Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenues
Investment banking	$ 16,254	$ 14,343	$ 31,884	$ 29,025
Brokerage	24,568	24,607	48,581	52,198
Management fees	9,932	11,857	19,649	23,021
Incentive income	580	675	1,271	5,056
Interest and dividends	5,868	5,840	11,240	10,399
Reimbursement from affiliates	1,381	981	2,426	1,990
Other revenues	831	232	1,698	922
Consolidated Funds
Interest and dividends, Consolidated Funds	30	136	91	305
Other revenues, Consolidated Funds	26	8	109	8
Total revenues	59,470	58,679	116,949	122,924
Expenses
Employee compensation and benefits	43,097	43,575	89,780	88,662
Floor brokerage and trade execution	4,182	3,685	7,934	7,795
Interest and dividends	3,207	3,115	4,931	5,724
Professional, advisory and other fees	3,695	10,398	7,621	17,538
Service fees	3,155	4,366	5,392	7,978
Communications	3,853	4,342	7,254	7,235
Occupancy and equipment	5,544	5,591	10,786	11,298
Depreciation and amortization	2,363	2,011	4,518	4,069
Client services and business development	3,753	4,132	7,579	8,809
Other expenses	3,941	(859)	7,360	2,849
Consolidated Funds
Interest and dividends, Consolidated Funds	4	40	20	87
Professional, advisory and other fees, Consolidated Funds	561	613	849	1,073
Other expenses, Consolidated Funds	70	219	140	341
Total expenses	77,425	81,228	154,164	163,458
Other income (loss)
Net gains (losses) on securities, derivatives and other investments	9,787	76	29,458	17,358
Bargain purchase gain	0	22,244	0	22,244
Consolidated Funds
Net realized and unrealized gains (losses) on investments and other transactions, Consolidated Funds	(2,417)	4,971	3,547	7,314
Net realized and unrealized gains (losses) on derivatives, Consolidated Funds	373	(84)	414	(525)
Net gains (losses) on foreign currency transactions, Consolidated Funds	23	(117)	(15)	(273)
Total other income (loss)	7,766	27,090	33,404	46,118
Income (loss) before income taxes	(10,189)	4,541	(3,811)	5,584
Income tax expense (benefit)	191	(17,954)	333	(17,791)
Net income (loss)	(10,380)	22,495	(4,144)	23,375
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	(2,434)	2,458	(193)	3,256
Net income (loss) attributable to Cowen Group, Inc. stockholders	$ (7,946)	$ 20,037	$ (3,951)	$ 20,119
Weighted average common shares outstanding:
Basic (in shares)	114,561	76,330	114,420	75,600
Diluted (in shares)	114,561	77,898	114,420	76,889
Earnings (loss) per share:
Basic (in dollars per share)	$ (0.07)	$ 0.26	$ (0.03)	$ 0.27
Diluted (in dollars per share)	$ (0.07)	$ 0.26	$ (0.03)	$ 0.26