$ICLR
ICON PLC Stock $iclr

$iclr Overview Financials Valuation SEC Filings Company Website

2023 Q4 Form 20-F Financial Statement

#000106095524000010 Filed on February 23, 2024

Income Statement

Concept	2023 Q4	2023
Revenue	$2.066B	$8.120B
YoY Change	5.31%	4.89%
Cost Of Revenue	$1.446B	$5.720B
YoY Change	4.89%	3.49%
Gross Profit	$620.5M	$2.400B
YoY Change	6.3%	8.39%
Gross Profit Margin	30.03%	29.56%
Selling, General & Admin	$195.6M	$768.6M
YoY Change	-14.66%	-1.31%
% of Gross Profit	31.52%	32.02%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$149.8M	$586.0M
YoY Change	5.29%	2.89%
% of Gross Profit	24.13%	24.41%
Operating Expenses	$345.3M	$768.6M
YoY Change	-7.02%	-1.31%
Operating Profit	$275.2M	$956.2M
YoY Change	29.62%	20.23%
Interest Expense	-$79.31M	$336.7M
YoY Change	6.37%	46.56%
% of Operating Profit	-28.82%	35.21%
Other Income/Expense, Net
YoY Change
Pretax Income	$186.3M	$624.5M
YoY Change	44.61%	9.97%
Income Tax	-$30.16M	$11.75M
% Of Pretax Income	-16.2%	1.88%
Net Earnings	$216.4M	$612.3M
YoY Change	84.27%	21.18%
Net Earnings / Revenue	10.47%	7.54%
Basic Earnings Per Share		$7.46
Diluted Earnings Per Share	$2.60	$7.40
COMMON SHARES
Basic Shares Outstanding	82.50M shares	82.10M shares
Diluted Shares Outstanding		82.72M shares

Balance Sheet

Concept	2023 Q4	2023
SHORT-TERM ASSETS
Cash & Short-Term Investments	$380.1M	$380.1M
YoY Change	30.86%	30.84%
Cash & Equivalents	$378.1M	$378.1M
Short-Term Investments	$2.000M	$1.954M
Other Short-Term Assets	$132.1M	$132.1M
YoY Change	-3.64%	-3.64%
Inventory
Prepaid Expenses
Receivables	$1.790B	$2.742B
Other Receivables	$157.1M	$157.1M
Total Short-Term Assets	$3.411B	$3.411B
YoY Change	5.65%	5.65%
LONG-TERM ASSETS
Property, Plant & Equipment	$361.2M	$501.5M
YoY Change	3.1%	-0.52%
Goodwill	$9.022B
YoY Change	0.56%
Intangibles
YoY Change
Long-Term Investments	$46.80M	$46.80M
YoY Change		43.43%
Other Assets	$78.47M	$73.66M
YoY Change	10.85%	-50.13%
Total Long-Term Assets	$13.58B	$13.58B
YoY Change	-2.71%	-2.71%
TOTAL ASSETS
Total Short-Term Assets	$3.411B	$3.411B
Total Long-Term Assets	$13.58B	$13.58B
Total Assets	$16.99B	$16.99B
YoY Change	-1.14%	-1.14%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$131.6M	$131.6M
YoY Change	62.06%	62.06%
Accrued Expenses	$36.41M	$421.9M
YoY Change	-16.59%	-4.01%
Deferred Revenue	$1.655B
YoY Change	9.76%
Short-Term Debt	$0.00	$0.00
YoY Change
Long-Term Debt Due	$110.2M	$110.2M
YoY Change	99.73%	99.73%
Total Short-Term Liabilities	$2.826B	$2.826B
YoY Change	5.02%	5.02%
LONG-TERM LIABILITIES
Long-Term Debt	$3.665B	$3.665B
YoY Change	-20.3%	-20.3%
Other Long-Term Liabilities	$46.00M	$359.0M
YoY Change	20.22%	-12.25%
Total Long-Term Liabilities	$3.711B	$4.024B
YoY Change	-19.97%	-19.64%
TOTAL LIABILITIES
Total Short-Term Liabilities	$2.826B	$2.826B
Total Long-Term Liabilities	$3.711B	$4.024B
Total Liabilities	$7.749B	$7.749B
YoY Change	-10.8%	-10.8%
SHAREHOLDERS EQUITY
Retained Earnings	$2.434B
YoY Change	33.62%
Common Stock	$6.949B
YoY Change	1.5%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$9.241B	$9.241B
YoY Change
Total Liabilities & Shareholders Equity	$16.99B	$16.99B
YoY Change	-1.14%	-1.14%

Cashflow Statement

Concept	2023 Q4	2023
OPERATING ACTIVITIES
Net Income	$216.4M	$612.3M
YoY Change	84.27%	21.18%
Depreciation, Depletion And Amortization	$149.8M	$586.0M
YoY Change	5.29%	2.89%
Cash From Operating Activities	$440.1M	$1.161B
YoY Change	-840.63%	106.11%
INVESTING ACTIVITIES
Capital Expenditures	$52.69M	$140.7M
YoY Change	-7.58%	-1.03%
Acquisitions
YoY Change
Other Investing Activities	-$69.76M	-$85.96M
YoY Change	3636.53%	2218.88%
Cash From Investing Activities	-$122.5M	-$226.7M
YoY Change	107.96%	55.38%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net		$0.00
YoY Change		-100.0%
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-255.5M	-$844.0M
YoY Change	32.31%	-2.33%
NET CHANGE
Cash From Operating Activities	440.1M	$1.161B
Cash From Investing Activities	-122.5M	-$226.7M
Cash From Financing Activities	-255.5M	-$844.0M
Net Change In Cash	62.13M	$89.33M
YoY Change	-119.95%	-119.28%
FREE CASH FLOW
Cash From Operating Activities	$440.1M	$1.161B
Capital Expenditures	$52.69M	$140.7M
Free Cash Flow	$387.4M	$1.020B
YoY Change	-432.73%	142.27%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2023	dei	Amendment Flag AmendmentFlag	false
CY2023	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2023
CY2023	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2023	dei	Entity Central Index Key EntityCentralIndexKey	0001060955
CY2023Q4	us-gaap	Derivative Liability Current Statement Of Financial Position Extensible Enumeration DerivativeLiabilityCurrentStatementOfFinancialPositionExtensibleEnumeration	http://fasb.org/us-gaap/2023#OtherLiabilitiesCurrent
CY2022Q4	us-gaap	Derivative Liability Current Statement Of Financial Position Extensible Enumeration DerivativeLiabilityCurrentStatementOfFinancialPositionExtensibleEnumeration	http://fasb.org/us-gaap/2023#OtherLiabilitiesCurrent
CY2023Q4	us-gaap	Derivative Asset Statement Of Financial Position Extensible Enumeration DerivativeAssetStatementOfFinancialPositionExtensibleEnumeration	http://fasb.org/us-gaap/2023#NontradeReceivablesCurrent
CY2023Q4	us-gaap	Derivative Liability Noncurrent Statement Of Financial Position Extensible Enumeration DerivativeLiabilityNoncurrentStatementOfFinancialPositionExtensibleEnumeration	http://fasb.org/us-gaap/2023#OtherLiabilitiesNoncurrent
CY2022Q4	us-gaap	Derivative Liability Noncurrent Statement Of Financial Position Extensible Enumeration DerivativeLiabilityNoncurrentStatementOfFinancialPositionExtensibleEnumeration	http://fasb.org/us-gaap/2023#OtherLiabilitiesNoncurrent
CY2023Q4	us-gaap	Operating Lease Liability Current Statement Of Financial Position Extensible List OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2023#OtherLiabilitiesCurrent
CY2022Q4	us-gaap	Operating Lease Liability Current Statement Of Financial Position Extensible List OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2023#OtherLiabilitiesCurrent
CY2023	dei	Document Type DocumentType	20-F
CY2023	dei	Document Registration Statement DocumentRegistrationStatement	false
CY2023	dei	Document Annual Report DocumentAnnualReport	true
CY2023	dei	Document Period End Date DocumentPeriodEndDate	2023-12-31
CY2023	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2023	dei	Document Transition Report DocumentTransitionReport	false
CY2023	dei	Document Shell Company Report DocumentShellCompanyReport	false
CY2023	dei	Entity File Number EntityFileNumber	333-08704
CY2023	dei	Entity Registrant Name EntityRegistrantName	ICON PLC
CY2023	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	L2
CY2023	dei	Entity Address Address Line1 EntityAddressAddressLine1	South County Business Park
CY2023	dei	Entity Address Address Line2 EntityAddressAddressLine2	Leopardstown
CY2023	dei	Entity Address City Or Town EntityAddressCityOrTown	Dublin 18
CY2023	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	D18 X5R3
CY2023	dei	Entity Address Country EntityAddressCountry	IE
CY2023	dei	Security12b Title Security12bTitle	ORDINARY SHARES, PAR VALUE €0.06 EACH
CY2023	dei	Trading Symbol TradingSymbol	ICLR
CY2023	dei	Security Exchange Name SecurityExchangeName	NASDAQ
CY2023Q4	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	82495086	shares
CY2023	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2023	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2023	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2023	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2023	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2023	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2023	dei	Icfr Auditor Attestation Flag IcfrAuditorAttestationFlag	true
CY2023	dei	Document Fin Stmt Error Correction Flag DocumentFinStmtErrorCorrectionFlag	false
CY2023	dei	Document Accounting Standard DocumentAccountingStandard	U.S. GAAP
CY2023	dei	Entity Shell Company EntityShellCompany	false
CY2023	dei	Auditor Firm AuditorFirmId	1116
CY2023	dei	Auditor Name AuditorName	KPMG
CY2023	dei	Auditor Location AuditorLocation	Dublin, Ireland
CY2023Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	378102000	usd
CY2022Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	288768000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Securities Current AvailableForSaleSecuritiesDebtSecuritiesCurrent	1954000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Securities Current AvailableForSaleSecuritiesDebtSecuritiesCurrent	1713000	usd
CY2023Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	1790322000	usd
CY2022Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	1731388000	usd
CY2023Q4	us-gaap	Contract With Customer Asset Gross Current ContractWithCustomerAssetGrossCurrent	951936000	usd
CY2022Q4	us-gaap	Contract With Customer Asset Gross Current ContractWithCustomerAssetGrossCurrent	957655000	usd
CY2023Q4	us-gaap	Nontrade Receivables Current NontradeReceivablesCurrent	65797000	usd
CY2022Q4	us-gaap	Nontrade Receivables Current NontradeReceivablesCurrent	63658000	usd
CY2023Q4	us-gaap	Prepaid Expense And Other Assets Current PrepaidExpenseAndOtherAssetsCurrent	132105000	usd
CY2022Q4	us-gaap	Prepaid Expense And Other Assets Current PrepaidExpenseAndOtherAssetsCurrent	137094000	usd
CY2023Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	91254000	usd
CY2022Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	48790000	usd
CY2023Q4	us-gaap	Assets Current AssetsCurrent	3411470000	usd
CY2022Q4	us-gaap	Assets Current AssetsCurrent	3229066000	usd
CY2023Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	361184000	usd
CY2022Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	350320000	usd
CY2023Q4	us-gaap	Goodwill Goodwill	9022075000	usd
CY2022Q4	us-gaap	Goodwill Goodwill	8971670000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	3855865000	usd
CY2022Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	4278659000	usd
CY2023Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	140333000	usd
CY2022Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	153832000	usd
CY2023Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	78470000	usd
CY2022Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	70790000	usd
CY2023Q4	us-gaap	Income Taxes Receivable Noncurrent IncomeTaxesReceivableNoncurrent	0	usd
CY2022Q4	us-gaap	Income Taxes Receivable Noncurrent IncomeTaxesReceivableNoncurrent	21380000	usd
CY2023Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	73662000	usd
CY2022Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	76930000	usd
CY2023Q4	us-gaap	Other Long Term Investments OtherLongTermInvestments	46804000	usd
CY2022Q4	us-gaap	Other Long Term Investments OtherLongTermInvestments	32631000	usd
CY2023Q4	us-gaap	Assets Assets	16989863000	usd
CY2022Q4	us-gaap	Assets Assets	17185278000	usd
CY2023Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	131584000	usd
CY2022Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	81194000	usd
CY2023Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	1654507000	usd
CY2022Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	1507449000	usd
CY2023Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	915399000	usd
CY2022Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	1005025000	usd
CY2023Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	13968000	usd
CY2022Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	41783000	usd
CY2023Q4	us-gaap	Lines Of Credit Current LinesOfCreditCurrent	110150000	usd
CY2022Q4	us-gaap	Lines Of Credit Current LinesOfCreditCurrent	55150000	usd
CY2023Q4	us-gaap	Liabilities Current LiabilitiesCurrent	2825608000	usd
CY2022Q4	us-gaap	Liabilities Current LiabilitiesCurrent	2690601000	usd
CY2023Q4	us-gaap	Long Term Line Of Credit LongTermLineOfCredit	3665439000	usd
CY2022Q4	us-gaap	Long Term Line Of Credit LongTermLineOfCredit	4599037000	usd
CY2023Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	126321000	usd
CY2022Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	131644000	usd
CY2023Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	45998000	usd
CY2022Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	38260000	usd
CY2023Q4	us-gaap	Accrued Income Taxes Noncurrent AccruedIncomeTaxesNoncurrent	186654000	usd
CY2022Q4	us-gaap	Accrued Income Taxes Noncurrent AccruedIncomeTaxesNoncurrent	239188000	usd
CY2023Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	899100000	usd
CY2022Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	988585000	usd
CY2023Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies	0	usd
CY2022Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies	0	usd
CY2023Q4	us-gaap	Liabilities Liabilities	7749120000	usd
CY2022Q4	us-gaap	Liabilities Liabilities	8687315000	usd
CY2023Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	6
CY2022Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	6
CY2023Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	100000000	shares
CY2022Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	100000000	shares
CY2023Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	82495086	shares
CY2023Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	82495086	shares
CY2022Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	81723555	shares
CY2022Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	81723555	shares
CY2023Q4	us-gaap	Common Stock Value CommonStockValue	6699000	usd
CY2022Q4	us-gaap	Common Stock Value CommonStockValue	6649000	usd
CY2023Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	6942669000	usd
CY2022Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	6840306000	usd
CY2023Q4	iclr	Other Undenominated Capital OtherUndenominatedCapital	1162000	usd
