Summary of Selected Information Related to Segments (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Segment Reporting Revenue Reconciling Item [Line Items]
Net income (loss) attributable to ICG Group, Inc.	$ (3,332)		$ 21,341		$ 8,878		$ 8,327
Corporate other income (loss) (Note 11)
Segment Reporting Revenue Reconciling Item [Line Items]
Net income (loss) attributable to ICG Group, Inc.	6		31,226		(97)		32,853
Noncontrolling interest (income) loss
Segment Reporting Revenue Reconciling Item [Line Items]
Net income (loss) attributable to ICG Group, Inc.	907		387		4,951		(417)
Other
Segment Reporting Revenue Reconciling Item [Line Items]
Net income (loss) attributable to ICG Group, Inc.	$ 913	[1]	$ 31,613	[1]	$ 4,854	[1]	$ 32,436	[1]

[1] (1) The following table reflects the components in Other (in thousands):  Three Months Ended September 30,Nine Months Ended September 30,  2013   2012   2013   2012  Corporate other income (loss) (Note 11)$6   $31,226    $(97)   $32,853   Noncontrolling interest (income) loss 907     387    4,951    (417)   $913    $31,613    $4,854    $32,436