ICON Public Limited (ICLR) 6-K 23 Jul 21 2021 Q2 Current report (foreign) Financial data

Cover

Cover	6 Months Ended
	Jun. 30, 2021
Cover [Abstract]
Document type	6-K
Document fiscal year focus	2021
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, 2021

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current Assets:
Cash and cash equivalents	$ 1,055,496	$ 840,305
Available for sale investments	1,729	1,729
Accounts receivable, net of allowance for credit losses	677,247	715,271
Unbilled revenue	415,390	428,684
Other receivables	32,289	35,394
Prepayments and other current assets	71,200	53,477
Income taxes receivable	32,037	28,118
Total current assets	2,285,388	2,102,978
Other Assets:
Property, plant and equipment, net	166,244	174,343
Goodwill	933,387	936,257
Operating right-of-use assets	69,238	84,561
Other non-current assets	22,445	20,773
Non-current income taxes receivable	12,373	17,230
Non-current deferred tax asset	12,282	12,705
Equity method investments	3,751	4,534
Investments in equity-long term	22,286	15,765
Intangible assets	57,070	66,460
Total Assets	3,584,464	3,435,606
Current Liabilities:
Accounts payable	37,818	51,113
Unearned revenue	675,234	660,883
Other liabilities	382,593	399,769
Income taxes payable	9,396	12,178
Total current liabilities	1,105,041	1,123,943
Other Liabilities:
Non-current bank credit lines and loan facilities	350,000	348,477
Non-current operating lease liabilities	47,334	60,801
Non-current other liabilities	26,541	26,366
Non-current government grants	795	838
Non-current income taxes payable	13,262	14,539
Non-current deferred tax liability	13,548	10,406
Commitments and contingencies	0	0
Total Liabilities	1,556,521	1,585,370
Shareholders' Equity:
Ordinary shares, par value 6 euro cents per share; 100,000,000 shares authorized, 52,958,063 shares issued and outstanding at June 30, 2021 and 52,788,093 shares issued and outstanding at December 31, 2020	4,592	4,580
Additional paid-in capital	632,069	617,104
Other undenominated capital	1,134	1,134
Accumulated other comprehensive income	(43,734)	(35,477)
Retained earnings	1,433,882	1,262,895
Total Shareholders' Equity	2,027,943	1,850,236
Total Liabilities and Shareholders' Equity	$ 3,584,464	$ 3,435,606
Common Stock, Shares, Issued	52,958,063	52,788,093
Ordinary shares, shares outstanding (in shares)	52,958,063	52,788,093

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - € / shares	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Ordinary shares, par value (in EUR cents per share)	€ 6	€ 6
Ordinary shares, shares authorized (in shares)	100,000,000	100,000,000
Ordinary shares, shares issued (in shares)	52,958,063	52,788,093
Ordinary shares, shares outstanding (in shares)	52,958,063	52,788,093

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Revenue	$ 871,155,000	$ 620,228,000	$ 1,729,353,000	$ 1,335,330,000
Costs and expenses:
Direct costs (excluding depreciation and amortization)	631,123,000	445,833,000	1,257,367,000	951,126,000
Selling, general and administrative expense	109,884,000	83,499,000	208,419,000	170,695,000
Depreciation and amortization	17,276,000	15,858,000	34,681,000	32,180,000
Restructuring	0	18,089,000	0	18,089,000
Total costs and expenses	758,283,000	563,279,000	1,500,467,000	1,172,090,000
Income from operations	112,872,000	56,949,000	228,886,000	163,240,000
Interest income	186,000	441,000	443,000	2,250,000
Interest expense	(24,551,000)	(3,220,000)	(27,278,000)	(6,401,000)
Income before provision for income taxes	88,507,000	54,170,000	202,051,000	159,089,000
Provision for income taxes	(14,133,000)	(6,410,000)	(30,281,000)	(19,000,000)
Income before share of earnings from equity method investments	74,374,000	47,760,000	171,770,000	140,089,000
Share of equity method investments	(509,000)	0	(783,000)	0
Net income	73,865,000	47,760,000	170,987,000	140,089,000
Net income attributable to noncontrolling interest	0	0	0	(633,000)
Net income attributable to the Group	$ 73,865,000	$ 47,760,000	$ 170,987,000	$ 139,456,000
Net income per Ordinary Share attributable to the Group (note 11):
Basic (USD per share)	$ 1.40	$ 0.91	$ 3.23	$ 2.55
Diluted (USD per share)	$ 1.38	$ 0.90	$ 3.21	$ 2.51
Weighted average number of Ordinary Shares outstanding:
Basic (in shares)	52,909,368	52,570,104	52,860,414	52,959,229
Diluted (in shares)	53,381,501	53,028,567	53,294,435	53,691,138

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 73,865,000	$ 47,760,000	$ 170,987,000	$ 140,089,000
Adjustments to reconcile net income to net cash provided by operating activities:
(Gain)/loss on disposal of property, plant and equipment			(5,000)	95,000
Depreciation expense			25,940,000	22,643,000
Impairment of right-of-use assets	0		0	5,411,000	$ 5,400,000
Reduction in carrying value of operating right-of-use assets			14,037,000	14,337,000
Amortization of intangibles			8,741,000	9,537,000
Amortization of government grants			(24,000)	(22,000)
Interest on non-current operating lease liability			870,000	1,006,000
Realized gain on sale of short term investments			0	(232,000)
Gain on re-measurement of financial assets			(4,750,000)	0
Loss on equity method investments	509,000	0	783,000	0
Stock compensation expense	8,480,000	7,117,000	14,874,000	13,186,000
Amortization of interest rate hedge			891,000	(482,000)
Amortization of financing costs			1,592,000	258,000
Loss on extinguishment of debt			14,434,000	0
Deferred taxes			3,313,000	(2,613,000)
Changes in assets and liabilities:
Decrease in accounts receivable			36,650,000	58,170,000
Decrease in unbilled revenue			12,690,000	12,226,000
Decrease in other receivables			2,406,000	2,689,000
Decrease in prepayments and other current assets			5,748,000	2,937,000
(Increase)/decrease in other non-current assets			(1,748,000)	486,000
Increase in unearned revenue			14,534,000	25,056,000
Decrease in other current liabilities			(50,981,000)	(33,507,000)
Decrease in operating lease liabilities			(14,951,000)	(15,416,000)
Increase in other non-current liabilities			1,151,000	2,355,000
Decrease in income taxes payable			(3,583,000)	(5,931,000)
(Decrease)/increase in accounts payable			(13,245,000)	8,370,000
Net cash provided by operating activities			240,354,000	260,648,000
Cash flows from investing activities:
Purchase of property, plant and equipment			(21,653,000)	(21,161,000)
Purchase of subsidiary undertakings			0	(47,367,000)
Purchase of equity method investments			(2,450,000)	0
Cash acquired with subsidiary undertaking			0	10,170,000
Sale of available for sale investments			0	47,902,000
Purchase of investments in equity - long term			(1,771,000)	(1,273,000)
Net cash used in investing activities			(25,874,000)	(11,729,000)
Cash flows from financing activities:
Proceeds from exercise of equity compensation			182,000	1,461,000
Share issue costs			(10,000)	(6,000)
Repurchase of ordinary shares			0	(175,000,000)
Share repurchase costs			0	(140,000)
Net cash provided by (used in) financing activities			172,000	(173,685,000)
Effect of exchange rate movements on cash			539,000	(3,443,000)
Net increase in cash and cash equivalents			215,191,000	71,791,000
Cash and cash equivalents at beginning of period			840,305,000	520,309,000	520,309,000
Cash and cash equivalents at end of period	$ 1,055,496,000	$ 592,100,000	$ 1,055,496,000	$ 592,100,000	$ 840,305,000

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY AND COMPREHENSIVE INCOME (UNAUDITED) - 6 months ended Jun. 30, 2021 - USD ($) $ in Thousands	Total	Ordinary Shares	Additional Paid-in Capital	Other Undenominated Capital	Accumulated Other Comprehensive Income	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2020	52,788,093	52,788,093
Beginning balance at Dec. 31, 2020	$ 1,850,236	$ 4,580	$ 617,104	$ 1,134	$ (35,477)	$ 1,262,895
Comprehensive income:
Net income	170,987					170,987
Currency translation adjustment	(8,909)				(8,909)
Currency impact of long term funding (net of tax)	(239)				(239)
Amortization of interest rate hedge	113				113
Write off of loss on interest rate hedge	778				778
Total comprehensive income	162,730				(8,257)	170,987
Exercise of share options (in shares)		4,020
Exercise of share options	170		170
Issue of restricted share units (in shares)		165,950
Issue of restricted share units	12	$ 12
Non-cash stock compensation expense	14,805		14,805
Share issuance costs	$ (10)		(10)
Ending balance (in shares) at Jun. 30, 2021	52,958,063	52,958,063
Ending balance at Jun. 30, 2021	$ 2,027,943	$ 4,592	$ 632,069	$ 1,134	$ (43,734)	$ 1,433,882

Basis of presentation

Basis of presentation	6 Months Ended
	Jun. 30, 2021
Accounting Policies [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, 2020 (see note 2 - Significant accounting policies for impact of adoption of any new accounting standards). Operating results for the six months ended June 30, 2021 are not necessarily indicative of the results that may be expected for the fiscal period ending December 31, 2021.

Significant accounting policies

Significant accounting policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Significant accounting policies	Significant accounting policies Redeemable noncontrolling interests and equity On May 23, 2019, ICON acquired a majority ownership interest in MeDiNova. Included in the purchase agreement were put and call option arrangements with the noncontrolling interest holders that required (put option) or enabled (call option) ICON to purchase the remaining minority ownership at a future date. The option was accounted for as temporary equity, which was presented separately as redeemable noncontrolling interest on the Condensed Consolidated Balance Sheet. This classification reflects the assessment that the instruments were contingently redeemable in accordance with ASC 480-10-S99 ' Distinguishing Liabilities from Equity '. Redeemable noncontrolling interests are accreted to their redemption value over the period from the date of issuance to the first date on which the option is exercisable. The change in the option's redemption value is recorded against retained earnings. In a computation of earnings per share, the accretion of redeemable noncontrolling interests to their redemption value is a reduction of net income attributable to the Group. Basic and diluted net income per ordinary share attributable to the Group includes the adjustment to reflect the accretion of the noncontrolling interest to its redemption value. On March 9, 2020 ICON exercised its option to call the outstanding shares in the noncontrolling interest to take 100% ownership of MeDiNova. On exercise of the call option, the noncontrolling interest is extinguished and a liability was recorded for the amount payable to the former noncontrolling interest holders. This liability was settled on July 17, 2020 for $43.9 million. Financial assets - credit losses On January 1, 2020, the Group adopted ASU 2016-13 'Measurement of Credit Losses on Financial Instruments (ASC 326)' , which significantly changes the way entities recognize impairment of many financial assets by requiring immediate recognition of estimated credit losses expected to occur over their remaining life. The update provides guidance on the measurement of credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The amendment replaces the current incurred loss impairment approach with a methodology to reflect expected credit losses and requires consideration of a broader range of reasonable and supportable information to explain credit loss estimates. The Group adopted ASC 326 using the modified retrospective measurement method for all in scope financial assets. Results for reporting periods beginning after January 1, 2020 are presented under ASC 326 while prior period amounts continue to be reported in accordance with previously applicable GAAP. The impact of transitioning to the new standard at January 1, 2020 was immaterial and no adjustment was recorded to retained earnings for the cumulative effect of adopting ASC 326. On transition to ASC 326, the Group has revised the methodology to calculate the allowance for credit losses. The Group's estimate of expected credit losses considers historical credit loss information that is adjusted, where necessary, for current conditions and reasonable and supportable forecasts. Historical credit loss experience provides the basis for the estimation of expected credit losses. The Group's receivables and unbilled services are predominantly due from large and mid-tier pharmaceutical and biotechnology companies that share similar risk characteristics. The Group monitors their portfolio of receivables and unbilled services for any deterioration in current or expected credit quality (for example, expected delinquency level), and adjusts the allowance for credit losses as required. Changes in the allowance for credit losses are recorded as a provision for (or reversal of) credit loss expense in the Condensed Consolidated Statement of Operations. Losses are charged against the allowance when management believes the uncollectibility of a previously provisioned amount is confirmed. Leases The new leasing standard ( ASC 842 'Leases' ) was effective and adopted by ICON from January 1, 2019. ASC 842 ' Leases ' supersedes the requirements in ASC 840 'Leases' and requires that lessees recognize rights and obligations from virtually all leases (other than leases that meet the definition of a short-term lease) on their balance sheets as right-of-use assets with corresponding lease liabilities. The ASU also provides additional guidance on how to classify leases and how to determine the lease term for accounting purposes. ICON adopted the new standard under the cumulative effect adjustment approach There was no impact of adopting ASC 842 on opening retained earnings at January 1, 2019.

Revenue

Revenue	6 Months Ended
	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Revenue disaggregated by customer profile is as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Top client $ 110,356 $ 74,932 $ 274,650 $ 156,199 Clients 2-5 246,094 179,018 475,994 381,996 Clients 6-10 116,237 86,449 239,130 160,800 Clients 11-25 158,577 101,417 296,432 231,501 Other 239,891 178,412 443,147 404,834 Total $ 871,155 $ 620,228 $ 1,729,353 $ 1,335,330 Accounts receivables and unbilled revenue are as follows: June 30, 2021 December 31, 2020 (in thousands) Contract assets: Billed services (accounts receivable) $ 684,355 $ 722,420 Unbilled services (unbilled revenue) 415,390 428,684 Accounts receivable and unbilled revenue 1,099,745 1,151,104 Allowance for credit losses (7,108) (7,149) Accounts receivable and unbilled revenue, net $ 1,092,637 $ 1,143,955 Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows: (in thousands, except percentages) June 30, 2021 December 31, 2020 $ Change % Change Unbilled services (unbilled revenue) $ 415,390 $ 428,684 $ (13,294) (3.1) % Unearned revenue (payments on account) (675,234) (660,883) (14,351) 2.2 % Net balance $ (259,844) $ (232,199) $ (27,645) 11.9 % 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, 2021 decreased by $13.3 million compared to December 31, 2020. Unearned revenue increased by $14.4 million over the same period resulting in a decrease of $27.6 million in the net balance of unbilled services and unearned revenue or payments on account between December 31, 2020 and June 30, 2021. 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. The credit loss expense and allowance for credit losses recognized on the Group's receivables and unbilled services were de minimis for the three and six months ended June 30, 2021 and June 30, 2020. As of June 30, 2021 approximately $6.6 billion (June 30, 2020: $5.7 billion) of revenue is expected to be recognized in the future in respect of unsatisfied performance obligations. The Company expects to recognize revenue on approximately 43% of the

Accounts receivable, unbilled r

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities)	6 Months Ended
	Jun. 30, 2021
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 profile is as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Top client $ 110,356 $ 74,932 $ 274,650 $ 156,199 Clients 2-5 246,094 179,018 475,994 381,996 Clients 6-10 116,237 86,449 239,130 160,800 Clients 11-25 158,577 101,417 296,432 231,501 Other 239,891 178,412 443,147 404,834 Total $ 871,155 $ 620,228 $ 1,729,353 $ 1,335,330 Accounts receivables and unbilled revenue are as follows: June 30, 2021 December 31, 2020 (in thousands) Contract assets: Billed services (accounts receivable) $ 684,355 $ 722,420 Unbilled services (unbilled revenue) 415,390 428,684 Accounts receivable and unbilled revenue 1,099,745 1,151,104 Allowance for credit losses (7,108) (7,149) Accounts receivable and unbilled revenue, net $ 1,092,637 $ 1,143,955 Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows: (in thousands, except percentages) June 30, 2021 December 31, 2020 $ Change % Change Unbilled services (unbilled revenue) $ 415,390 $ 428,684 $ (13,294) (3.1) % Unearned revenue (payments on account) (675,234) (660,883) (14,351) 2.2 % Net balance $ (259,844) $ (232,199) $ (27,645) 11.9 % 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, 2021 decreased by $13.3 million compared to December 31, 2020. Unearned revenue increased by $14.4 million over the same period resulting in a decrease of $27.6 million in the net balance of unbilled services and unearned revenue or payments on account between December 31, 2020 and June 30, 2021. 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. The credit loss expense and allowance for credit losses recognized on the Group's receivables and unbilled services were de minimis for the three and six months ended June 30, 2021 and June 30, 2020. As of June 30, 2021 approximately $6.6 billion (June 30, 2020: $5.7 billion) of revenue is expected to be recognized in the future in respect of unsatisfied performance obligations. The Company expects to recognize revenue on approximately 43% of the

Goodwill

Goodwill	6 Months Ended
	Jun. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill Six Months Ended Year Ended June 30, 2021 December 31, 2020 (in thousands) Opening balance $ 936,257 $ 883,170 Current period acquisitions (Note 6) — 27,191 Prior period acquisitions — 123 Foreign exchange movement (2,870) 25,773 Closing balance $ 933,387 $ 936,257

Business combinations

Business combinations	6 Months Ended
	Jun. 30, 2021
Business Combinations [Abstract]
Business combinations	Business combinations PRA Health Sciences Inc - Merger Completion On July 1, 2021, ICON plc announced the completion of its Merger with PRA Health Sciences Inc ("PRA"). The combined company will retain the name ICON and will bring together approximately 38,000 employees across 47 countries, creating the world’s most advanced healthcare intelligence and clinical research organization. The combined company will leverage its enhanced operations to transform clinical trials and accelerate biopharma customers’ commercial success through the development of much needed medicines and medical devices. The new ICON will have a renewed focus on leveraging data, applying technology and accessing diverse patient populations to speed up drug development. Upon completion of the Merger, pursuant to the terms of the merger agreement, PRA became a wholly owned subsidiary of ICON plc. Under the terms of the Merger, PRA shareholders received per share $80 in cash and 0.4125 shares of ICON stock. The trading of PRA common stock on NASDAQ was suspended prior to market open on July 1, 2021. The consideration for the Merger is estimated at approximately $12.5 billion. The opening balance sheet remains under preparation but we expect to record additional intangible assets of approximately $5.5 billion from the acquisition. The purchase accounting associated with the PRA Merger remains ongoing and we await formal valuations reports to support the assets acquired and the liabilities assumed. We expect to conclude the purchase accounting exercise within the next 12 months. Acquisitions – MedPass Group ("MedPass") On January 22, 2020 a subsidiary of the Company, ICON Investments Limited acquired 100% of the equity share capital of the MedPass Group. MedPass is the leading European medical device CRO, regulatory and reimbursement consultancy, that specializes in medical device development and market access. The acquisition of MedPass further enhances ICON’s Medical Device and Diagnostic Research services, through the addition of new regulatory and clinical capabilities in Europe. The integration of MedPass’s services brings noted expertise in complex class 3 medical devices, interventional cardiology and structural heart devices . Accounting for the acquisition of MedPass was finalized in the period ended December 31, 2020. The acquisition of MedPass has been accounted for as a business combination in accordance with ASC 805 ' Business Combinations' . The Company has made an assessment of the fair value of assets acquired and liabilities assumed as at that date. The following table summarizes the Company’s fair values of the assets acquired and liabilities assumed: January 22, 2020 (in thousands) Cash & cash equivalents $ 10,170 Property, plant and equipment 45 Operating right of use assets 539 Goodwill * 27,191 Customer relationships 11,725 Order backlog 2,883 Accounts receivable 3,033 Prepayments and other current assets 158 Accounts payable (368) Unearned revenue (989) Other liabilities (2,202) Current lease liabilities (219) Non-current lease liabilities (320) Non-current deferred tax liability (4,090) Net assets acquired $ 47,556 Cash outflows $ 46,992 Working capital adjustment paid 564 Contingent consideration ** — Total consideration $ 47,556 * Goodwill represents the acquisition of an established workforce that specializes in medical device development and market access. None of the goodwill recognized is expected to be deductible for income tax purposes. ** The fair value of the contingent consideration was estimated at the date of acquisition as $Nil. Depending on performance of MedPass for the 12 month period ended December 31, 2020, the total consideration could have increased by a maximum of $6.7 million in contingent consideration. In January 2021, the contingent consideration was finalized and a value of $Nil was payable. Acquisitions – CRN Holdings LLC (trading as Symphony Clinical Research ("Symphony")) On September 24, 2019 a subsidiary of the Company, ICON Clinical Research LLC, acquired a 100% interest in Symphony. Symphony is a leading provider of at-home trial services and site support services. The acquisition of Symphony further enhances our site & patient services offering. Accounting for the acquisition of Symphony was finalized in the period ended September 30, 2020. The total consideration was $37.8 million and resulted in the recognition of $22.9 million in Goodwill. The total consideration included $2.5 million in contingent consideration, which was dependent on Symphony meeting certain revenue targets. The fair value of the contingent consideration was estimated at the date of acquisition. On June 12, 2020 the contingent consideration was settled at its revised fair value in the amount of $0.5 million. The change in fair value has been recorded in the selling, general and administrative expense line of the Condensed Consolidated Statement of Operations in the year ended December 31, 2020. Acquisitions – MeDiNova On May 23, 2019 a subsidiary of the Company, ICON Clinical Research (U.K.) Limited acquired a 60% majority shareholding in MeDiNova, a site network with research sites in key markets in Europe and Africa. On March 9, 2020 ICON exercised its option to call the outstanding shares in the noncontrolling interest to take 100% ownership of MeDiNova. The acquisition further enhances ICON's patient recruitment capabilities in EMEA and complements ICON's existing site network in the US, PMG Research. Accounting for the acquisition of MeDiNova was finalized in the period ended June 30, 2020. The total consideration was $86.2 million and resulted in the recognition of $81.8 million in Goodwill. The total consideration included $32.6 million to reflect the fair value of the redeemable noncontrolling interest. The fair value of the redeemable noncontrolling interest was estimated by applying an income based approach. The valuation approach used was based on the future earnings of the company times an appropriate earnings multiple. Effective from March 9, 2020, the noncontrolling interest was derecognized and a liability was recognized, representing the assessment of the redemption value of the noncontrolling interest. This liability was settled on July 17, 2020 for $43.9 million. Acquisitions – MolecularMD Corp ("MMD") On January 25, 2019 a subsidiary of the Company, ICON Laboratory Services, Inc. acquired 100% of the share capital of MMD. MMD is a molecular diagnostic specialty laboratory that enables the development and commercialization of precision medicines in oncology. Accounting for the acquisition of MMD was finalized in the year ended December 31, 2019. The total consideration was $42.2 million and resulted in the recognition of $22.4 million in Goodwill.

