,188 Total $ 4,351,213 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 On July 1, 2021, the Company completed the acquisition of PRA Health Sciences, Inc. ("PRA") by means of a merger whereby Indigo Merger Sub, Inc., a Delaware corporation and subsidiary of ICON, merged with and into PRA, the parent of the PRA Health Sciences ("the Merger"). In conjunction with the completion of the Merger, on July 1, 2021, ICON entered into a credit agreement providing for a senior secured term loan facility of $5,515 million and a senior secured revolving loan facility in an initial aggregate principal amount of $300 million (the "Senior Secured Credit Facilities"). On May 2, 2023, the Company agreed with its lenders to increase the aggregate principal amount of the senior secured revolving loan facility from $300 million to $500 million. Borrowings under the senior secured term loan facility amortize in equal quarterly installments in an amount equal to 1.00% per annum of the principal amount, with the remaining balance due at final maturity. The interest rate margin applicable to borrowings under the senior secured term loan facility is USD Term SOFR and a Term SOFR Adjustment depending on the interest period chosen plus an applicable margin which is dependent on the Company's net leverage ratio. At June 30, 2023, the applicable margin is 2.25%. The senior secured term loan facility is subject to a floor of 0.50%. The interest rate margin applicable to borrowings under the revolving loan facility will be, at the option of the borrower, either (i) the applicable base rate plus an applicable margin of 1.00%, 0.60% or 0.25% based on ICON’s current corporate family rating assigned by S&P of BB- (or lower), BB or BB+ (or higher), respectively, or (ii) Term SOFR plus a Term SOFR Adjustment on the interest period chosen plus an applicable margin of 2.00%, 1.60% or 1.25% based on ICON’s current corporate family rating assigned by S&P of BB- (or lower), BB or BB+ (or higher), respectively. In addition, lenders under the revolving loan facility are entitled to commitment fees as a percentage of the applicable margin at the time of drawing and utilization fees dependent on the proportion of the facility drawn. In January 2023, $100.0 million of the senior secured revolving loan facility was drawn down, in the aggregate, at interest rates of 5.89% and 5.80%, representing one month SOFR plus a margin of 1.25%. This was repaid in full in March 2023. On March 31, 2023, $80.0 million of the senior secured revolving loan facility was drawn down at an interest rate of 6.17%, representing one month SOFR plus a margin of 1.25%. In April 2023, the Company drew down $50.0 million of the senior secured revolving loan facility at an interest rate of 6.25%, representing one month SOFR plus a margin of 1.25%. The Company repaid $80.0 million of the senior secured revolving loan facility on June 30, 2023. As at June 30, 2023, interest on the senior secured revolving loan facility is at 6.51% following facility renewal, representing one month SOFR plus a margin of 1.25%. The Borrowers’ (as defined in the Senior Secured Credit Facility) obligations under the Senior Secured Credit Facilities are guaranteed by ICON and the subsidiary guarantors. The Senior Secured Credit Facilities are secured by a lien on substantially all of ICON’s, the Borrowers’ and each of the subsidiary guarantor’s assets (subject to certain exceptions), and the Senior Secured Credit Facilities have a first-priority lien on such assets, which will rank pari passu with the lien securing the Senior Secured Notes, subject to other permitted liens. The Company is permitted to make prepayments on the senior secured term loan without penalty. On March 31, 2023 the Company repaid $250.0 million of the senior secured term loan facility and made a quarterly interest payment of $75.3 million. This repayment resulted in an additional charge associated with previously capitalized fees of $2.2 million. On June 30, 2023 the Company repaid $150.0 million of the senior secured term loan facility and made a quarterly interest payment of $74.0 million. This repayment resulted in an additional charge associated with previously capitalized fees of $1.2 million. Senior Secured Notes In addition to the Senior Secured Credit Facilities, on July 1, 2021, a subsidiary of the Company issued $500 million in aggregate principal amount of 2.875% senior secured notes due 2026 (the "Senior Secured Notes") in a private offering (the “Offering”). The Senior Secured Notes will mature on July 15, 2026. Fair Value of Debt

Derivatives

Derivatives	6 Months Ended
	Jun. 30, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Derivatives On November 29, 2022, the Company entered into two interest rate cap agreements ("2022 Caps") with an initial total notional value of $2,101 million to limit its exposure to changes in the variable interest rate on its Senior Secured Credit Facilities. Interest on the 2022 Caps began accruing on December 30, 2022 and the interest rate cap expires on December 31, 2024. The Company pays a fixed rate of 0.42% and receives a variable rate equal to the amount that the three-month SOFR rate exceeds 4.75%. On November 29, 2022, the Company entered into an interest rate swap agreement ("2022 Swap") with an initial notional value of $1,101 million to limit its exposure to changes in the variable interest rate on its Senior Secured Credit Facilities. Interest on the 2022 Swaps begins accruing on December 31, 2024 and the interest rate swap expires on December 31, 2026. The Company pays a fixed rate of 3.4% and receives a variable rate of interest equal to the three-month SOFR on the 2022 Swap. The fair value of the Company’s derivative financial instruments, on a gross basis, and the line items on the accompanying consolidated balance sheets to which they were recorded are summarized in the following table: June 30, 2023 December 31, 2022 Asset Liability Notional Asset Liability Notional (in thousands) (in thousands) Derivatives designated as hedging instruments: Interest Rate Caps Other Current Liabilities, Other Assets and Liabilities $4,461 $— $1,900,606 $12 $3,363 $2,100,606 Interest Rate Swap Other Assets and Liabilities $2,972 $— $1,100,606 $— $307 $1,100,606 Total derivatives designated as hedging instruments $7,433 $— $3,001,212 $12 $3,670 $3,201,212 During the next 12 months, the Company estimates that an additional $1.2 million will be reflected as interest income in the consolidated statements. The Company recognized $14.9 million of a gain within other comprehensive income ("OCI") for the three months ended June 30, 2023 (June 30, 2022: $nil) after a reclassification of $1.4 million of a loss from OCI to the income statement (June 30, 2022: $nil). The Company recognized $10.1 million of a net gain within OCI for the six months ended June 30, 2023 (June 30, 2022: $nil ) after a reclassification of $3.6 million of a loss from OCI to the income statement (June 30, 2022

Income taxes

Income taxes	6 Months Ended
	Jun. 30, 2023
Income Tax Disclosure [Abstract]
Income taxes	Income taxes Income taxes recognized during the three and six months ended June 30, 2023 and June 30, 2022, comprise: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Provision for income taxes $ 9,629 $ 14,254 $ 23,902 $ 27,540 As at June 30, 2023 the Company maintains a $249.6 million liability (December 31, 2022: $240.2 million) for unrecognized tax benefit, which is comprised of $220.4 million (December 31, 2022: $217.6 million) related to items generating unrecognized tax benefits and $29.2 million (December 31, 2022: $22.6 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 2022 tax years. During such audits, local tax authorities may challenge the positions taken by us in our tax returns.

