Summary of Selected Information Related to Segments (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	$ (10,150)	$ 19,068
General and administrative
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	(6,551)	(5,552)
Corporate other income (loss)
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	294	(58)
Interest income
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	81	29
Noncontrolling interest (income) loss
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	904	3,586
Other
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	$ (5,272)	$ (1,995)