Calculations of Net Income (Loss) Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Basic and Diluted:
Income (loss) from continuing operations	$ (6,958)	$ (5,764)	$ (17,880)	$ (12,252)
Net income (loss) from discontinued operations	100	(230)	30,090	(762)
Net income (loss) attributable to ICG Group, Inc.	$ (6,858)	$ (5,994)	$ 12,210	$ (13,014)
Basic and Diluted:
Income (loss) from continuing operations per share	$ (0.19)	$ (0.16)	$ (0.49)	$ (0.34)
Income (loss) from discontinued operations per share		$ (0.01)	$ 0.82	$ (0.02)
Net income (loss) attributable to ICG Group, Inc. per share	$ (0.19)	$ (0.17)	$ 0.33	$ (0.36)
Shares used in computation of basic and diluted income (loss) per share	36,468	35,917	36,590	36,037