CY2022Q4	iclr	Other Undenominated Capital OtherUndenominatedCapital	1162000	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-143506000	usd
CY2022Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-171538000	usd
CY2023Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	2433719000	usd
CY2022Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1821384000	usd
CY2023Q4	us-gaap	Stockholders Equity StockholdersEquity	9240743000	usd
CY2022Q4	us-gaap	Stockholders Equity StockholdersEquity	8497963000	usd
CY2023Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	16989863000	usd
CY2022Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	17185278000	usd
CY2023	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	8120176000	usd
CY2022	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	7741386000	usd
CY2021	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5480826000	usd
CY2023	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	5719949000	usd
CY2022	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	5527045000	usd
CY2021	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	3972612000	usd
CY2023	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	768559000	usd
CY2022	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	778753000	usd
CY2021	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	585330000	usd
CY2023	us-gaap	Depreciation And Amortization DepreciationAndAmortization	585950000	usd
CY2022	us-gaap	Depreciation And Amortization DepreciationAndAmortization	569513000	usd
CY2021	us-gaap	Depreciation And Amortization DepreciationAndAmortization	314987000	usd
CY2023	us-gaap	Business Combination Integration Related Costs BusinessCombinationIntegrationRelatedCosts	44176000	usd
CY2022	us-gaap	Business Combination Integration Related Costs BusinessCombinationIntegrationRelatedCosts	39695000	usd
CY2021	us-gaap	Business Combination Integration Related Costs BusinessCombinationIntegrationRelatedCosts	198263000	usd
CY2023	us-gaap	Restructuring Costs RestructuringCosts	45390000	usd
CY2022	us-gaap	Restructuring Costs RestructuringCosts	31143000	usd
CY2021	us-gaap	Restructuring Costs RestructuringCosts	31105000	usd
CY2023	us-gaap	Costs And Expenses CostsAndExpenses	7164024000	usd
CY2022	us-gaap	Costs And Expenses CostsAndExpenses	6946149000	usd
CY2021	us-gaap	Costs And Expenses CostsAndExpenses	5102297000	usd
CY2023	us-gaap	Operating Income Loss OperatingIncomeLoss	956152000	usd
CY2022	us-gaap	Operating Income Loss OperatingIncomeLoss	795237000	usd
CY2021	us-gaap	Operating Income Loss OperatingIncomeLoss	378529000	usd
CY2023	us-gaap	Investment Income Interest InvestmentIncomeInterest	5014000	usd
CY2022	us-gaap	Investment Income Interest InvestmentIncomeInterest	2345000	usd
CY2021	us-gaap	Investment Income Interest InvestmentIncomeInterest	574000	usd
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CY2022	us-gaap	Interest Expense InterestExpense	229731000	usd
CY2021	us-gaap	Interest Expense InterestExpense	182423000	usd
CY2023	us-gaap	Income Loss Including Portion Attributable To Noncontrolling Interest IncomeLossIncludingPortionAttributableToNoncontrollingInterest	624467000	usd
CY2022	us-gaap	Income Loss Including Portion Attributable To Noncontrolling Interest IncomeLossIncludingPortionAttributableToNoncontrollingInterest	567851000	usd
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CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	11749000	usd
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	59411000	usd
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	41334000	usd
CY2023	iclr	Income Loss From Continuing Operations Before Equity Method Investments Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeEquityMethodInvestmentsNoncontrollingInterest	612718000	usd
CY2022	iclr	Income Loss From Continuing Operations Before Equity Method Investments Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeEquityMethodInvestmentsNoncontrollingInterest	508440000	usd
CY2021	iclr	Income Loss From Continuing Operations Before Equity Method Investments Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeEquityMethodInvestmentsNoncontrollingInterest	155346000	usd
CY2023	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-383000	usd
CY2022	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-3136000	usd
CY2021	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-2161000	usd
CY2023	us-gaap	Net Income Loss NetIncomeLoss	612335000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	505304000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	153185000	usd
CY2023	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	7.46
CY2022	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.20
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.28
CY2023	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	7.40
CY2022	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.13
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.25
CY2023	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	82101813	shares
CY2022	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	81532320	shares
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	67110186	shares
CY2023	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	82717640	shares
CY2022	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	82468363	shares
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	68068311	shares
CY2023	us-gaap	Profit Loss ProfitLoss	612335000	usd
CY2022	us-gaap	Profit Loss ProfitLoss	505304000	usd
CY2021	us-gaap	Profit Loss ProfitLoss	153185000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	26221000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-89530000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-60617000	usd
CY2023	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	244000	usd
CY2022	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	12657000	usd
CY2021	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	4266000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	0	usd
CY2022	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	0	usd
CY2021	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	-113000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	1567000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	-3728000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	778000	usd
CY2023	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	640367000	usd
CY2022	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	424703000	usd
CY2021	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	97725000	usd
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	1850236000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	153185000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-60617000	usd
CY2021	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	4266000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	-113000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	778000	usd
CY2021	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	97725000	usd
CY2021	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	118589000	usd
CY2021	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	23000	usd
CY2021	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	133553000	usd
CY2021	us-gaap	Adjustments To Additional Paid In Capital Stock Issued Issuance Costs AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts	853000	usd
CY2021	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	5658155000	usd
CY2021	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Other Longterm Incentive Plans Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationOtherLongtermIncentivePlansRequisiteServicePeriodRecognition	209399000	usd
CY2021Q4	us-gaap	Stockholders Equity StockholdersEquity	8066827000	usd
CY2021Q4	us-gaap	Stockholders Equity StockholdersEquity	8066827000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	505304000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-89530000	usd
CY2022	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	12657000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	-3728000	usd
CY2022	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	424703000	usd
CY2022	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	35828000	usd
CY2022	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	16000	usd
CY2022	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	70606000	usd
CY2022	us-gaap	Adjustments To Additional Paid In Capital Stock Issued Issuance Costs AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts	17000	usd
CY2022	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	99983000	usd
CY2022	iclr	Adjustment To Retained Earning Share Repurchase Costs AdjustmentToRetainedEarningShareRepurchaseCosts	17000	usd
CY2022Q4	us-gaap	Stockholders Equity StockholdersEquity	8497963000	usd
CY2022Q4	us-gaap	Stockholders Equity StockholdersEquity	8497963000	usd
CY2023	us-gaap	Net Income Loss NetIncomeLoss	612335000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	26221000	usd
CY2023	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	244000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	1567000	usd
CY2023	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	640367000	usd
CY2023	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	50958000	usd
CY2023	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	15000	usd
CY2023	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	51456000	usd
CY2023	us-gaap	Adjustments To Additional Paid In Capital Stock Issued Issuance Costs AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts	16000	usd
CY2023Q4	us-gaap	Stockholders Equity StockholdersEquity	9240743000	usd
CY2023	us-gaap	Profit Loss ProfitLoss	612335000	usd
CY2022	us-gaap	Profit Loss ProfitLoss	505304000	usd
CY2021	us-gaap	Profit Loss ProfitLoss	153185000	usd
CY2023	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	585950000	usd
CY2022	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	569513000	usd
CY2021	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	314987000	usd
CY2023	us-gaap	Impairment Of Long Lived Assets Held For Use ImpairmentOfLongLivedAssetsHeldForUse	8686000	usd
CY2022	us-gaap	Impairment Of Long Lived Assets Held For Use ImpairmentOfLongLivedAssetsHeldForUse	28767000	usd
CY2021	us-gaap	Impairment Of Long Lived Assets Held For Use ImpairmentOfLongLivedAssetsHeldForUse	20037000	usd
CY2023	us-gaap	Operating Lease Right Of Use Asset Amortization Expense OperatingLeaseRightOfUseAssetAmortizationExpense	41546000	usd
CY2022	us-gaap	Operating Lease Right Of Use Asset Amortization Expense OperatingLeaseRightOfUseAssetAmortizationExpense	45215000	usd
CY2021	us-gaap	Operating Lease Right Of Use Asset Amortization Expense OperatingLeaseRightOfUseAssetAmortizationExpense	45339000	usd
CY2023	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-383000	usd
CY2022	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-3136000	usd
CY2021	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-2161000	usd
CY2023	us-gaap	Business Combination Bargain Purchase Gain Recognized Amount BusinessCombinationBargainPurchaseGainRecognizedAmount	6160000	usd
CY2022	us-gaap	Business Combination Bargain Purchase Gain Recognized Amount BusinessCombinationBargainPurchaseGainRecognizedAmount	0	usd
CY2021	us-gaap	Business Combination Bargain Purchase Gain Recognized Amount BusinessCombinationBargainPurchaseGainRecognizedAmount	0	usd
CY2023	us-gaap	Amortization Of Deferred Hedge Gains AmortizationOfDeferredHedgeGains	2407000	usd
CY2022	us-gaap	Amortization Of Deferred Hedge Gains AmortizationOfDeferredHedgeGains	0	usd
CY2021	us-gaap	Amortization Of Deferred Hedge Gains AmortizationOfDeferredHedgeGains	0	usd
CY2023	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	16402000	usd
CY2022	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	17749000	usd
CY2021	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	12890000	usd
CY2023	us-gaap	Share Based Compensation ShareBasedCompensation	55667000	usd
CY2022	us-gaap	Share Based Compensation ShareBasedCompensation	70523000	usd
CY2021	us-gaap	Share Based Compensation ShareBasedCompensation	133844000	usd
CY2023	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	usd
CY2022	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	usd
CY2021	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-14434000	usd
CY2023	iclr	Gain Loss On Issuance Of Debt GainLossOnIssuanceOfDebt	0	usd
CY2022	iclr	Gain Loss On Issuance Of Debt GainLossOnIssuanceOfDebt	0	usd
CY2021	iclr	Gain Loss On Issuance Of Debt GainLossOnIssuanceOfDebt	-59460000	usd
CY2023	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-85403000	usd
CY2022	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-124985000	usd
CY2021	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-60616000	usd
CY2023	us-gaap	Foreign Currency Transaction Gain Loss Unrealized ForeignCurrencyTransactionGainLossUnrealized	-19706000	usd
CY2022	us-gaap	Foreign Currency Transaction Gain Loss Unrealized ForeignCurrencyTransactionGainLossUnrealized	13009000	usd
CY2021	us-gaap	Foreign Currency Transaction Gain Loss Unrealized ForeignCurrencyTransactionGainLossUnrealized	6054000	usd
CY2023	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-24332000	usd
CY2022	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-11324000	usd
CY2021	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-4480000	usd
CY2023	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	83296000	usd
CY2022	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	420695000	usd
CY2021	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-113513000	usd
CY2023	us-gaap	Increase Decrease In Contract With Customer Asset IncreaseDecreaseInContractWithCustomerAsset	-4716000	usd
CY2022	us-gaap	Increase Decrease In Contract With Customer Asset IncreaseDecreaseInContractWithCustomerAsset	332592000	usd
CY2021	us-gaap	Increase Decrease In Contract With Customer Asset IncreaseDecreaseInContractWithCustomerAsset	17656000	usd
CY2023	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	134566000	usd
CY2022	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	192944000	usd
CY2021	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	-69121000	usd
CY2023	us-gaap	Increase Decrease In Other Current Liabilities IncreaseDecreaseInOtherCurrentLiabilities	-170810000	usd
CY2022	us-gaap	Increase Decrease In Other Current Liabilities IncreaseDecreaseInOtherCurrentLiabilities	10121000	usd
CY2021	us-gaap	Increase Decrease In Other Current Liabilities IncreaseDecreaseInOtherCurrentLiabilities	108259000	usd
CY2023	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1161027000	usd
CY2022	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	563315000	usd
CY2021	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	829142000	usd
CY2023	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	140692000	usd
CY2022	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	142160000	usd
CY2021	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	93750000	usd
CY2023	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	71766000	usd
CY2022	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	0	usd
CY2021	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	5914475000	usd
CY2023	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	0	usd
CY2022	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	0	usd
CY2021	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	2450000	usd
CY2023	us-gaap	Payments To Fund Longterm Loans To Related Parties PaymentsToFundLongtermLoansToRelatedParties	0	usd
CY2022	us-gaap	Payments To Fund Longterm Loans To Related Parties PaymentsToFundLongtermLoansToRelatedParties	0	usd
CY2021	us-gaap	Payments To Fund Longterm Loans To Related Parties PaymentsToFundLongtermLoansToRelatedParties	10000000	usd
CY2023	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	2616000	usd
CY2022	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	481000	usd
CY2021	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	497000	usd
CY2023	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	2857000	usd
CY2022	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	482000	usd
CY2021	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	480000	usd
CY2023	us-gaap	Proceeds From Sale Of Longterm Investments ProceedsFromSaleOfLongtermInvestments	0	usd
CY2022	us-gaap	Proceeds From Sale Of Longterm Investments ProceedsFromSaleOfLongtermInvestments	1906000	usd
CY2021	us-gaap	Proceeds From Sale Of Longterm Investments ProceedsFromSaleOfLongtermInvestments	500000	usd
CY2023	us-gaap	Payments To Acquire Longterm Investments PaymentsToAcquireLongtermInvestments	13954000	usd
CY2022	us-gaap	Payments To Acquire Longterm Investments PaymentsToAcquireLongtermInvestments	5612000	usd
CY2021	us-gaap	Payments To Acquire Longterm Investments PaymentsToAcquireLongtermInvestments	4077000	usd
CY2023	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-226653000	usd
CY2022	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-145867000	usd
CY2021	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-6024235000	usd
CY2023	us-gaap	Payments Of Financing Costs PaymentsOfFinancingCosts	0	usd
CY2022	us-gaap	Payments Of Financing Costs PaymentsOfFinancingCosts	0	usd
CY2021	us-gaap	Payments Of Financing Costs PaymentsOfFinancingCosts	30328000	usd
CY2023	us-gaap	Proceeds From Lines Of Credit ProceedsFromLinesOfCredit	370000000	usd
CY2022	us-gaap	Proceeds From Lines Of Credit ProceedsFromLinesOfCredit	75000000	usd
CY2021	us-gaap	Proceeds From Lines Of Credit ProceedsFromLinesOfCredit	5905100000	usd
CY2023	us-gaap	Repayments Of Lines Of Credit RepaymentsOfLinesOfCredit	1265000000	usd
CY2022	us-gaap	Repayments Of Lines Of Credit RepaymentsOfLinesOfCredit	875000000	usd
CY2021	us-gaap	Repayments Of Lines Of Credit RepaymentsOfLinesOfCredit	877780000	usd
CY2023	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	50973000	usd
CY2022	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	35844000	usd
CY2021	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	118589000	usd
CY2023	us-gaap	Payments Of Stock Issuance Costs PaymentsOfStockIssuanceCosts	16000	usd
CY2022	us-gaap	Payments Of Stock Issuance Costs PaymentsOfStockIssuanceCosts	17000	usd
CY2021	us-gaap	Payments Of Stock Issuance Costs PaymentsOfStockIssuanceCosts	853000	usd
CY2023	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	usd
CY2022	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	99983000	usd
CY2021	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	usd
CY2023	iclr	Payments For Share Repurchase Costs PaymentsForShareRepurchaseCosts	0	usd
CY2022	iclr	Payments For Share Repurchase Costs PaymentsForShareRepurchaseCosts	17000	usd
CY2021	iclr	Payments For Share Repurchase Costs PaymentsForShareRepurchaseCosts	0	usd
CY2023	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-844043000	usd
CY2022	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-864173000	usd
CY2021	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	5114728000	usd
CY2023	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-997000	usd
CY2022	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-16720000	usd
CY2021	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-7727000	usd
CY2023	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	89334000	usd
CY2022	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-463445000	usd
CY2021	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-88092000	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	288768000	usd
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	752213000	usd
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	840305000	usd
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	378102000	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	288768000	usd
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	752213000	usd
CY2023	us-gaap	Nature Of Operations NatureOfOperations	Description of Business <div style="text-align:justify;text-indent:36pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">ICON plc and its subsidiaries ("the Company" or "ICON") is a clinical research organization ("CRO"), providing outsourced development services on a global basis to the pharmaceutical, biotechnology and medical device industries. We specialize 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. Our mission is to improve the lives of patients by accelerating the development of our customers' drugs and devices through innovative solutions.</span></div><div><span><br/></span></div><div style="text-align:justify;text-indent:36pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">We believe that we are one of a select group of CROs with the expertise and capability to conduct clinical trials in most major therapeutic areas on a global basis and have the operational flexibility to provide development serv</span><span style="color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">ices on a stand-alone basis or as part of an integrated "full-service" solution. At December 31, 2023 we had approximately 41,100 employees, in 106 locations in 53 countries. During the year ended December 31, 2023, we derived approximate</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">ly 40.4%, 48.7% and 10.9% </span><span style="color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">of our revenue in the United States, Europe and Rest of World, respectively.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify;text-indent:36pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">ICON’s ordinary shares are traded on the NASDAQ Global Select Market under the symbol “ICLR”.</span></div><div><span><br/></span></div><div style="text-align:justify;text-indent:36pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">We began operations in 1990 and have expanded our business through internal growth, together with a number of strategic acquisitions to enhance our capabilities and expertise in certain areas of the clinical development process. We are incorporated in Ireland and our principal executive office is located at: South County Business Park, Leopardstown, Dublin 18, Republic of Ireland. The contact telephone number of this office is +353 1 2912000.</span></div>
CY2023Q4	dei	Entity Number Of Employees EntityNumberOfEmployees	41100	employee
CY2023Q4	iclr	Number Of Locations NumberOfLocations	106	location
CY2023Q4	us-gaap	Number Of Countries In Which Entity Operates NumberOfCountriesInWhichEntityOperates	53	country
CY2023	us-gaap	Use Of Estimates UseOfEstimates	<div style="text-align:justify;text-indent:36pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-style:italic;font-weight:700;line-height:120%">Use of estimates</span></div><div><span><br/></span></div><div style="text-align:justify;text-indent:36pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">The preparation of financial statements in conformity with generally accepted accounting principles in the United States requires management to make estimates and judgments that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reported period. Actual results could differ from those estimates. The principal management estimates and judgments used in preparing the financial statements relate to revenue recognition, intangible assets acquired in a business combination and income taxation.</span></div>
CY2023	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-12916000	usd
CY2022	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	25997000	usd
CY2021	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	14316000	usd
CY2023	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	8120176000	usd
CY2022	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	7741386000	usd
CY2021	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5480826000	usd
CY2023Q4	us-gaap	Billed Contract Receivables BilledContractReceivables	1821855000	usd
CY2022Q4	us-gaap	Billed Contract Receivables BilledContractReceivables	1751950000	usd
CY2023Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	31533000	usd
CY2022Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	20562000	usd
CY2023Q4	iclr	Contracts Receivable Gross ContractsReceivableGross	1790322000	usd
CY2022Q4	iclr	Contracts Receivable Gross ContractsReceivableGross	1731388000	usd
CY2023Q4	us-gaap	Contract With Customer Asset Gross Current ContractWithCustomerAssetGrossCurrent	951936000	usd
CY2022Q4	us-gaap	Contract With Customer Asset Gross Current ContractWithCustomerAssetGrossCurrent	957655000	usd
CY2023Q4	iclr	Contracts Receivable Net ContractsReceivableNet	2742258000	usd
CY2022Q4	iclr	Contracts Receivable Net ContractsReceivableNet	2689043000	usd
CY2023Q4	us-gaap	Contract With Customer Asset Gross Current ContractWithCustomerAssetGrossCurrent	951936000	usd
CY2022Q4	us-gaap	Contract With Customer Asset Gross Current ContractWithCustomerAssetGrossCurrent	957655000	usd
CY2023	iclr	Increase Decrease In Contractwith Customer Asset Gross Current IncreaseDecreaseInContractwithCustomerAssetGrossCurrent	-5719000	usd
CY2023	iclr	Increase Decrease In Contractwith Customer Asset Gross Current Percent IncreaseDecreaseInContractwithCustomerAssetGrossCurrentPercent	-0.006
CY2023Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	1654507000	usd
CY2022Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	1507449000	usd
CY2023	iclr	Increase Decrease In Contracts With Customers Liability Current IncreaseDecreaseInContractsWithCustomersLiabilityCurrent	147058000	usd
CY2023	iclr	Increase Decrease In Contract With Customer Liability Gross Current Percent IncreaseDecreaseInContractWithCustomerLiabilityGrossCurrentPercent	0.098
CY2023Q4	iclr	Advance Payments Netted Against Unbilled Contracts Receivable AdvancePaymentsNettedAgainstUnbilledContractsReceivable	-702571000	usd
CY2022Q4	iclr	Advance Payments Netted Against Unbilled Contracts Receivable AdvancePaymentsNettedAgainstUnbilledContractsReceivable	-549794000	usd
CY2023	iclr	Changein Advance Payments Netted Against Unbilled Contracts Receivable ChangeinAdvancePaymentsNettedAgainstUnbilledContractsReceivable	-152777000	usd
CY2023	iclr	Changein Advance Payments Netted Against Unbilled Contracts Receivable Percent ChangeinAdvancePaymentsNettedAgainstUnbilledContractsReceivablePercent	0.278
CY2023Q4	iclr	Other Liabilities Amount Payable To Third Parties For Reimbursable Expenses OtherLiabilitiesAmountPayableToThirdPartiesForReimbursableExpenses	333000000	usd
CY2022Q4	iclr	Other Liabilities Amount Payable To Third Parties For Reimbursable Expenses OtherLiabilitiesAmountPayableToThirdPartiesForReimbursableExpenses	406300000	usd
CY2023	iclr	Increase Decrease In Contractwith Customer Asset Gross Current IncreaseDecreaseInContractwithCustomerAssetGrossCurrent	-5700000	usd
CY2023	iclr	Increase Decrease In Contracts With Customers Liability Current IncreaseDecreaseInContractsWithCustomersLiabilityCurrent	147100000	usd
CY2023	iclr	Changein Advance Payments Netted Against Unbilled Contracts Receivable ChangeinAdvancePaymentsNettedAgainstUnbilledContractsReceivable	-152800000	usd
CY2023	us-gaap	Contract With Customer Asset Credit Loss Expense ContractWithCustomerAssetCreditLossExpense	24600000	usd
CY2022	us-gaap	Contract With Customer Asset Credit Loss Expense ContractWithCustomerAssetCreditLossExpense	17800000	usd
CY2023Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	14800000000	usd
CY2022Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	13700000000	usd
CY2023Q4	us-gaap	Revenue Remaining Performance Obligation Percentage RevenueRemainingPerformanceObligationPercentage	0.52
CY2023Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P12M
CY2022Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P12M
CY2022Q4	us-gaap	Revenue Remaining Performance Obligation Percentage RevenueRemainingPerformanceObligationPercentage	0.52
CY2022Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	20562000	usd
CY2021Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	7081000	usd
CY2023	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	13358000	usd
CY2022	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	3913000	usd
CY2023	iclr	Accounts Receivable Credit Loss Expense AccountsReceivableCreditLossExpense	24550000	usd
CY2022	iclr	Accounts Receivable Credit Loss Expense AccountsReceivableCreditLossExpense	17800000	usd
CY2023	iclr	Allowance For Doubtful Accounts Foreign Currency Translation Adjustments AllowanceForDoubtfulAccountsForeignCurrencyTranslationAdjustments	-221000	usd
CY2022	iclr	Allowance For Doubtful Accounts Foreign Currency Translation Adjustments AllowanceForDoubtfulAccountsForeignCurrencyTranslationAdjustments	-406000	usd
CY2023Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	31533000	usd
CY2022Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	20562000	usd
CY2021Q3	dei	Entity Number Of Employees EntityNumberOfEmployees	38000	employee
CY2023	us-gaap	Business Combination Integration Related Costs BusinessCombinationIntegrationRelatedCosts	44200000	usd
CY2022	us-gaap	Business Combination Integration Related Costs BusinessCombinationIntegrationRelatedCosts	39700000	usd
CY2021	us-gaap	Business Combination Integration Related Costs BusinessCombinationIntegrationRelatedCosts	198300000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Securities Current AvailableForSaleSecuritiesDebtSecuritiesCurrent	1954000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Securities Noncurrent AvailableForSaleSecuritiesDebtSecuritiesNoncurrent	46804000	usd
CY2023Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	48758000	usd
CY2023Q4	us-gaap	Liabilities Fair Value Disclosure LiabilitiesFairValueDisclosure	2411000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Securities Current AvailableForSaleSecuritiesDebtSecuritiesCurrent	1713000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Securities Noncurrent AvailableForSaleSecuritiesDebtSecuritiesNoncurrent	32631000	usd
CY2022Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	34356000	usd
CY2022Q4	us-gaap	Liabilities Fair Value Disclosure LiabilitiesFairValueDisclosure	3670000	usd
CY2023Q4	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	3793500000	usd
CY2022Q4	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	4650300000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Securities Current AvailableForSaleSecuritiesDebtSecuritiesCurrent	2000000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Securities Current AvailableForSaleSecuritiesDebtSecuritiesCurrent	1700000	usd
CY2023	iclr	Short Term Available For Sale Investments Average Remaining Maturity Period ShortTermAvailableForSaleInvestmentsAverageRemainingMaturityPeriod	P3Y7M6D
CY2022	iclr	Short Term Available For Sale Investments Average Remaining Maturity Period ShortTermAvailableForSaleInvestmentsAverageRemainingMaturityPeriod	P2Y9M18D
CY2023Q4	iclr	Debt Securities Available For Sale Cumulative Amount Advanced Under Subscription Agreements DebtSecuritiesAvailableForSaleCumulativeAmountAdvancedUnderSubscriptionAgreements	14000000	usd
CY2022Q4	iclr	Debt Securities Available For Sale Cumulative Amount Advanced Under Subscription Agreements DebtSecuritiesAvailableForSaleCumulativeAmountAdvancedUnderSubscriptionAgreements	3700000	usd
CY2023	us-gaap	Increase Decrease In Equity Securities Fv Ni IncreaseDecreaseInEquitySecuritiesFvNi	200000	usd
CY2022	us-gaap	Increase Decrease In Equity Securities Fv Ni IncreaseDecreaseInEquitySecuritiesFvNi	6300000	usd
CY2023Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	46800000	usd