Net income per ordinary share

Net income per ordinary share	6 Months Ended
	Jun. 30, 2023
Earnings Per Share [Abstract]
Net income per ordinary share	Net income per ordinary share Basic net income per ordinary share attributable to the Group has been computed by dividing net income available to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period. Diluted net income per ordinary share is computed by adjusting the weighted average number of ordinary shares outstanding during the period for all potentially dilutive ordinary shares outstanding during the period and adjusting net income for any changes in income or loss that would result from the conversion of such potential ordinary shares. There is no difference in net income used for basic and diluted net income per ordinary share. The reconciliation of the number of shares used in the computation of basic and diluted net income per ordinary share is as follows: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 Weighted average number of ordinary shares outstanding for basic net income per ordinary share 81,999,746 81,398,071 81,892,662 81,430,507 Effect of dilutive share options and other awards outstanding under share based compensation programs 628,187 914,875 724,729 1,032,335 Weighted average number of ordinary shares outstanding for diluted net income per ordinary share 82,627,933 82,312,946 82,617,391 82,462,842 Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 Net income per Ordinary Share attributable to the Group: Basic 1.41 1.42 2.84 2.80 Diluted 1.40 1.41 2.81 2.76

Share-based awards

Share-based awards	6 Months Ended
	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Share-based awards	Share-based awards Share Options The following table summarizes option activity for the six months ended June 30, 2023: Options Weighted Weighted Weighted Outstanding at December 31, 2022 1,378,119 $ 119.86 4.69 Granted 82,472 $ 232.48 Exercised (229,953) $ 87.69 Canceled/expired (6,885) $ 116.33 Outstanding at June 30, 2023 1,223,753 $ 133.51 4.67 Exercisable at June 30, 2023 952,614 $ 113.27 4.20 The Company issues ordinary shares for all options exercised. The total amount of fully vested share options which remained outstanding at June 30, 2023 was 952,614. Fully vested share options at June 30, 2023 have an average remaining contractual term of 4.20 years and an average exercise price of $113.27. Fair value of Stock Options Assumptions The weighted average fair value of options granted during the six months ended June 30, 2023 and June 30, 2022 was calculated using the Black-Scholes option pricing model. The weighted average grant date fair values and assumptions used were as follows: Six Months Ended June 30, 2023 June 30, 2022 Weighted average grant date fair value $ 85.12 $ 68.40 Assumptions: Expected volatility 33 % 31 % Dividend yield — % — % Risk-free interest rate 3.98 % 1.85 % 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 23, 2013 the Company adopted the 2013 Employees Restricted Share Unit and Performance Share Unit Plan (the "2013 RSU Plan") pursuant to which the Compensation and Organization Committee of the Company's Board of Directors may select any employee, or any Director holding a salaried office or employment with the Company, or a Subsidiary to receive an award under the plan. On May 11, 2015 the 20 13 RSU Plan was amended and restated in order to increase the number of shares that can be issued under the RSU Plan by 2.5 million shares. Accordingly, an aggregate of 4.1 million ordinary shares have been reserved for issuance under the 2013 RSU Plan. The shares are awarded at par value and vest over a service period. Awards under the 2013 RSU Plan may be settled in cash or shares at the option of the Company. No awards may be granted under the 2013 RSU Plan after May 11, 2025. On April 30 2019, the Company approved the 2019 Consultants and Directors Restricted Share Unit Plan (the “2019 Consultants RSU Plan”), which was effective as of May 16, 2019, pursuant to which the Compensation and Organization Committee of the Company’s Board of Directors may select any consultant, adviser or non-executive Director retained by the Company, or a Subsidiary to receive an award under the plan. 250,000 ordinary shares have been reserved for issuance under the 2019 Consultants RSU Plan. The awards are at par value and vest over a service period. Awards granted to non-executive directors during 2020, 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 six months ended June 30, 2023: Outstanding at December 31, 2022 152,420 $ 192.29 582,612 $ 207.73 Granted 60,374 $ 232.51 294,683 $ 217.52 Shares vested (47,026) $ 159.57 (150,515) $ 187.96 Forfeited — $ — (31,396) $ 209.13 Outstanding at June 30, 2023 165,768 $ 216.22 695,384 $ 216.09 The fair value of PSUs vested for the six months ended June 30, 2023 totaled $7.5 million (full year 2022: $6.5 million). The fair value of RSUs vested for the six months ended June 30, 2023 totaled $28.3 million (full year 2022: $34.1 million). The PSUs vest based on service and specified EPS targets over the periods 2021 - 2023, 2022 - 2024, and 2023 - 2025. Depending on the amount of EPS from 2021 to 2025, up to an additional 82,884 PSUs may also be granted. Non-cash stock compensation expense Non-cash stock compensation expense for the three and six months ended June 30, 2023 and June 30, 2022 has been allocated as follows: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Direct costs $ 6,420 $ 5,833 $ 12,088 $ 10,832 Selling, general and administrative $ 10,178 $ 13,450 $ 19,269 $ 27,354 Total $ 16,598 $ 19,283 $ 31,357 $ 38,186

Share capital

Share capital	6 Months Ended
	Jun. 30, 2023
Equity [Abstract]
Share capital	Share capital The Company can acquire up to 10% of its outstanding ordinary shares (by way of redemption), in accordance with Irish law and the Company’s constitutional documents through open market share acquisitions. 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	6 Months Ended
	Jun. 30, 2023
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 geographical distribution of the Company’s segment measures for the three and six months ended June 30, 2023 and June 30, 2022 and at June 30, 2023 and December 31, 2022 is as follows: a) The distribution of revenue by geographical area was as follows: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Ireland $ 593,407 $ 500,972 $ 1,105,241 $ 868,330 Rest of Europe 373,810 428,393 788,033 884,458 U.S. 848,019 894,016 1,692,423 1,864,645 Rest of World 205,015 111,812 413,132 219,524 Total $ 2,020,251 $ 1,935,193 $ 3,998,829 $ 3,836,957 b) The distribution of income from operations by geographical area was as follows: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Ireland * $ 125,896 $ 55,544 $ 177,223 $ 65,418 Rest of Europe 22,489 59,173 82,255 118,682 U.S. 55,744 53,321 143,833 113,789 Rest of World 5,355 9,751 22,962 50,239 Total $ 209,484 $ 177,789 $ 426,273 $ 348,128 * Includes the full amount of the amortization charge associated with the intangible asset acquired in the Merger. c) The distribution of long-lived assets (property, plant and equipment and operating right-of-use assets), net, by geographical area was as follows: June 30, 2023 December 31, 2022 (in thousands) Ireland $ 148,242 $ 143,025 Rest of Europe 95,048 99,721 U.S. 195,407 213,311 Rest of World 52,338 48,095 Total $ 491,035 $ 504,152

Subsequent events

Subsequent events	6 Months Ended
	Jun. 30, 2023
Subsequent Events [Abstract]
Subsequent Events	Subsequent eventsThe Company has evaluated subsequent events from the balance sheet date through to the date at which the financial statements were available to be issued. The Company has determined that there are no items to disclose.

