Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Segment information
Revenue	$ 45,078	$ 35,328	$ 81,708	$ 69,282
Net income (loss) attributable to ICG Group, Inc.	(5,994)	(3,233)	(13,014)	12,657
Components of Other
Corporate other income (loss) (Note 10)	1,470	1,601	1,627	26,465
Non controlling interest	(652)	(254)	(804)	(606)
Other Net Income Loss of Parent Entity			823	25,859
Assets
Total Assets	303,885		303,885		306,820
Core [Member]
Segment information
Revenue	45,078	35,328	81,708	69,282
Net income (loss) attributable to ICG Group, Inc.	(1,500)	(12)	(2,185)	150
Assets
Total Assets	237,438		237,438		172,416
Venture [Member]
Segment information
Net income (loss) attributable to ICG Group, Inc.	(1,836)	(1,118)	(3,054)	(2,629)
Assets
Total Assets	13,074		13,074		7,157
Total Segment [Member]
Segment information
Revenue	45,078	35,328	81,708	69,282
Net income (loss) attributable to ICG Group, Inc.	(3,336)	(1,130)	(5,239)	(2,479)
Assets
Total Assets	250,512		250,512		179,573
Dispositions [Member]
Segment information
Net income (loss) attributable to ICG Group, Inc.		(974)		(2,100)
Assets
Total Assets
Corporate [Member]
Segment information
Net income (loss) attributable to ICG Group, Inc.	(3,476)	(2,476)	(8,598)	(8,623)
Assets
Total Assets	53,373		53,373		127,247
Other [Member]
Segment information
Net income (loss) attributable to ICG Group, Inc.	818	1,347	823	25,859
Components of Other
Other Net Income Loss of Parent Entity	818	1,347
Assets
Total Assets