Note 2 - Contract Receivables (Details Textual)	6 Months Ended
Jun. 30, 2017
Majority of Unbilled Receivables Will Be Substantially Billed and Collected	1 year

Represents the the period the majority of unbilled receivables that will be substantially billed and collected.

No definition available.

Name:	icfi_MajorityOfUnbilledReceivablesWillBeSubstantiallyBilledAndCollected1
Namespace Prefix:	icfi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration