XML 115 R99.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Income Taxes - Components of Income Before Provision for Income Taxes (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items] |  |  |
Income before income tax expense | $ 196,680 | $ 381,205 | $ 426,989
Ireland |  |  |
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items] |  |  |
Income before income tax expense | 231,893 | 280,310 | 323,726
United States |  |  |
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items] |  |  |
Income before income tax expense | (278,413) | 41,950 | 21,073
Other |  |  |
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items] |  |  |
Income before income tax expense | $ 243,200 | $ 58,945 | $ 82,190

X
- Definition Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items] + References No definition available. + Details
Name: | iclr_ScheduleOfComponentsOfIncomeBeforeIncomeTaxExpenseBenefitLineItems
Namespace Prefix: | iclr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 31 -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599 + Details
Name: | us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | srt_StatementGeographicalAxis=country_IE
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=country_US
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=iclr_RestOfEuropeAndOtherCountriesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |