XML 130 R120.htm IDEA: XBRL DOCUMENT v3.10.0.1

Business Segment and Geographical Information - Distribution of Interest Income by Geographical Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Interest income	$ 4,759	$ 2,346	$ 1,484
Ireland
Segment Reporting Information [Line Items]
Interest income	2,620	1,084	407
Rest of Europe
Segment Reporting Information [Line Items]
Interest income	1,750	1,222	1,040
U.S.
Segment Reporting Information [Line Items]
Interest income	17	16	2
Other
Segment Reporting Information [Line Items]
Interest income	$ 372	$ 24	$ 35

X

- Definition

Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7(b))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

Name:	us-gaap_InvestmentIncomeInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_SegmentReportingInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_StatementGeographicalAxis=country_IE
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementGeographicalAxis=iclr_RestOfEuropeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementGeographicalAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementGeographicalAxis=iclr_OtherCountriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: