0001628280-26-044957 | 6-K | XBRL Viewer

Print Document

Business Segment and Geographical Information - Schedule of Distribution of Revenue by Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Revenue	$ 2,033,999	$ 2,015,320
Ireland
Segment Reporting Information [Line Items]
Revenue	761,360	734,340
Rest of Europe
Segment Reporting Information [Line Items]
Revenue	390,847	375,865
U.S.
Segment Reporting Information [Line Items]
Revenue	642,602	672,424
Rest of World
Segment Reporting Information [Line Items]
Revenue	$ 239,190	$ 232,691

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-4

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-14

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-41

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

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

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 8: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 9: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

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

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-5

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-30

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-40

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-4

+ Details

Intangible assets - Schedule of Carrying Amount of Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Cost
Total cost	$ 5,206,220	$ 5,207,518
Accumulated amortization	(2,009,516)	(1,873,663)
Impairment	0	(86,737)
Net book value	3,196,704	3,247,118
Customer relationships
Cost
Total cost	4,133,727	4,134,478
Order backlog
Cost
Total cost	545,727	546,054
Trade names & brands
Cost
Total cost	204,700	204,721
Patient database
Cost
Total cost	170,484	170,511
Technology assets
Cost
Total cost	$ 151,582	$ 151,754

Summary of significant accounting policies

3 Months Ended

Mar. 31, 2026

Accounting Policies [Abstract]

Summary of significant accounting policies

Revenue recognition

The Company earns revenues by providing a number of different services to its customers. These services, which are integral elements of the clinical development process, include clinical trials management, consulting, contract staffing, data services and laboratory services. These services, which are described below, can be purchased collectively or individually as part of a clinical trial contract. There is not significant variability in how economic factors affect these services. Contracts range in duration from a number of months to several years.

ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”) requires application of five steps: (1) identify the contract(s) with a customer; (2) identify the performance obligation in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the entity satisfies the performance obligation(s), which have been applied to revenue recognized from each service described below.

Clinical trial service revenue

A clinical trial service is a single performance obligation satisfied over time. It represents the full-service obligation in respect of a clinical trial (including those services performed by investigators and other parties) and is considered a single performance obligation. Promises offered to the customer are not distinct within the context of the contract. ICON is the contract principal in respect of both direct services and in the use of third parties (principally investigator services) that support the clinical research projects. The transaction price is determined by reference to the contract or change order value (total service revenue and pass-through / reimbursable expenses) adjusted to reflect a realizable contract value. Revenue is recognized over time as the single performance obligation is satisfied. The progress towards completion for clinical service contracts is measured based on an input measure being total project costs incurred (inclusive of pass-through / reimbursable expenses) at each reporting period as a percentage of forecasted total project costs.

Laboratory services revenue

Revenue is recognized when, or as, obligations under the terms of a contract are satisfied, which occurs when control of the products or services is transferred to the customer. Revenue for laboratory services is measured as the amount of consideration we expect to receive in exchange for transferring products or services. Where contracts with customers contain multiple performance obligations, the transaction price is allocated to each performance obligation based on the estimated relative selling price of the promised good or service. Service revenue is recognized over time as the services are delivered to the customer based on the extent of progress towards completion of the performance obligation. The determination of the methodology to measure progress requires judgment and is based on the nature of services provided. This requires an assessment of the transfer of value to the customer. The right to invoice measure of progress is generally related to rate per unit contracts, as the extent of progress towards completion is measured based on discrete service or time-based increments, such as samples tested or labor hours incurred. Revenue is recorded in the amount invoiced since that amount corresponds to the value of the Company's performance and the transfer of value to the customer.

Contracting services revenue

The Company has availed of the practical expedient which results in recognition of revenue on a right to invoice basis. Application of the practical expedient reflects the right to consideration from the customer in an amount that corresponds directly with the value to the customer of the performance completion to date. This reflects hours performed by contract staff.

Consulting services revenue

Our consulting services contracts represent a single performance obligation satisfied over time. The transaction price is determined by reference to contract or change order value. Revenue is recognized over time as the performance obligation is satisfied. The progress towards completion for consulting contracts is measured based on total project inputs (time) at each reporting period as a percentage of forecasted total project inputs.

Data services revenue

The Company provides data reports and analytics to customers based on agreed-upon specifications, including the timing of delivery, which is typically either weekly, monthly, or quarterly. If a customer requests more than one type of data report or series of data reports within a contract, each distinct type of data report is a separate performance obligation. The contracts provide for the Company to be compensated for the value of each deliverable. The transaction price is determined using list prices, discount agreements, if any, and negotiations with the customers, and generally includes any out-of-pocket expenses. Typically, the Company bills in advance of services being provided with the amount being recorded as unearned revenue.

When multiple performance obligations exist, the transaction price is allocated to performance obligations on a relative standalone selling price basis. In cases where the Company contracts to provide a series of data reports, or in some cases data, the Company recognizes revenue over time using the “units delivered” output method as the data or reports are delivered. Expense reimbursements are recorded to revenue as the expenses are incurred as they relate directly to the services performed.

Certain arrangements include upfront customization or consultative services for customers. These arrangements often include payments based on the achievement of certain contractual milestones. Under these arrangements, the Company contracts with a customer to carry out a specific study, ultimately resulting in delivery of a custom report or data product. These arrangements are a single performance obligation given the integrated nature of the service being provided. The Company typically recognizes revenue under these contracts over time, using an appropriate measure of progress, generally time elapsed, to measure progress and transfer of control of the performance obligation to the customer. Expense reimbursements are recorded to revenue as the expenses are incurred as they relate directly to the service performed.

The Company enters into contracts with some of its larger data suppliers that involve non-monetary terms. The Company issues purchase credits to be used toward the data supplier's purchase of the Company's services based on the fair value of the data obtained. In exchange, the Company receives monetary discounts on the data received from the data suppliers. The fair value of the revenue earned from the customer purchases is recognized as services are delivered as described above. At the end of the contract year, any unused customer purchase credits may be forfeited or carried over to the next contract year based on the terms of the data supplier contract.

Commissions

Incremental costs of obtaining a contract are recognized as an asset on the Consolidated Balance Sheets in respect of those contracts that exceed one year. Where commission costs relate to contracts that are less than one year, the practical expedient is applied as the amortization period of the asset which would arise on deferral would be one year or less.

Intangible Assets

Intangible assets are measured at fair value at the date of acquisition and amortized on a straight-line basis over their respective estimated useful lives. The Company has no indefinite-lived intangible assets. The Company evaluates its intangible assets for impairment when indicators of impairment exist.

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


			Estimated Useful Life
Customer relationships			8 - 23 years
Order backlog			3 - 5 years


Technology assets			5 years

The Company periodically assesses the estimated useful lives of intangible assets to evaluate whether what was established at acquisition continues to be appropriate.

Income taxes

The Company applies the asset and liability method of accounting for income taxes. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amount of existing assets and liabilities and their respective tax bases and for operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which these temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the provision of income taxes in the period that includes the enactment date. Deferred tax assets are reduced by a valuation allowance to the amount that is more likely than not to be realized. The Company recognizes the effect of income tax positions only if those positions will more likely than not be sustained. Recognized income tax positions are measured at the largest amount of tax benefit that is greater than 50 percent likely of being realized upon settlement. Interest and penalties related to income taxes are included in income tax expense and classified with the related liability on the Consolidated Balance Sheets. The Company accounts for the impact of Global Intangible Low-Taxed Income (“GILTI”) in the period it arises and has therefore not provided for deferred taxes in respect of this item.

Basis of presentation	3 Months Ended
Basis of presentation	Mar. 31, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	Basis of presentation These condensed consolidated financial statements which have been prepared in accordance with United States Generally Accepted Accounting Principles (“U.S. 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 U.S. 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 Annual Report on Form 20-F for the year ended December 31, 2025 (see Note 2 Summary of significant accounting policies). Operating results for the three months ended March 31, 2026 are not necessarily indicative of the results that may be expected for the fiscal period ending December 31, 2026.

Net income per ordinary share - Schedule of Reconciliation of Number of Shares Used in Computation of Basic and Diluted Net Income Per Ordinary Share (Details) - shares	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Earnings Per Share [Abstract]
Weighted average number of ordinary shares outstanding for basic net income per ordinary share (in shares)	76,579,420	80,552,734
Effect of dilutive share options and other awards outstanding under share based compensation programs (in shares)	682,393	371,621
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share (in shares)	77,261,813	80,924,355

Share capital - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended		12 Months Ended	15 Months Ended
	Sep. 19, 2025	Aug. 20, 2025	Jun. 23, 2025	Mar. 19, 2025	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Mar. 31, 2026	Jul. 22, 2025	Feb. 18, 2025
Equity [Abstract]
Total number of shares purchased (in shares)	866,512	560,100	1,717,181	1,360,537	0		4,504,330	4,504,330
Stock repurchase program, additional amount authorized									$ 500,000	$ 750,000
Remaining authorization to repurchase	$ 750,000	$ 900,200	$ 500,000	$ 750,000	$ 750,000			$ 750,000
Average price paid per share (in USD per share)	$ 173.33	$ 178.20	$ 145.59	$ 183.75			$ 166.51	$ 166.51
Share repurchase program, value of shares repurchased						$ 250,000	$ 750,000

Subsequent events (Details) - USD ($) $ in Thousands	Jun. 24, 2026	May 08, 2026	Apr. 27, 2026	Mar. 31, 2026	Dec. 31, 2025	Jul. 01, 2021
Business Combination [Line Items]
Total debt				$ 3,409,248	$ 3,416,688
Subsequent Event \| HealthVerity, Inc.
Business Combination [Line Items]
Aggregate purchase price		$ 37,500
Carrying value		$ 0
Bridge Secured Credit Facility \| Senior Secured Term Loan \| Subsequent Event
Business Combination [Line Items]
Debt instrument, principal amount			$ 500,000
Basis spread on variable rate (in percent)	1.00%
Bridge Secured Credit Facility \| Senior Secured Term Loan \| Subsequent Event \| Minimum
Business Combination [Line Items]
Basis spread on variable rate (in percent)			1.00%
Bridge Secured Credit Facility \| Senior Secured Term Loan \| Subsequent Event \| Maximum
Business Combination [Line Items]
Basis spread on variable rate (in percent)			2.25%
Senior Secured Notes (the "2026 Notes") \| Senior Subordinated Notes
Business Combination [Line Items]
Total debt				$ 500,000	$ 500,000
Debt instrument, interest rate (in percent)				2.875%	2.875%	2.875%

Intangible assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 50.3	$ 58.9
Additions to intangible assets	$ 0.0

- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-18

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-11

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 24
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-24

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476148/220-40-50-12

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 40
-SubTopic 30
-Topic 350
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482640/350-30-55-40

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482665/350-30-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482686/350-30-45-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476148/220-40-50-6

+ Details

Fair value measurements

3 Months Ended

Mar. 31, 2026

Fair Value Disclosures [Abstract]

Fair value measurements

The Company records certain assets and liabilities at fair value. Fair value is defined as the price that would be received to sell an asset, or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. A three-level fair value hierarchy that prioritizes the inputs used to measure fair value is described below. This hierarchy requires entities to maximize the use of observable inputs and minimize the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows:

•Level 1 — Quoted prices in active markets for identical assets or liabilities.

•Level 2 — Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data.

•Level 3 — Unobservable inputs that are supported by little or no market activity. This includes certain pricing models, discounted cash flow methodologies, and similar techniques that use significant unobservable inputs.

The carrying amounts of financial instruments, including cash and cash equivalents, accounts receivable and accounts payable approximate fair value due to the short maturities of these instruments.