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	6 Months Ended
	Jun. 30, 2023
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 below, can be purchased collectively or individually as part of a clinical trial contract. There is not significant variability in how economic factors affect these services. Contracts range in duration from a number of months to several years. ASC 606 requires application of five steps: (1) identify the contract(s) with a customer; (2) identify the performance obligation in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the entity satisfies the performance obligation(s), which have been applied to revenue recognized from each service described below. Clinical trial service revenue A clinical trial service is a single performance obligation satisfied over time, i.e. the full-service obligation in respect of a clinical trial (including those services performed by investigators and other parties) is considered a single performance obligation. Promises offered to the customer are not distinct within the context of the contract. ICON is the contract principal in respect of both direct services and in the use of third parties (principally investigator services) that support the clinical research projects. The transaction price is determined by reference to the contract or change order value (total service revenue and pass-through/ reimbursable expenses) adjusted to reflect a realizable contract value. Revenue is recognized over time as the single performance obligation is satisfied. The progress towards completion for clinical service contracts is measured based on an input measure being total project costs incurred (inclusive of pass-through/ reimbursable expenses) at each reporting period as a percentage of forecasted total project costs. Laboratory services revenue Revenue is recognized when, or as, obligations under the terms of a contract are satisfied, which occurs when control of the products or services are transferred to the customer. Revenue for laboratory services is measured as the amount of consideration we expect to receive in exchange for transferring products or services. Where contracts with customers contain multiple performance obligations, the transaction price is allocated to each performance obligation based on the estimated relative selling price of the promised good or service. Service revenue is recognized over time as the services are delivered to the customer based on the extent of progress towards completion of the performance obligation. The determination of the methodology to measure progress requires judgment and is based on the nature of services provided. This requires an assessment of the transfer of value to the customer. The right to invoice measure of progress is generally related to rate per unit contracts, as the extent of progress towards completion is measured based on discrete service or time-based increments, such as samples tested or labor hours incurred. Revenue is recorded in the amount invoiced since that amount corresponds to the value of the Company's performance and the transfer of value to the customer. Contracting services revenue The Company has availed of the practical expedient which results in recognition of revenue on a right to invoice basis. Application of the practical expedient reflects the right to consideration from the customer in an amount that corresponds directly with the value to the customer of the performance completion to date. This reflects hours performed by contract staff. Consulting services revenue Our consulting services contracts represent a single performance obligation satisfied over time. The transaction price is determined by reference to contract or change order value. Revenue is recognized over time as the performance obligation is satisfied. The progress towards completion for consulting contracts is measured based on total project inputs (time) at each reporting period as a percentage of forecasted total project inputs. Data services revenue The Company provides data reports and analytics to customers based on agreed-upon specifications, including the timing of delivery, which is typically either weekly, monthly, or quarterly. If a customer requests more than one type of data report or series of data reports within a contract, each distinct type of data report is a separate performance obligation. The contracts provide for the Company to be compensated for the value of each deliverable. The transaction price is determined using list prices, discount agreements, if any, and negotiations with the customers, and generally includes any out-of-pocket expenses. Typically, the Company bills in advance of services being provided with the amount being recorded as unearned revenue. When multiple performance obligations exist, the transaction price is allocated to performance obligations on a relative standalone selling price basis. In cases where the Company contracts to provide a series of data reports, or in some cases data, the Company recognizes revenue over time using the “units delivered” output method as the data or reports are delivered. Expense reimbursements are recorded to revenue as the expenses are incurred as they relate directly to the services performed. Certain arrangements include upfront customization or consultative services for customers. These arrangements often include payments based on the achievement of certain contractual milestones. Under these arrangements, the Company contracts with a customer to carry out a specific study, ultimately resulting in delivery of a custom report or data product. These arrangements are a single performance obligation given the integrated nature of the service being provided. The Company typically recognizes revenue under these contracts over time, using an output-based measure, generally time elapsed, to measure progress and transfer of control of the performance obligation to the customer. Expense reimbursements are recorded to revenue as the expenses are incurred as they relate directly to the service performed. The Company enters into contracts with some of its larger data suppliers that involve non-monetary terms. The Company issues purchase credits to be used toward the data supplier's purchase of the Company's services based on the fair value of the data obtained. In exchange, the Company receives monetary discounts on the data received from the data suppliers. The fair value of the revenue earned from the customer purchases is recognized as services are delivered as described above. At the end of the contract year, any unused customer purchase credits may be forfeited or carried over to the next contract year based on the terms of the data supplier contract. Commissions Incremental costs of obtaining a contract are recognized as an asset on the Consolidated Balance Sheet in respect of those contracts that exceed one year. Where commission costs relate to contracts that are less than one year, the practical expedient is applied as the amortization period of the asset which would arise on deferral would be one year or less.
Business Combinations	Business Combinations The cost of a business combination is measured as the aggregate of the fair value of assets received, liabilities assumed and equity instruments issued in exchange for control. The Company records and allocates to its reporting units the excess of the cost over the fair value of the net assets acquired, known as goodwill. Where a business combination agreement provides for an adjustment to the cost of the acquisition which is contingent upon future events, the amount of the estimated adjustment is recognized at the acquisition date at the fair value of the contingent consideration. Any changes to this estimate outside the measurement period will depend on the classification of the contingent consideration. If the contingent consideration is classified as equity it shall not be re-measured and the settlement shall be accounted for within equity. If the contingent consideration is classified as a liability any adjustments will be accounted for through the Consolidated Statement of Operations or Other Comprehensive Income depending on whether the liability is considered a financial instrument. The assets, liabilities and contingent liabilities of businesses acquired are measured at their fair values at the date of acquisition. In the case of a business combination which is completed in stages, the fair values of the identifiable assets, liabilities and contingent liabilities are determined at the date of each exchange transaction. When the initial accounting for a business combination is determined provisionally, any subsequent adjustments to the provisional values allocated to the identifiable assets, liabilities and contingent liabilities are made within twelve months of the acquisition date and presented as adjustments to goodwill in the reporting period in which the adjustments are determined.
Intangible Assets	Intangible Assets Intangible assets are measured at their fair value when acquired and amortized on the straight line basis over their respective useful lives. The Company has no indefinite life intangibles other than goodwill. The Company evaluates its intangibles for impairment when indicators of impairment exist. Intangible assets are amortized on a straight-line basis over the expected useful life, as set forth in the table below: Estimated Useful Life Customer relationships 23 years Order backlog 3 years Trade names 3 years Patient database 7 years Technology assets 5 years The Company periodically assesses the useful lives of intangible assets to evaluate whether what was established at acquisition continues to be appropriate.
Income taxes	Income taxes The Company applies the asset and liability method of accounting for income taxes. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amount of existing assets and liabilities and their respective tax bases and for operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which these temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Deferred tax assets are reduced by a valuation allowance to the amount that is more likely than not to be realized. The Company recognizes the effect of income tax positions only if those positions will more likely than not be sustained. Recognized income tax positions are measured at the largest amount of tax benefit that is greater than 50 percent likely of being realized upon settlement. Interest and penalties related to income taxes are included in income tax expense and classified with the related liability on the Consolidated Balance Sheet. The Company accounts for the impact of GILTI (“global intangible low-taxed income”) in the period it arises and has therefore not provided for deferred taxes in respect of this item.

Summary of significant accoun_3

Summary of significant accounting policies (Tables)	6 Months Ended
	Jun. 30, 2023
Accounting Policies [Abstract]
Schedule of Finite-Lived Intangible Assets	Intangible assets are amortized on a straight-line basis over the expected useful life, as set forth in the table below: Estimated Useful Life Customer relationships 23 years Order backlog 3 years Trade names 3 years Patient database 7 years Technology assets 5 years Intangible assets, net consisted of the following: Six Months Ended Year Ended June 30, 2023 December 31, 2022 Cost (in thousands) Customer relationships $ 4,077,225 $ 4,076,435 Order backlog 537,182 536,934 Trade names & brands 204,636 204,621 Patient database 170,342 170,238 Technology assets 121,110 120,984 Total cost 5,110,495 5,109,212 Accumulated amortization (1,060,702) (830,553) Net book value $ 4,049,793 $ 4,278,659

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Jun. 30, 2023
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	Revenue disaggregated by customer concentration is as follows: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Clients 1-5 $ 529,792 $ 525,938 $ 1,092,220 $ 1,065,641 Clients 6-10 $ 284,382 $ 260,689 $ 563,908 $ 553,350 Clients 11-25 $ 420,880 $ 368,675 $ 829,047 $ 726,985 Other $ 785,197 $ 779,891 $ 1,513,654 $ 1,490,981 Total $ 2,020,251 $ 1,935,193 $ 3,998,829 $ 3,836,957 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)	6 Months Ended
	Jun. 30, 2023
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: June 30, 2023 December 31, 2022 (in thousands) Contract assets: Billed services (accounts receivable) $ 1,788,140 $ 1,751,950 Unbilled services (unbilled revenue) 985,034 957,655 Accounts receivable and unbilled revenue, gross 2,773,174 2,709,605 Allowance for credit losses (29,029) (20,562) Accounts receivable and unbilled revenue, net $ 2,744,145 $ 2,689,043 Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows: (in thousands, except percentages) June 30, 2023 December 31, 2022 $ Change % Change Unbilled services (unbilled revenue) $ 985,034 $ 957,655 $ 27,379 2.9 % Unearned revenue (payments on account) (1,573,311) (1,507,449) (65,862) 4.4 % Net balance $ (588,277) $ (549,794) $ (38,483) 7.0 %

Goodwill (Tables)

Goodwill (Tables)	6 Months Ended
	Jun. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	Six Months Ended Year Ended June 30, 2023 December 31, 2022 (in thousands) Opening balance $ 8,971,670 $ 9,037,931 Current period acquisition 13,379 — Prior period acquisition — (35,692) Foreign exchange movement 8,534 (30,569) Closing balance $ 8,993,583 $ 8,971,670

Intangible assets (Tables)

Intangible assets (Tables)	6 Months Ended
	Jun. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	Intangible assets are amortized on a straight-line basis over the expected useful life, as set forth in the table below: Estimated Useful Life Customer relationships 23 years Order backlog 3 years Trade names 3 years Patient database 7 years Technology assets 5 years Intangible assets, net consisted of the following: Six Months Ended Year Ended June 30, 2023 December 31, 2022 Cost (in thousands) Customer relationships $ 4,077,225 $ 4,076,435 Order backlog 537,182 536,934 Trade names & brands 204,636 204,621 Patient database 170,342 170,238 Technology assets 121,110 120,984 Total cost 5,110,495 5,109,212 Accumulated amortization (1,060,702) (830,553) Net book value $ 4,049,793 $ 4,278,659

Fair Value Measures and Disclos

Fair Value Measures and Disclosures (Tables)	6 Months Ended
	Jun. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value, Liabilities Measured on Recurring Basis	As of June 30, 2023, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows (in thousands): Level 1 Level 2 Level 3 Investments Measured at Net Asset Value Total (in thousands) Assets: Available for sale securities (short-term) (a) 1,653 — — — 1,653 Available for sale investments (long-term) (b) — — — 35,298 35,298 Derivative instruments (c) — 7,433 — — 7,433 Total assets $ 1,653 $ 7,433 $ — $ 35,298 $ 44,384 Liabilities: Derivative instruments (c) — — — — — Total liabilities $ — $ — $ — $ — $ — As of December 31, 2022, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows (in thousands): Level 1 Level 2 Level 3 Investments Measured at Net Asset Value Total (in thousands) Assets: Available for sale securities (short-term) (a) 1,713 — — — 1,713 Available for sale investments (long-term) (b) — — — 32,631 32,631 Derivative instruments (c) — 12 — — 12 Total assets $ 1,713 $ 12 $ — $ 32,631 $ 34,356 Liabilities: Derivative instruments (c) — 3,670 — — 3,670 Total liabilities $ — $ 3,670 $ — $ — $ 3,670 (a) Represents the fair value of investments in highly liquid investments with maturities of greater than three months and a minimum "A-" rated fixed term deposits and are based on quoted market prices. (b) To determine the classification of its interests in long-term investments, the Company considered the nature of its investment, the extent of influence over operating and financial decisions and the availability of readily determinable fair values. The Company determined that the interests in funds meet the definition of equity securities without readily determinable fair values, which qualify for the Net Asset Value (NAV) practical expedient in ASC 820 'Fair value measurements and disclosures'. Any increases or decreases in fair value are recognized in net income in the period.
Fair Value, Assets Measured on Recurring Basis	As of June 30, 2023, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows (in thousands): Level 1 Level 2 Level 3 Investments Measured at Net Asset Value Total (in thousands) Assets: Available for sale securities (short-term) (a) 1,653 — — — 1,653 Available for sale investments (long-term) (b) — — — 35,298 35,298 Derivative instruments (c) — 7,433 — — 7,433 Total assets $ 1,653 $ 7,433 $ — $ 35,298 $ 44,384 Liabilities: Derivative instruments (c) — — — — — Total liabilities $ — $ — $ — $ — $ — As of December 31, 2022, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows (in thousands): Level 1 Level 2 Level 3 Investments Measured at Net Asset Value Total (in thousands) Assets: Available for sale securities (short-term) (a) 1,713 — — — 1,713 Available for sale investments (long-term) (b) — — — 32,631 32,631 Derivative instruments (c) — 12 — — 12 Total assets $ 1,713 $ 12 $ — $ 32,631 $ 34,356 Liabilities: Derivative instruments (c) — 3,670 — — 3,670 Total liabilities $ — $ 3,670 $ — $ — $ 3,670 (a) Represents the fair value of investments in highly liquid investments with maturities of greater than three months and a minimum "A-" rated fixed term deposits and are based on quoted market prices. (b) To determine the classification of its interests in long-term investments, the Company considered the nature of its investment, the extent of influence over operating and financial decisions and the availability of readily determinable fair values. The Company determined that the interests in funds meet the definition of equity securities without readily determinable fair values, which qualify for the Net Asset Value (NAV) practical expedient in ASC 820 'Fair value measurements and disclosures'. Any increases or decreases in fair value are recognized in net income in the period.

Restructuring (Tables)

Restructuring (Tables)	6 Months Ended
	Jun. 30, 2023
Restructuring and Related Activities [Abstract]
Summary of Restructuring Charges	Six Months Ended June 30, 2023 June 30, 2022 (in thousands) Restructuring charges $ 45,390 $ 26,693 Net charge $ 45,390 $ 26,693
Summary of details of movement in restructuring charges	Six Months Ended Year ended June 30, 2023 December 31, 2022 (in thousands) Opening provision $ 6,022 $ 10,311 Additional provisions 39,338 4,364 Utilization (10,188) (8,653) Ending provision $ 35,172 $ 6,022

Operating leases (Tables)

Operating leases (Tables)	6 Months Ended
	Jun. 30, 2023
Leases [Abstract]
Schedule of Lease Costs	Lease costs recorded under operating leases for the six months ended June 30, 2023 and June 30, 2022 were as follows: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Operating lease costs 12,818 13,548 $ 25,689 $ 28,812 Income from sub-leases (283) (303) (561) (630) Net operating lease costs 12,535 13,245 $ 25,128 $ 28,182
Schedule of Operating Lease Maturity	Future minimum lease payments under non-cancelable leases as of June 30, 2023 were as follows: Minimum rental payments (in thousands) June 30, 2023 Year 1 $ 44,466 Year 2 33,902 Year 3 26,909 Year 4 22,801 Year 5 16,924 Thereafter 38,952 Total future minimum lease payments 183,954 Lease imputed interest (14,729) Total $ 169,225

Bank credit lines and loan fa_2

Bank credit lines and loan facilities (Tables)	6 Months Ended
	Jun. 30, 2023
Debt Disclosure [Abstract]
Schedule of Outstanding Debt	The Company had the following debt outstanding as of June 30, 2023 and December 31, 2022: Principal amount Interest rate as of Interest rate as of June 30, December 31, (in thousands) June 30, 2023 December 31, 2022 2023 2022 Maturity Date Credit Facilities: Senior Secured Term Loan 7.41 % 7.09 % $ 3,801,213 $ 4,201,213 July 2028 Senior Secured Notes 2.88 % 2.88 % $ 500,000 $ 500,000 July 2026 Senior Secured Revolving Loan Facility 6.51 % — 50,000 — July 2023 Total debt 4,351,213 4,701,213 Less current portion of long-term debt (105,150) (55,150) Total long-term debt 4,246,063 4,646,063 Less debt issuance costs and debt discount (39,127) (47,026) Total long-term debt, net $ 4,206,936 $ 4,599,037
Schedule of Contractual Maturities of Debt	As of June 30, 2023, the contractual maturities of the Company's debt obligations were as follows: Contractual maturities of long-term debt: (in thousands) 2023 (remaining) $ 77,575 2024 55,150 2025 55,150 2026 55,150 2027 and thereafter 4,108,188 Total $ 4,351,213

Derivatives (Tables)

Derivatives (Tables)	6 Months Ended
	Jun. 30, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The fair value of the Company’s derivative financial instruments, on a gross basis, and the line items on the accompanying consolidated balance sheets to which they were recorded are summarized in the following table: June 30, 2023 December 31, 2022 Asset Liability Notional Asset Liability Notional (in thousands) (in thousands) Derivatives designated as hedging instruments: Interest Rate Caps Other Current Liabilities, Other Assets and Liabilities $4,461 $— $1,900,606 $12 $3,363 $2,100,606 Interest Rate Swap Other Assets and Liabilities $2,972 $— $1,100,606 $— $307 $1,100,606 Total derivatives designated as hedging instruments $7,433 $— $3,001,212 $12 $3,670 $3,201,212

Income taxes (Tables)

Income taxes (Tables)	6 Months Ended
	Jun. 30, 2023
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense	Income taxes recognized during the three and six months ended June 30, 2023 and June 30, 2022, comprise: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Provision for income taxes $ 9,629 $ 14,254 $ 23,902 $ 27,540

Net income per ordinary share (

Net income per ordinary share (Tables)	6 Months Ended
	Jun. 30, 2023
Earnings Per Share [Abstract]
Schedule of reconciliation of number of shares used in computation of basic and diluted net income per ordinary share	The reconciliation of the number of shares used in the computation of basic and diluted net income per ordinary share is as follows: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 Weighted average number of ordinary shares outstanding for basic net income per ordinary share 81,999,746 81,398,071 81,892,662 81,430,507 Effect of dilutive share options and other awards outstanding under share based compensation programs 628,187 914,875 724,729 1,032,335 Weighted average number of ordinary shares outstanding for diluted net income per ordinary share 82,627,933 82,312,946 82,617,391 82,462,842 Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 Net income per Ordinary Share attributable to the Group: Basic 1.41 1.42 2.84 2.80 Diluted 1.40 1.41 2.81 2.76

Share-based awards (Tables)

Share-based awards (Tables)	6 Months Ended
	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Summary of stock option activity	The following table summarizes option activity for the six months ended June 30, 2023: Options Weighted Weighted Weighted Outstanding at December 31, 2022 1,378,119 $ 119.86 4.69 Granted 82,472 $ 232.48 Exercised (229,953) $ 87.69 Canceled/expired (6,885) $ 116.33 Outstanding at June 30, 2023 1,223,753 $ 133.51 4.67 Exercisable at June 30, 2023 952,614 $ 113.27 4.20
Schedule of weighted average fair values and assumptions used	The weighted average grant date fair values and assumptions used were as follows: Six Months Ended June 30, 2023 June 30, 2022 Weighted average grant date fair value $ 85.12 $ 68.40 Assumptions: Expected volatility 33 % 31 % Dividend yield — % — % Risk-free interest rate 3.98 % 1.85 % Expected life 5 years 5 years
Summary of RSU and PSU activity	The following table summarizes RSU and PSU activity for the six months ended June 30, 2023: Outstanding at December 31, 2022 152,420 $ 192.29 582,612 $ 207.73 Granted 60,374 $ 232.51 294,683 $ 217.52 Shares vested (47,026) $ 159.57 (150,515) $ 187.96 Forfeited — $ — (31,396) $ 209.13 Outstanding at June 30, 2023 165,768 $ 216.22 695,384 $ 216.09
Schedule of non-cash stock compensation expense	Non-cash stock compensation expense for the three and six months ended June 30, 2023 and June 30, 2022 has been allocated as follows: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Direct costs $ 6,420 $ 5,833 $ 12,088 $ 10,832 Selling, general and administrative $ 10,178 $ 13,450 $ 19,269 $ 27,354 Total $ 16,598 $ 19,283 $ 31,357 $ 38,186

Business Segment and Geograph_2

Business Segment and Geographical Information (Tables)	6 Months Ended
	Jun. 30, 2023
Segment Reporting [Abstract]
Schedule of Distribution of Revenue by Geographical Area	The distribution of revenue by geographical area was as follows: Three Months Ended Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Ireland $ 593,407 $ 500,972 $ 1,105,241 $ 868,330 Rest of Europe 373,810 428,393 788,033 884,458 U.S. 848,019 894,016 1,692,423 1,864,645 Rest of World 205,015 111,812 413,132 219,524 Total $ 2,020,251 $ 1,935,193 $ 3,998,829 $ 3,836,957
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 Six Months Ended June 30, 2023 June 30, 2022 June 30, 2023 June 30, 2022 (in thousands) (in thousands) Ireland * $ 125,896 $ 55,544 $ 177,223 $ 65,418 Rest of Europe 22,489 59,173 82,255 118,682 U.S. 55,744 53,321 143,833 113,789 Rest of World 5,355 9,751 22,962 50,239 Total $ 209,484 $ 177,789 $ 426,273 $ 348,128
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: June 30, 2023 December 31, 2022 (in thousands) Ireland $ 148,242 $ 143,025 Rest of Europe 95,048 99,721 U.S. 195,407 213,311 Rest of World 52,338 48,095 Total $ 491,035 $ 504,152

Summary of significant accoun_4

Summary of significant accounting policies - Estimated Useful Lives of Intangible Assets (Details)	Jun. 30, 2023
Customer relationships
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	23 years
Order backlog
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	3 years
Trade names
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	3 years
Patient database
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	7 years
Technology assets
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years

Revenue (Details)

Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue	$ 2,020,251	$ 1,935,193	$ 3,998,829	$ 3,836,957
Clients 1-5
Disaggregation of Revenue [Line Items]
Revenue	529,792	525,938	1,092,220	1,065,641
Clients 6-10
Disaggregation of Revenue [Line Items]
Revenue	284,382	260,689	563,908	553,350
Clients 11-25
Disaggregation of Revenue [Line Items]
Revenue	420,880	368,675	829,047	726,985
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 785,197	$ 779,891	$ 1,513,654	$ 1,490,981

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	Jun. 30, 2023	Dec. 31, 2022
Contract Assets [Abstract]
Billed services (accounts receivable)	$ 1,788,140	$ 1,751,950
Unbilled services (unbilled revenue)	985,034	957,655
Accounts receivable and unbilled revenue, gross	2,773,174	2,709,605
Allowance for credit losses	(29,029)	(20,562)
Accounts receivable and unbilled revenue, net	$ 2,744,145	$ 2,689,043

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	6 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Unbilled services (unbilled revenue)	$ 985,034	$ 957,655
Change in unbilled services (unbilled revenue)	$ 27,379
Percentage change in unbilled services (unbilled revenue)	2.90%
Unearned revenue (payments on account)	$ (1,573,311)	(1,507,449)
Change in unearned revenue (payments on account)	$ (65,862)
Percentage change in unearned revenue (payments on account)	4.40%
Net balance	$ (588,277)	$ (549,794)
Change in net balance	$ (38,483)
Percentage change in net balance	7%

Accounts receivable, unbilled_5

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Increase in unbilled services (unbilled revenue)	$ 27,379
Decrease in unearned revenue (payments on account)	65,862
Increase in net balance	(38,483)
Revenue, remaining performance obligation	$ 13,900,000	$ 13,900,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation percentage	51%
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months

Goodwill - Schedule of Goodwill

Goodwill - Schedule of Goodwill (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Goodwill [Roll Forward]
Opening balance	$ 8,971,670	$ 9,037,931
Current period acquisition	13,379	0
Prior period acquisition	0	(35,692)
Foreign exchange movement	8,534	(30,569)
Closing balance	$ 8,993,583	$ 8,971,670

Goodwill - Narrative (Details)

Goodwill - Narrative (Details) - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Apr. 20, 2023
Acquired Finite-Lived Intangible Assets [Line Items]
Current period acquisition	$ 13,379,000		$ 0
Accumulated impairment loss	0		$ 0
Acquisition-related gain	6,160,000	$ 0
Oncacare
Acquired Finite-Lived Intangible Assets [Line Items]
Percentage of share capital acquired				51%
Current period acquisition	$ 13,400,000

Intangible assets (Details)

Intangible assets (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Total cost	$ 5,110,495	$ 5,109,212
Accumulated amortization	(1,060,702)	(830,553)
Net book value	4,049,793	4,278,659
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Total cost	4,077,225	4,076,435
Order backlog
Finite-Lived Intangible Assets [Line Items]
Total cost	537,182	536,934
Trade names & brands
Finite-Lived Intangible Assets [Line Items]
Total cost	204,636	204,621
Patient database
Finite-Lived Intangible Assets [Line Items]
Total cost	170,342	170,238
Technology assets
Finite-Lived Intangible Assets [Line Items]
Total cost	$ 121,110	$ 120,984

Fair value measurements - Measu

Fair value measurements - Measurement of Fair Value of Major Asset and Liability classed (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities (short-term)	$ 1,653	$ 1,713
Available for sale investments (long-term)	35,298	32,631
Total assets	44,384	34,356
Total liabilities	0	3,670
Interest rate cap and interest rate swap | Total derivatives designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments	7,433	12
Derivative instruments	0	3,670
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities (short-term)	1,653	1,713
Available for sale investments (long-term)	0	0
Total assets	1,653	1,713
Total liabilities	0	0
Level 1 | Interest rate cap and interest rate swap | Total derivatives designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments	0	0
Derivative instruments	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities (short-term)	0	0
Available for sale investments (long-term)	0	0
Total assets	7,433	12
Total liabilities	0	3,670
Level 2 | Interest rate cap and interest rate swap | Total derivatives designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments	7,433	12
Derivative instruments	0	3,670
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities (short-term)	0	0
Available for sale investments (long-term)	0	0
Total assets	0	0
Total liabilities	0	0
Level 3 | Interest rate cap and interest rate swap | Total derivatives designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments	0	0
Derivative instruments	0	0
Investments Measured at Net Asset Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities (short-term)	0	0
Available for sale investments (long-term)	35,298	32,631
Total assets	35,298	32,631
Total liabilities	0	0
Investments Measured at Net Asset Value | Interest rate cap and interest rate swap | Total derivatives designated as hedging instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments	0	0
Derivative instruments	$ 0	$ 0

Fair value measurements - Narra

Fair value measurements - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	$ 44,384	$ 34,356
Long-term debt at fair value	4,310,100
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	$ 0
Level 3 | Fair value, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	13,043,400
Goodwill at fair value	8,993,600
Net intangible assets at fair value	$ 4,049,800

Restructuring - Narrative (Deta

Restructuring - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 35,661	$ 22,486	$ 45,390	$ 26,693
Other Restructuring Costs			11,300
Provision balance	35,172		35,172		$ 6,022	$ 10,311
2021 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Severance Costs			34,100
Personnel related liabilities
Restructuring Cost and Reserve [Line Items]
Provision balance	29,400		29,400
Facility liability
Restructuring Cost and Reserve [Line Items]
Provision balance	5,800		5,800
Other liability | Other liabilities
Restructuring Cost and Reserve [Line Items]
Provision balance	3,200		3,200
Other liability | Non-current other liabilities
Restructuring Cost and Reserve [Line Items]
Provision balance	$ 2,600		$ 2,600

Restructuring - Summary of Rest

Restructuring - Summary of Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Restructuring and Related Activities [Abstract]
Restructuring charges	$ 35,661	$ 22,486	$ 45,390	$ 26,693

Restructuring - Summary of Deta

Restructuring - Summary of Details of Movement in Restructuring Charges (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Restructuring Reserve [Roll Forward]
Opening provision	$ 6,022	$ 10,311
Additional provisions	39,338	4,364
Utilization	(10,188)	(8,653)
Ending provision	$ 35,172	$ 6,022

Operating leases - Schedule of

Operating leases - Schedule of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Leases [Abstract]
Operating lease costs	$ 12,818	$ 13,548	$ 25,689	$ 28,812
Income from sub-leases	(283)	(303)	(561)	(630)
Net operating lease costs	$ 12,535	$ 13,245	$ 25,128	$ 28,182