Equity method investments

Equity method investments	6 Months Ended
	Jun. 30, 2021
Equity Method Investments and Joint Ventures [Abstract]
Equity method investments	Equity method investments The Company has invested $4.9 million to obtain a 49% interest in the voting share capital of Oncacare Limited ("Oncacare"). The Company’s investment in Oncacare is accounted for under the equity method due to the Company's ability to exercise significant influence over Oncacare that is considered to be greater than minor. The Company records its pro rata share of the earnings/losses of this investment in 'Share of equity method investments' in the Condensed Consolidated Statement of Operations. The majority investor has the right to sell the 51% majority voting share capital exclusively to the Company in a two and half year period commencing from January 1, 2023 and ICON also has the right to acquire the 51% majority voting share capital from August 1, 2025. The following table represents our equity method investments at June 30, 2021: Ownership Percentage Carrying Value Carrying Value June 30, 2021 June 30, 2021 December 31, 2020 (in thousands) Oncacare Limited 49 % $ 3,751 $ 4,534 The Company has invested $4.9 million in Oncacare, which includes $2.5 million that was paid on June 30, 2021. The Company has recorded a loss of $0.5 million representing its pro rata share of the losses in Oncacare for the three month period ended June 30, 2021. The Company recorded a loss of $0.8 million for the six months ended June 30, 2021.

Restructuring

Restructuring	6 Months Ended
	Jun. 30, 2021
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring Restructuring charges No restructuring charge was recognized during the six months ended June 30, 2021 (June 30, 2020: $18.1 million). Prior Period Restructuring charges A restructuring charge of $18.1 million was recognized in the year ended December 31, 2020 under a restructuring plan adopted following a review of operations. The restructuring plan reflected resource rationalization across the business to improve resource utilization, resulting in a charge of $11.4 million and office consolidation resulting in a charge for onerous lease obligations of $6.7 million, including the recognition of an impairment of right of use assets of $5.4 million and provision for other related costs of $1.3 million. No additional charge was recorded during the three and six months ended June 30, 2021. Workforce reductions Onerous Lease Total (in thousands) Initial restructuring charge recorded $ 11,391 $ 6,698 $ 18,089 Utilization (6,987) (1,309) (8,296) Foreign exchange movement — 325 325 Provision at December 31, 2020 4,404 5,714 10,118 Utilization (2,299) (1,345) (3,644) Foreign exchange movement — 4 4 Provision at June 30, 2021 $ 2,105 $ 4,373 $ 6,478 Future minimum lease payments (including related costs), associated with the 2020 restructuring plan, under the non-cancelable onerous leases as at June 30, 2021 were as follows: Minimum rental payments (in thousands) June 30, 2021 2021 $ 1,210 2022 1,872 2023 1,015 2024 142 2025 141 Thereafter 401 Total future minimum lease payments (including related costs) 4,781 Lease imputed interest (408) Total $ 4,373 A restructuring charge of $12.5 million was recognized during the year ended December 31, 2018 under a restructuring plan adopted following a review of operations. The restructuring plan reflected resource rationalization across the business to improve resource utilization, resulting in a charge of $9.7 million and office consolidation resulting in the recognition of an onerous lease obligation of $2.8 million. No additional charge was recorded during the six months ended June 30, 2021. Workforce reductions Onerous Lease Total (in thousands) Initial restructuring charge recorded $ 9,684 $ 2,806 $ 12,490 Utilization (5,399) (672) (6,071) Provision at December 31, 2018 $ 4,285 $ 2,134 $ 6,419 Utilization (3,554) (1,228) (4,782) Provision at December 31, 2019 $ 731 $ 906 $ 1,637 Utilization (731) (276) (1,007) Provision at December 31, 2020 $ — $ 630 $ 630 Utilization — (97) (97) Provision at June 30, 2021 $ — $ 533 $ 533 At June 30, 2021, $4.4 million is included within other liabilities and $2.6 million within non-current other liabilities.

Operating leases

Operating leases	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Operating leases	Operating leases Lease costs recorded under operating leases for the three and six months ended June 30, 2021 and June 30, 2020 were as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Operating lease costs $ 7,549 $ 7,768 $ 15,338 $ 15,857 Income from sub-leases (220) (246) (431) (514) Net operating lease costs $ 7,329 $ 7,522 $ 14,907 $ 15,343 Of the total cost of $14.9 million incurred in the six months ended June 30, 2021 (June 30, 2020: $15.3 million), $13.8 million (June 30, 2020: $14.0 million) is recorded within selling, general and administration costs and $1.1 million (June 30, 2020: $1.3 million) is recorded within direct costs. During the three and six months ended June 30, 2021 and June 30, 2020, costs incurred by the Group related to variable lease payments was de minimis. Right-of-use assets obtained during the three months ended June 30, 2021 excluding early termination options, now reasonably certain to be exercised of $Nil (June 30, 2020: $1.6 million), totaled $1.0 million (June 30, 2020: $0.2 million). Right-of-use assets obtained during the six months ended June 30, 2021, excluding early termination options now reasonably certain to be exercised of $4.2 million (June 30, 2020: $1.6 million), totaled $3.8 million (June 30, 2020: $4.5 million). In the three and six months ended June 30, 2020, office consolidations resulted in the recognition of an onerous lease obligation. The right-of-use assets related to these offices have been impaired to the extent they are considered onerous and a loss $5.4 million was recorded (see note 8 - Restructuring ). No impairment losses were recognized in the three and six months ended June 30, 2021. The weighted average remaining lease term and weighted-average discount rate at June 30, 2021 were 3.93 years and 2.52%, respectively. Future minimum lease payments under non-cancelable leases as of June 30, 2021 were as follows: Minimum rental payments (in thousands) June 30, 2021 Due within 1 year $ 24,293 Due between 1 and 5 years 43,579 Thereafter 6,377 Total future minimum lease payments 74,249 Lease imputed interest (4,107) Total $ 70,142 other liabilities

Income taxes

Income taxes	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Income taxes	Income taxes Income taxes recognized during the six months ended June 30, 2021 and June 30, 2020, comprise: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Provision for income taxes (excluding restructuring) $ 14,133 $ 8,671 $ 30,281 $ 21,261 Tax impact of restructuring — (2,261) — (2,261) Provision for income taxes $ 14,133 $ 6,410 $ 30,281 $ 19,000 As at June 30, 2021 the Company maintains a $17.4 million liability (December 31, 2020: $19.6 million) for unrecognized tax benefit, which is comprised of $17.1 million (December 31, 2020: $19.1 million) related to items generating unrecognized tax benefits and $0.3 million (December 31, 2020: $0.5 million) for interest and penalties related to such items. The Company recognizes interest accrued on unrecognized tax benefits as an additional income tax expense.

Net income per ordinary share

Net income per ordinary share	6 Months Ended
	Jun. 30, 2021
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. Basic and diluted net income per ordinary share attributable to the Group includes the adjustment to reflect the accretion of the noncontrolling interest in MeDiNova to its redemption value. 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, 2021 June 30, 2020 June 30, 2021 June 30, 2020 Weighted average number of ordinary shares outstanding for basic net income per ordinary share 52,909,368 52,570,104 52,860,414 52,959,229 Effect of dilutive share options outstanding 472,133 458,463 434,021 731,909 Weighted average number of ordinary shares outstanding for diluted net income per ordinary share 53,381,501 53,028,567 53,294,435 53,691,138 The reconciliation of net income attributable to the Group and net income attributable to the Group (including NCI redemption amount) as used to calculate net income per ordinary share attributable to the Group is as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Net income attributable to the Group $ 73,865 $ 47,760 $ 170,987 $ 139,456 Noncontrolling interest adjustment to redemption amount — — — (4,522) Net income attributable to the Group (including NCI redemption adjustment) $ 73,865 $ 47,760 $ 170,987 $ 134,934 Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 Net income per Ordinary Share attributable to the Group (including NCI redemption adjustment): Basic $ 1.40 $ 0.91 $ 3.23 $ 2.55 Diluted $ 1.38 $ 0.90 $ 3.21 $ 2.51

Share-based awards

Share-based awards	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Share-based awards	Share-based awards Share Options On July 21, 2008, the Company adopted the Employee Share Option Plan 2008 (the “2008 Employee Plan”) pursuant to which the Compensation and Organization Committee of the Company’s Board of Directors may grant options to any employee, or any Director holding a salaried office or employment with the Company or a Subsidiary for the purchase of ordinary shares. On the same date, the Company also adopted the Consultants Share Option Plan 2008 (the “2008 Consultants Plan”), pursuant to which the Compensation and Organization Committee of the Company’s Board of Directors may grant options to any consultant, adviser or non-executive Director retained by the Company or any Subsidiary for the purchase of ordinary shares. On February 14, 2017, both the 2008 Employee Plan and the 2008 Consultants Plan (together the “2008 Option Plans”) were amended and restated in order to increase the number of options that can be issued under the 2008 Consultants Plan from 0.4 million to 1.0 million and to extend the date for options to be granted under the 2008 Option Plans. An aggregate of 6.0 million ordinary shares have been reserved under the 2008 Employee Plan, as reduced by any shares issued or to be issued pursuant to options granted under the 2008 Consultants Plan, under which a limit of 1.0 million shares applies. Further, the maximum number of ordinary shares with respect to which options may be granted under the 2008 Employee Option Plan, during any calendar year to any employee shall be 0.4 million ordinary shares. There is no individual limit under the 2008 Consultants Plan. No options may be granted under the 2008 Option Plans after February 14, 2027. Each option granted under the 2008 Option Plans will be an employee stock option, or NSO, as described in Section 422 or 423 of the Internal Revenue Code. Each grant of an option under the 2008 Options Plans will be evidenced by a Stock Option Agreement between the optionee and the Company. The exercise price will be specified in each Stock Option Agreement, however option prices will not be less than 100% of the fair market value of an ordinary share on the date the option is granted. On January 17, 2003, the Company adopted the Share Option Plan 2003 (the “2003 Share Option Plan”) pursuant to which the Compensation and Organization Committee of the Board could grant options to officers and other employees of the Company or its subsidiaries for the purchase of ordinary shares. An aggregate of 6.0 million ordinary shares were reserved under the 2003 Share Option Plan; and, in no event could the number of ordinary shares issued pursuant to options awarded under this plan exceed 10% of the outstanding shares, as defined in the 2003 Share Option Plan, at the time of the grant, unless the Board expressly determined otherwise. Further, the maximum number of ordinary shares with respect to which options could be granted under the 2003 Share Option Plan during any calendar year to any employee was 0.4 million ordinary shares. The 2003 Share Option Plan expired on January 17, 2013. No new options may be granted under this plan. Share option awards are granted with an exercise price equal to the market price of the Company’s shares at date of grant. Prior to 2018, share options typically vest over a period of five years from date of grant and expire eight years from date of grant. Share options granted to non-executive directors during 2018 vest over 12 months and expire eight years from the date of grant. The maximum contractual term of options outstanding at June 30, 2021 is eight years. The following table summarizes option activity for the six months ended June 30, 2021: Options Weighted Weighted Weighted Outstanding at December 31, 2020 553,746 $ 108.53 $ 31.63 4.86 Granted 100,299 $ 177.76 $ 49.15 Exercised (4,020) $ 42.24 $ 14.07 Canceled/expired — $ — $ — Outstanding at June 30, 2021 650,025 $ 119.62 $ 34.44 4.90 Exercisable at June 30, 2021 336,942 $ 92.71 $ 27.42 3.63 The Company has outstanding options with fair values ranging from $12.24 to $64.07 per option or a weighted average fair value of $25.97 per option. The Company issues ordinary shares for all options exercised. The total amount of fully vested share options which remained outstanding at June 30, 2021 was 336,942. Fully vested share options at June 30, 2021 have an average remaining contractual term of 3.63 years, an average exercise price of $92.71 and a total intrinsic value of $38.4 million. The total intrinsic value of options exercised during the six months ended June 30, 2021 was $0.7 million (June 30, 2020: $4.3 million). The following table summarizes the movement in non-vested share options for the six months ended June 30, 2021: Options Weighted Average Weighted Average Non-vested outstanding at December 31, 2020 328,901 $ 125.89 $ 36.24 Granted 100,299 $ 177.76 $ 49.15 Vested (116,117) $ 109.53 $ 31.84 Forfeited — $ — $ — Non-vested outstanding at June 30, 2021 313,083 $ 148.58 $ 42.00 Fair value of Stock Options Assumptions The weighted average fair value of options granted during the six months ended June 30, 2021 and June 30, 2020 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, 2021 June 30, 2020 Weighted average grant date fair value $ 49.15 $ 42.43 Assumptions: Expected volatility 30 % 30 % Dividend yield — % — % Risk-free interest rate 0.78 % 0.57 % 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 2013 RSU Plan was amended and restated in order to increase the number of shares that can be issued under the RSU Plan by 2.5 million shares. Accordingly, an aggregate of 4.1 million ordinary shares have been reserved for issuance under the 2013 RSU Plan. The shares are awarded at par value and vest over a service period. Awards under the 2013 RSU Plan may be settled in cash or shares at the option of the Company. 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 2019, 2020 and 2021 vest over twelve months. The Company has awarded RSUs and PSUs to certain key individuals of the Group. The following table summarizes RSU and PSU activity for the six months ended June 30, 2021: PSU RSU Outstanding at December 31, 2020 159,641 $ 137.64 1.14 341,424 $ 145.77 1.41 Granted 55,444 $ 177.77 144,274 $ 207.29 Shares vested (44,132) $ 115.61 (122,331) $ 131.37 Forfeited (3,159) $ 115.61 (9,818) $ 146.64 Outstanding at June 30, 2021 167,794 $ 159.18 1.35 353,549 $ 175.83 1.87 The fair value of PSUs vested for the six months ended June 30, 2021 totaled $5.1 million (full year 2020: $5.3 million). The fair value of RSUs vested for the six months ended June 30, 2021 totaled $16.1 million (full year 2020: $14.3 million). The PSUs vest based on service and specified EPS targets over the periods 2019 – 2021, 2020 – 2022 and 2021 - 2023. Depending on the amount of EPS from 2019 to 2023, up to an additional 83,897 PSUs may also be granted. Non-cash stock compensation expense Non-cash stock compensation expense for the six months ended June 30, 2021 and June 30, 2020 has been allocated as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Direct costs $ 3,101 $ 2,353 $ 5,156 $ 4,188 Selling, general and administrative 5,379 4,764 9,718 8,998 $ 8,480 $ 7,117 $ 14,874 $ 13,186 Total non-cash stock compensation expense not yet recognized at June 30, 2021 amounted to $72.6 million. The weighted average period over which this is expected to be recognized is 2.42 years.

Share capital

Share capital	6 Months Ended
	Jun. 30, 2021
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, the United States securities laws, and the Company’s constitutional documents through open market share acquisitions. On January 8, 2019, the Company commenced a share buyback program of up to 1.0 million ordinary shares which was completed during the year ended December 31, 2019 for total consideration of $141.6 million. On October 22, 2019, the Company commenced a further share buyback program. At December 31, 2019, 35,100 ordinary shares were redeemed for a total consideration of $5.3 million. During the year ended December 31, 2020, 1,235,218 ordinary shares were redeemed by the Company under this buyback program for a total consideration of $175.0 million. During the six months ended June 30, 2021 , no ordinary shares were redeemed by the Company under this buyback program. 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 information

Business segment information	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Business segment information	Business segment information 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 determines and presents operating segments based on the information that is provided to the CODM. The Company operates as one single business segment, which is the provision of outsourced development services on a global basis to the pharmaceutical, biotechnology and medical devices industries. There have been no changes to the basis of segmentation or the measurement basis for the segment results in the period. 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 predominately 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 is generally awarded projects based upon responses to requests for proposals received from companies in the pharmaceutical, biotechnology and medical device industries or work orders executed under our strategic partnership arrangements. Contracts with customers are generally entered into centrally, in most cases with ICON Clinical Research Limited (“ICON Ireland”), the Company’s principal operating subsidiary in Ireland. Revenues, which consist primarily of fees earned under these contracts, are allocated to individual entities within the Group, based on where the work is performed in accordance with the Company’s global transfer pricing model. ICON Ireland acts as the group entrepreneur under the Company’s global transfer pricing model given its role in the development and management of the Group, its ownership of key intellectual property and customer relationships, its key role in the mitigation of risks faced by the Group and its responsibility for maintaining the Company’s global network. ICON Ireland enters into the majority of the Company’s customer contracts. ICON Ireland remunerates other operating entities in the ICON Group on the basis of a guaranteed cost plus mark-up for the services they perform in each of their local territories. The cost plus mark-up for each ICON entity is established to ensure that each of ICON Ireland and the ICON entities that are involved in the conduct of services for customers, earn an appropriate arms-length return having regard to the assets owned, risks borne, and functions performed by each entity from these intercompany transactions. The cost plus mark-up policy is reviewed annually to ensure that it is market appropriate. The 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 Company's areas of operation outside of Ireland include the United States, United Kingdom, Austria, Belgium, Bulgaria, Czechia, France, Germany, Hungary, Italy, Latvia, Lithuania, Poland, Portugal, Romania, Russia, Serbia, Slovakia, Spain, Sweden, Switzerland, The Netherlands, Turkey, Ukraine, Canada, Argentina, Brazil, Chile, Colombia, Mexico, Peru, China (including Hong Kong), India, Israel, Japan, Malaysia, Singapore, South Korea, The Philippines, Taiwan, Thailand, Australia, New Zealand and South Africa. The geographical distribution of the Company’s segment measures as at June 30, 2021 and December 31, 2020 and for the six months ended June 30, 2021 and June 30, 2020 is as follows: a) The distribution of revenue by geographical area was as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Ireland * $ 363,730 $ 279,743 $ 671,851 $ 594,715 Rest of Europe 118,579 89,387 238,933 191,818 U.S. 313,113 189,466 665,609 414,933 Rest of World 75,733 61,632 152,960 133,864 Total $ 871,155 $ 620,228 $ 1,729,353 $ 1,335,330 * All sales shown for Ireland are export sales. b) The distribution of income from operations including restructuring by geographical area was as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Ireland $ 85,736 $ 38,655 $ 174,648 $ 112,590 Rest of Europe 8,794 7,120 16,404 17,816 U.S. 12,470 9,377 25,707 23,268 Rest of World 5,872 1,797 12,127 9,566 Total $ 112,872 $ 56,949 $ 228,886 $ 163,240 c) The distribution of income from operations excluding restructuring by geographical area was as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Ireland $ 85,736 $ 56,744 $ 174,648 $ 130,679 Rest of Europe 8,794 7,120 16,404 17,816 U.S. 12,470 9,377 25,707 23,268 Rest of World 5,872 1,797 12,127 9,566 Total $ 112,872 $ 75,038 $ 228,886 $ 181,329 d) The distribution of long-lived assets (including right-of-use assets), net, by geographical area was as follows: June 30, 2021 December 31, 2020 (in thousands) Ireland $ 113,132 $ 118,361 Rest of Europe 29,724 36,723 U.S. 60,676 65,152 Rest of World 31,950 38,668 Total $ 235,482 $ 258,904 e) The distribution of depreciation, amortization and reduction in carrying value of the right-of-use assets by geographical area was as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Ireland $ 9,385 $ 7,951 $ 18,424 $ 16,192 Rest of Europe 3,681 3,672 7,648 7,487 U.S. 8,168 6,201 16,716 14,840 Rest of World 2,964 5,043 5,930 7,998 Total $ 24,198 $ 22,867 $ 48,718 $ 46,517 f) The distribution of total assets by geographical area was as follows: June 30, 2021 December 31, 2020 (in thousands) Ireland $ 1,936,492 $ 1,675,980 Rest of Europe 639,961 671,218 U.S. 830,877 909,202 Rest of World 177,134 179,206 Total $ 3,584,464 $ 3,435,606

Impact of change in accounting

Impact of change in accounting policies	6 Months Ended
	Jun. 30, 2021
Accounting Changes and Error Corrections [Abstract]
Impact of change in accounting policies	Impact of change in accounting policies ASC 326 Financial Instruments - Credit Losses ASU 2016-13 'Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments' (ASU 2016-13) was effective, and adopted by the Group, from January 1, 2020. Primarily, ASU 2016-13 introduces an expected loss methodology that is referred to as the current expected credit loss (CECL) methodology. The objectives of previous loss methodologies for instruments within the scope of this update generally delayed recognition of the full amount of credit losses until the loss was probable of occurring. Under ASU 2016-13, losses reflect an entity’s current estimate of all expected credit losses including, in addition to the consideration of past events and current conditions, as under the current guidance, incorporating the use of forecast information to provide more timely and accurate credit loss estimates. The measurement of expected credit losses under the CECL methodology is applicable to financial assets measured at amortized cost, including loan receivables and held-to-maturity debt securities. It also applies to off-balance sheet credit exposures not accounted as insurance (loan commitments, standby letters of credit, financial guarantees, and other similar instruments) and net investments in leases recognized by a lessor in accordance with ASC 842 on leases. In addition, ASC 326 changed the accounting for available-for-sale (AFS) debt securities to require credit losses to be presented as an allowance rather than as a write-down to align the income statement recognition of credit losses on AFS debt securities with the reporting period in which the changes occur. The Group adopted ASC 326 using the modified retrospective measurement method on January 1, 2020. The adoption of ASC 326 did not have a material impact on the Group and there was no impact of adopting ASC 326 on opening balances at January 1, 2020.