As of March 31, 2026, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows:


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
	(in thousands)
Assets:

Investments in equity1	$	—	$	—	$	—	$	94,466	$	94,466

Total assets	$	—	$	—	$	—	$	94,466	$	94,466

As of December 31, 2025, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows:


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
	(in thousands)
Assets:

Investments in equity1	$	—	$	—	$	—	$	79,550	$	79,550
Total assets	$	—	$	—	$	—	$	79,550	$	79,550

1To determine the classification of its investments in equity, the Company considered the nature of its investment, the extent of influence over operating and financial decisions and the availability of readily determinable fair values. The Company determined that certain interests in funds meet the definition of equity securities without readily determinable fair values, which qualify for the Net Asset Value (NAV) practical expedient in ASC 820, Fair value measurement. Any increases or decreases in fair value are recognized in net income in the period. As at March 31, 2026 investments in equity excludes investments in equity securities recorded at cost, net of impairment of $2.5 million (December 31, 2025: $2.5 million) which do not qualify for the NAV practical expedient.

Non-recurring fair value measurements

Certain assets and liabilities are carried on the accompanying Condensed Consolidated Balance Sheets at cost and are not re-measured to fair value on a recurring basis. These assets include finite-lived intangible assets that are tested for impairment when a triggering event occurs and goodwill that is tested for impairment annually or when a triggering event occurs. As at March 31, 2026, assets carried on the Condensed Consolidated Balance Sheets which are not re-measured to fair value on a recurring basis totaled $11,925.0 million (December 31, 2025: $11,981.3 million). These assets are comprised of goodwill of $8,725.8 million (December 31, 2025: $8,731.7 million), intangible assets of $3,196.7 million (December 31, 2025: $3,247.1 million) and investments in equity recorded at cost, net of impairment of $2.5 million (December 31, 2025: $2.5 million).

The estimated fair value of the Company’s debt was $3,432.1 million at March 31, 2026 (December 31, 2025: $3,500.1 million). The fair values of the senior secured term loan facility, the 2026 Notes and the New Notes (as defined in Note 10 Bank credit lines, loan facilities and notes) were determined based on rates at which the debt is traded among financial institutions.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 107
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-107

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

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

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

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

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

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

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

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 940
-SubTopic 820
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478119/940-820-50-1

+ Details

Summary of significant accounting policies (Policies)

3 Months Ended

Mar. 31, 2026

Accounting Policies [Abstract]

Revenue recognition

Clinical trial service revenue

Laboratory services revenue

Contracting services revenue

Consulting services revenue

Data services revenue

Commissions

Intangible assets

Intangible Assets

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


			Estimated Useful Life
Customer relationships			8 - 23 years
Order backlog			3 - 5 years


Technology assets			5 years

The Company periodically assesses the estimated useful lives of intangible assets to evaluate whether what was established at acquisition continues to be appropriate.

Income taxes

- Definition

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.

+ References + Details

- Definition

Disclosure of accounting policy for revenue from contract with customer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 19
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-19

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-18

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-18

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 20
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-20

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 20
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-20

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 20
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-20

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 20
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-20

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (e)
-SubTopic 10
-Topic 235
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483426/235-10-50-4

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

+ Details

Intangible assets (Tables)

3 Months Ended

Mar. 31, 2026

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Carrying Amount of Intangible Assets

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


			Estimated Useful Life
Customer relationships			8 - 23 years
Order backlog			3 - 5 years


Technology assets			5 years

The carrying amount of intangible assets as of March 31, 2026 and December 31, 2025 is as follows:



	March 31, 2026		December 31, 2025
	(in thousands)
Cost
Customer relationships	$	4,133,727	$	4,134,478
Order backlog	545,727		546,054
Trade names & brands	204,700		204,721
Patient database	170,484		170,511
Technology assets	151,582		151,754



Total cost	5,206,220		5,207,518
Accumulated amortization	(2,009,516)		(1,873,663)
Impairment	—		(86,737)
Net book value	$	3,196,704	$	3,247,118

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Schedule of Unbilled Services and Unearned Revenue or Payments on Account (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Revenue from Contract with Customer [Abstract]
Unbilled revenue (Unbilled services)	$ 1,090,950	$ 1,096,592
Change in unbilled revenue (unbilled services)	$ (5,642)
Percentage change in unbilled revenue (unbilled services)	(0.50%)
Unearned revenue (Payments on account)	$ (1,547,527)	$ (1,550,471)
Change in unearned revenue (payments on account)	$ 2,944
Percentage change in unearned revenue (payments on account)	(0.20%)

Income taxes (Tables)

3 Months Ended

Mar. 31, 2026

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense

Income taxes recognized during the three months ended March 31, 2026 and March 31, 2025, comprise:


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Income tax expense	$	22,807	$	20,351
Total	$	22,807	$	20,351

Summary of significant accounting policies (Details)	Mar. 31, 2026
Technology assets
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years
Minimum \| Customer relationships
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	8 years
Minimum \| Order backlog
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	3 years
Maximum \| Customer relationships
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	23 years
Maximum \| Order backlog
Indefinite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 38
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479876/805-20-55-38

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 31
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479876/805-20-55-31

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479876/805-20-55-31

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479876/805-20-55-14

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479876/805-20-55-14

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479876/805-20-55-14

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 40
-SubTopic 30
-Topic 350
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482640/350-30-55-40

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482686/350-30-45-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482665/350-30-50-3

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482665/350-30-50-2

+ Details

Share based awards (Tables)

3 Months Ended

Mar. 31, 2026

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

The following table summarizes option activity for the three months ended March 31, 2026:


	Options Outstanding Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life
Outstanding at December 31, 2025	639,184	$	179.12	3.90
Granted	—	—
Exercised	(10,174)	$	106.64
Expired	(31,560)	$	116.06
Outstanding at March 31, 2026	597,450	$	183.69	3.92
Exercisable at March 31, 2026	517,846	$	178.31	3.58

Schedule of Weighted Average Fair Values and Assumptions Used

The weighted average grant date fair values and assumptions used were as follows:


	Three Months Ended
	March 31, 2026		March 31, 2025
Weighted average grant date fair value	$	—	$	64.42
Assumptions:
Expected volatility	—		35		%
Dividend yield	—		—		%
Risk-free interest rate	—		4.00		%
Expected life	—		4.4 years

Schedule of RSU and PSU Activity

The following table summarizes RSU and PSU activity for the three months ended March 31, 2026:


	PSU Outstanding Number of Shares	PSU Weighted Average Grant Date Fair Value		RSU Outstanding Number of Shares	RSU Weighted Average Grant Date Fair Value
Outstanding at December 31, 2025	16,474	$	185.18	1,476,169	$	162.53
Granted	—	—		—	—
Shares vested	—	—		(24,039)	$	179.56
Forfeited	(6,177)	$	185.18	(22,944)	$	172.47
Outstanding at March 31, 2026	10,297	$	185.18	1,429,186	$	162.09

Schedule of Stock Compensation Expense

Stock compensation expense for the three months ended March 31, 2026 and March 31, 2025 has been allocated as follows:


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Direct costs	$	18,296	$	5,381
Selling, general and administrative	8,686		6,913
Total	$	26,982	$	12,294

Net income per ordinary share (Tables)

3 Months Ended

Mar. 31, 2026

Earnings Per Share [Abstract]

Schedule of Reconciliation of Number of Shares Used in Computation of Basic and Diluted Net Income per Ordinary Share

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


	Three Months Ended
	March 31, 2026	March 31, 2025
Weighted average number of ordinary shares outstanding for basic net income per ordinary share	76,579,420	80,552,734
Effect of dilutive share options and other awards outstanding under share based compensation programs	682,393	371,621
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share	77,261,813	80,924,355


	Three Months Ended
	March 31, 2026		March 31, 2025
Net income per Ordinary Share:
Basic	$	1.37	$	2.00
Diluted	$	1.36	$	1.99

Revenue

3 Months Ended

Mar. 31, 2026

Revenue from Contract with Customer [Abstract]

Revenue

Revenue disaggregated by customer concentration is as follows:


	Three Months Ended
	March 31, 2026		March 31, 2025



Clients 1-5	$	507,997	$	496,118
Clients 6-10	310,359		309,562
Clients 11-25	469,397		475,299
Other	746,246		734,341
Total	$	2,033,999	$	2,015,320

There was no revenue from individual customers greater than 10% of consolidated revenue in the respective periods.

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

Accounts receivables and unbilled revenue are as follows:


	March 31, 2026		December 31, 2025
	(in thousands)
Accounts receivable (Billed services)	$	1,512,822	$	1,517,217
Allowance for credit losses	(41,518)		(42,319)
Accounts receivable (net)	1,471,304		1,474,898
Unbilled revenue (Unbilled services)	1,090,950		1,096,592
Accounts receivable and unbilled revenue, net	$	2,562,254	$	2,571,490

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


	March 31, 2026		December 31, 2025		$ Change		% Change
	(in thousands, except percentages)
Unbilled revenue (Unbilled services)	$	1,090,950	$	1,096,592	$	(5,642)	(0.5)	%
Unearned revenue (Payments on account)	(1,547,527)		(1,550,471)		2,944		(0.2)	%

Timing may differ between the satisfaction of performance obligations and the invoicing and collection of amounts related to our contracts with customers. We record assets for amounts related to performance obligations that are satisfied but not yet billed and/or collected. These assets are recorded as unbilled revenue and therefore contract assets rather than accounts receivable when receipt of the consideration is conditional on something other than the passage of time. Liabilities are recorded for amounts that are collected in advance of the satisfaction of performance obligations or billed in advance of the revenue being earned.

Unbilled services/revenue balances arise where invoicing or billing is based on the timing of agreed milestones related to service contracts for clinical research. Contractual billing arrangements in respect of certain reimbursable expenses (principally investigators) require billing by the investigator to the Company prior to billing by the Company to the customer. As there is no contractual right of set-off between unbilled services (contract assets) and unearned revenue (contract liabilities), each are separately presented gross on the Condensed Consolidated Balance Sheet.

Unbilled services as at March 31, 2026 decreased by $5.6 million compared to December 31, 2025. Unearned revenue decreased by $2.9 million compared to December 31, 2025. These fluctuations are primarily due to the timing of payments and invoicing related to the Company's clinical trial management contracts. Billings and payments are established by contractual provisions on the delivery of units/milestones including predetermined payment schedules which may or may not correspond to the timing of the transfer of control of the Company's services under the contract. Unbilled services arise from long-term contracts when a cost-based input method of revenue recognition is applied and revenue recognized exceeds the amount billed to the customer.

As of March 31, 2026, approximately $15.0 billion (December 31, 2025, $14.9 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 48% of the unsatisfied performance obligations over the next 12 months (December 31, 2025: 48%), with the remainder expected to be recognized thereafter over the duration of the customer contracts. We believe that our unsatisfied performance obligation as of any date is not necessarily a meaningful predictor of future results due to the potential for cancellation or delay of the projects included in the unsatisfied performance obligation, and no assurances can be given on the extent to which we will be able to realize this unsatisfied performance obligation as revenue.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-9

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-10

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-15

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-13

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org/606/tableOfContent

+ Details

Restructuring (Tables)

3 Months Ended

Mar. 31, 2026

Restructuring and Related Activities [Abstract]

Schedule of Restructuring Charges


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Restructuring charges	$	10,076	$	39,346
Total	$	10,076	$	39,346

Schedule of Details of Movement in Restructuring Charges


	Three Months Ended		Year Ended
	March 31, 2026		December 31, 2025
	(in thousands)
Opening provision	$	12,525	$	31,474
Charge during the period	10,076		75,386
Utilization	(7,512)		(94,335)
Closing provision	$	15,089	$	12,525

Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
Revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Revenue	$ 2,033,999	$ 2,015,320
Clients 1-5
Disaggregation of Revenue [Line Items]
Revenue	507,997	496,118
Clients 6-10
Disaggregation of Revenue [Line Items]
Revenue	310,359	309,562
Clients 11-25
Disaggregation of Revenue [Line Items]
Revenue	469,397	475,299
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 746,246	$ 734,341

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-5

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Goodwill - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Goodwill - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Goodwill and Intangible Assets Disclosure [Abstract]
Impairment	$ 0	$ 364,248

- Definition

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

+ References + Details

Goodwill (Tables)

3 Months Ended

Mar. 31, 2026

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

The change in the carrying amount of goodwill between December 31, 2025 and March 31, 2026 is as follows:



	Three Months Ended		Year Ended
	March 31, 2026		December 31, 2025
	(in thousands)
Opening balance	$	8,731,689	$	9,051,410

Prior period acquisition	—		5,109
Impairment	—		(364,248)
Foreign exchange movement	(5,909)		39,418
Closing balance	$	8,725,780	$	8,731,689

- Definition

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

+ References

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

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1A

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

+ Details

Income taxes - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Income Tax Disclosure [Abstract]
Unrecognized tax benefits and related interest and penalties	$ 104.5	$ 103.3
Unrecognized tax benefits	80.4	81.0
Interest and related penalties	$ 24.1	$ 22.3

Share based awards - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions				3 Months Ended
	Oct. 25, 2024	May 16, 2019	May 11, 2015	Mar. 31, 2026	Mar. 31, 2025
Employee Stock Option
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Number of shares exercisable (in shares)				517,846
Weighted average contractual term of options exercisable				3 years 6 months 29 days
Weighted average exercise price of options exercisable (in USD per share)				$ 178.31
Restricted stock units 2013
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Additional ordinary shares which have been reserved for issuance (in shares)	2,500,000		2,500,000
Ordinary shares which have been reserved for issuance (in shares)	6,600,000
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 \| Outside Director
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				$ 0.0	$ 1.9
Restricted Stock Units (RSUs)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Fair value of stock units vested				$ 4.3	$ 5.0
PSUs based on service and EPS targets \| Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock units to be granted (in shares)				47,779

Subsequent events	3 Months Ended
Subsequent events	Mar. 31, 2026
Subsequent Events [Abstract]
Subsequent events	Subsequent events The Company has evaluated subsequent events from the Balance Sheet date through to the date at which the financial statements were available to be issued. Bridge Secured Credit Facility On April 27, 2026, ICON Global Treasury Unlimited Company (the “Bridge Facility Borrower”) entered into a bridge facility credit agreement for an aggregate principal amount of $500 million (the "Bridge Secured Credit Facility"). The proceeds of the Bridge Secured Credit Facility may be used to discharge and repay in full $500 million aggregate principal amount of 2.875% Senior Secured Notes (the “2026 Notes”) issued by a subsidiary of the Group in July 2021. The Bridge Secured Credit Facility will mature on April 26, 2027. The Borrowings under the Bridge Secured Credit Facility do not amortize and are due at final maturity. The interest rate margin applicable to borrowings under the Bridge Secured Credit Facility is USD Term SOFR plus a fixed calendared applicable margin ranging from 1.00% to 2.25%. At June 23, 2026, the applicable margin was 1.00%. The Bridge Facility Borrower’s obligations under the Bridge Secured Credit Facility are guaranteed by ICON and the subsidiary guarantors party thereto. The Bridge Secured Credit Facility is secured by a lien on substantially all of the assets (subject to certain exceptions) of ICON, the Bridge Facility Borrower and each of the subsidiary guarantors, and the Bridge Secured Credit Facility will have a first-priority lien on such assets which will rank pari passu with the lien securing ICON’s other first lien secured indebtedness and is subject to other permitted liens. The Company is permitted to make voluntary prepayments under the Bridge Secured Credit Facility without premium or penalty (subject to customary break funding payments). The Bridge Secured Credit Facility contains customary negative covenants, including, but not limited to, restrictions on the ability of ICON and its subsidiaries to merge and consolidate with other companies, incur indebtedness, grant liens or security interests on assets, pay dividends or make other restricted payments, sell or otherwise transfer assets or enter into transactions with affiliates. The Bridge Secured Credit Facility provides that, upon the occurrence of certain events of default, the obligations under the credit agreement may be accelerated. Such events of default will include payment defaults to the lenders thereunder, material inaccuracies of representations and warranties, covenant defaults, cross-defaults to other material indebtedness, voluntary and involuntary bankruptcy proceedings, material money judgments, material pension-plan events, change of control and other customary events of default. Disposal of Symphony Health Solutions Corporation On May 8, 2026, ICON completed the disposition of Symphony Health Solutions Corporation ("Symphony") pursuant to a merger agreement, by and among HealthVerity, Inc. ("HealthVerity"), Symphony, Pharmaceutical Research Associates, Inc. and HealthVerity Merger Sub, Inc. ("HV Merger Sub"), a wholly owned subsidiary of HealthVerity. Pursuant to the merger agreement, HV Merger Sub merged with and into Symphony, with Symphony surviving the merger as a wholly owned subsidiary of HealthVerity. The consideration payable by HealthVerity in connection with the merger consisted of shares of stock in HealthVerity, subject to customary adjustments as set forth in the merger agreement. In connection with the merger, ICON also purchased additional shares of stock in HealthVerity for an aggregate purchase price of $37.5 million. As a result, ICON holds a minority equity interest in HealthVerity. As of May 8, 2026, the Company’s investment in HealthVerity has been recorded at a carrying value of $nil. Waivers to the debt agreements On April 27, 2026, the parties (limited to the borrowers and revolving lenders under the senior secured revolving loan facility only) to the Credit Agreement (as defined below) entered into a Consent to Credit Agreement pursuant to which such revolving lenders agreed to provide a limited and temporary waiver of the requirement to deliver certain financial statements under the senior secured revolving credit facility in connection with the borrowings thereunder. The waiver applied solely for the specified consent period ending May 31, 2026. On May 18, 2026, the Company launched a consent and waiver to the Credit Agreement (applicable to all facilities thereunder) in order to request that the requisite lenders thereunder agree to (i) waive the technical default caused by the Company’s late delivery of annual financial statements for the fiscal year ending December 31, 2025, (ii) provide an extension of the delivery of the Company’s annual financial statements for the fiscal year ending December 31, 2025 to July 16, 2026 and (iii) provide an extension of the delivery of the Company’s quarterly financial statements for the fiscal quarter ending March 31, 2026 to July 31, 2026. Consent to the waiver was received on May 22, 2026. The Company filed its Annual Report on Form 20-F for the year ended December 31, 2025 on May 27, 2026. On May 29, 2026, the Annual Report on Form 20-F that was subject to the April 27, 2026 and May 18, 2026 waivers was delivered to the requisite parties under the Credit Agreement. The Company has determined that there are no other items to disclose.

Business Segment and Geographical Information (Tables)

3 Months Ended

Mar. 31, 2026

Segment Reporting [Abstract]

Schedule of Distribution of Revenue by Geographical Area

The distribution of revenue by geographical area was as follows:


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Ireland	$	761,360	$	734,340
Rest of Europe	390,847		375,865
U.S.	642,602		672,424
Rest of World	239,190		232,691
Total	$	2,033,999	$	2,015,320

Schedule of Distribution of Income from Operations by Geographical Area

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


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Ireland	$	125,204	$	163,378
Rest of Europe	31,725		36,843
U.S.	49,698		68,487
Rest of World	17,386		17,208
Sub-total	$	224,013	$	285,916
Amortization of intangible assets	(50,279)		(58,946)
Total	$	173,734	$	226,970

Schedule of Distribution of Long-Lived Assets, Net by Geographic Area

The distribution of long-lived assets (property, plant and equipment and operating right-of-use assets), net, by geographical area was as follows:



	March 31, 2026		December 31, 2025
	(in thousands)
Ireland	$	243,396	$	250,566
Rest of Europe	90,056		94,920
U.S.	119,604		122,896
Rest of World	55,300		56,290
Total	$	508,356	$	524,672

Net income per ordinary share - Schedule of Reconciliation of Net Income Attributable to the Group (Details) - $ / shares	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Net income per Ordinary Share:
Basic (in USD per share)	$ 1.37	$ 2.00
Diluted (in USD per share)	$ 1.36	$ 1.99

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482662/260-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 105
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 9
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479343/105-10-65-9

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 17
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480336/718-10-65-17

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 52
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-52

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-15

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-7

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-10

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-7

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 65
-Paragraph 4
-Subparagraph (f)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481538/470-20-65-4

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482662/260-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 105
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 9
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479343/105-10-65-9

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 17
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480336/718-10-65-17

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 52
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-52

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-15

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-7

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-7

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 65
-Paragraph 4
-Subparagraph (f)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481538/470-20-65-4

+ Details

Fair value measurements - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities recorded at cost	$ 2.5	$ 2.5
Long-term debt at fair value	3,432.1	3,500.1
Fair value, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	11,925.0	11,981.3
Goodwill at fair value	8,725.8	8,731.7
Net intangible assets at fair value	$ 3,196.7	$ 3,247.1

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-SubTopic 10
-Topic 825
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482881/825-10-55-10

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-11

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-11

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-10

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482881/825-10-55-12

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

+ Details

Bank credit lines, loan facilities and notes

3 Months Ended

Mar. 31, 2026

Debt Disclosure [Abstract]

Bank credit lines, loan facilities and notes

The Company had the following debt outstanding as of March 31, 2026 and December 31, 2025:


		Interest rate as of				Principal amount
	Maturity Date	March 31, 2026		December 31, 2025		March 31, 2026		December 31, 2025
						(in thousands)
Senior Secured Term Loan	July 2028	5.700	%	5.672	%	$	909,248	$	916,688
Senior Secured Notes (the "2026 Notes")	July 2026	2.875	%	2.875	%	500,000		500,000

Senior Secured Notes (the "2027 Notes")*	May 2027	5.809	%	5.809	%	750,000		750,000
Senior Secured Notes (the "2029 Notes")*	May 2029	5.849	%	5.849	%	750,000		750,000
Senior Secured Notes (the "2034 Notes")*	May 2034	6.000	%	6.000	%	500,000		500,000
Total debt						3,409,248		3,416,688
Less current portion of debt						(529,762)		(529,762)
Total long-term debt						2,879,486		2,886,926
Less debt issuance costs and debt discount						(12,791)		(14,310)
Total long-term debt, net						$	2,866,695	$	2,872,616

*Issued May 8, 2024

As of March 31, 2026, the contractual maturities of the Company's debt obligations were as follows:


Contractual maturities of debt	(in thousands)
2026 (remaining)		$	522,322
2027		779,762
2028		857,164
2029		750,000
2030 and thereafter		500,000
Total		$	3,409,248

The Company's primary financing arrangements are its senior secured credit facilities (the "Senior Secured Credit Facilities"), which consists of a senior secured term loan and a revolving credit facility, the 2026 Notes and the New Notes.

The New Notes

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

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

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

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

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

Senior Secured Credit Facilities

On July 1, 2021, the Company completed the acquisition of PRA Health Sciences, Inc. (“PRA”) by means of a merger whereby Indigo Merger Sub, Inc., a Delaware corporation and subsidiary of ICON, merged with and into PRA, the parent of PRA Health Sciences (the “Merger”). In conjunction with the completion of the Merger, on July 1, 2021, ICON entered into a credit agreement (the “Credit Agreement”) providing for a senior secured term loan facility of $5,515 million and a senior secured revolving loan facility in an initial aggregate principal amount of $300 million (the “Senior Secured Credit Facilities”). On May 2, 2023, the Company agreed with its lenders to increase the aggregate principal amount of the senior secured revolving loan facility from $300 million to $500 million. The Senior Secured Credit Facilities and the 2026 Notes were issued at a discount of $27.6 million.