Operating leases - Narrative (D

Operating leases - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Lessee, Lease, Description [Line Items]
Total lease cost	$ 12,535	$ 13,245	$ 25,128	$ 28,182
Right-of-use assets obtained in exchange for lease obligations	$ 10,200	$ 29,000	$ 22,500	$ 35,800
Weighted average remaining lease term	7 years 3 days		7 years 3 days
Weighted average discount rate	2.66%		2.66%
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	$ 40,100	$ 47,000	$ 40,100	$ 47,000
Selling, general and administration costs
Lessee, Lease, Description [Line Items]
Total lease cost			19,300	27,100
Direct costs
Lessee, Lease, Description [Line Items]
Total lease cost			$ 5,800	$ 1,100

Operating leases - Schedule o_2

Operating leases - Schedule of Operating Lease Maturity (Details) $ in Thousands	Jun. 30, 2023 USD ($)
Leases [Abstract]
Year 1	$ 44,466
Year 2	33,902
Year 3	26,909
Year 4	22,801
Year 5	16,924
Thereafter	38,952
Total future minimum lease payments	183,954
Lease imputed interest	(14,729)
Total	$ 169,225

Bank credit lines and loan fa_3

Bank credit lines and loan facilities - Schedule of Outstanding Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Apr. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jul. 01, 2021
Debt Instrument [Line Items]
Total debt	$ 4,351,213			$ 4,701,213
Less current portion of long-term debt	(105,150)			(55,150)
Total long-term debt	4,246,063			4,646,063
Less debt issuance costs and debt discount	(39,127)			(47,026)
Total long-term debt, net	$ 4,206,936			$ 4,599,037
Senior Secured Term Loan | Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, interest rate	7.41%			7.09%	1%
Total debt	$ 3,801,213			$ 4,201,213
Senior Secured Notes | Senior Secured Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	2.88%			2.88%	2.875%
Total debt	$ 500,000			$ 500,000
Senior Secured Revolving Loan Facility | Senior Secured Revolving Loan Facility | Senior Secured Revolving Loan Facility
Debt Instrument [Line Items]
Debt instrument, interest rate	6.51%	6.25%	6.17%
Line of credit facility, interest rate at period end	6.51%
Total debt	$ 50,000			$ 0

Bank credit lines and loan fa_4

Bank credit lines and loan facilities - Narrative (Details) - USD ($) $ in Thousands			1 Months Ended		6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Apr. 30, 2023	Jan. 31, 2023	Jun. 30, 2023	Jun. 30, 2022	May 02, 2023	Jan. 13, 2023	Dec. 31, 2022	Jul. 01, 2021
Debt Instrument [Line Items]
Drawdown of bank credit lines and loan facilities					$ 230,000	$ 25,000
Long-term debt at fair value	$ 4,310,100				$ 4,310,100
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 | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)	0.50%
Senior Secured Term Loan | SOFR
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)	2.25%
Senior Secured Term Loan | Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, principal amount										$ 5,515,000
Debt instrument, interest rate	7.41%				7.41%				7.09%	1%
Repayments of senior debt	$ 150,000	$ 250,000
Interest paid	74,000	75,300
Payments of debt restructuring costs	1,200	$ 2,200
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 | SOFR | Variable rate component two
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)					1.60%
Senior Secured Revolving Loan Facility | SOFR | Maximum | Variable rate component two
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)					2%
Senior Secured Revolving Loan Facility | SOFR | Minimum | Variable rate component two
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)					1.25%
Senior Secured Revolving Loan Facility | Senior Secured Revolving Loan Facility
Debt Instrument [Line Items]
Repayments of senior debt	$ 80,000
Senior Secured Revolving Loan Facility | Senior Secured Revolving Loan Facility | Senior Secured Revolving Loan Facility
Debt Instrument [Line Items]
Debt instrument, maximum borrowing capacity							$ 500,000			$ 300,000
Debt instrument, interest rate	6.51%	6.17%	6.25%		6.51%
Drawdown of bank credit lines and loan facilities		$ 80,000	$ 50,000	$ 100,000
Senior Secured Revolving Loan Facility | Senior Secured Revolving Loan Facility | Senior Secured Revolving Loan Facility | Maximum
Debt Instrument [Line Items]
Debt instrument, interest rate				5.89%
Senior Secured Revolving Loan Facility | Senior Secured Revolving Loan Facility | Senior Secured Revolving Loan Facility | Minimum
Debt Instrument [Line Items]
Debt instrument, interest rate								5.80%
Senior Secured Revolving Loan Facility | Senior Secured Revolving Loan Facility | Senior Secured Revolving Loan Facility | SOFR
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)	1.25%	1.25%	1.25%	1.25%
Senior Secured Notes | Senior Secured Notes
Debt Instrument [Line Items]
Debt instrument, principal amount										$ 500,000
Debt instrument, interest rate	2.88%				2.88%				2.88%	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	Jun. 30, 2023	Dec. 31, 2022
Debt Disclosure [Abstract]
2023 (remaining)	$ 77,575
2024	55,150
2025	55,150
2026	55,150
2027 and thereafter	4,108,188
Total debt	$ 4,351,213	$ 4,701,213

Derivatives - Narrative (Detail

Derivatives - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Nov. 29, 2022 USD ($) instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months, net	$ (1,200)		$ (1,200)
Other comprehensive income (loss), cash flow hedge, gain (loss), before reclassification and tax	14,900	$ 0	(10,100)	$ 0
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, before tax	$ 1,400	$ 0	$ 3,600	$ 0
Interest Rate Caps | Total derivatives designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of interest rate derivatives held | instrument					2
Derivative, notional amount					$ 2,101,000
Derivative, fixed interest rate					0.42%
Interest Rate Caps | Total derivatives designated as hedging instruments | SOFR
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, variable interest rate, reference rate in excess of					4.75%
Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, notional amount					$ 1,101,000
Derivative, fixed interest rate					3.40%

Derivatives - Effect of Derivat

Derivatives - Effect of Derivative Financial Instruments on Statement of Financial Position (Details) - USD ($)	Jun. 30, 2023	Dec. 31, 2022
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other receivables
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Other liabilities
Interest Rate Caps | Total derivatives designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative assets	$ 4,461,000	$ 12,000
Derivative liability	0	3,363,000
Notional	1,900,606,000	2,100,606,000
Interest Rate Swap | Total derivatives designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative assets	2,972,000	0
Derivative liability	0	307,000
Notional	1,100,606,000	1,100,606,000
Interest rate cap and interest rate swap | Total derivatives designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative assets	7,433,000	12,000
Derivative liability	0	3,670,000
Notional	3,001,212,000	3,201,212,000
Interest rate cap and interest rate swap | Total derivatives designated as hedging instruments | Level 2
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative assets	7,433,000	12,000
Derivative liability	$ 0	$ 3,670,000

Income taxes - Components of Ta

Income taxes - Components of Tax (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 9,629	$ 14,254	$ 23,902	$ 27,540

Income taxes - Narrative (Detai

Income taxes - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Liability for unrecognized tax benefit	$ 249.6	$ 240.2
Items generating unrecognized tax benefits	220.4	217.6
Interest and related penalties	$ 29.2	$ 22.6

