Summary of Selected Information Related to Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenue	$ 19,029	$ 13,476	$ 37,451	$ 25,450
Net income (loss) attributable to ICG Group, Inc.	(12,894)	(6,858)	(23,044)	12,210
Assets	501,426		501,426		529,718
Operating Segments
Segment Reporting Information [Line Items]
Revenue	19,029	13,476	37,451	25,450
Net income (loss) attributable to ICG Group, Inc.	(6,332)	(5,371)	(11,258)	(12,265)
Assets	197,338		197,338		195,680
Vertical Cloud | Operating Segments
Segment Reporting Information [Line Items]
Revenue	19,029	13,476	37,451	25,021
Net income (loss) attributable to ICG Group, Inc.	(6,012)	(4,964)	(10,626)	(10,776)
Assets	181,892		181,892		179,801
Vertical Cloud Venture | Operating Segments
Segment Reporting Information [Line Items]
Revenue				429
Net income (loss) attributable to ICG Group, Inc.	(320)	(407)	(632)	(1,489)
Assets	15,446		15,446		15,879
Dispositions
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	1,315	2,448	1,363	30,132
Other
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	(7,877)	(3,935)	(13,149)	(5,657)
Assets	$ 304,088		$ 304,088		$ 334,038