Significant accounting polici_2

Significant accounting policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Redeemable noncontrolling interests and equity	Redeemable noncontrolling interests and equity On May 23, 2019, ICON acquired a majority ownership interest in MeDiNova. Included in the purchase agreement were put and call option arrangements with the noncontrolling interest holders that required (put option) or enabled (call option) ICON to purchase the remaining minority ownership at a future date. The option was accounted for as temporary equity, which was presented separately as redeemable noncontrolling interest on the Condensed Consolidated Balance Sheet. This classification reflects the assessment that the instruments were contingently redeemable in accordance with ASC 480-10-S99 ' Distinguishing Liabilities from Equity '. Redeemable noncontrolling interests are accreted to their redemption value over the period from the date of issuance to the first date on which the option is exercisable. The change in the option's redemption value is recorded against retained earnings. In a computation of earnings per share, the accretion of redeemable noncontrolling interests to their redemption value is a reduction of net income attributable to the Group. Basic and diluted net income per ordinary share attributable to the Group includes the adjustment to reflect the accretion of the noncontrolling interest to its redemption value.
New accounting pronouncements	Financial assets - credit losses On January 1, 2020, the Group adopted ASU 2016-13 'Measurement of Credit Losses on Financial Instruments (ASC 326)' , which significantly changes the way entities recognize impairment of many financial assets by requiring immediate recognition of estimated credit losses expected to occur over their remaining life. The update provides guidance on the measurement of credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The amendment replaces the current incurred loss impairment approach with a methodology to reflect expected credit losses and requires consideration of a broader range of reasonable and supportable information to explain credit loss estimates. The Group adopted ASC 326 using the modified retrospective measurement method for all in scope financial assets. Results for reporting periods beginning after January 1, 2020 are presented under ASC 326 while prior period amounts continue to be reported in accordance with previously applicable GAAP. The impact of transitioning to the new standard at January 1, 2020 was immaterial and no adjustment was recorded to retained earnings for the cumulative effect of adopting ASC 326. On transition to ASC 326, the Group has revised the methodology to calculate the allowance for credit losses. The Group's estimate of expected credit losses considers historical credit loss information that is adjusted, where necessary, for current conditions and reasonable and supportable forecasts. Historical credit loss experience provides the basis for the estimation of expected credit losses. The Group's receivables and unbilled services are predominantly due from large and mid-tier pharmaceutical and biotechnology companies that share similar risk characteristics. The Group monitors their portfolio of receivables and unbilled services for any deterioration in current or expected credit quality (for example, expected delinquency level), and adjusts the allowance for credit losses as required. Changes in the allowance for credit losses are recorded as a provision for (or reversal of) credit loss expense in the Condensed Consolidated Statement of Operations. Losses are charged against the allowance when management believes the uncollectibility of a previously provisioned amount is confirmed. Leases The new leasing standard ( ASC 842 'Leases' ) was effective and adopted by ICON from January 1, 2019. ASC 842 ' Leases ' supersedes the requirements in ASC 840 'Leases' and requires that lessees recognize rights and obligations from virtually all leases (other than leases that meet the definition of a short-term lease) on their balance sheets as right-of-use assets with corresponding lease liabilities. The ASU also provides additional guidance on how to classify leases and how to determine the lease term for accounting purposes. ICON adopted the new standard under the cumulative effect adjustment approach There was no impact of adopting ASC 842 on opening retained earnings at January 1, 2019.

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	Revenue disaggregated by customer profile is as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Top client $ 110,356 $ 74,932 $ 274,650 $ 156,199 Clients 2-5 246,094 179,018 475,994 381,996 Clients 6-10 116,237 86,449 239,130 160,800 Clients 11-25 158,577 101,417 296,432 231,501 Other 239,891 178,412 443,147 404,834 Total $ 871,155 $ 620,228 $ 1,729,353 $ 1,335,330

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, 2021
Revenue from Contract with Customer [Abstract]
Schedule of Contracts with Customers, Asset and Liabilities	Accounts receivables and unbilled revenue are as follows: June 30, 2021 December 31, 2020 (in thousands) Contract assets: Billed services (accounts receivable) $ 684,355 $ 722,420 Unbilled services (unbilled revenue) 415,390 428,684 Accounts receivable and unbilled revenue 1,099,745 1,151,104 Allowance for credit losses (7,108) (7,149) Accounts receivable and unbilled revenue, net $ 1,092,637 $ 1,143,955 Unbilled services and unearned revenue or payments on account (contract assets and liabilities) were as follows: (in thousands, except percentages) June 30, 2021 December 31, 2020 $ Change % Change Unbilled services (unbilled revenue) $ 415,390 $ 428,684 $ (13,294) (3.1) % Unearned revenue (payments on account) (675,234) (660,883) (14,351) 2.2 % Net balance $ (259,844) $ (232,199) $ (27,645) 11.9 %

Goodwill (Tables)

Goodwill (Tables)	6 Months Ended
	Jun. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	Six Months Ended Year Ended June 30, 2021 December 31, 2020 (in thousands) Opening balance $ 936,257 $ 883,170 Current period acquisitions (Note 6) — 27,191 Prior period acquisitions — 123 Foreign exchange movement (2,870) 25,773 Closing balance $ 933,387 $ 936,257

Business combinations (Tables)

Business combinations (Tables)	6 Months Ended
	Jun. 30, 2021
Business Combinations [Abstract]
Schedule of Summary of Estimates of Fair Values of Assets Acquired and Liabilities Assumed	The following table summarizes the Company’s fair values of the assets acquired and liabilities assumed: January 22, 2020 (in thousands) Cash & cash equivalents $ 10,170 Property, plant and equipment 45 Operating right of use assets 539 Goodwill * 27,191 Customer relationships 11,725 Order backlog 2,883 Accounts receivable 3,033 Prepayments and other current assets 158 Accounts payable (368) Unearned revenue (989) Other liabilities (2,202) Current lease liabilities (219) Non-current lease liabilities (320) Non-current deferred tax liability (4,090) Net assets acquired $ 47,556 Cash outflows $ 46,992 Working capital adjustment paid 564 Contingent consideration ** — Total consideration $ 47,556 * Goodwill represents the acquisition of an established workforce that specializes in medical device development and market access. None of the goodwill recognized is expected to be deductible for income tax purposes. ** The fair value of the contingent consideration was estimated at the date of acquisition as $Nil. Depending on performance of MedPass for the 12 month period ended December 31, 2020, the total consideration could have increased by a maximum of $6.7 million in contingent consideration. In January 2021, the contingent consideration was finalized and a value of $Nil was payable.

Equity method investments (Tabl

Equity method investments (Tables)	6 Months Ended
	Jun. 30, 2021
Equity Method Investments and Joint Ventures [Abstract]
Equity method investments	The following table represents our equity method investments at June 30, 2021: Ownership Percentage Carrying Value Carrying Value June 30, 2021 June 30, 2021 December 31, 2020 (in thousands) Oncacare Limited 49 % $ 3,751 $ 4,534

Restructuring (Tables)

Restructuring (Tables)	6 Months Ended
	Jun. 30, 2021
Restructuring and Related Activities [Abstract]
Details of movement in restructuring charge	Workforce reductions Onerous Lease Total (in thousands) Initial restructuring charge recorded $ 11,391 $ 6,698 $ 18,089 Utilization (6,987) (1,309) (8,296) Foreign exchange movement — 325 325 Provision at December 31, 2020 4,404 5,714 10,118 Utilization (2,299) (1,345) (3,644) Foreign exchange movement — 4 4 Provision at June 30, 2021 $ 2,105 $ 4,373 $ 6,478 Workforce reductions Onerous Lease Total (in thousands) Initial restructuring charge recorded $ 9,684 $ 2,806 $ 12,490 Utilization (5,399) (672) (6,071) Provision at December 31, 2018 $ 4,285 $ 2,134 $ 6,419 Utilization (3,554) (1,228) (4,782) Provision at December 31, 2019 $ 731 $ 906 $ 1,637 Utilization (731) (276) (1,007) Provision at December 31, 2020 $ — $ 630 $ 630 Utilization — (97) (97) Provision at June 30, 2021 $ — $ 533 $ 533
Schedule of Operating Lease Maturity	Future minimum lease payments (including related costs), associated with the 2020 restructuring plan, under the non-cancelable onerous leases as at June 30, 2021 were as follows: Minimum rental payments (in thousands) June 30, 2021 2021 $ 1,210 2022 1,872 2023 1,015 2024 142 2025 141 Thereafter 401 Total future minimum lease payments (including related costs) 4,781 Lease imputed interest (408) Total $ 4,373 Minimum rental payments (in thousands) June 30, 2021 Due within 1 year $ 24,293 Due between 1 and 5 years 43,579 Thereafter 6,377 Total future minimum lease payments 74,249 Lease imputed interest (4,107) Total $ 70,142

Operating leases (Tables)

Operating leases (Tables)	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Schedule of Lease Costs	Lease costs recorded under operating leases for the three and six months ended June 30, 2021 and June 30, 2020 were as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Operating lease costs $ 7,549 $ 7,768 $ 15,338 $ 15,857 Income from sub-leases (220) (246) (431) (514) Net operating lease costs $ 7,329 $ 7,522 $ 14,907 $ 15,343
Schedule of Operating Lease Maturity	Future minimum lease payments (including related costs), associated with the 2020 restructuring plan, under the non-cancelable onerous leases as at June 30, 2021 were as follows: Minimum rental payments (in thousands) June 30, 2021 2021 $ 1,210 2022 1,872 2023 1,015 2024 142 2025 141 Thereafter 401 Total future minimum lease payments (including related costs) 4,781 Lease imputed interest (408) Total $ 4,373 Minimum rental payments (in thousands) June 30, 2021 Due within 1 year $ 24,293 Due between 1 and 5 years 43,579 Thereafter 6,377 Total future minimum lease payments 74,249 Lease imputed interest (4,107) Total $ 70,142

