Net Income (Loss) per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Basic and Diluted:
Net income (loss) attributable to ICG Group, Inc.	$ (5,994)	$ (3,233)	$ (13,014)	$ 12,657
Basic:
Net income (loss) attributable to ICG Group, Inc. per share	$ (0.17)	$ (0.09)	$ (0.36)	$ 0.34
Diluted:
Net income (loss) per diluted share attributable to ICG Group, Inc.	$ (0.17)	$ (0.09)	$ (0.36)	$ 0.33
Shares used in computation of basic income (loss) per share	35,917	36,961	36,037	36,953
Shares used in computation of diluted income (loss) per share	35,917	36,961	36,037	37,976
Stock options [Member]
Diluted:
Number of dilutive shares				102
Restricted stock [Member]
Diluted:
Number of dilutive shares				23
DSUs [Member]
Diluted:
Number of dilutive shares				12
SARs [Member]
Diluted:
Number of dilutive shares				886