Summary of Selected Information Related to Segments (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	$ (12,894)	$ (6,858)	$ (23,044)	$ 12,210
General and administrative
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	(9,375)	(4,957)	(15,926)	(10,509)
Impairment related and other
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	(763)	(33)	(763)	(33)
Corporate other income (loss)
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	653	(45)	947	(103)
Interest income
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	133	41	214	70
Income tax benefit (expense)
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.		601		874
Noncontrolling interest (income) loss
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	1,475	458	2,379	4,044
Other
Segment Reporting Information [Line Items]
Net income (loss) attributable to ICG Group, Inc.	$ (7,877)	$ (3,935)	$ (13,149)	$ (5,657)