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, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Basic and Diluted:
Income (loss) from continuing operations	$ (14,209)	$ (9,025)	$ (24,407)	$ (20,451)
Income (loss) from discontinued operations	1,315	2,167	1,363	32,661
Net income (loss) attributable to ICG Group, Inc	$ (12,894)	$ (6,858)	$ (23,044)	$ 12,210
Income (loss) from continuing operations per share	$ (0.38)	$ (0.25)	$ (0.66)	$ (0.56)
Income (loss) from discontinued operations per share	$ 0.03	$ 0.06	$ 0.04	$ 0.89
Net income (loss) attributable to ICG Group, Inc. per share	$ (0.35)	$ (0.19)	$ (0.62)	$ 0.33
Shares used in computation of basic and diluted income (loss) per share	37,313	36,468	37,205	36,590