Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Investment banking		$ 223,614	$ 133,279	$ 222,781
Brokerage		293,610	199,180	157,722
Management fees		33,245	40,612	41,906
Incentive income		5,383	8,334	1,466
Interest and dividends		49,440	14,732	13,796
Reimbursement from affiliates		2,860	10,504	21,557
Aircraft lease revenue		3,751	4,161	0
Reinsurance premiums		30,996	32,459	0
Other revenue		8,561	22,355	3,726
Consolidated Funds
Interest and dividends		5,870	4,792	1,086
Other revenues		1,451	1,157	527
Total revenues		658,781	471,565	464,567
Expenses
Employee compensation and benefits		404,087	310,038	321,386
Floor brokerage and trade execution		75,601	32,286	27,460
Interest and dividends		60,949	29,308	26,220
Professional, advisory and other fees		31,942	23,190	25,578
Service fees		14,999	7,918	7,535
Communications		23,460	17,768	14,325
Occupancy and equipment		35,184	32,286	29,055
Depreciation and amortization		13,078	12,713	9,498
Client services and business development		28,327	27,828	25,413
Reinsurance claims, commissions and amortization of deferred acquisition costs		30,486	29,904	0
Restructuring Costs		8,763	0	0
Other Expenses		18,196	14,815	15,594
Consolidated Funds
Interest and dividends		9,836	6,434	1,104
Professional, advisory and other fees		1,145	1,148	654
Floor brokerage and trade execution		318	431	51
Other expenses		1,227	1,051	501
Total expenses		757,598	547,118	504,374
Other income (loss)
Net gains (losses) on securities, derivatives and other investments		76,179	23,381	36,789
Bargain purchase gain, net of tax		6,914	0	0
Gain (Loss) on Extinguishment of Debt		(16,039)	0	0
Consolidated Funds
Net realized and unrealized gains (losses) on investments and other transactions		19,660	7,085	12,517
Net realized and unrealized gains (losses) on derivatives		19,476	13,503	2,071
Net gains (losses) on foreign currency transactions		(411)	97	(91)
Total other income (loss)		105,779	44,066	51,286
Income (loss) before income taxes		6,962	(31,487)	11,479
Income tax expense (benefit)		44,053	(19,092)	(47,496)
Net income (loss)		(37,091)	(12,395)	58,975
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		(23,791)	(6,882)	(15,246)
Net income (loss) attributable to Cowen Inc.		(60,882)	(19,277)	43,729
Preferred stock dividends		6,792	6,792	4,075
Net income (loss) attributable to Cowen Group, Inc. common stockholders		$ (67,674)	$ (26,069)	$ 39,654
Weighted average common shares outstanding:
Basic (in shares)	[1]	29,492	26,857	27,522
Diluted (in shares)	[1]	29,492	26,857	29,043
Earnings (loss) per share:
Earnings Per Share, Basic (in dollars per share)	[1]	$ (2.29)	$ (0.97)	$ 1.44
Earnings Per Share, Diluted (in dollars per share)	[1]	$ (2.29)	$ (0.97)	$ 1.37

[1] Share and per share amounts have been retroactively updated to reflect the one-for-four reverse stock split effective as of December 5, 2016.