Condensed Consolidated Statements of Changes in Equity (USD $) In Thousands, except Share data	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings/(Accumulated Deficit)	Redeemable Non-controlling Interest
Balance at Dec. 31, 2011	$ 508,465	$ 1,135	$ (16,902)	$ 688,427	$ (215)	$ (163,980)	$ 104,587
Balance, shares at Dec. 31, 2011		114,047,637
Net income (loss) attributable to Cowen Group, Inc. stockholders	3,995					3,995
Net income (loss) attributable to redeemable non-controlling interest	2,241						2,241
Defined benefit plans	107				107
Foreign currency translation	(67)				(67)
Deconsolidation of funds							(17,104)
Consolidation of funds							19,073
Capital withdrawals to non-controlling interests in Consolidated Funds							(5,368)
Restricted stock awards issued, shares		279,298
Amortization of share based compensation	5,944			5,944
Purchase of treasury stock, at cost	(948)		(948)
Purchase of treasury stock, at cost, Shares		(350,469)
Balance at Mar. 31, 2012	$ 517,496	$ 1,135	$ (17,850)	$ 694,371	$ (175)	$ (159,985)	$ 103,429
Balance, shares at Mar. 31, 2012		113,976,466