Borrowings under the senior secured term loan facility amortize in equal quarterly installments in an amount equal to 1.00% per annum of the principal amount, with the remaining balance due at final maturity. The interest rate margin applicable to borrowings under the senior secured term loan facility is USD Term SOFR plus an applicable margin which is dependent on the Company's net leverage ratio. At December 31, 2025, the applicable margin is 2.0% (which reflects the Third Amendment). The senior secured term loan facility is subject to a floor of 0.50%.

On November 26, 2025, the parties to the Credit Agreement entered into a Fourth Amendment (the “Fourth Amendment”) to reprice and extend the senior secured revolving credit facility.

As a result of the Fourth Amendment, the maturity was extended from a five-year term to a seven-year term ending July 1, 2028. Reflecting the Fourth Amendment, the interest rate margin applicable to borrowings under the revolving loan facility will be, at the option of the borrower, either (i) the applicable base rate plus an applicable margin of 0.35% or 0.00%, based on the Company’s current corporate family rating assigned by S&P of BB (or lower) or BB+ (or higher), respectively, or (ii) Term SOFR plus an applicable margin of 1.35%, 1.00%, 0.75%, 0.55%, or 0.40% based on the Company’s current corporate family rating assigned by S&P of BB (or lower), BB+, BBB-, BBB or BBB+ (or higher), respectively. In addition, lenders under the revolving loan facility are entitled to commitment fees as a percentage of the applicable margin at the time of drawing and utilization fees dependent on the proportion of the facility drawn.

The Borrowers’ (as defined in the Senior Secured Credit Facility) obligations under the Senior Secured Credit Facilities are guaranteed by ICON and the subsidiary guarantors. The Senior Secured Credit Facilities are secured by a lien on substantially all of ICON’s, the Borrowers’ and each of the subsidiary guarantor’s assets (subject to certain exceptions), and the Senior Secured Credit Facilities will have a first-priority lien on such assets, which will rank pari passu with the lien securing the 2026 Notes and the New Notes subject to other permitted liens. The Company is permitted to make prepayments on the senior secured term loan without penalty.

Principal repayments on the senior secured term loan, comprising mandatory repayments, during the three months ended March 31, 2026 and year ended December 31, 2025 were as follows:


Principal repayments	(in thousands)
Quarter 1, 2025		$	(7,440)
Quarter 2, 2025		(7,441)
Quarter 3, 2025		(7,440)
Quarter 4, 2025		(7,441)
Total repayments in 2025		$	(29,762)
Quarter 1, 2026		(7,440)


Total repayments in 2026		$	(7,440)

During the quarter ended March 31, 2026, the Company drew down $nil (year ended December 31, 2025: $50.0 million) of the senior secured revolving loan facility and repaid $nil (year ended December 31, 2025: $50.0 million) as shown below. As at March 31, 2026, $nil (December 31, 2025: $nil) was drawn under the senior secured revolving loan facility.


	Drawdown		Repayment		Closing Balance
	(in thousands)

Quarter 1, 2025	$	50,000	$	(50,000)	$	—
Quarter 2, 2025	—		—		—
Quarter 3, 2025	—		—		—
Quarter 4, 2025	—		—		—
Total drawdown / (repayment) in 2025	50,000		(50,000)		—
Quarter 1, 2026	—		—		—
Total drawdown / (repayment) in 2026	$	—	$	—	$	—

2026 Notes

In addition to the Senior Secured Credit Facilities, on July 1, 2021, a subsidiary of the Company issued the 2026 Notes of $500 million in aggregate principal amount of 2.875% senior secured notes in a private offering (the “Offering”). The 2026 Notes will mature on July 15, 2026.

Fair Value of Debt

The estimated fair value of the Company’s debt was $3,432.1 million at March 31, 2026 (December 31, 2025: $3,500.1 million). The fair values of the senior secured term loan facility, the 2026 Notes and the New Notes were determined based on rates at which the debt is traded among financial institutions.

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Change in unbilled revenue (unbilled services)	$ (5,642)
Increase in unearned revenue (payments on account)	(2,944)
Revenue, remaining performance obligation	$ 15,000,000	$ 14,900,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation percentage		48.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period		12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation percentage	48.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months

Bank credit lines, loan facilities and notes - Schedule of Principal Payments on Debt Instruments (Details) - Senior Secured Term Loan - Senior Secured Term Loan - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Dec. 31, 2025	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025
Debt Instrument [Line Items]
Periodic principal payment	$ (7,440)	$ (7,441)	$ (7,440)	$ (7,441)	$ (7,440)
Annual principal payment	$ (7,440)	$ (29,762)

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-8A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477314/942-235-S99-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-4

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-3

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482949/835-30-55-8

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69B

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69C

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69E

Reference 12: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69F
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69F

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 15: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1D
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1D

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1D
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1D

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1D
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1D

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1E

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1E

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1E

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1I

Reference 30: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

Reference 31: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482900/835-30-50-1

+ Details

Operating leases - Schedule of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Leases [Abstract]
Operating lease costs	$ 10,780	$ 11,199
Income from sub-leases	(379)	(768)
Net operating lease costs	$ 10,401	$ 10,431

Bank credit lines, loan facilities and notes - Schedule of Contractual Maturities of Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Debt Disclosure [Abstract]
2026 (remaining)	$ 522,322
2027	779,762
2028	857,164
2029	750,000
2030 and thereafter	500,000
Total debt	$ 3,409,248	$ 3,416,688

Restructuring - Schedule of Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Restructuring and Related Activities [Abstract]
Restructuring charges	$ 10,076	$ 39,346

Operating leases

3 Months Ended

Mar. 31, 2026

Leases [Abstract]

Operating leases

Lease costs recorded under operating leases for three months ended March 31, 2026 and March 31, 2025 were as follows:


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Operating lease costs	$	10,780	$	11,199
Income from sub-leases	(379)		(768)
Net operating lease costs	$	10,401	$	10,431

Of the total cost of $10.4 million incurred in the three months ended March 31, 2026 (March 31, 2025: $10.4 million), $8.7 million (March 31, 2025: $8.9 million) is recorded within selling, general and administration costs and $1.7 million (March 31, 2025: $1.5 million) is recorded within direct costs.

During the three months ended March 31, 2026 and March 31, 2025, costs incurred by the Group related to variable lease payments were de minimis.

Right-of-use assets obtained, in exchange for lease obligations during the three months ended March 31, 2026, totaled $5.0 million (March 31, 2025: $7.0 million).

The weighted average remaining lease term and weighted-average discount rate at March 31, 2026 were 5.73 years and 3.84%, respectively. The weighted average remaining lease term and weighted-average discount rate at December 31, 2025 were 5.96 years and 4.04%, respectively.

Future minimum lease payments under non-cancelable leases as of March 31, 2026 were as follows:



	(in thousands)
Year 1		$	40,077
Year 2		35,506
Year 3		26,223
Year 4		19,239
Year 5		10,721
Thereafter		30,662
Total future minimum lease payments		162,428
Lease imputed interest		(15,899)
Total		$	146,529

Operating lease liabilities are presented as current and non-current. As at March 31, 2026, operating lease liabilities of $35.2 million have been included in Other liabilities (December 31, 2025: $36.3 million) and $111.3 million have been classified as Non-Current Lease Liabilities (December 31, 2025: $117.1 million).

Cover	3 Months Ended
Cover	Mar. 31, 2026
Cover [Abstract]
Document Type	6-K
Document Fiscal Year Focus	2026
Entity Registrant Name	ICON plc
Amendment Flag	false
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001060955
Current Fiscal Year End Date	--12-31
Document Period End Date	Mar. 31, 2026

Fair value measurements - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Assets:
Investments in equity	$ 96,966	$ 82,050
Investments in equity securities recorded at cost	2,500	2,500
Fair value, recurring
Assets:
Investments in equity	94,466	79,550
Total assets	94,466	79,550
Level 1 \| Fair value, recurring
Assets:
Investments in equity	0	0
Total assets	0	0
Level 2 \| Fair value, recurring
Assets:
Investments in equity	0	0
Total assets	0	0
Level 3 \| Fair value, recurring
Assets:
Investments in equity	0	0
Total assets	0	0
Investments Measured at Net Asset Value \| Fair value, recurring
Assets:
Investments in equity	94,466	79,550
Total assets	$ 94,466	$ 79,550

Net income per ordinary share

3 Months Ended

Mar. 31, 2026

Earnings Per Share [Abstract]

Net income per ordinary share

Basic net income per ordinary share has been computed by dividing net income available to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period.

Diluted net income per ordinary share is computed by adjusting the weighted average number of ordinary shares outstanding during the period for all potentially dilutive ordinary shares outstanding during the period and adjusting net income for any changes in income or loss that would result from the conversion of such potential ordinary shares.

There is no difference in net income used for basic and diluted net income per ordinary share.

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


	Three Months Ended
	March 31, 2026	March 31, 2025
Weighted average number of ordinary shares outstanding for basic net income per ordinary share	76,579,420	80,552,734
Effect of dilutive share options and other awards outstanding under share based compensation programs	682,393	371,621
Weighted average number of ordinary shares outstanding for diluted net income per ordinary share	77,261,813	80,924,355


	Three Months Ended
	March 31, 2026		March 31, 2025
Net income per Ordinary Share:
Basic	$	1.37	$	2.00
Diluted	$	1.36	$	1.99

Restructuring - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 10,076	$ 39,346
Restructuring reserve	15,089		$ 12,525	$ 31,474
Personnel related liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	12,000		9,100
Facility liability
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	3,100		3,400
Restructuring reserve, current	1,200		1,300
Restructuring reserve, noncurrent	$ 1,900		$ 2,100

- Definition

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

+ References + Details

Commitments and contingencies	3 Months Ended
Commitments and contingencies	Mar. 31, 2026
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies Other than as described below, we do not expect any current litigation to have a materially adverse effect on our financial condition or results of operations. However, from time to time, we may become involved in various lawsuits and legal proceedings which arise in the ordinary course of business. Litigation is subject to inherent uncertainties, and an adverse result in these or other matters may arise from time to time that may harm our business, and one or more unfavorable outcomes could adversely affect us for the period in which they are resolved. In addition, regardless of their merits or their ultimate outcomes, lawsuits and legal proceedings are costly, divert management attention, and may adversely affect our reputation, even if they are resolved in our favor. The Company, its former Chief Executive Officer, and its former Chief Financial Officer were named as defendants in two class action lawsuits involving similar claims, filed in the United States District Court for the Eastern District of New York on February 10, 2025 (Shing v. ICON plc, et al.) and April 2, 2025 (Police and Fire Retirement System of the City of Detroit v. ICON plc), respectively, alleging that defendants made misleading statements regarding the Company’s financial performance and future business prospects in violation of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934. The two cases have been consolidated and are proceeding under the caption In re ICON plc Securities Litigation, No. 2:25-cv-00763 (the "Putative Class Action"). Lead plaintiffs and lead counsel for the putative class were appointed on June 10, 2025. On September 12, 2025, the lead plaintiffs filed an amended complaint that names the Company’s current Chief Executive Officer in addition to the original defendants. On November 12, 2025, the defendants filed a motion to dismiss the amended complaint. Lead plaintiffs filed an opposition on January 13, 2026. On February 13, 2026, the parties filed a stipulation that the lead plaintiffs may file a further amended complaint within 30 days after the Company publicly reports full-year 2025 results. Given the preliminary stage of the litigation and inherent uncertainties in light of the forthcoming further amended complaint, we are unable at this time to form a view as to whether an adverse outcome is either probable or remote or to estimate the amount or range of potential loss in the event of an adverse outcome.

Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Schedule of Accounts Receivables and Unbilled Revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Revenue from Contract with Customer [Abstract]
Accounts receivable (Billed services)	$ 1,512,822	$ 1,517,217
Allowance for credit losses	(41,518)	(42,319)
Accounts receivable (net)	1,471,304	1,474,898
Unbilled revenue (Unbilled services)	1,090,950	1,096,592
Accounts receivable and unbilled revenue, net	$ 2,562,254	$ 2,571,490

Goodwill - Schedule of Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Goodwill [Roll Forward]
Opening balance	$ 8,731,689	$ 9,051,410
Prior period acquisition	0	5,109
Impairment	0	(364,248)
Foreign exchange movement	(5,909)	39,418
Closing balance	$ 8,725,780	$ 8,731,689

- Definition

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

+ References

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

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-8

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 41
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479303/805-10-55-41

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 740
-Name Accounting Standards Codification
-Section 55
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478064/805-740-55-13

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 39
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479303/805-10-55-39

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 49
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-49

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 852
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481372/852-10-55-10

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(15))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482598/350-20-45-1

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482573/350-20-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 14: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479581/805-30-50-4

+ Details

- Definition

+ References + Details

Share based awards

3 Months Ended

Mar. 31, 2026

Share-Based Payment Arrangement [Abstract]

Share based awards

Share Options

The following table summarizes option activity for the three months ended March 31, 2026:


	Options Outstanding Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life
Outstanding at December 31, 2025	639,184	$	179.12	3.90
Granted	—	—
Exercised	(10,174)	$	106.64
Expired	(31,560)	$	116.06
Outstanding at March 31, 2026	597,450	$	183.69	3.92
Exercisable at March 31, 2026	517,846	$	178.31	3.58

The Company issues ordinary shares for all options exercised. The total amount of fully vested share options which remained outstanding at March 31, 2026 was 517,846. Fully vested share options at March 31, 2026 have an average remaining contractual term of 3.58 years and an average exercise price of $178.31.

Fair value of Stock Options Assumptions

There were no options granted during the three months ended March 31, 2026. The weighted average fair value of options granted during March 31, 2025 was calculated using the Black-Scholes option pricing model. The weighted average grant date fair values and assumptions used were as follows:


	Three Months Ended
	March 31, 2026		March 31, 2025
Weighted average grant date fair value	$	—	$	64.42
Assumptions:
Expected volatility	—		35		%
Dividend yield	—		—		%
Risk-free interest rate	—		4.00		%
Expected life	—		4.4 years

Expected volatility is based on the historical volatility of our common stock over a period equal to the expected term of the options; the expected life represents the weighted average period of time that options granted are expected to be outstanding given consideration to vesting schedules and our historical experience of past vesting and termination patterns. The risk-free rate is based on the U.S. government zero-coupon bonds yield curve in effect at time of the grant for periods corresponding with the expected life of the option.

Restricted Share Units and Performance Share Units

On April 23, 2013, the Company adopted the 2013 Employees Restricted Share Unit Plan (the “2013 RSU Plan”) pursuant to which the Compensation and Organization Committee of the Company's Board of Directors may select any employee, or any Director holding a salaried office or employment with the Company, or a Subsidiary to receive an award under the plan. On May 11, 2015, the 2013 RSU Plan was amended and restated in order to increase the number of shares that can be issued under the RSU Plan by 2.5 million shares. Further, on October 25, 2024, the 2013 RSU Plan was amended and restated effective as of November 6, 2024 in order to increase the number of ordinary shares that can be issued under the 2013 RSU Plan by a further 2.5 million shares. Accordingly, an aggregate of 6.6 million ordinary shares have been reserved for issuance under the 2013 RSU Plan. The shares are awarded at par value and vest over a service period. Awards under the 2013 RSU Plan may be settled in cash or shares at the option of the Company. No awards may be granted under the 2013 RSU Plan after November 6, 2034.

On April 30 2019, the Company approved the 2019 Consultants and Directors Restricted Share Unit Plan (the “2019 Consultants RSU Plan”), which was effective as of May 16, 2019, pursuant to which the Compensation and Organization Committee of the Company’s Board of Directors may select any consultant, adviser or Outside 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 Outside Directors vest over twelve months. No awards may be granted under the 2019 Consultants RSU Plan after May 16, 2029.

The following table summarizes RSU and PSU activity for the three months ended March 31, 2026:


	PSU Outstanding Number of Shares	PSU Weighted Average Grant Date Fair Value		RSU Outstanding Number of Shares	RSU Weighted Average Grant Date Fair Value
Outstanding at December 31, 2025	16,474	$	185.18	1,476,169	$	162.53
Granted	—	—		—	—
Shares vested	—	—		(24,039)	$	179.56
Forfeited	(6,177)	$	185.18	(22,944)	$	172.47
Outstanding at March 31, 2026	10,297	$	185.18	1,429,186	$	162.09

The fair value of PSUs vested for the three months ended March 31, 2026 were nil (March 31, 2025: $1.9 million).

The fair value of RSUs vested for the three months ended March 31, 2026 totaled $4.3 million (March 31, 2025: $5.0 million).

The PSUs vest based on service and specified EPS targets over the periods 2023 - 2025, 2024 - 2026, and 2025 - 2027. Depending on the amount of EPS from 2023 to 2027, up to an additional 47,779 PSUs may also be granted.

Stock compensation expense

Stock compensation expense for the three months ended March 31, 2026 and March 31, 2025 has been allocated as follows:


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Direct costs	$	18,296	$	5,381
Selling, general and administrative	8,686		6,913
Total	$	26,982	$	12,294

Fair value measurements (Tables)

3 Months Ended

Mar. 31, 2026

Fair Value Disclosures [Abstract]

Schedule of Assets Measured at Fair Value on a Recurring Basis

As of March 31, 2026, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows:


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
	(in thousands)
Assets:

Investments in equity1	$	—	$	—	$	—	$	94,466	$	94,466

Total assets	$	—	$	—	$	—	$	94,466	$	94,466

As of December 31, 2025, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows:


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
	(in thousands)
Assets:

Investments in equity1	$	—	$	—	$	—	$	79,550	$	79,550
Total assets	$	—	$	—	$	—	$	79,550	$	79,550

Schedule of Liabilities Measured at Fair Value on a Recurring Basis

As of March 31, 2026, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows:


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
	(in thousands)
Assets:

Investments in equity1	$	—	$	—	$	—	$	94,466	$	94,466

Total assets	$	—	$	—	$	—	$	94,466	$	94,466

As of December 31, 2025, the fair value of the major classes of the Company's assets and liabilities measured at fair value on a recurring basis were as follows:


	Level 1		Level 2		Level 3		Investments Measured at Net Asset Value		Total
	(in thousands)
Assets:

Investments in equity1	$	—	$	—	$	—	$	79,550	$	79,550
Total assets	$	—	$	—	$	—	$	79,550	$	79,550

Goodwill

3 Months Ended

Mar. 31, 2026

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill

The change in the carrying amount of goodwill between December 31, 2025 and March 31, 2026 is as follows:



	Three Months Ended		Year Ended
	March 31, 2026		December 31, 2025
	(in thousands)
Opening balance	$	8,731,689	$	9,051,410

Prior period acquisition	—		5,109
Impairment	—		(364,248)
Foreign exchange movement	(5,909)		39,418
Closing balance	$	8,725,780	$	8,731,689

There were no impairment charges during the three months ended March 31, 2026 (during the year ended December 31, 2025: $364.2 million related to the Company's Data Solutions reporting unit).

- Definition

The entire disclosure for goodwill.

+ References + Details

Share based awards - Schedule of Stock Option Activity (Details) - Employee Stock Option - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Options Outstanding Number of Shares
Beginning balance (in shares)	639,184
Granted (in shares)	0
Exercised (in shares)	(10,174)
Expired (in shares)	(31,560)
Ending balance (in shares)	597,450	639,184
Exercisable at end of period (in shares)	517,846
Weighted Average Exercise Price
Beginning balance (in USD per share)	$ 179.12
Granted (in USD per share)	0
Exercised (in USD per share)	106.64
Expired (in USD per share)	116.06
Ending balance (in USD per share)	183.69	$ 179.12
Exercisable at end of period (in USD per share)	$ 178.31
Weighted Average Remaining Contractual Life
Weighted average contractual term of options outstanding	3 years 11 months 1 day	3 years 10 months 24 days
Weighted average contractual term of options exercisable	3 years 6 months 29 days

Restructuring - Schedule of Details of Movement in Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Restructuring Reserve [Roll Forward]
Opening provision	$ 12,525	$ 31,474
Charge during the period	10,076	75,386
Utilization	(7,512)	(94,335)
Closing provision	$ 15,089	$ 12,525

- Definition

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ References + Details

Share based awards - Schedule of Weighted Average Fair Values and Assumptions Used (Details) - Employee Stock Option - $ / shares	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (USD per share)	$ 0	$ 64.42
Assumptions:
Expected volatility	0.00%	35.00%
Dividend yield	0.00%	0.00%
Risk-free interest rate	0.00%	4.00%
Expected life		4 years 4 months 24 days

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (l)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480483/718-10-35-1D

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480483/718-10-35-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(02)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(03)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(02)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(03)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Operating leases - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Lessee, Lease, Description [Line Items]
Total lease cost	$ 10,401	$ 10,431
Right-of-use assets obtained in exchange for lease obligations	$ 5,000	7,000
Weighted average remaining lease term	5 years 8 months 23 days		5 years 11 months 15 days
Weighted average discount rate	3.84%		4.04%
Operating lease liabilities, current	$ 35,200		$ 36,300
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities		Other Liabilities
Operating lease liabilities, non-current	$ 111,329	117,100	$ 117,122
Selling, general and administration costs
Lessee, Lease, Description [Line Items]
Total lease cost	8,700	8,900
Direct costs
Lessee, Lease, Description [Line Items]
Total lease cost	$ 1,700	$ 1,500

Operating leases - Schedule of Future Minimum Lease Payments (Details) $ in Thousands	Mar. 31, 2026 USD ($)
Leases [Abstract]
Year 1	$ 40,077
Year 2	35,506
Year 3	26,223
Year 4	19,239
Year 5	10,721
Thereafter	30,662
Total future minimum lease payments	162,428
Lease imputed interest	(15,899)
Total	$ 146,529

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Current assets:
Cash and cash equivalents	$ 765,164	$ 647,295
Accounts receivable, net of allowance for credit losses	1,471,304	1,474,898
Unbilled revenue	1,090,950	1,096,592
Other receivables	91,804	116,750
Prepayments and other current assets	144,150	105,316
Income taxes receivable	43,965	60,824
Total current assets	3,607,337	3,501,675
Non-current assets:
Property, plant and equipment, net	384,750	395,724
Goodwill	8,725,780	8,731,689
Intangible assets, net	3,196,704	3,247,118
Operating right-of-use assets	123,606	128,948
Other receivables	74,442	75,707
Deferred tax asset	109,437	106,871
Investments in equity	96,966	82,050
Total Assets	16,319,022	16,269,782
Current liabilities:
Accounts payable	99,846	192,117
Unearned revenue	1,547,527	1,550,471
Other liabilities	964,790	904,826
Income taxes payable	27,611	18,999
Current bank credit lines, loan facilities and notes	529,762	529,762
Total current liabilities	3,169,536	3,196,175
Non-current liabilities:
Non-current bank credit lines, loan facilities and notes, net	2,866,695	2,872,616
Lease liabilities	111,329	117,122
Non-current other liabilities	72,337	72,807
Non-current income taxes payable	104,509	103,251
Deferred tax liability	694,320	714,427
Commitments and contingencies	0	0
Total Liabilities	7,018,726	7,076,398
Shareholders' Equity:
Ordinary shares, issued and outstanding	6,307	6,305
Additional paid‑in capital	7,160,610	7,131,956
Other undenominated capital	1,606	1,606
Accumulated other comprehensive loss	(95,029)	(68,534)
Retained earnings	2,226,802	2,122,051
Total Shareholders' Equity	9,300,296	9,193,384
Total Liabilities and Shareholders' Equity	$ 16,319,022	$ 16,269,782

