3.26.1 html 321 134 1 false 21 0 false 4 false false R1.htm 0000001 - Document - Cover Sheet http://www.iconplc.com/role/Cover Cover Cover 1 false false R2.htm 9952151 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) Sheet http://www.iconplc.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSUNAUDITEDParenthetical CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) Statements 2 false false R3.htm 9952152 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) Sheet http://www.iconplc.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSEQUITYUNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) Statements 3 false false R4.htm 9952153 - Disclosure - CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) Sheet http://www.iconplc.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONSUNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) Notes 4 false false R5.htm 9952154 - Disclosure - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) Sheet http://www.iconplc.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMEUNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) Notes 5 false false R6.htm 9952155 - Disclosure - CONSOLIDATED BALANCE SHEETS (UNAUDITED) Sheet http://www.iconplc.com/role/CONSOLIDATEDBALANCESHEETSUNAUDITED CONSOLIDATED BALANCE SHEETS (UNAUDITED) Notes 6 false false R7.htm 9952156 - Disclosure - Restated Consolidated Statements of Cash Flows Sheet http://www.iconplc.com/role/RestatedConsolidatedStatementsofCashFlows Restated Consolidated Statements of Cash Flows Notes 7 false false R8.htm 9952157 - Disclosure - Disaggregation of revenue Sheet http://www.iconplc.com/role/Disaggregationofrevenue Disaggregation of revenue Notes 8 false false R9.htm 9952158 - Disclosure - Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) Sheet http://www.iconplc.com/role/Accountsreceivableunbilledrevenuecontractassetsandunearnedrevenueorpaymentsonaccountcontractliabilities Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) Notes 9 false false R10.htm 9952159 - Disclosure - Goodwill Sheet http://www.iconplc.com/role/Goodwill Goodwill Notes 10 false false R11.htm 9952160 - Disclosure - Intangible assets Sheet http://www.iconplc.com/role/Intangibleassets Intangible assets Notes 11 false false R12.htm 9952161 - Disclosure - Business Segment and Geographical Information Sheet http://www.iconplc.com/role/BusinessSegmentandGeographicalInformation Business Segment and Geographical Information Notes 12 false false R13.htm 9955511 - Disclosure - Disaggregation of revenue (Tables) Sheet http://www.iconplc.com/role/DisaggregationofrevenueTables Disaggregation of revenue (Tables) Tables http://www.iconplc.com/role/Disaggregationofrevenue 13 false false R14.htm 9955512 - Disclosure - Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) (Tables) Sheet http://www.iconplc.com/role/AccountsreceivableunbilledrevenuecontractassetsandunearnedrevenueorpaymentsonaccountcontractliabilitiesTables Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) (Tables) Tables http://www.iconplc.com/role/Accountsreceivableunbilledrevenuecontractassetsandunearnedrevenueorpaymentsonaccountcontractliabilities 14 false false R15.htm 9955513 - Disclosure - Goodwill (Tables) Sheet http://www.iconplc.com/role/GoodwillTables Goodwill (Tables) Tables http://www.iconplc.com/role/Goodwill 15 false false R16.htm 9955514 - Disclosure - Intangible assets (Tables) Sheet http://www.iconplc.com/role/IntangibleassetsTables Intangible assets (Tables) Tables http://www.iconplc.com/role/Intangibleassets 16 false false R17.htm 9955515 - Disclosure - Business Segment and Geographical Information (Tables) Sheet http://www.iconplc.com/role/BusinessSegmentandGeographicalInformationTables Business Segment and Geographical Information (Tables) Tables http://www.iconplc.com/role/BusinessSegmentandGeographicalInformation 17 false false R18.htm 9955516 - Disclosure - Disaggregation of revenue - Schedule of Disaggregation of Revenue (Details) Sheet http://www.iconplc.com/role/DisaggregationofrevenueScheduleofDisaggregationofRevenueDetails Disaggregation of revenue - Schedule of Disaggregation of Revenue (Details) Details 18 false false R19.htm 9955517 - Disclosure - Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Schedule of Accounts Receivables and Unbilled Revenue (Details) Sheet http://www.iconplc.com/role/AccountsreceivableunbilledrevenuecontractassetsandunearnedrevenueorpaymentsonaccountcontractliabilitiesScheduleofAccountsReceivablesandUnbilledRevenueDetails Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Schedule of Accounts Receivables and Unbilled Revenue (Details) Details http://www.iconplc.com/role/AccountsreceivableunbilledrevenuecontractassetsandunearnedrevenueorpaymentsonaccountcontractliabilitiesTables 19 false false R20.htm 9955518 - Disclosure - 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) Sheet http://www.iconplc.com/role/AccountsreceivableunbilledrevenuecontractassetsandunearnedrevenueorpaymentsonaccountcontractliabilitiesScheduleofUnbilledServicesandUnearnedRevenueorPaymentsonAccountDetails 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) Details http://www.iconplc.com/role/AccountsreceivableunbilledrevenuecontractassetsandunearnedrevenueorpaymentsonaccountcontractliabilitiesTables 20 false false R21.htm 9955519 - Disclosure - Goodwill - Schedule of Goodwill (Details) Sheet http://www.iconplc.com/role/GoodwillScheduleofGoodwillDetails Goodwill - Schedule of Goodwill (Details) Details 21 false false R22.htm 9955520 - Disclosure - Goodwill - Narrative (Details) Sheet http://www.iconplc.com/role/GoodwillNarrativeDetails Goodwill - Narrative (Details) Details 22 false false R23.htm 9955521 - Disclosure - Intangible assets - Schedule of Finite-Lived Intangible Assets (Details) Sheet http://www.iconplc.com/role/IntangibleassetsScheduleofFiniteLivedIntangibleAssetsDetails Intangible assets - Schedule of Finite-Lived Intangible Assets (Details) Details 23 false false R24.htm 9955522 - Disclosure - Intangible assets - Narrative (Details) Sheet http://www.iconplc.com/role/IntangibleassetsNarrativeDetails Intangible assets - Narrative (Details) Details 24 false false R25.htm 9955523 - Disclosure - Business Segment and Geographical Information - Schedule of Distribution of Revenue by Geographical Area (Details) Sheet http://www.iconplc.com/role/BusinessSegmentandGeographicalInformationScheduleofDistributionofRevenuebyGeographicalAreaDetails Business Segment and Geographical Information - Schedule of Distribution of Revenue by Geographical Area (Details) Details 25 false false R26.htm 9955524 - Disclosure - Business Segment and Geographical Information - Schedule of Distribution of Income from Operations by Geographical Area (Details) Sheet http://www.iconplc.com/role/BusinessSegmentandGeographicalInformationScheduleofDistributionofIncomefromOperationsbyGeographicalAreaDetails Business Segment and Geographical Information - Schedule of Distribution of Income from Operations by Geographical Area (Details) Details 26 false false All Reports Book All Reports iclr-20250930.htm iclr-20250930.xsd iclr-20250930_cal.xml iclr-20250930_def.xml iclr-20250930_lab.xml iclr-20250930_pre.xml http://fasb.org/us-gaap/2025 http://xbrl.sec.gov/dei/2025 true true