Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues
Investment banking	$ 71,762	$ 50,976	$ 38,965
Brokerage	91,167	99,611	112,217
Management fees	38,116	52,466	38,847
Incentive income	5,411	3,265	11,363
Interest and dividends	24,608	22,306	11,547
Reimbursement from affiliates	5,239	4,322	6,816
Other revenues	3,668	1,583	1,936
Consolidated Funds
Interest and dividends, Consolidated Funds	136	569	11,733
Other revenues, Consolidated Funds	373	180	386
Total revenues	240,480	235,278	233,810
Expenses
Employee compensation and benefits	194,034	203,767	194,919
Floor brokerage and trade execution	14,684	16,475	17,143
Interest and dividends	11,760	8,839	8,971
Professional, advisory and other fees	16,339	33,702	14,547
Service fees	11,281	16,365	15,814
Communications	15,704	16,350	13,972
Occupancy and equipment	22,087	27,887	19,717
Depreciation and amortization	9,437	15,472	11,543
Client services and business development	14,069	16,725	14,470
Goodwill impairment	0	7,151	0
Other expenses	15,829	10,140	20,725
Consolidated Funds
Interest and dividends, Consolidated Funds	22	147	3,078
Professional, advisory and other fees, Consolidated Funds	1,361	2,136	3,094
Floor Brokerage and trade executions, Consolidated Fund	0	0	995
Other expenses, Consolidated Funds	293	499	954
Total expenses	326,900	375,655	339,942
Other income (loss)
Net gains (losses) on securities, derivatives and other investments	55,665	15,128	21,980
Bargain purchase gain	0	22,244	0
Consolidated Funds
Net realized and unrealized gains (losses) on investments and other transactions, Consolidated Funds	6,376	4,925	33,116
Net realized and unrealized gains (losses) on derivatives, Consolidated Funds	877	(583)	(761)
Net gains (losses) on foreign currency transactions, Consolidated Funds	(7)	53	(1,293)
Total other income (loss)	62,911	41,767	53,042
Income (loss) before income taxes	(23,509)	(98,610)	(53,090)
Income tax expense (benefit)	448	(20,073)	(21,400)
Net income (loss) from continuing operations	(23,957)	(78,537)	(31,690)
Net income (loss) from discontinued operations, net of tax	0	(23,646)	0
Net income (loss)	(23,957)	(102,183)	(31,690)
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	(72)	5,827	13,727
Net income (loss) attributable to Cowen Group, Inc. stockholders	$ (23,885)	$ (108,010)	$ (45,417)
Weighted average common shares outstanding:
Basic (in shares)	114,400	95,532	73,149
Diluted (in shares)	114,400	95,532	73,149
Earnings (loss) per share:
Income (loss) from continuing operations, basic (in dollars per share)	$ (0.21)	$ (0.88)	$ (0.62)
Income (loss) from discontinued operations, basic (in dollars per share)	$ 0.00	$ (0.25)	$ 0.00
Income (loss) from continuing operations, diluted (in dollars per share)	$ (0.21)	$ (0.88)	$ (0.62)
Income (loss) from discontinued operations, diluted (in dollars per share)	$ 0.00	$ (0.25)	$ 0.00