Income taxes (Tables)

Income taxes (Tables)	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense	Income taxes recognized during the six months ended June 30, 2021 and June 30, 2020, comprise: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Provision for income taxes (excluding restructuring) $ 14,133 $ 8,671 $ 30,281 $ 21,261 Tax impact of restructuring — (2,261) — (2,261) Provision for income taxes $ 14,133 $ 6,410 $ 30,281 $ 19,000

Net income per ordinary share (

Net income per ordinary share (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	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, 2021 June 30, 2020 June 30, 2021 June 30, 2020 Weighted average number of ordinary shares outstanding for basic net income per ordinary share 52,909,368 52,570,104 52,860,414 52,959,229 Effect of dilutive share options outstanding 472,133 458,463 434,021 731,909 Weighted average number of ordinary shares outstanding for diluted net income per ordinary share 53,381,501 53,028,567 53,294,435 53,691,138 The reconciliation of net income attributable to the Group and net income attributable to the Group (including NCI redemption amount) as used to calculate net income per ordinary share attributable to the Group is as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Net income attributable to the Group $ 73,865 $ 47,760 $ 170,987 $ 139,456 Noncontrolling interest adjustment to redemption amount — — — (4,522) Net income attributable to the Group (including NCI redemption adjustment) $ 73,865 $ 47,760 $ 170,987 $ 134,934 Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 Net income per Ordinary Share attributable to the Group (including NCI redemption adjustment): Basic $ 1.40 $ 0.91 $ 3.23 $ 2.55 Diluted $ 1.38 $ 0.90 $ 3.21 $ 2.51

Share-based awards (Tables)

Share-based awards (Tables)	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Schedule of Share Option Activity	The following table summarizes option activity for the six months ended June 30, 2021: Options Weighted Weighted Weighted Outstanding at December 31, 2020 553,746 $ 108.53 $ 31.63 4.86 Granted 100,299 $ 177.76 $ 49.15 Exercised (4,020) $ 42.24 $ 14.07 Canceled/expired — $ — $ — Outstanding at June 30, 2021 650,025 $ 119.62 $ 34.44 4.90 Exercisable at June 30, 2021 336,942 $ 92.71 $ 27.42 3.63
Schedule of Movement in Non-vested Share Options	The following table summarizes the movement in non-vested share options for the six months ended June 30, 2021: Options Weighted Average Weighted Average Non-vested outstanding at December 31, 2020 328,901 $ 125.89 $ 36.24 Granted 100,299 $ 177.76 $ 49.15 Vested (116,117) $ 109.53 $ 31.84 Forfeited — $ — $ — Non-vested outstanding at June 30, 2021 313,083 $ 148.58 $ 42.00
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, 2021 June 30, 2020 Weighted average grant date fair value $ 49.15 $ 42.43 Assumptions: Expected volatility 30 % 30 % Dividend yield — % — % Risk-free interest rate 0.78 % 0.57 % Expected life 5 years 5 years
Schedule of RSU and PSU Activity	The following table summarizes RSU and PSU activity for the six months ended June 30, 2021: PSU RSU Outstanding at December 31, 2020 159,641 $ 137.64 1.14 341,424 $ 145.77 1.41 Granted 55,444 $ 177.77 144,274 $ 207.29 Shares vested (44,132) $ 115.61 (122,331) $ 131.37 Forfeited (3,159) $ 115.61 (9,818) $ 146.64 Outstanding at June 30, 2021 167,794 $ 159.18 1.35 353,549 $ 175.83 1.87
Schedule of Non-cash Stock Compensation Expense	Non-cash stock compensation expense for the six months ended June 30, 2021 and June 30, 2020 has been allocated as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Direct costs $ 3,101 $ 2,353 $ 5,156 $ 4,188 Selling, general and administrative 5,379 4,764 9,718 8,998 $ 8,480 $ 7,117 $ 14,874 $ 13,186

Business segment information (T

Business segment information (Tables)	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Distribution of Revenue by Geographical Area	The distribution of revenue by geographical area was as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Ireland * $ 363,730 $ 279,743 $ 671,851 $ 594,715 Rest of Europe 118,579 89,387 238,933 191,818 U.S. 313,113 189,466 665,609 414,933 Rest of World 75,733 61,632 152,960 133,864 Total $ 871,155 $ 620,228 $ 1,729,353 $ 1,335,330
Distribution of income from operations by geographical area	The distribution of income from operations including restructuring by geographical area was as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Ireland $ 85,736 $ 38,655 $ 174,648 $ 112,590 Rest of Europe 8,794 7,120 16,404 17,816 U.S. 12,470 9,377 25,707 23,268 Rest of World 5,872 1,797 12,127 9,566 Total $ 112,872 $ 56,949 $ 228,886 $ 163,240 Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Ireland $ 85,736 $ 56,744 $ 174,648 $ 130,679 Rest of Europe 8,794 7,120 16,404 17,816 U.S. 12,470 9,377 25,707 23,268 Rest of World 5,872 1,797 12,127 9,566 Total $ 112,872 $ 75,038 $ 228,886 $ 181,329
Distribution of Long-lived Assets, Net, by Geographical Area	The distribution of long-lived assets (including right-of-use assets), net, by geographical area was as follows: June 30, 2021 December 31, 2020 (in thousands) Ireland $ 113,132 $ 118,361 Rest of Europe 29,724 36,723 U.S. 60,676 65,152 Rest of World 31,950 38,668 Total $ 235,482 $ 258,904
Distribution of Depreciation and Amortization by Geographical Area	The distribution of depreciation, amortization and reduction in carrying value of the right-of-use assets by geographical area was as follows: Three Months Ended Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 (in thousands) (in thousands) Ireland $ 9,385 $ 7,951 $ 18,424 $ 16,192 Rest of Europe 3,681 3,672 7,648 7,487 U.S. 8,168 6,201 16,716 14,840 Rest of World 2,964 5,043 5,930 7,998 Total $ 24,198 $ 22,867 $ 48,718 $ 46,517
Distribution of Total Assets by Geographical Area	The distribution of total assets by geographical area was as follows: June 30, 2021 December 31, 2020 (in thousands) Ireland $ 1,936,492 $ 1,675,980 Rest of Europe 639,961 671,218 U.S. 830,877 909,202 Rest of World 177,134 179,206 Total $ 3,584,464 $ 3,435,606

Significant accounting polici_3

Significant accounting policies (Details) - USD ($)	Jul. 17, 2020	Jun. 30, 2021	Dec. 31, 2020	Mar. 09, 2020	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounting Standards Update [Extensible List]		Accounting Standards Update 2016-02
Change in accounting principle, Accounting Standards Update, transition option elected [Extensible List]		us-gaap:AccountingStandardsUpdate201602CumulativeEffectPeriodOfAdoptionMember
Operating right-of-use assets		$ 69,238,000	$ 84,561,000
Operating lease, liability		70,142,000
Opening retained earnings		2,027,943,000	1,850,236,000
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Opening retained earnings		$ 1,433,882,000	$ 1,262,895,000
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating right-of-use assets					$ 106,500,000
Operating lease, liability					106,500,000
Accounting Standards Update 2016-02 | Retained Earnings | Cumulative effect, period of adoption, adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Opening retained earnings					$ 0
MeDiNova
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percentage of interest acquired				100.00%
Settlement of liability	$ 43,900,000

Revenue (Details)

Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 871,155	$ 620,228	$ 1,729,353	$ 1,335,330
Top client
Disaggregation of Revenue [Line Items]
Revenue	110,356	74,932	274,650	156,199
Clients 2-5
Disaggregation of Revenue [Line Items]
Revenue	246,094	179,018	475,994	381,996
Clients 6-10
Disaggregation of Revenue [Line Items]
Revenue	116,237	86,449	239,130	160,800
Clients 11-25
Disaggregation of Revenue [Line Items]
Revenue	158,577	101,417	296,432	231,501
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 239,891	$ 178,412	$ 443,147	$ 404,834

Accounts receivable, unbilled_3

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Billed services (accounts receivable)	$ 684,355	$ 722,420
Unbilled services (unbilled revenue)	415,390	428,684
Accounts receivable and unbilled revenue	1,099,745	1,151,104
Allowance for credit losses	(7,108)	(7,149)
Accounts receivable and unbilled revenue, net	1,092,637	1,143,955
Change in unbilled services (unbilled revenue)	$ (13,294)
Percentage change in unbilled services (unbilled revenue)	(3.10%)
Unearned revenue (payments on account)	$ (675,234)	(660,883)
Change in unearned revenue (payments on account)	$ (14,351)
Percentage change in unearned revenue (payments on account)	2.20%
Net balance	$ (259,844)	$ (232,199)
Change in net balance	$ (27,645)
Percentage change in net balance	11.90%

Accounts receivable, unbilled_4

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, 2021	Jun. 30, 2020
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Decrease in unbilled services (unbilled revenue)	$ 13,294
Decrease in unearned revenue (payments on account)	(14,351)
Increase in net balance	(27,645)
Revenue, remaining performance obligation	$ 6,600,000	$ 5,700,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	43.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months

Goodwill (Details)

Goodwill (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Opening balance	$ 936,257	$ 883,170
Current period acquisitions (Note 6)	0	27,191
Prior period acquisitions	0	123
Foreign exchange movement	(2,870)	25,773
Closing balance	$ 933,387	$ 936,257

Business combinations - Narrati

Business combinations - Narrative (Details)

Jul. 01, 2021USD ($)EmployeeCountry$ / sharesshares

Jul. 17, 2020USD ($)

Jan. 22, 2020USD ($)

Sep. 24, 2019USD ($)

Jan. 25, 2019USD ($)

Jul. 17, 2020USD ($)

Jun. 30, 2021USD ($)

Jan. 31, 2021USD ($)

Dec. 31, 2020USD ($)

Jun. 12, 2020USD ($)

Mar. 09, 2020

Dec. 31, 2019USD ($)

May 23, 2019USD ($)

Business Acquisition [Line Items]

Goodwill

$ 933,387,000

$ 936,257,000

$ 883,170,000

Subsequent event

Business Acquisition [Line Items]

Entity number of employees | Employee

38,000

Number of countries in which entity operates | Country

47

PRA Health Sciences Inc | Subsequent event

Business Acquisition [Line Items]

Business acquisition, share price (in USD per share) | $ / shares

$ 80

Business acquisition, number of shares issued (in shares) | shares

0.4125

PRA Health Sciences Inc | Subsequent event | Forecast

Business Acquisition [Line Items]

Total consideration

$ 12,500,000,000

Additional intangible assets recorded from acquisition

$ 5,500,000,000

Medpass

Business Acquisition [Line Items]

Total consideration

$ 47,556,000

Percentage of share capital acquired

100.00%

Goodwill

$ 27,191,000

Contingent consideration

$ 0

$ 0

Symphony

Business Acquisition [Line Items]

Total consideration

$ 37,800,000

Percentage of share capital acquired

100.00%

Goodwill

$ 22,900,000

Contingent consideration

$ 2,500,000

$ 500,000

MeDiNova

Business Acquisition [Line Items]

Total consideration

$ 86,200,000

Percentage of share capital acquired

60.00%

Goodwill

$ 81,800,000

Percentage of interest acquired

100.00%

Redeemable noncontrolling interest

$ 32,600,000

Settlement of liability

$ 43,900,000

MMD

Business Acquisition [Line Items]

Total consideration

$ 42,200,000

Percentage of share capital acquired

100.00%

Goodwill

$ 22,400,000

Business combinations - Schedul

Business combinations - Schedule of Acquisitions (Details) - USD ($)	Jan. 22, 2020	Jun. 30, 2021	Jun. 30, 2020	Jan. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill		$ 933,387,000			$ 936,257,000	$ 883,170,000
Cash outflows		$ 0	$ 47,367,000
Medpass
Business Acquisition [Line Items]
Cash & cash equivalents	$ 10,170,000
Property, plant and equipment	45,000
Operating right of use assets	539,000
Goodwill	27,191,000
Accounts receivable	3,033,000
Prepayments and other current assets	158,000
Accounts payable	(368,000)
Unearned revenue	(989,000)
Other liabilities	(2,202,000)
Current lease liabilities	(219,000)
Non-current lease liabilities	(320,000)
Non-current deferred tax liability	(4,090,000)
Net assets acquired	47,556,000
Cash outflows	46,992,000
Working capital adjustment paid	(564,000)
Contingent consideration	0			$ 0
Total consideration	47,556,000
Goodwill expected to be tax deductible	0
Contingent consideration, maximum amount	6,700,000
Customer Relationships | Medpass
Business Acquisition [Line Items]
Customer relationships/ Order backlog	11,725,000
Order backlog | Medpass
Business Acquisition [Line Items]
Customer relationships/ Order backlog	$ 2,883,000

Equity method investments (Deta

Equity method investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Jul. 24, 2020
Equity Method Investments and Joint Ventures [Abstract]
Oncacare Limited	$ 3,751		$ 3,751		$ 4,534	$ 4,900
Equity method investment, ownership percentage	49.00%		49.00%
Equity method investment, majority ownership percentage	51.00%		51.00%
Equity method investment, period majority voting share capital can be sold to the company			2 years 6 months
Payments to Acquire Equity Method Investments			$ 2,450	$ 0
Loss from equity method investments	$ 509	$ 0	$ 783	$ 0

Restructuring - Narrative (Deta

Restructuring - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 0	$ 18,089,000	$ 0	$ 18,089,000
Impairment of right-of-use assets	0		0	$ 5,411,000	$ 5,400,000
Other liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, current	4,400,000		4,400,000
Non-current other liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, noncurrent	2,600,000		2,600,000
Resource rationalization, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 0		0		18,089,000
Resource rationalization, 2020 | Workforce reductions
Restructuring Cost and Reserve [Line Items]
Restructuring Charges					11,391,000
Resource rationalization, 2020 | Onerous Lease
Restructuring Cost and Reserve [Line Items]
Restructuring Charges					6,698,000
Resource rationalization, 2020 | Other restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring Charges					$ 1,300,000
Resource rationalizations 2018
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			$ 0			$ 12,490,000
Resource rationalizations 2018 | Workforce reductions
Restructuring Cost and Reserve [Line Items]
Restructuring Charges						9,684,000
Resource rationalizations 2018 | Onerous Lease
Restructuring Cost and Reserve [Line Items]
Restructuring Charges						$ 2,806,000

Restructuring - Rollforward Act

Restructuring - Rollforward Activity (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Reserve [Roll Forward]
Restructuring Charges	$ 0	$ 18,089,000	$ 0	$ 18,089,000
Resource rationalization, 2020
Restructuring Reserve [Roll Forward]
Restructuring Charges	0		0		$ 18,089,000
Utilization			(3,644,000)		(8,296,000)
Foreign exchange movement			4,000		325,000
Provision balance	6,478,000		6,478,000		10,118,000
Resource rationalization, 2020 | Workforce reductions
Restructuring Reserve [Roll Forward]
Restructuring Charges					11,391,000
Utilization			(2,299,000)		(6,987,000)
Foreign exchange movement			0		0
Provision balance	2,105,000		2,105,000		4,404,000
Resource rationalization, 2020 | Onerous Lease
Restructuring Reserve [Roll Forward]
Restructuring Charges					6,698,000
Utilization			(1,345,000)		(1,309,000)
Foreign exchange movement			4,000		325,000
Provision balance	4,373,000		4,373,000		5,714,000
Resource rationalizations 2018
Restructuring Reserve [Roll Forward]
Restructuring Charges			0				$ 12,490,000
Utilization			(97,000)		(1,007,000)	$ (4,782,000)	(6,071,000)
Provision balance	533,000		533,000		630,000	1,637,000	6,419,000
Resource rationalizations 2018 | Workforce reductions
Restructuring Reserve [Roll Forward]
Restructuring Charges							9,684,000
Utilization			0		(731,000)	(3,554,000)	(5,399,000)
Provision balance	0		0		0	731,000	4,285,000
Resource rationalizations 2018 | Onerous Lease
Restructuring Reserve [Roll Forward]
Restructuring Charges							2,806,000
Utilization			(97,000)		(276,000)	(1,228,000)	(672,000)
Provision balance	$ 533,000		$ 533,000		$ 630,000	$ 906,000	$ 2,134,000

Restructuring charges - Future

Restructuring charges - Future Minimum Lease Payments (Details) $ in Thousands	Jun. 30, 2021USD ($)
Operating Lease - Future Minimum Lease Payments [Line Items]
Total future minimum lease payments (including related costs)	$ 74,249
Lease imputed interest	(4,107)
Total	70,142
Onerous Lease | Resource rationalization, 2020
Operating Lease - Future Minimum Lease Payments [Line Items]
2021	1,210
2022	1,872
2023	1,015
2024	142
2025	141
Thereafter	401
Total future minimum lease payments (including related costs)	4,781
Lease imputed interest	(408)
Total	$ 4,373

Operating leases - Lease Costs

Operating leases - Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Operating lease costs	$ 7,549	$ 7,768	$ 15,338	$ 15,857
Income from sub-leases	(220)	(246)	(431)	(514)
Net operating lease costs	$ 7,329	$ 7,522	$ 14,907	$ 15,343

Operating leases - Narrative (D

Operating leases - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Total lease cost	$ 7,329,000	$ 7,522,000	$ 14,907,000	$ 15,343,000
Early termination options reasonably certain to be exercised	0	1,600,000	4,200,000	1,600,000
Right-of-use assets obtained in exchange for lease obligations	1,000,000	200,000	3,800,000	4,500,000
Impairment of right-of-use assets	$ 0		$ 0	5,411,000	$ 5,400,000
Weighted average remaining lease term	3 years 11 months 4 days		3 years 11 months 4 days
Weighted average discount rate	2.52%		2.52%
Operating lease liabilities	$ 22,800,000	$ 23,100,000	$ 22,800,000	23,100,000
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other liabilities		Other liabilities		Other liabilities
Selling, general and administration costs
Lessee, Lease, Description [Line Items]
Total lease cost			$ 13,800,000	14,000,000
Direct costs
Lessee, Lease, Description [Line Items]
Total lease cost			$ 1,100,000	$ 1,300,000

Operating leases - Operating Le

Operating leases - Operating Lease Maturity (Details) $ in Thousands	Jun. 30, 2021USD ($)
Leases [Abstract]
Due within 1 year	$ 24,293
Due between 1 and 5 years	43,579
Thereafter	6,377
Total future minimum lease payments	74,249
Lease imputed interest	(4,107)
Total	$ 70,142

Income taxes - Income Taxes Rec

Income taxes - Income Taxes Recognized During Period (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Provision for income taxes (excluding restructuring)	$ 14,133	$ 8,671	$ 30,281	$ 21,261
Tax impact of restructuring	0	(2,261)	0	(2,261)
Provision for income taxes	$ 14,133	$ 6,410	$ 30,281	$ 19,000

Income taxes - Narrative (Detai

Income taxes - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Liability for unrecognized tax benefit	$ 17.4	$ 19.6
Items generating unrecognized tax benefits	17.1	19.1
Interest and related penalties	$ 0.3	$ 0.5

Net income per ordinary share -

Net income per ordinary share - 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, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Weighted average number of ordinary shares outstanding for basic net income per ordinary share (in shares)	52,909,368	52,570,104	52,860,414	52,959,229
Effect of dilutive share options outstanding (in shares)	472,133	458,463	434,021	731,909
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share (in shares)	53,381,501	53,028,567	53,294,435	53,691,138

Net income per ordinary share_2

Net income per ordinary share - Reconciliation of Net Income Attributable to the Group and Net Income Attributable To the Group (Including NCI Redemption Amount) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income attributable to the Group	$ 73,865	$ 47,760	$ 170,987	$ 139,456
Noncontrolling interest adjustment to redemption amount	0	0	0	(4,522)
Net income attributable to the Group (including NCI redemption adjustment)	$ 73,865	$ 47,760	$ 170,987	$ 134,934
Net income per Ordinary Share attributable to the Group (including NCI redemption adjustment):
Basic (USD per share)	$ 1.40	$ 0.91	$ 3.23	$ 2.55
Diluted (USD per share)	$ 1.38	$ 0.90	$ 3.21	$ 2.51

