Summary of Selected Information Related to Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenue	$ 18,422	$ 11,974
Net income (loss) attributable to ICG Group, Inc.	(10,150)	19,068
Assets	515,996		529,718
Operating Segments
Segment Reporting Information [Line Items]
Revenue	18,422	11,974
Net income (loss) attributable to ICG Group, Inc.	(4,926)	(6,621)
Assets	198,868		195,680
Vertical Cloud | Operating Segments
Segment Reporting Information [Line Items]
Revenue	18,422	11,545
Net income (loss) attributable to ICG Group, Inc.	(4,614)	(5,539)
Assets	183,300		179,801
Vertical Cloud Venture | Operating Segments
Segment Reporting Information [Line Items]
Revenue		429
Net income (loss) attributable to ICG Group, Inc.	(312)	(1,082)
Assets	15,568		15,879
Dispositions
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	48	27,684
Other
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	(5,272)	(1,995)
Assets	$ 317,128		$ 334,038