CY2022Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	32600000	usd
CY2023Q4	iclr	Commitment To Acquire Long Term Investments CommitmentToAcquireLongTermInvestments	66400000	usd
CY2023Q4	us-gaap	Land Land	3724000	usd
CY2022Q4	us-gaap	Land Land	3724000	usd
CY2023Q4	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	70072000	usd
CY2022Q4	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	70880000	usd
CY2023Q4	us-gaap	Capitalized Computer Software Gross CapitalizedComputerSoftwareGross	550119000	usd
CY2022Q4	us-gaap	Capitalized Computer Software Gross CapitalizedComputerSoftwareGross	500135000	usd
CY2023Q4	us-gaap	Furniture And Fixtures Gross FurnitureAndFixturesGross	45856000	usd
CY2022Q4	us-gaap	Furniture And Fixtures Gross FurnitureAndFixturesGross	50600000	usd
CY2023Q4	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	56217000	usd
CY2022Q4	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	59946000	usd
CY2023Q4	us-gaap	Leasehold Improvements Gross LeaseholdImprovementsGross	55000000	usd
CY2022Q4	us-gaap	Leasehold Improvements Gross LeaseholdImprovementsGross	65167000	usd
CY2023Q4	iclr	Vehicles Gross VehiclesGross	79000	usd
CY2022Q4	iclr	Vehicles Gross VehiclesGross	41000	usd
CY2023Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	781067000	usd
CY2022Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	750493000	usd
CY2023Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	419883000	usd
CY2022Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	400173000	usd
CY2023Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	361184000	usd
CY2022Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	350320000	usd
CY2023	us-gaap	Depreciation Depreciation	126100000	usd
CY2022	us-gaap	Depreciation Depreciation	106400000	usd
CY2021	us-gaap	Depreciation Depreciation	75500000	usd
CY2022Q4	us-gaap	Goodwill Goodwill	8971670000	usd
CY2021Q4	us-gaap	Goodwill Goodwill	9037931000	usd
CY2023	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	36750000	usd
CY2022	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	0	usd
CY2023	us-gaap	Goodwill Purchase Accounting Adjustments GoodwillPurchaseAccountingAdjustments	0	usd
CY2022	us-gaap	Goodwill Purchase Accounting Adjustments GoodwillPurchaseAccountingAdjustments	-35692000	usd
CY2023	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	13655000	usd
CY2022	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	-30569000	usd
CY2023Q4	us-gaap	Goodwill Goodwill	9022075000	usd
CY2022Q4	us-gaap	Goodwill Goodwill	8971670000	usd
CY2023	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	usd
CY2022	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	5147971000	usd
CY2022Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	5109212000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	1292106000	usd
CY2022Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	830553000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	3855865000	usd
CY2022Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	4278659000	usd
CY2023	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	459900000	usd
CY2022	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	463100000	usd
CY2021	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	239500000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	344518000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	229106000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	214869000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	202539000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	189539000	usd
CY2023Q4	iclr	Finite Lived Intangible Assets Amortization Expense Net FiniteLivedIntangibleAssetsAmortizationExpenseNet	1180571000	usd
CY2023Q4	us-gaap	Other Sundry Liabilities Current OtherSundryLiabilitiesCurrent	463882000	usd
CY2022Q4	us-gaap	Other Sundry Liabilities Current OtherSundryLiabilitiesCurrent	530204000	usd
CY2023Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	385499000	usd
CY2022Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	395862000	usd
CY2023Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	36414000	usd
CY2022Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	43657000	usd
CY2023Q4	us-gaap	Accrued Utilities Current AccruedUtilitiesCurrent	11078000	usd
CY2022Q4	us-gaap	Accrued Utilities Current AccruedUtilitiesCurrent	16896000	usd
CY2023Q4	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	13532000	usd
CY2022Q4	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	12852000	usd
CY2023Q4	iclr	Restructuring Reserveand Other Liabilities Current RestructuringReserveandOtherLiabilitiesCurrent	4951000	usd
CY2022Q4	iclr	Restructuring Reserveand Other Liabilities Current RestructuringReserveandOtherLiabilitiesCurrent	5512000	usd
CY2023Q4	iclr	Capital Government Grants Current CapitalGovernmentGrantsCurrent	43000	usd
CY2022Q4	iclr	Capital Government Grants Current CapitalGovernmentGrantsCurrent	42000	usd
CY2023Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	915399000	usd
CY2022Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	1005025000	usd
CY2023Q4	iclr	Other Liabilities Amount Payable To Third Parties For Reimbursable Expenses OtherLiabilitiesAmountPayableToThirdPartiesForReimbursableExpenses	333000000	usd
CY2022Q4	iclr	Other Liabilities Amount Payable To Third Parties For Reimbursable Expenses OtherLiabilitiesAmountPayableToThirdPartiesForReimbursableExpenses	406300000	usd
CY2023Q4	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	3806213000	usd
CY2022Q4	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	4701213000	usd
CY2023Q4	iclr	Long Term Debt Current Maturities Gross LongTermDebtCurrentMaturitiesGross	110150000	usd
CY2022Q4	iclr	Long Term Debt Current Maturities Gross LongTermDebtCurrentMaturitiesGross	55150000	usd
CY2023Q4	iclr	Long Term Debt Excluding Current Maturities Gross LongTermDebtExcludingCurrentMaturitiesGross	3696063000	usd
CY2022Q4	iclr	Long Term Debt Excluding Current Maturities Gross LongTermDebtExcludingCurrentMaturitiesGross	4646063000	usd
CY2023Q4	us-gaap	Debt Instrument Unamortized Discount Premium And Debt Issuance Costs Net DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	30624000	usd
CY2022Q4	us-gaap	Debt Instrument Unamortized Discount Premium And Debt Issuance Costs Net DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	47026000	usd
CY2023Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	3665439000	usd
CY2022Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	4599037000	usd
CY2023	us-gaap	Interest Expense Debt InterestExpenseDebt	311019000	usd
CY2022	us-gaap	Interest Expense Debt InterestExpenseDebt	209189000	usd
CY2021	us-gaap	Interest Expense Debt InterestExpenseDebt	93809000	usd
CY2023	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	16402000	usd
CY2022	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	17749000	usd
CY2021	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	12890000	usd
CY2023	iclr	Transaction And One Time Financing Costs TransactionAndOneTimeFinancingCosts	0	usd
CY2022	iclr	Transaction And One Time Financing Costs TransactionAndOneTimeFinancingCosts	0	usd
CY2021	iclr	Transaction And One Time Financing Costs TransactionAndOneTimeFinancingCosts	75391000	usd
CY2023	iclr	Interest Expense Credit Other InterestExpenseCreditOther	9278000	usd
CY2022	iclr	Interest Expense Credit Other InterestExpenseCreditOther	2793000	usd
CY2021	iclr	Interest Expense Credit Other InterestExpenseCreditOther	333000	usd
CY2023	us-gaap	Interest Expense InterestExpense	336699000	usd
CY2022	us-gaap	Interest Expense InterestExpense	229731000	usd
CY2021	us-gaap	Interest Expense InterestExpense	182423000	usd
CY2023Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	110150000	usd
CY2023Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	55150000	usd
CY2023Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	555150000	usd
CY2023Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	55150000	usd
CY2023Q4	iclr	Long Term Debt Maturity Year Five And Thereafter LongTermDebtMaturityYearFiveAndThereafter	3030613000	usd
CY2023Q4	us-gaap	Long Term Debt LongTermDebt	3806213000	usd
CY2023	us-gaap	Proceeds From Lines Of Credit ProceedsFromLinesOfCredit	370000000	usd
CY2022	us-gaap	Proceeds From Lines Of Credit ProceedsFromLinesOfCredit	75000000	usd
CY2023	us-gaap	Repayments Of Senior Debt RepaymentsOfSeniorDebt	315000000	usd
CY2022	us-gaap	Repayments Of Senior Debt RepaymentsOfSeniorDebt	75000000	usd
CY2023Q4	us-gaap	Line Of Credit Facility Remaining Borrowing Capacity LineOfCreditFacilityRemainingBorrowingCapacity	55000000	usd
CY2022Q4	us-gaap	Line Of Credit Facility Remaining Borrowing Capacity LineOfCreditFacilityRemainingBorrowingCapacity	0	usd
CY2023Q4	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	3793500000	usd
CY2022Q4	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	4650300000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	1600000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	-3700000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	2400000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	100000	usd
CY2023Q4	us-gaap	Interest Rate Cash Flow Hedge Gain Loss To Be Reclassified During Next12 Months Net InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet	3200000	usd
CY2023	us-gaap	Operating Lease Cost OperatingLeaseCost	46820000	usd
CY2022	us-gaap	Operating Lease Cost OperatingLeaseCost	53880000	usd
CY2021	us-gaap	Operating Lease Cost OperatingLeaseCost	51200000	usd
CY2023	us-gaap	Sublease Income SubleaseIncome	1103000	usd
CY2022	us-gaap	Sublease Income SubleaseIncome	1165000	usd
CY2021	us-gaap	Sublease Income SubleaseIncome	1338000	usd
CY2023	us-gaap	Lease Cost LeaseCost	45717000	usd
CY2022	us-gaap	Lease Cost LeaseCost	52715000	usd
CY2021	us-gaap	Lease Cost LeaseCost	49862000	usd
CY2023	us-gaap	Lease Cost LeaseCost	45700000	usd
CY2022	us-gaap	Lease Cost LeaseCost	52700000	usd
CY2021	us-gaap	Lease Cost LeaseCost	49900000	usd
CY2023	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	37700000	usd
CY2022	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	28700000	usd
CY2023	us-gaap	Operating Lease Impairment Loss OperatingLeaseImpairmentLoss	8700000	usd
CY2022	us-gaap	Operating Lease Impairment Loss OperatingLeaseImpairmentLoss	24800000	usd
CY2021	us-gaap	Operating Lease Impairment Loss OperatingLeaseImpairmentLoss	15400000	usd
CY2023Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P6Y8M19D
CY2023Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0329
CY2022Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P6Y10M24D
CY2022Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0245
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	40894000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	34585000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	29172000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	23254000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	15023000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	33998000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	176926000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	14191000	usd
CY2023Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	162735000	usd
CY2023Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	36400000	usd
CY2022Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	43700000	usd
CY2023Q4	us-gaap	Defined Benefit Pension Plan Liabilities Noncurrent DefinedBenefitPensionPlanLiabilitiesNoncurrent	14738000	usd
CY2022Q4	us-gaap	Defined Benefit Pension Plan Liabilities Noncurrent DefinedBenefitPensionPlanLiabilitiesNoncurrent	13033000	usd
CY2023Q4	us-gaap	Other Sundry Liabilities Noncurrent OtherSundryLiabilitiesNoncurrent	31260000	usd
CY2022Q4	us-gaap	Other Sundry Liabilities Noncurrent OtherSundryLiabilitiesNoncurrent	25227000	usd
CY2023Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	45998000	usd
CY2022Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	38260000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Term Of Contract LesseeOperatingLeaseTermOfContract	P16Y
CY2023	iclr	Number Of Votes NumberOfVotes	1	vote
CY2023	iclr	Number Of Votes NumberOfVotes	1	vote
CY2023	us-gaap	Restructuring Costs RestructuringCosts	45390000	usd
CY2022	us-gaap	Restructuring Costs RestructuringCosts	31143000	usd
CY2021	us-gaap	Restructuring Costs RestructuringCosts	31105000	usd
CY2023	us-gaap	Restructuring Costs RestructuringCosts	45390000	usd
CY2022	us-gaap	Restructuring Costs RestructuringCosts	31143000	usd
CY2021	us-gaap	Restructuring Costs RestructuringCosts	31105000	usd
CY2023Q4	us-gaap	Restructuring Reserve RestructuringReserve	7000000	usd
CY2022Q4	us-gaap	Restructuring Reserve RestructuringReserve	6022000	usd
CY2021Q4	us-gaap	Restructuring Reserve RestructuringReserve	10311000	usd
CY2023	us-gaap	Restructuring Charges RestructuringCharges	36704000	usd
CY2022	us-gaap	Restructuring Charges RestructuringCharges	4364000	usd
CY2023	iclr	Restructuring Reserve Utilizations RestructuringReserveUtilizations	35727000	usd
CY2022	iclr	Restructuring Reserve Utilizations RestructuringReserveUtilizations	8653000	usd
CY2023Q4	us-gaap	Restructuring Reserve RestructuringReserve	6999000	usd
CY2022Q4	us-gaap	Restructuring Reserve RestructuringReserve	6022000	usd
CY2023	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	624467000	usd
CY2022	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	567851000	usd
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	196680000	usd
CY2023	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	97152000	usd
CY2022	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	184396000	usd
CY2021	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	101950000	usd
CY2023	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-85403000	usd
CY2022	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-124985000	usd
CY2021	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-60616000	usd
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	11749000	usd
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	59411000	usd
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	41334000	usd
CY2023	us-gaap	Other Comprehensive Income Foreign Currency Translation Gain Loss Arising During Period Tax OtherComprehensiveIncomeForeignCurrencyTranslationGainLossArisingDuringPeriodTax	-3903000	usd
CY2022	us-gaap	Other Comprehensive Income Foreign Currency Translation Gain Loss Arising During Period Tax OtherComprehensiveIncomeForeignCurrencyTranslationGainLossArisingDuringPeriodTax	7211000	usd
CY2021	us-gaap	Other Comprehensive Income Foreign Currency Translation Gain Loss Arising During Period Tax OtherComprehensiveIncomeForeignCurrencyTranslationGainLossArisingDuringPeriodTax	1776000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	301000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	0	usd
CY2021	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	0	usd
CY2023	us-gaap	Income Tax Effects Allocated Directly To Equity IncomeTaxEffectsAllocatedDirectlyToEquity	8147000	usd
CY2022	us-gaap	Income Tax Effects Allocated Directly To Equity IncomeTaxEffectsAllocatedDirectlyToEquity	66622000	usd
CY2021	us-gaap	Income Tax Effects Allocated Directly To Equity IncomeTaxEffectsAllocatedDirectlyToEquity	43110000	usd
CY2023	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	78058000	usd
CY2022	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	70980000	usd
CY2021	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	24586000	usd
CY2023	us-gaap	Income Tax Reconciliation Nondeductible Expense Amortization IncomeTaxReconciliationNondeductibleExpenseAmortization	-71223000	usd
CY2022	us-gaap	Income Tax Reconciliation Nondeductible Expense Amortization IncomeTaxReconciliationNondeductibleExpenseAmortization	-59330000	usd
CY2021	us-gaap	Income Tax Reconciliation Nondeductible Expense Amortization IncomeTaxReconciliationNondeductibleExpenseAmortization	-31228000	usd
CY2023	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	35778000	usd
CY2022	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	52464000	usd
CY2021	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	51273000	usd
CY2023	us-gaap	Income Tax Reconciliation Tax Credits Research IncomeTaxReconciliationTaxCreditsResearch	3868000	usd
CY2022	us-gaap	Income Tax Reconciliation Tax Credits Research IncomeTaxReconciliationTaxCreditsResearch	2608000	usd
CY2021	us-gaap	Income Tax Reconciliation Tax Credits Research IncomeTaxReconciliationTaxCreditsResearch	3120000	usd
CY2023	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	-1068000	usd
CY2022	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	-777000	usd
CY2021	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	3101000	usd
CY2023	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	3154000	usd
CY2022	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	-300000	usd
CY2021	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	-128000	usd
CY2023	us-gaap	Unrecognized Tax Benefits Period Increase Decrease UnrecognizedTaxBenefitsPeriodIncreaseDecrease	-54347000	usd
CY2022	us-gaap	Unrecognized Tax Benefits Period Increase Decrease UnrecognizedTaxBenefitsPeriodIncreaseDecrease	8392000	usd
CY2021	us-gaap	Unrecognized Tax Benefits Period Increase Decrease UnrecognizedTaxBenefitsPeriodIncreaseDecrease	5246000	usd
CY2023	iclr	Effective Income Tax Rate Reconciliation Deferred Tax Provision On Unrepatriated Earnings Amount EffectiveIncomeTaxRateReconciliationDeferredTaxProvisionOnUnrepatriatedEarningsAmount	39165000	usd
CY2023	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	-11487000	usd
CY2022	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	-8756000	usd
CY2021	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	-9083000	usd
CY2023	us-gaap	Income Tax Reconciliation Other Reconciling Items IncomeTaxReconciliationOtherReconcilingItems	-2413000	usd
CY2022	us-gaap	Income Tax Reconciliation Other Reconciling Items IncomeTaxReconciliationOtherReconcilingItems	-654000	usd
CY2021	us-gaap	Income Tax Reconciliation Other Reconciling Items IncomeTaxReconciliationOtherReconcilingItems	687000	usd
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	11749000	usd
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	59411000	usd
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	41334000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	7547000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	10927000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	16108000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	23260000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Goodwill DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsGoodwill	39014000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Goodwill DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsGoodwill	37150000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Other Finite Lived Assets DeferredTaxLiabilitiesOtherFiniteLivedAssets	950055000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Other Finite Lived Assets DeferredTaxLiabilitiesOtherFiniteLivedAssets	1078302000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Undistributed Foreign Earnings DeferredTaxLiabilitiesUndistributedForeignEarnings	52408000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Undistributed Foreign Earnings DeferredTaxLiabilitiesUndistributedForeignEarnings	1587000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	7982000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	7467000	usd
CY2023Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	1073114000	usd
CY2022Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	1158693000	usd
CY2023Q4	iclr	Deferred Tax Assets Operating Loss And Tax Credits Carryforwards DeferredTaxAssetsOperatingLossAndTaxCreditsCarryforwards	124150000	usd
CY2022Q4	iclr	Deferred Tax Assets Operating Loss And Tax Credits Carryforwards DeferredTaxAssetsOperatingLossAndTaxCreditsCarryforwards	88697000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	9082000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	6010000	usd
CY2023Q4	iclr	Deferred Tax Assets Operating Lease Liability DeferredTaxAssetsOperatingLeaseLiability	20190000	usd
CY2022Q4	iclr	Deferred Tax Assets Operating Lease Liability DeferredTaxAssetsOperatingLeaseLiability	27593000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Goodwill And Intangible Assets DeferredTaxAssetsGoodwillAndIntangibleAssets	2166000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Goodwill And Intangible Assets DeferredTaxAssetsGoodwillAndIntangibleAssets	3602000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Other DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsOther	17605000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Other DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsOther	21862000	usd
CY2023Q4	iclr	Deferred Tax Assets Tax Deferred Expense Other Liabilities DeferredTaxAssetsTaxDeferredExpenseOtherLiabilities	84928000	usd