Share-based awards - Narrative

Share-based awards - Narrative (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020	Feb. 14, 2017	May 11, 2015	Jan. 17, 2003	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	May 16, 2019	Feb. 13, 2017
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Non-cash stock compensation expense not yet recognized	$ 72,600,000					$ 72,600,000
Unrecognized stock-based compensation expense, weighted average period	2 years 5 months 1 day
Consultants Stock Plan, 2008 Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)			1,000,000							400,000
Limit of shares issued or to be issued pursuant to options granted (in shares)			1,000,000
Employee Stock Plan, 2008 Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)			6,000,000
Maximum number of shares per employee (in shares)			400,000
Option Plans 2008 | Minimum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Percentage of option price for fair value of ordinary share (percentage)			100.00%
Employee Stock Plan, 2003 Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)					6,000,000
Maximum number of shares per employee (in shares)					400,000
Maximum number of award as percentage of shares outstanding (percentage)					10.00%
Employee Stock Option
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Weighted average contractual term of options outstanding	4 years 10 months 24 days	4 years 10 months 9 days
Weighted average fair value per option (USD per share)						$ 25.97
Exercisable - number of shares (in shares)	336,942					336,942
Exercisable - weighted average remaining contractual life	3 years 7 months 17 days
Exercisable - weighted average exercise price (USD per share)	$ 92.71					$ 92.71
Fully vested total intrinsic value	$ 38,400,000					$ 38,400,000
Intrinsic value of option exercised						$ 700,000	$ 4,300,000
Employee Stock Option | Award Date, All years excluding 2018
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Shares vesting period						5 years
Shares expiration period						8 years
Employee Stock Option | Non-executive directors | Award Date, 2018
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Shares vesting period						12 months
Shares expiration period						8 years
Employee Stock Option | Minimum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Options outstanding fair value (USD per share)	$ 12.24					$ 12.24
Employee Stock Option | Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Weighted average contractual term of options outstanding	8 years
Options outstanding fair value (USD per share)	$ 64.07					$ 64.07
Restricted Stock Units 2013
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)				4,100,000
Ordinary shares which have been reserved for issuance (in shares)				2,500,000
Consultants Restricted Stock Units 2019
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Ordinary shares which have been reserved for issuance (in shares)									250,000
Consultants Restricted Stock Units 2019 | Non-executive directors
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Shares vesting period						12 months
Performance Share Unit (PSUs)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Fair value of stock units vested						$ 5,100,000		$ 5,300,000
Restricted Stock Units (RSUs)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Fair value of stock units vested						$ 16,100,000		$ 14,300,000
PSUs Based on Service and EPS Targets | Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock units to be granted (in shares)	83,897					83,897

Share-based awards - Summary of

Share-based awards - Summary of Stock Option Activity (Details) - Employee Stock Option - $ / shares	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Options Outstanding Number of Shares
Outstanding at beginning of period (in shares)			553,746
Granted (in shares)			100,299
Exercised (in shares)			(4,020)
Canceled/expired (in shares)			0
Outstanding at end of period (in shares)	650,025	553,746	650,025
Exercisable at end of period (in shares)	336,942		336,942
Weighted Average Exercise Price
Outstanding at beginning of period (USD per share)			$ 108.53
Granted (USD per share)			177.76
Exercised (USD per share)			42.24
Canceled/expired (USD per share)			0
Outstanding at end of period (USD per share)	$ 119.62	$ 108.53	119.62
Exercisable at end of period (USD per share)	92.71		92.71
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (USD per share)			31.63
Granted (USD per share)			49.15	$ 42.43
Exercised (USD per share)			14.07
Canceled/expired (USD per share)			0
Outstanding at end of period (USD per share)	34.44	$ 31.63	34.44
Exercisable at end of period (USD per share)	$ 27.42		$ 27.42
Weighted Average Remaining Contractual Life
Outstanding at end of period	4 years 10 months 24 days	4 years 10 months 9 days
Exercisable at end of period	3 years 7 months 17 days

Share-based awards - Summary _2

Share-based awards - Summary of Movement in Non-Vested Share Options (Details) - Employee Stock Option - $ / shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Options Outstanding Number of Shares
Non-vested outstanding at beginning of period (in shares)	328,901
Granted (in shares)	100,299
Vested (in shares)	(116,117)
Forfeited (in shares)	0
Non-vested outstanding at end of period (in shares)	313,083
Weighted Average Exercise Price
Non-vested outstanding at beginning of period (USD per share)	$ 125.89
Granted (USD per share)	177.76
Vested (USD per share)	109.53
Forfeited (USD per share)	0
Non-vested outstanding at end of period (USD per share)	148.58
Weighted Average Grant Date Fair Value
Non-vested outstanding at beginning of period (USD per share)	36.24
Granted (USD per share)	49.15	$ 42.43
Vested (USD per share)	31.84
Forfeited (USD per share)	0
Non-vested outstanding at end of period (USD per share)	$ 42

Share-based awards - Schedule o

Share-based awards - Schedule of Weighted Average Fair Values and Assumptions Used (Details) - Employee Stock Option - $ / shares	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value			$ 49.15	$ 42.43
Assumptions:
Expected volatility			30.00%	30.00%
Dividend yield			0.00%	0.00%
Risk-free interest rate			0.78%	0.57%
Expected life	5 years	5 years

Share-based awards - Summary _3

Share-based awards - Summary of RSU and PSU Activity (Details) - $ / shares	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2021
Performance Share Unit (PSUs)
Outstanding Number of Shares
Outstanding at beginning of period (in shares)			159,641
Granted (in shares)			55,444
Shares vested (in shares)			(44,132)
Forfeited (in shares)			(3,159)
Outstanding at end of period (in shares)	167,794	159,641	167,794
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (USD per share)			$ 137.64
Granted (USD per share)			177.77
Shares vested (USD per share)			115.61
Forfeited (USD per share)			115.61
Outstanding at end of period (USD per share)	$ 159.18	$ 137.64	$ 159.18
Weighted Average Remaining Contractual Life
Outstanding at end of period (in years)	1 year 4 months 6 days	1 year 1 month 20 days
Restricted Stock Units (RSUs)
Outstanding Number of Shares
Outstanding at beginning of period (in shares)			341,424
Granted (in shares)			144,274
Shares vested (in shares)			(122,331)
Forfeited (in shares)			(9,818)
Outstanding at end of period (in shares)	353,549	341,424	353,549
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (USD per share)			$ 145.77
Granted (USD per share)			207.29
Shares vested (USD per share)			131.37
Forfeited (USD per share)			146.64
Outstanding at end of period (USD per share)	$ 175.83	$ 145.77	$ 175.83
Weighted Average Remaining Contractual Life
Outstanding at end of period (in years)	1 year 10 months 13 days	1 year 4 months 28 days

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, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 8,480	$ 7,117	$ 14,874	$ 13,186
Direct costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	3,101	2,353	5,156	4,188
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 5,379	$ 4,764	$ 9,718	$ 8,998

Share capital (Details)

Share capital (Details) - Buyback Program - USD ($) $ in Millions	Dec. 31, 2019	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 08, 2019
Equity, Class of Treasury Stock [Line Items]
Share repurchase program, number of shares authorized to be repurchased (in shares)					1,000,000
Shares redeemed, value	$ 5.3		$ 175	$ 141.6
Shares redeemed (in shares)	35,100	0	1,235,218
Maximum
Equity, Class of Treasury Stock [Line Items]
Share repurchase program, authorized percentage		10.00%

Business segment information -

Business segment information - Narrative (Details)	6 Months Ended
	Jun. 30, 2021segment
Segment Reporting [Abstract]
Number of operating segments	1

Business segment information _2

Business segment information - Distribution of Revenue by Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Revenue	$ 871,155	$ 620,228	$ 1,729,353	$ 1,335,330
Ireland
Segment Reporting Information [Line Items]
Revenue	363,730	279,743	671,851	594,715
Rest of Europe
Segment Reporting Information [Line Items]
Revenue	118,579	89,387	238,933	191,818
U.S.
Segment Reporting Information [Line Items]
Revenue	313,113	189,466	665,609	414,933
Rest of World
Segment Reporting Information [Line Items]
Revenue	$ 75,733	$ 61,632	$ 152,960	$ 133,864

Business segment information _3

Business segment information - Distribution of Income from Operations, Including Restructuring, by Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Income from operations, including restructuring	$ 112,872	$ 56,949	$ 228,886	$ 163,240
Ireland
Segment Reporting Information [Line Items]
Income from operations, including restructuring	85,736	38,655	174,648	112,590
Rest of Europe
Segment Reporting Information [Line Items]
Income from operations, including restructuring	8,794	7,120	16,404	17,816
U.S.
Segment Reporting Information [Line Items]
Income from operations, including restructuring	12,470	9,377	25,707	23,268
Rest of World
Segment Reporting Information [Line Items]
Income from operations, including restructuring	$ 5,872	$ 1,797	$ 12,127	$ 9,566

Business segment information _4

Business segment information - Distribution of Income from Operations, Excluding Restructuring by Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Operating income (loss) excluding restructuring	$ 112,872	$ 75,038	$ 228,886	$ 181,329
Ireland
Segment Reporting Information [Line Items]
Operating income (loss) excluding restructuring	85,736	56,744	174,648	130,679
Rest of Europe
Segment Reporting Information [Line Items]
Operating income (loss) excluding restructuring	8,794	7,120	16,404	17,816
U.S.
Segment Reporting Information [Line Items]
Operating income (loss) excluding restructuring	12,470	9,377	25,707	23,268
Rest of World
Segment Reporting Information [Line Items]
Operating income (loss) excluding restructuring	$ 5,872	$ 1,797	$ 12,127	$ 9,566

Business segment information _5

Business segment information - Distribution of Long-lived Assets, Net, by Geographical Area (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Long-lived assets, net	$ 235,482	$ 258,904
Ireland
Segment Reporting Information [Line Items]
Long-lived assets, net	113,132	118,361
Rest of Europe
Segment Reporting Information [Line Items]
Long-lived assets, net	29,724	36,723
U.S.
Segment Reporting Information [Line Items]
Long-lived assets, net	60,676	65,152
Rest of World
Segment Reporting Information [Line Items]
Long-lived assets, net	$ 31,950	$ 38,668

Business segment information _6

Business segment information - Distribution of Depreciation and Amortization by Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Depreciation, amortization and reduction in carrying value of right-of-use assets	$ 24,198	$ 22,867	$ 48,718	$ 46,517
Ireland
Segment Reporting Information [Line Items]
Depreciation, amortization and reduction in carrying value of right-of-use assets	9,385	7,951	18,424	16,192
Rest of Europe
Segment Reporting Information [Line Items]
Depreciation, amortization and reduction in carrying value of right-of-use assets	3,681	3,672	7,648	7,487
U.S.
Segment Reporting Information [Line Items]
Depreciation, amortization and reduction in carrying value of right-of-use assets	8,168	6,201	16,716	14,840
Rest of World
Segment Reporting Information [Line Items]
Depreciation, amortization and reduction in carrying value of right-of-use assets	$ 2,964	$ 5,043	$ 5,930	$ 7,998

Business segment information _7

Business segment information - Distribution of Total Assets by Geographical Area (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Assets	$ 3,584,464	$ 3,435,606
Ireland
Segment Reporting Information [Line Items]
Assets	1,936,492	1,675,980
Rest of Europe
Segment Reporting Information [Line Items]
Assets	639,961	671,218
U.S.
Segment Reporting Information [Line Items]
Assets	830,877	909,202
Rest of World
Segment Reporting Information [Line Items]
Assets	$ 177,134	$ 179,206