Calculations of Net Income (Loss) Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Basic and Diluted:
Income (loss) from continuing operations	$ (10,198)	$ (11,426)
Income (loss) from discontinued operations	48	30,494
Net income (loss) attributable to ICG Group, Inc.	$ (10,150)	$ 19,068
Income (loss) from continuing operations per share	$ (0.27)	$ (0.31)
Income (loss) from discontinued operations per share	$ 0.00	$ 0.83
Net income (loss) attributable to ICG Group, Inc. per share	$ (0.27)	$ 0.52
Shares used in computation of basic and diluted income (loss) per share	37,096	36,713