Bank credit lines, loan facilities and notes - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended					12 Months Ended
	May 08, 2024	Mar. 31, 2026	Dec. 31, 2025	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2025	Nov. 26, 2025	May 02, 2023	Jul. 01, 2021
Debt Instrument [Line Items]
Drawdown of credit lines and loan facilities		$ 0				$ 50,000
Repayment		(7,440)				(57,440)
Long-term debt at fair value		$ 3,432,100	$ 3,500,100				$ 3,500,100
The New Notes \| Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 2,000,000
Debt discount paid	6,800
Senior Secured Notes (the "2027 Notes") \| Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 750,000
Debt instrument, interest rate (in percent)	5.809%	5.809%	5.809%				5.809%
Debt instrument, discount rate on underwriting (in percent)	0.00250
Senior Secured Notes (the "2029 Notes") \| Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 750,000
Debt instrument, interest rate (in percent)	5.849%	5.849%	5.849%				5.849%
Debt instrument, discount rate on underwriting (in percent)	0.00350
Senior Secured Notes (the "2034 Notes") \| Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 500,000
Debt instrument, interest rate (in percent)	6.00%	6.00%	6.00%				6.00%
Debt discount paid	$ 500
Debt instrument, discount rate on underwriting (in percent)	0.00450
Debt instrument, redemption price, percentage of principal amount redeemed	99.896%
Senior Secured Term Loan
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)							2.00%
Senior Secured Term Loan \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)							0.50%
Senior Secured Term Loan \| Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, principal amount										$ 5,515,000
Debt instrument, interest rate (in percent)		5.70%	5.672%				5.672%			1.00%
Senior Secured Revolving Loan
Debt Instrument [Line Items]
Long-term debt, term								7 years		5 years
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BB Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		1.35%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BB+ Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		1.00%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BBB- Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		0.75%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BBB Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		0.55%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BBB+ Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		0.40%
Senior Secured Revolving Loan \| Minimum \| Variable rate component one \| Base rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		0.00%
Senior Secured Revolving Loan \| Maximum \| Variable rate component one \| Base rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		0.35%
Senior Secured Revolving Loan \| Senior Secured Revolving Loan \| Senior Secured Revolving Loan
Debt Instrument [Line Items]
Debt instrument, maximum borrowing capacity									$ 500,000	$ 300,000
Drawdown of credit lines and loan facilities		$ 0	$ 0	$ 0	$ 0	50,000	$ 50,000
Repayment		0	0	0	0	(50,000)	(50,000)
Long-term debt		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Senior Secured Credit Facility And Senior Secured Notes \| Senior Secured Term Loan
Debt Instrument [Line Items]
Debt discount paid										27,600
Senior Secured Notes \| Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, principal amount										$ 500,000
Debt instrument, interest rate (in percent)										2.875%

Share based awards - Schedule of Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	$ 26,982	$ 12,294
Direct costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	18,296	5,381
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	$ 8,686	$ 6,913

- Definition

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

+ References

+ Details

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Income Statement [Abstract]
Revenue	$ 2,033,999	$ 2,015,320
Costs and expenses:
Direct costs	1,556,073	1,449,258
Selling, general and administrative	200,598	198,384
Depreciation and amortization	90,331	95,958
Transaction and integration related	3,187	5,404
Restructuring	10,076	39,346
Total costs and expenses	1,860,265	1,788,350
Income from operations	173,734	226,970
Interest income	1,821	1,802
Interest expense	(47,997)	(47,609)
Income before income tax expense	127,558	181,163
Income tax expense	(22,807)	(20,351)
Net income	$ 104,751	$ 160,812
Net income per ordinary share:
Basic (in USD per share)	$ 1.37	$ 2.00
Diluted (in USD per share)	$ 1.36	$ 1.99
Weighted average number of ordinary shares outstanding:
Basic (in shares)	76,579,420	80,552,734
Diluted (in shares)	77,261,813	80,924,355

Restructuring

3 Months Ended

Mar. 31, 2026

Restructuring and Related Activities [Abstract]

Restructuring

In the three months ended March 31, 2026, a $10.1 million restructuring charge (March 31, 2025: $39.3 million) was recorded in the Condensed Consolidated Statement of Operations under a restructuring plan reflecting a workforce reduction.


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Restructuring charges	$	10,076	$	39,346
Total	$	10,076	$	39,346

At March 31, 2026, a total liability of $15.1 million (December 31, 2025: $12.5 million) was recorded on the Condensed Consolidated Balance Sheet relating to restructuring activities.


	Three Months Ended		Year Ended
	March 31, 2026		December 31, 2025
	(in thousands)
Opening provision	$	12,525	$	31,474
Charge during the period	10,076		75,386
Utilization	(7,512)		(94,335)
Closing provision	$	15,089	$	12,525

The closing provision as at March 31, 2026 of $15.1 million (December 31, 2025: $12.5 million) reflects:

(1) $12.0 million (December 31, 2025: $9.1 million) of personnel related liabilities as a result of the workforce reduction; all of which have been classified as short-term within Other Liabilities, and

(2) $3.1 million (December 31, 2025: $3.4 million) of facilities related liabilities of which $1.2 million (December 31, 2025: $1.3 million) is included within Other Liabilities and $1.9 million (December 31, 2025: $2.1 million) is included within Non-Current Other Liabilities.

Business Segment and Geographical Information - Schedule of Distribution of Income from Operations by Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Income from operations	$ 173,734	$ 226,970
Amortization of intangible assets	(50,300)	(58,900)
Operating Segments
Segment Reporting Information [Line Items]
Income from operations	224,013	285,916
Amortization of intangible assets	(50,279)	(58,946)
Ireland
Segment Reporting Information [Line Items]
Income from operations	125,204	163,378
Rest of Europe
Segment Reporting Information [Line Items]
Income from operations	31,725	36,843
U.S.
Segment Reporting Information [Line Items]
Income from operations	49,698	68,487
Rest of World
Segment Reporting Information [Line Items]
Income from operations	$ 17,386	$ 17,208

The net result for the period of deducting operating expenses from operating revenues.

+ References

+ Details

Intangible assets

3 Months Ended

Mar. 31, 2026

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible assets

The carrying amount of intangible assets as of March 31, 2026 and December 31, 2025 is as follows:



	March 31, 2026		December 31, 2025
	(in thousands)
Cost
Customer relationships	$	4,133,727	$	4,134,478
Order backlog	545,727		546,054
Trade names & brands	204,700		204,721
Patient database	170,484		170,511
Technology assets	151,582		151,754



Total cost	5,206,220		5,207,518
Accumulated amortization	(2,009,516)		(1,873,663)
Impairment	—		(86,737)
Net book value	$	3,196,704	$	3,247,118

In the three months ended March 31, 2026, the amortization expense recognized by the Company was $50.3 million (three months ended March 31, 2025: $58.9 million).

There were no additions to intangible assets during the three months ended March 31, 2026.

Business Segment and Geographical Information

3 Months Ended

Mar. 31, 2026

Segment Reporting [Abstract]

Business Segment and Geographical Information

The Company is a CRO providing outsourced services on a global basis to pharmaceutical, biotechnology, medical device and government and public health organizations. It specializes in the strategic development, management and analysis of programs that support all stages of the clinical development process - from compound selection to Phase I-IV clinical studies. The Company has the expertise and capability to conduct clinical trials in most major therapeutic areas on a global basis and has the operational flexibility to provide development services on a stand-alone basis or as part of an integrated "full-service" or “blended-service” solution. The Company has expanded through internal growth, together with a number of strategic acquisitions to enhance its expertise and capabilities in certain areas of the clinical development process.

The Company operates as one reportable segment, which is the provision of outsourced development services on a global basis to the pharmaceutical, biotechnology and medical devices industries. During the three months ended March 31, 2026, the Company determined that the Chief Operating Decision Maker (“CODM”) was comprised of the Chief Executive Officer and the Chief Financial Officer. As the Company is managed on a consolidated basis, the CODM evaluates performance and allocates resources based on consolidated net income. The CODM uses consolidated net income, as reported on the Consolidated Statements of Operations, to evaluate income generated from segment assets and for decisions related to the deployment of operating and capital resources. The measure of segment assets is reported on the Consolidated Balance Sheets as total consolidated assets.

The accounting policies of the reportable segment are the same as those described in ICON’s Annual Report on Form 20-F for the year ended December 31, 2025 (see Note 2 Summary of significant accounting policies). In the context of considerations around significant segment expenses, as the expense information that is regularly provided to the CODM is aligned with the respective consolidated expenses for direct costs and selling, general, and administrative expenses, as presented on the Condensed Consolidated Statement of Operations, such expense disclosures are not replicated here. Furthermore, as the Company consists of a single reportable segment, other quantitative disclosures, as required by Topic 280, are as presented on the Consolidated Statement of Operations.

Revenues are allocated to individual entities based on where the work is performed in accordance with the Company's global transfer pricing model. Revenues and income from operations in Ireland are a function of our global contracting model and the Group’s transfer pricing model.

ICON Clinical Research Limited and Accellacare Limited (collectively “ICON Ireland”) acts as the Group entrepreneur under the Company’s global transfer pricing model given its role in the development and management of the Group, its ownership of key intellectual property and customer relationships, its key role in the mitigation of risks faced by the Group and its responsibility for maintaining the Company’s global network. ICON Ireland enters into the majority of the Company’s customer contracts.

ICON Ireland remunerates other operating entities in the Group on the basis of an arm’s length return, in accordance with the 2022 OECD transfer pricing guidelines, for the services they perform in each of their local territories. The arm’s length return for each ICON entity is established to ensure that each of ICON Ireland and the ICON entities that are involved in the conduct of services for customers, earn an appropriate return having regard to their respective functions performed, assets owned, and risks assumed in these intercompany transactions. The arm’s length return is reviewed annually to ensure that it is market appropriate.

The geographic split of revenue disclosed for each region outside Ireland is the arm’s length revenue attributable to these entities. The residual revenues of the Group, once each ICON entity has been paid its respective intercompany service fee, generally fall to be retained by ICON Ireland. As such, revenues and income from operations in Ireland are a function of this global transfer pricing model and comprise revenues of the Group after deducting the arm’s length revenues attributable to the activities performed outside Ireland.