CY2022Q4	iclr	Deferred Tax Assets Tax Deferred Expense Other Liabilities DeferredTaxAssetsTaxDeferredExpenseOtherLiabilities	66933000	usd
CY2023Q4	iclr	Deferred Tax Asset Contract With Customer Liability DeferredTaxAssetContractWithCustomerLiability	23748000	usd
CY2022Q4	iclr	Deferred Tax Asset Contract With Customer Liability DeferredTaxAssetContractWithCustomerLiability	66565000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Other DeferredTaxAssetsTaxDeferredExpenseOther	8774000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Other DeferredTaxAssetsTaxDeferredExpenseOther	9155000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	290643000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	290417000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	42967000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	43379000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	247676000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	247038000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	825438000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	911655000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	43000000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	43400000	usd
CY2021Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	45500000	usd
CY2023	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	-400000	usd
CY2022	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	-2100000	usd
CY2023	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	-400000	usd
CY2022	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	-2100000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Undistributed Foreign Earnings DeferredTaxLiabilitiesUndistributedForeignEarnings	52400000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Undistributed Foreign Earnings DeferredTaxLiabilitiesUndistributedForeignEarnings	1600000	usd
CY2022Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	217584000	usd
CY2021Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	202065000	usd
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	19078000	usd
CY2023	us-gaap	Unrecognized Tax Benefits Increases Resulting From Acquisition UnrecognizedTaxBenefitsIncreasesResultingFromAcquisition	0	usd
CY2022	us-gaap	Unrecognized Tax Benefits Increases Resulting From Acquisition UnrecognizedTaxBenefitsIncreasesResultingFromAcquisition	0	usd
CY2021	us-gaap	Unrecognized Tax Benefits Increases Resulting From Acquisition UnrecognizedTaxBenefitsIncreasesResultingFromAcquisition	170047000	usd
CY2023	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	1161000	usd
CY2022	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	16098000	usd
CY2021	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	204000	usd
CY2023	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	918000	usd
CY2022	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	5442000	usd
CY2021	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	1695000	usd
CY2023	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	4552000	usd
CY2022	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	5701000	usd
CY2021	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	18613000	usd
CY2023	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	usd
CY2022	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	usd
CY2021	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	844000	usd
CY2023	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	62363000	usd
CY2022	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	838000	usd
CY2021	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	3338000	usd
CY2023Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	160016000	usd
CY2022Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	217584000	usd
CY2021Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	202065000	usd
CY2023Q4	us-gaap	Significant Change In Unrecognized Tax Benefits Is Reasonably Possible Amount Of Unrecorded Benefit SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleAmountOfUnrecordedBenefit	65000000	usd
CY2023Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	160000000	usd
CY2022Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	217600000	usd
CY2021Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	202100000	usd
CY2023	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	4200000	usd
CY2022	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	7100000	usd
CY2021	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	1900000	usd
CY2023Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	27100000	usd
CY2022Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	22600000	usd
CY2022	us-gaap	Employee Service Share Based Compensation Tax Benefit From Exercise Of Stock Options EmployeeServiceShareBasedCompensationTaxBenefitFromExerciseOfStockOptions	7700000	usd
CY2021	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	22700000	usd
CY2021	us-gaap	Employee Service Share Based Compensation Tax Benefit From Exercise Of Stock Options EmployeeServiceShareBasedCompensationTaxBenefitFromExerciseOfStockOptions	23900000	usd
CY2023	us-gaap	Share Based Compensation ShareBasedCompensation	55667000	usd
CY2022	us-gaap	Share Based Compensation ShareBasedCompensation	70523000	usd
CY2021	us-gaap	Share Based Compensation ShareBasedCompensation	133844000	usd
CY2023	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P4Y5M1D
CY2023	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1	P3Y10M20D
CY2022	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P4Y8M8D
CY2022	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1	P4Y3M
CY2023	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Lower Range Limit ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit	20.83
CY2023	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Upper Range Limit ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit	233.88
CY2023	us-gaap	Share Based Compensation ShareBasedCompensation	55700000	usd
CY2023	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	20000000	usd
CY2023	us-gaap	Employee Service Share Based Compensation Tax Benefit From Exercise Of Stock Options EmployeeServiceShareBasedCompensationTaxBenefitFromExerciseOfStockOptions	10900000	usd
CY2022	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	12900000	usd
CY2023	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	82101813	shares
CY2023	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	1	segment
CY2023	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	8120176000	usd
CY2022	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	7741386000	usd
CY2021	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5480826000	usd
CY2023	iclr	Operating Income Loss Before Restructuring Charges Transaction And Integration Expenses OperatingIncomeLossBeforeRestructuringChargesTransactionAndIntegrationExpenses	956152000	usd
CY2022	iclr	Operating Income Loss Before Restructuring Charges Transaction And Integration Expenses OperatingIncomeLossBeforeRestructuringChargesTransactionAndIntegrationExpenses	795237000	usd
CY2021	iclr	Operating Income Loss Before Restructuring Charges Transaction And Integration Expenses OperatingIncomeLossBeforeRestructuringChargesTransactionAndIntegrationExpenses	378529000	usd
CY2023Q4	us-gaap	Noncurrent Assets NoncurrentAssets	501517000	usd
CY2022Q4	us-gaap	Noncurrent Assets NoncurrentAssets	504152000	usd
CY2022	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	81532320	shares
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	67110186	shares
CY2023	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	615827	shares
CY2022	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	936043	shares
CY2021	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	958125	shares
CY2023	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	82717640	shares
CY2022	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	82468363	shares
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	68068311	shares
CY2023	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	7.46
CY2022	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.20
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.28
CY2023	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	7.40
CY2022	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.13
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.25
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	-149148000	usd
CY2022Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	-175369000	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Net Of Tax AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax	-7803000	usd
CY2022Q4	us-gaap	Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Net Of Tax AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax	-7559000	usd
CY2023Q4	iclr	Acumulated Other Comprehensive Loss Cash Flow Hedge Loss Reclassification After Tax AcumulatedOtherComprehensiveLossCashFlowHedgeLossReclassificationAfterTax	-2161000	usd
CY2022Q4	iclr	Acumulated Other Comprehensive Loss Cash Flow Hedge Loss Reclassification After Tax AcumulatedOtherComprehensiveLossCashFlowHedgeLossReclassificationAfterTax	-3728000	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-143506000	usd
CY2022Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-171538000	usd
CY2023	us-gaap	Interest Paid Net InterestPaidNet	317975000	usd
CY2022	us-gaap	Interest Paid Net InterestPaidNet	210918000	usd
CY2021	us-gaap	Interest Paid Net InterestPaidNet	106205000	usd
CY2023	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	163778000	usd
CY2022	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	116322000	usd
CY2021	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	55105000	usd
CY2020Q3	us-gaap	Equity Method Investments EquityMethodInvestments	4900000	usd

Files In Submission

Name	View Source	Status
0001060955-24-000010-index-headers.html	Edgar Link	pending
0001060955-24-000010-index.html	Edgar Link	pending
0001060955-24-000010.txt	Edgar Link	pending
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exhibit121-2023.htm	Edgar Link	pending
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iclr-20231231_lab.xml	Edgar Link	unprocessable

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$ICLR
ICON PLC Stock $iclr

2023 Q4 Form 20-F Financial Statement

#000106095524000010 Filed on February 23, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ICLR ICON PLC Stock $iclr

2023 Q4 Form 20-F Financial Statement

#000106095524000010 Filed on February 23, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ICLR
ICON PLC Stock $iclr