Net income per ordinary share -

Net income 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		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Earnings Per Share [Abstract]
Weighted average number of ordinary shares outstanding for basic net income per ordinary share (in shares)	81,999,746	81,398,071	81,892,662	81,430,507
Effect of dilutive share options and other awards outstanding under share based compensation programs (in shares)	628,187	914,875	724,729	1,032,335
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share (in shares)	82,627,933	82,312,946	82,617,391	82,462,842

Net income per ordinary share_2

Net income per ordinary share - Schedule of Reconciliation of Net Income Attributable to the Group (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Net income per Ordinary Share attributable to the Group:
Basic (in USD per share)	$ 1.41	$ 1.42	$ 2.84	$ 2.80
Diluted (in USD per share)	$ 1.40	$ 1.41	$ 2.81	$ 2.76

Share-based awards - Summary of

Share-based awards - Summary of Stock Option Activity (Details) - Employee Stock Option			6 Months Ended
	Jun. 30, 2023 $ / shares shares	Dec. 31, 2022 $ / shares shares	Jun. 30, 2023 $ / shares shares
Options Outstanding Number of Shares
Outstanding at beginning of period (in shares) | shares			1,378,119
Granted (in shares) | shares			82,472
Exercised (in shares) | shares			(229,953)
Canceled/expired (in shares) | shares			(6,885)
Outstanding at end of period (in shares) | shares	1,223,753	1,378,119	1,223,753
Exercisable at end of period (in shares) | shares	952,614		952,614
Weighted Average Exercise Price
Outstanding at beginning of period (in USD per share) | $ / shares			$ 119.86
Granted (in USD per share) | $ / shares			232.48
Exercised (in USD per share) | $ / shares			87.69
Canceled/expired (in USD per share) | $ / shares			116.33
Outstanding at end of period (in USD per share) | $ / shares	$ 133.51	$ 119.86	133.51
Exercisable at end of period (in USD per share) | $ / shares	$ 113.27		$ 113.27
Weighted Average Remaining Contractual Life
Weighted average contractual term of options outstanding	4 years 8 months 1 day	4 years 8 months 8 days
Weighted average contractual term of options exercisable	4 years 2 months 12 days

Share-based awards - Narrative

Share-based awards - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions			6 Months Ended	12 Months Ended	50 Months Ended
	Jun. 30, 2023	May 11, 2015	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2023	May 16, 2019
Employee Stock Option
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Number of shares exercisable (in shares)	952,614		952,614		952,614
Weighted average contractual term of options exercisable	4 years 2 months 12 days
Weighted average exercise price of options exercisble (USD per share)	$ 113.27		$ 113.27		$ 113.27
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
Restricted stock units 2013
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)		2,500,000
Ordinary shares which have been reserved for issuance (in shares)		4,100,000
Performance Share Unit (PSUs)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Fair value of stock units vested			$ 7.5	$ 6.5
Restricted Stock Units (RSUs)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Fair value of stock units vested			$ 28.3	$ 34.1
PSUs based on service and EPS targets | Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock units to be granted (in shares)	82,884		82,884		82,884

Share-based awards - Schedule o

Share-based awards - Schedule of Weighted Average Fair Values and Assumptions Used (Details) - Employee Stock Option - $ / shares	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value	$ 85.12	$ 68.40
Assumptions:
Expected volatility	33%	31%
Dividend yield	0%	0%
Risk-free interest rate	3.98%	1.85%
Expected life	5 years	5 years

Share-based awards - Summary _2

Share-based awards - Summary of RSU and PSU Activity (Details)	6 Months Ended
	Jun. 30, 2023 $ / shares shares
Performance Share Unit (PSUs)
Outstanding Number of Shares
Outstanding at beginning of period (in shares) | shares	152,420
Granted (in shares) | shares	60,374
Shares vested (in shares) | shares	(47,026)
Forfeited (in shares) | shares	0
Outstanding at end of period (in shares) | shares	165,768
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in USD per share) | $ / shares	$ 192.29
Granted (in USD per share) | $ / shares	232.51
Shares vested (in USD per share) | $ / shares	159.57
Forfeited (in USD per share) | $ / shares	0
Outstanding at end of period (in USD per share) | $ / shares	$ 216.22
Restricted Stock Units (RSUs)
Outstanding Number of Shares
Outstanding at beginning of period (in shares) | shares	582,612
Granted (in shares) | shares	294,683
Shares vested (in shares) | shares	(150,515)
Forfeited (in shares) | shares	(31,396)
Outstanding at end of period (in shares) | shares	695,384
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in USD per share) | $ / shares	$ 207.73
Granted (in USD per share) | $ / shares	217.52
Shares vested (in USD per share) | $ / shares	187.96
Forfeited (in USD per share) | $ / shares	209.13
Outstanding at end of period (in USD per share) | $ / shares	$ 216.09

Share-based awards - Schedule_2

Share-based awards - Schedule of Non-cash Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 16,598	$ 19,283	$ 31,357	$ 38,186
Direct costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	6,420	5,833	12,088	10,832
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 10,178	$ 13,450	$ 19,269	$ 27,354

Share capital (Details)

Share capital (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	6 Months Ended
	Mar. 31, 2022	Mar. 31, 2022	Jun. 30, 2023
Equity, Class of Treasury Stock [Line Items]
Share repurchase program, value of shares repurchased		$ 99,983
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)	6 Months Ended
	Jun. 30, 2023 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		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information [Line Items]
Revenue	$ 2,020,251	$ 1,935,193	$ 3,998,829	$ 3,836,957
Ireland
Segment Reporting Information [Line Items]
Revenue	593,407	500,972	1,105,241	868,330
Rest of Europe
Segment Reporting Information [Line Items]
Revenue	373,810	428,393	788,033	884,458
U.S.
Segment Reporting Information [Line Items]
Revenue	848,019	894,016	1,692,423	1,864,645
Rest of World
Segment Reporting Information [Line Items]
Revenue	$ 205,015	$ 111,812	$ 413,132	$ 219,524

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		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information [Line Items]
Income from operations	$ 209,484	$ 177,789	$ 426,273	$ 348,128
Ireland
Segment Reporting Information [Line Items]
Income from operations	125,896	55,544	177,223	65,418
Rest of Europe
Segment Reporting Information [Line Items]
Income from operations	22,489	59,173	82,255	118,682
U.S.
Segment Reporting Information [Line Items]
Income from operations	55,744	53,321	143,833	113,789
Rest of World
Segment Reporting Information [Line Items]
Income from operations	$ 5,355	$ 9,751	$ 22,962	$ 50,239

Business Segment and Geograph_6

Business Segment and Geographical Information - Schedule of Distribution of Depreciation and Amortization by Geographical Area (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Long-lived assets	$ 491,035	$ 504,152
Ireland
Segment Reporting Information [Line Items]
Long-lived assets	148,242	143,025
Rest of Europe
Segment Reporting Information [Line Items]
Long-lived assets	95,048	99,721
U.S.
Segment Reporting Information [Line Items]
Long-lived assets	195,407	213,311
Rest of World
Segment Reporting Information [Line Items]
Long-lived assets	$ 52,338	$ 48,095