Summary of Selected Information Related to Segments (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Segment Reporting, Revenue Reconciling Item [Line Items]
Corporate other income (loss) (Note 13)									$ 57,826		$ 43,207		$ 74,507
Noncontrolling interest	(175)	387	(652)	(152)	(1,294)	(335)	(254)	(352)	(592)		(2,235)		(1,319)
Net income (loss) attributable to ICG Group, Inc.	14,662	21,341	(5,994)	(7,020)	17,866	(2,957)	(3,233)	15,890	22,989		27,566		46,589
Other
Segment Reporting, Revenue Reconciling Item [Line Items]
Net income (loss) attributable to ICG Group, Inc.									$ 57,234	[1]	$ 40,972	[1]	$ 73,188	[1]

[1] The following table reflects the components in Other (in thousands): Year Ended December 31, 2012 2011 2010 Corporate other income (loss) (Note 13) $ 57,826 $ 43,207 $ 74,507 Noncontrolling interest (592 ) (2,235 ) (1,319 ) $ 57,234 $ 40,972 $ 73,188