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

The geographical distribution of the Company’s segment measures for the three months ended March 31, 2026 and March 31, 2025 and as at March 31, 2026 and December 31, 2025 is as follows:

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


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Ireland	$	761,360	$	734,340
Rest of Europe	390,847		375,865
U.S.	642,602		672,424
Rest of World	239,190		232,691
Total	$	2,033,999	$	2,015,320

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


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Ireland	$	125,204	$	163,378
Rest of Europe	31,725		36,843
U.S.	49,698		68,487
Rest of World	17,386		17,208
Sub-total	$	224,013	$	285,916
Amortization of intangible assets	(50,279)		(58,946)
Total	$	173,734	$	226,970

c) The distribution of long-lived assets (property, plant and equipment and operating right-of-use assets), net, by geographical area was as follows:



	March 31, 2026		December 31, 2025
	(in thousands)
Ireland	$	243,396	$	250,566
Rest of Europe	90,056		94,920
U.S.	119,604		122,896
Rest of World	55,300		56,290
Total	$	508,356	$	524,672

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

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

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-31

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-15

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 48
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

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

Reference 11: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 12: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 13: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 14: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 15: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 16: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 17: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-34

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26C

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26B

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-40

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/280/tableOfContent

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-41

+ Details

Income taxes - Schedule of Components of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Income Tax Disclosure [Abstract]
Income tax expense	$ 22,807	$ 20,351

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-4

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-21

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 231
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-9

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.7)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-8

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

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Subparagraph (a)
-SubTopic 20
-Topic 740
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482659/740-20-45-2

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h))
-SubTopic 10
-Topic 235
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

+ Details

Share capital (Tables)

3 Months Ended

Mar. 31, 2026

Equity [Abstract]

Schedule of Shares Redeemed Under Buyback Program


	Total number of shares purchased	Average price paid per share	Total number of shares purchased as part of publicly announced program	Approximate dollar value of shares that may yet be purchased under the program (in millions)
March 3/12/2025 - 3/19/2025	1,360,537	$183.75	1,360,537	$750.0
June 6/13/2025 - 6/23/2025	1,717,181	$145.59	1,717,181	$500.0
August 8/15/2025 - 8/20/2025	560,100	$178.20	560,100	$900.2
September 9/10/2025 - 9/19/2025	866,512	$173.33	866,512	$750.0
	4,504,330	$166.51	4,504,330

Bank credit lines, loan facilities and notes (Tables)

3 Months Ended

Mar. 31, 2026

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

The Company had the following debt outstanding as of March 31, 2026 and December 31, 2025:


		Interest rate as of				Principal amount
	Maturity Date	March 31, 2026		December 31, 2025		March 31, 2026		December 31, 2025
						(in thousands)
Senior Secured Term Loan	July 2028	5.700	%	5.672	%	$	909,248	$	916,688
Senior Secured Notes (the "2026 Notes")	July 2026	2.875	%	2.875	%	500,000		500,000

Senior Secured Notes (the "2027 Notes")*	May 2027	5.809	%	5.809	%	750,000		750,000
Senior Secured Notes (the "2029 Notes")*	May 2029	5.849	%	5.849	%	750,000		750,000
Senior Secured Notes (the "2034 Notes")*	May 2034	6.000	%	6.000	%	500,000		500,000
Total debt						3,409,248		3,416,688
Less current portion of debt						(529,762)		(529,762)
Total long-term debt						2,879,486		2,886,926
Less debt issuance costs and debt discount						(12,791)		(14,310)
Total long-term debt, net						$	2,866,695	$	2,872,616

*Issued May 8, 2024


	Drawdown		Repayment		Closing Balance
	(in thousands)

Quarter 1, 2025	$	50,000	$	(50,000)	$	—
Quarter 2, 2025	—		—		—
Quarter 3, 2025	—		—		—
Quarter 4, 2025	—		—		—
Total drawdown / (repayment) in 2025	50,000		(50,000)		—
Quarter 1, 2026	—		—		—
Total drawdown / (repayment) in 2026	$	—	$	—	$	—

Schedule of Contractual Maturities of Debt

As of March 31, 2026, the contractual maturities of the Company's debt obligations were as follows:


Contractual maturities of debt	(in thousands)
2026 (remaining)		$	522,322
2027		779,762
2028		857,164
2029		750,000
2030 and thereafter		500,000
Total		$	3,409,248

Schedule of Principal Payments on Debt Instrument

Principal repayments on the senior secured term loan, comprising mandatory repayments, during the three months ended March 31, 2026 and year ended December 31, 2025 were as follows:


Principal repayments	(in thousands)
Quarter 1, 2025		$	(7,440)
Quarter 2, 2025		(7,441)
Quarter 3, 2025		(7,440)
Quarter 4, 2025		(7,441)
Total repayments in 2025		$	(29,762)
Quarter 1, 2026		(7,440)


Total repayments in 2026		$	(7,440)

Business Segment and Geographical Information - Schedule of Distribution of Long-Lived Assets, Net by Geographic Area (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Segment Reporting Information [Line Items]
Long-lived assets	$ 508,356	$ 524,672
Ireland
Segment Reporting Information [Line Items]
Long-lived assets	243,396	250,566
Rest of Europe
Segment Reporting Information [Line Items]
Long-lived assets	90,056	94,920
U.S.
Segment Reporting Information [Line Items]
Long-lived assets	119,604	122,896
Rest of World
Segment Reporting Information [Line Items]
Long-lived assets	$ 55,300	$ 56,290

Bank credit lines, loan facilities and notes - Schedule of Movement on Debt Instrument (Details) - USD ($) $ in Thousands	3 Months Ended					12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2025
Debt Instrument [Line Items]
Drawdown	$ 0				$ 50,000
Repayment	(7,440)				(57,440)
Senior Secured Revolving Loan \| Senior Secured Revolving Loan \| Senior Secured Revolving Loan
Debt Instrument [Line Items]
Drawdown	0	$ 0	$ 0	$ 0	50,000	$ 50,000
Repayment	0	0	0	0	(50,000)	(50,000)
Closing Balance	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0

- Definition

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

+ References

+ Details

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-SubTopic 10
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477314/942-235-S99-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-4

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-3

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482949/835-30-55-8

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69B

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69C

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1D
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1D

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-4

+ Details

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

3 Months Ended

Mar. 31, 2026

Revenue from Contract with Customer [Abstract]

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

Revenue

Revenue disaggregated by customer concentration is as follows:


	Three Months Ended
	March 31, 2026		March 31, 2025



Clients 1-5	$	507,997	$	496,118
Clients 6-10	310,359		309,562
Clients 11-25	469,397		475,299
Other	746,246		734,341
Total	$	2,033,999	$	2,015,320

There was no revenue from individual customers greater than 10% of consolidated revenue in the respective periods.

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

Accounts receivables and unbilled revenue are as follows:


	March 31, 2026		December 31, 2025
	(in thousands)
Accounts receivable (Billed services)	$	1,512,822	$	1,517,217
Allowance for credit losses	(41,518)		(42,319)
Accounts receivable (net)	1,471,304		1,474,898
Unbilled revenue (Unbilled services)	1,090,950		1,096,592
Accounts receivable and unbilled revenue, net	$	2,562,254	$	2,571,490

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


	March 31, 2026		December 31, 2025		$ Change		% Change
	(in thousands, except percentages)
Unbilled revenue (Unbilled services)	$	1,090,950	$	1,096,592	$	(5,642)	(0.5)	%
Unearned revenue (Payments on account)	(1,547,527)		(1,550,471)		2,944		(0.2)	%

- Definition

+ References

+ Details

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Cash flows provided by operating activities:
Net income	$ 104,751	$ 160,812
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	90,331	95,958
Reduction in carrying value of operating right-of-use assets	8,980	9,384
Amortization of financing costs and debt discount	1,519	1,480
Stock compensation expense	27,574	12,359
Deferred tax benefit	(22,861)	(25,014)
Unrealized foreign exchange movements	(13,076)	18,081
Other non-cash items	224	8,240
Changes in operating assets and liabilities:
Accounts receivable	(3,188)	481
Unbilled revenue	6,766	(66,376)
Unearned revenue	(1,967)	23,463
Other net assets	(32,047)	29,372
Net cash provided by operating activities	167,006	268,240
Cash flows used in investing activities:
Purchase of property, plant and equipment	(30,771)	(28,907)
Purchase of subsidiary undertakings (net of cash acquired)	0	(2,537)
Proceeds from investments in equity	263	103
Purchase of investments in equity	(8,930)	(5,941)
Net cash used in investing activities	(39,438)	(37,282)
Cash flows used in financing activities:
Drawdown of credit lines and loan facilities	0	50,000
Repayment of credit lines and loan facilities	(7,440)	(57,440)
Proceeds from exercise of equity compensation	1,087	4,763
Share issue costs	(5)	(5)
Repurchase of ordinary shares	0	(250,000)
Share repurchase costs	0	(150)
Net cash used in financing activities	(6,358)	(252,832)
Effect of exchange rate movements on cash	(3,341)	9,787
Net increase / (decrease) in cash and cash equivalents	117,869	(12,087)
Cash and cash equivalents at beginning of period	647,295	538,785	$ 538,785
Cash and cash equivalents at end of period	$ 765,164	$ 526,698	$ 647,295

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Ordinary Shares	Additional Paid-in Capital	Other Undenominated Capital	Accumulated Other Comprehensive Loss	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2024		80,756,860
Beginning balance at Dec. 31, 2024	$ 9,441,354	$ 6,586	$ 7,020,231	$ 1,304	$ (229,929)	$ 2,643,162
Comprehensive income (net of tax):
Net income	160,812					160,812
Currency translation adjustment	59,158				59,158
Movement on cash flow hedge	(2,420)				(2,420)
Total comprehensive income	217,550
Exercise of share options (in shares)		40,883
Exercise of share options	4,762	$ 3	4,759
Issue of restricted share units / performance share units (in shares)		27,046
Issue of restricted share units / performance share units	1	$ 1
Share based compensation expense	12,359		12,359
Share issuance costs	(5)		(5)
Repurchase of ordinary shares (in shares)		(1,360,537)
Repurchase of ordinary shares	(250,000)	$ (85)		85		(250,000)
Share repurchase costs	(150)					(150)
Ending balance (in shares) at Mar. 31, 2025		79,464,252
Ending balance at Mar. 31, 2025	9,425,871	$ 6,505	7,037,344	1,389	(173,191)	2,553,824
Beginning balance (in shares) at Dec. 31, 2024		80,756,860
Beginning balance at Dec. 31, 2024	$ 9,441,354	$ 6,586	7,020,231	1,304	(229,929)	2,643,162
Comprehensive income (net of tax):
Repurchase of ordinary shares (in shares)	(4,504,330)
Repurchase of ordinary shares	$ (750,000)
Ending balance (in shares) at Dec. 31, 2025	76,567,325	76,567,325
Ending balance at Dec. 31, 2025	$ 9,193,384	$ 6,305	7,131,956	1,606	(68,534)	2,122,051
Beginning balance (in shares) at Dec. 31, 2024		80,756,860
Beginning balance at Dec. 31, 2024	$ 9,441,354	$ 6,586	7,020,231	1,304	(229,929)	2,643,162
Comprehensive income (net of tax):
Repurchase of ordinary shares (in shares)	(4,504,330)
Ending balance (in shares) at Mar. 31, 2026	76,601,538	76,601,538
Ending balance at Mar. 31, 2026	$ 9,300,296	$ 6,307	7,160,610	1,606	(95,029)	2,226,802
Beginning balance (in shares) at Dec. 31, 2025	76,567,325	76,567,325
Beginning balance at Dec. 31, 2025	$ 9,193,384	$ 6,305	7,131,956	1,606	(68,534)	2,122,051
Comprehensive income (net of tax):
Net income	104,751					104,751
Currency translation adjustment	(26,495)				(26,495)
Movement on cash flow hedge	0
Total comprehensive income	78,256
Exercise of share options (in shares)		10,174
Exercise of share options	1,086	$ 1	1,085
Issue of restricted share units / performance share units (in shares)		24,039
Issue of restricted share units / performance share units	1	$ 1
Share based compensation expense	27,574		27,574
Share issuance costs	$ (5)		(5)
Repurchase of ordinary shares (in shares)	0
Ending balance (in shares) at Mar. 31, 2026	76,601,538	76,601,538
Ending balance at Mar. 31, 2026	$ 9,300,296	$ 6,307	$ 7,160,610	$ 1,606	$ (95,029)	$ 2,226,802

Business Segment and Geographical Information - Narrative (Details)	3 Months Ended
	Mar. 31, 2026 reportingSegment
Segment Reporting [Abstract]
Number of operating segments	1
Number of reportable segments	1

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - € / shares	Mar. 31, 2026	Dec. 31, 2025
Statement of Financial Position [Abstract]
Ordinary shares, par value (in EUR cents per share)	€ 0.06	€ 0.06
Ordinary shares, shares authorized (in shares)	100,000,000	100,000,000
Ordinary shares, shares issued (in shares)	76,601,538	76,567,325
Ordinary shares, shares outstanding (in shares)	76,601,538	76,567,325

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

3 Months Ended

Mar. 31, 2026

Revenue from Contract with Customer [Abstract]

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

Accounts receivables and unbilled revenue are as follows:


	March 31, 2026		December 31, 2025
	(in thousands)
Accounts receivable (Billed services)	$	1,512,822	$	1,517,217
Allowance for credit losses	(41,518)		(42,319)
Accounts receivable (net)	1,471,304		1,474,898
Unbilled revenue (Unbilled services)	1,090,950		1,096,592
Accounts receivable and unbilled revenue, net	$	2,562,254	$	2,571,490

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


	March 31, 2026		December 31, 2025		$ Change		% Change
	(in thousands, except percentages)
Unbilled revenue (Unbilled services)	$	1,090,950	$	1,096,592	$	(5,642)	(0.5)	%
Unearned revenue (Payments on account)	(1,547,527)		(1,550,471)		2,944		(0.2)	%

Summary of significant accounting policies (Tables)

3 Months Ended

Mar. 31, 2026

Accounting Policies [Abstract]

Schedule of Estimated Useful Lives

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


			Estimated Useful Life
Customer relationships			8 - 23 years
Order backlog			3 - 5 years


Technology assets			5 years

The carrying amount of intangible assets as of March 31, 2026 and December 31, 2025 is as follows:



	March 31, 2026		December 31, 2025
	(in thousands)
Cost
Customer relationships	$	4,133,727	$	4,134,478
Order backlog	545,727		546,054
Trade names & brands	204,700		204,721
Patient database	170,484		170,511
Technology assets	151,582		151,754



Total cost	5,206,220		5,207,518
Accumulated amortization	(2,009,516)		(1,873,663)
Impairment	—		(86,737)
Net book value	$	3,196,704	$	3,247,118

Income taxes

3 Months Ended

Mar. 31, 2026

Income Tax Disclosure [Abstract]

Income taxes

Income taxes recognized during the three months ended March 31, 2026 and March 31, 2025, comprise:


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Income tax expense	$	22,807	$	20,351
Total	$	22,807	$	20,351

In the normal course of business, the Company provides for uncertain tax positions and the related interest and adjusts its unrecognized tax benefits and accrued interest accordingly. As at March 31, 2026 the Company maintains a $104.5 million liability (December 31, 2025: $103.3 million) for unrecognized tax benefits, which is comprised of $80.4 million (December 31, 2025: $81.0 million) inclusive of $24.1 million (December 31, 2025: $22.3 million) for interest and penalties related to such items. The Company recognizes interest accrued on unrecognized tax benefits as an additional income tax expense.

The Company has analyzed the filing positions in all of the significant jurisdictions where it is required to file income tax returns, as well as open tax years in these jurisdictions. The only periods subject to audit by the major tax jurisdictions where the Company does business are the 2015 through 2025 tax years. During such audits, local tax authorities may challenge the positions taken by us in our tax returns.

- Definition

The entire disclosure for income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477617/942-740-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478822/944-740-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 231
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12C

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12B

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477891/740-270-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-13

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/740/tableOfContent

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-14

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-21

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-17

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482603/740-30-50-2

+ Details

Revenue (Tables)

3 Months Ended

Mar. 31, 2026

Revenue from Contract with Customer [Abstract]

Schedule of Disaggregation of Revenue

Revenue disaggregated by customer concentration is as follows:


	Three Months Ended
	March 31, 2026		March 31, 2025



Clients 1-5	$	507,997	$	496,118
Clients 6-10	310,359		309,562
Clients 11-25	469,397		475,299
Other	746,246		734,341
Total	$	2,033,999	$	2,015,320

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Net Income (Loss) Attributable to Parent [Abstract]
Net income	$ 104,751	$ 160,812
Other comprehensive (loss) / income, net of tax:
Currency translation adjustment	(26,495)	59,158
Movement on cash flow hedge	0	(2,420)
Total comprehensive income	$ 78,256	$ 217,550

- Definition

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

+ References + Details

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478671/942-235-S50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477314/942-235-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 105
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 9
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479343/105-10-65-9

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 17
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480336/718-10-65-17

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-9

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-8

Reference 18: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 830
-Name Accounting Standards Codification
-Section 55
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479168/946-830-55-11

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 205
-Name Accounting Standards Codification
-Section 45
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478009/946-205-45-3

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479105/946-220-45-7

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(16))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(1)(d))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 19
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481231/810-10-45-19

Reference 25: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482765/220-10-50-6

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 27: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 35: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 36: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483499/205-20-50-7

Reference 37: http://www.xbrl.org/2003/role/exampleRef
-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 4J
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481175/810-10-55-4J

Reference 38: http://www.xbrl.org/2003/role/exampleRef
-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 4K
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481175/810-10-55-4K

Reference 39: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1A

Reference 40: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1B

Reference 41: http://www.xbrl.org/2003/role/disclosureRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-2

Reference 42: http://www.xbrl.org/2003/role/disclosureRef
-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481203/810-10-50-1A

Reference 43: http://www.xbrl.org/2003/role/disclosureRef
-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481203/810-10-50-1A

Reference 44: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 65
-Paragraph 4
-Subparagraph (f)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481538/470-20-65-4

+ Details

Operating leases (Tables)

3 Months Ended

Mar. 31, 2026

Leases [Abstract]

Schedule of Lease Costs

Lease costs recorded under operating leases for three months ended March 31, 2026 and March 31, 2025 were as follows:


	Three Months Ended
	March 31, 2026		March 31, 2025
	(in thousands)
Operating lease costs	$	10,780	$	11,199
Income from sub-leases	(379)		(768)
Net operating lease costs	$	10,401	$	10,431

Schedule of Future Minimum Lease Payments

Future minimum lease payments under non-cancelable leases as of March 31, 2026 were as follows:



	(in thousands)
Year 1		$	40,077
Year 2		35,506
Year 3		26,223
Year 4		19,239
Year 5		10,721
Thereafter		30,662
Total future minimum lease payments		162,428
Lease imputed interest		(15,899)
Total		$	146,529

Share capital - Schedule of Shares Redeemed Under Buyback Program (Details) - USD ($) $ / shares in Units, $ in Millions					3 Months Ended	12 Months Ended	15 Months Ended
	Sep. 19, 2025	Aug. 20, 2025	Jun. 23, 2025	Mar. 19, 2025	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2026
Equity [Abstract]
Total number of shares purchased (in shares)	866,512	560,100	1,717,181	1,360,537	0	4,504,330	4,504,330
Average price paid per share (in USD per share)	$ 173.33	$ 178.20	$ 145.59	$ 183.75		$ 166.51	$ 166.51
Approximate dollar value of shares that may yet be purchased under the program (in millions)	$ 750.0	$ 900.2	$ 500.0	$ 750.0	$ 750.0		$ 750.0

Bank credit lines, loan facilities and notes - Schedule of Long-term Debt Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	May 08, 2024	Jul. 01, 2021
Debt Instrument [Line Items]
Total debt	$ 3,409,248	$ 3,416,688
Less current portion of debt	(529,762)	(529,762)
Total long-term debt	2,879,486	2,886,926
Less debt issuance costs and debt discount	(12,791)	(14,310)
Total long-term debt, net	$ 2,866,695	$ 2,872,616
Senior Secured Term Loan \| Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	5.70%	5.672%		1.00%
Total debt	$ 909,248	$ 916,688
Senior Subordinated Notes \| Senior Secured Notes (the "2026 Notes")
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	2.875%	2.875%		2.875%
Total debt	$ 500,000	$ 500,000
Senior Subordinated Notes \| Senior Secured Notes (the "2027 Notes")
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	5.809%	5.809%	5.809%
Total debt	$ 750,000	$ 750,000
Senior Subordinated Notes \| Senior Secured Notes (the "2029 Notes")
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	5.849%	5.849%	5.849%
Total debt	$ 750,000	$ 750,000
Senior Subordinated Notes \| Senior Secured Notes (the "2034 Notes")
Debt Instrument [Line Items]
Debt instrument, interest rate (in percent)	6.00%	6.00%	6.00%
Total debt	$ 500,000	$ 500,000

Share based awards - Schedule of RSU and PSU Activity (Details)	3 Months Ended
	Mar. 31, 2026 $ / shares shares
Performance Share Unit (PSUs)
Outstanding Number of Shares
Outstanding at beginning of period (in shares) \| shares	16,474
Granted (in shares) \| shares	0
Shares vested (in shares) \| shares	0
Forfeited (in shares) \| shares	(6,177)
Outstanding at end of period (in shares) \| shares	10,297
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in USD per share) \| $ / shares	$ 185.18
Granted (in USD per share) \| $ / shares	0
Shares vested (in USD per share) \| $ / shares	0
Forfeited (in USD per share) \| $ / shares	185.18
Outstanding at end of period (in USD per share) \| $ / shares	$ 185.18
Restricted Stock Units (RSUs)
Outstanding Number of Shares
Outstanding at beginning of period (in shares) \| shares	1,476,169
Granted (in shares) \| shares	0
Shares vested (in shares) \| shares	(24,039)
Forfeited (in shares) \| shares	(22,944)
Outstanding at end of period (in shares) \| shares	1,429,186
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in USD per share) \| $ / shares	$ 162.53
Granted (in USD per share) \| $ / shares	0
Shares vested (in USD per share) \| $ / shares	179.56
Forfeited (in USD per share) \| $ / shares	172.47
Outstanding at end of period (in USD per share) \| $ / shares	$ 162.09

Share capital

3 Months Ended

Mar. 31, 2026

Equity [Abstract]

Share capital

No ordinary shares were redeemed by the Company during the quarter ended March 31, 2026.

On February 18, 2025, the Company's Board of Directors authorized an additional share repurchase program under which the Company may repurchase up to $750.0 million of the outstanding ordinary shares of the Company by way of redemption. On July 22, 2025, the Company's Board of Directors authorized a further additional repurchase program under which the Company could repurchase up to $500.0 million of the outstanding ordinary shares of the Company by way of redemption.

As of March 31, 2026, the Company had remaining authorization (which includes unutilized amounts from previous authorizations) to repurchase up to $750.0 million of ordinary shares under the repurchase program.

During the year ended December 31, 2025, 4,504,330 ordinary shares were redeemed by the Company at an average price of $166.51 per share for a total consideration of $750.0 million.


	Total number of shares purchased	Average price paid per share	Total number of shares purchased as part of publicly announced program	Approximate dollar value of shares that may yet be purchased under the program (in millions)
March 3/12/2025 - 3/19/2025	1,360,537	$183.75	1,360,537	$750.0
June 6/13/2025 - 6/23/2025	1,717,181	$145.59	1,717,181	$500.0
August 8/15/2025 - 8/20/2025	560,100	$178.20	560,100	$900.2
September 9/10/2025 - 9/19/2025	866,512	$173.33	866,512	$750.0
	4,504,330	$166.51	4,504,330

Under the repurchase program, a broker purchased or may purchase the Company's shares from time to time on the open market or in privately negotiated transactions in accordance with agreed terms and limitations. The program was and may be in the future designed to allow share repurchases during periods when the Company would ordinarily not be permitted to do so because it may be in possession of material non-public or price-sensitive information or due to applicable insider trading laws or self-imposed trading blackout periods. The Company's instructions to the broker in such cases were or may in the future be irrevocable and the trading decisions in respect of the repurchase program were made or will be made independently of and uninfluenced by the Company. The Company confirms that on entering the share repurchase plans it had no material non-public, price-sensitive or inside information regarding the Company or its securities. Furthermore, the Company will not enter into additional plans whilst in possession of such information. The timing and actual number of shares acquired by way of the redemption will be dependent on market conditions, legal and regulatory requirements and the other terms and limitations contained in the program. In addition, acquisitions under the program may be suspended or discontinued in certain circumstances in accordance with the agreed terms. Therefore, there can be no assurance as to the timing or number of shares that may be acquired under the program.

- Definition

The entire disclosure for equity.

+ References

+ Details