Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues
Investment banking	$ 18,666	$ 10,816	$ 50,550	$ 39,841
Brokerage	22,701	25,670	71,282	77,868
Management fees	8,866	14,778	28,515	37,799
Incentive income	1,416	(1,823)	2,687	3,233
Interest and dividends	3,605	10,930	14,845	21,330
Reimbursement from affiliates	1,370	978	3,796	2,968
Other revenues	701	309	2,398	1,230
Consolidated Funds
Interest and dividends, Consolidated Funds	24	138	115	443
Other revenues, Consolidated Funds	249	163	359	171
Total revenues	57,598	61,959	174,547	184,883
Expenses
Employee compensation and benefits	47,322	43,651	137,102	132,313
Floor brokerage and trade execution	3,058	4,488	10,992	12,283
Interest and dividends	1,957	1,904	6,888	7,627
Professional, advisory and other fees	3,534	8,063	11,158	25,601
Service fees	2,807	3,815	8,198	11,792
Communications	4,522	3,636	11,775	10,872
Occupancy and equipment	5,808	6,225	16,594	17,523
Depreciation and amortization	2,427	2,421	6,945	6,490
Client services and business development	3,510	3,534	11,089	12,343
Other expenses	3,779	2,158	11,138	5,007
Consolidated Funds
Interest and dividends, Consolidated Funds	2	51	22	137
Professional, advisory and other fees, Consolidated Funds	263	1,002	1,112	2,075
Other expenses, Consolidated Funds	65	82	205	423
Total expenses	79,054	81,030	233,218	244,486
Other income (loss)
Net gains (losses) on securities, derivatives and other investments	12,510	(21,989)	41,969	(4,631)
Bargain purchase gain	0	0	0	22,244
Consolidated Funds
Net realized and unrealized gains (losses) on investments and other transactions, Consolidated Funds	(2,730)	(3,181)	817	4,133
Net realized and unrealized gains (losses) on derivatives, Consolidated Funds	212	70	626	(456)
Net gains (losses) on foreign currency transactions, Consolidated Funds	9	313	(6)	40
Total other income (loss)	10,001	(24,787)	43,406	21,330
Income (loss) before income taxes	(11,455)	(43,858)	(15,265)	(38,273)
Income tax expense (benefit)	163	72	496	(17,720)
Net income (loss) from continuing operations	(11,618)	(43,930)	(15,761)	(20,553)
Net income (loss) from discontinued operations, net of tax	0	(5,087)	0	(5,087)
Net income (loss)	(11,618)	(49,017)	(15,761)	(25,640)
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	(1,033)	(783)	(1,225)	2,473
Net income (loss) attributable to Cowen Group, Inc. stockholders	$ (10,585)	$ (48,234)	$ (14,536)	$ (28,113)
Weighted average common shares outstanding:
Basic (in shares)	114,989	115,664	114,587	89,118
Diluted (in shares)	114,989	115,664	114,587	89,118
Earnings (loss) per share:
Income (loss) from continuing operations, basic (in dollars per share)	$ (0.09)	$ (0.37)	$ (0.13)	$ (0.26)
Income (loss) from discontinued operations, basic (in dollars per share)	$ 0.00	$ (0.04)	$ 0.00	$ (0.06)
Income (loss) from continuing operations, diluted (in dollars per share)	$ (0.09)	$ (0.37)	$ (0.13)	$ (0.26)
Income (loss) from discontinued operations, diluted (in dollars per share)	$ 0.00	$ (0.04)	$ 0.00	$ (0.06)