Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Investment banking	$ 357,222	$ 223,614	$ 133,279
Brokerage	413,582	293,610	199,180
Management fees	29,658	33,245	40,612
Incentive income	3,117	5,383	8,334
Interest and dividends	108,009	49,440	14,732
Reimbursement from affiliates	1,038	2,860	10,504
Aircraft lease revenue	1,852	3,751	4,161
Reinsurance premiums	38,096	30,996	32,459
Other revenues	4,504	8,561	22,355
Consolidated Funds
Interest and dividends	9,816	5,870	4,792
Other revenues	22	1,451	1,157
Total revenues	966,916	658,781	471,565
Interest and dividends expense	104,116	60,949	29,308
Total net revenues	862,800	597,832	442,257
Expenses
Employee compensation and benefits	509,289	404,087	310,038
Floor brokerage and trade execution	109,399	75,601	32,286
Underwriting expenses	15,282	0	0
Professional, advisory and other fees	40,957	31,942	23,190
Service fees	20,198	14,999	7,918
Communications	30,801	23,460	17,768
Occupancy and equipment	41,602	35,184	32,286
Depreciation and amortization	12,436	13,078	12,713
Client services and business development	35,927	28,327	27,828
Reinsurance claims, commissions and amortization of deferred acquisition costs	41,086	30,486	29,904
Restructuring costs	0	8,763	0
Other expenses	22,014	18,196	14,815
Consolidated Funds
Interest and dividends	6,534	9,836	6,434
Professional, advisory and other fees	938	1,145	1,148
Floor brokerage and trade execution	256	318	431
Other expenses	887	1,227	1,051
Total expenses	887,606	696,649	517,810
Other income (loss)
Net gains (losses) on securities, derivatives and other investments	68,043	76,179	23,381
Bargain purchase gain, net of tax	0	6,914	0
Gain (loss) on debt extinguishment	(556)	(16,039)	0
Consolidated Funds
Net realized and unrealized gains (losses) on investments and other transactions	46,656	19,660	7,085
Net realized and unrealized gains (losses) on derivatives	9,408	19,476	13,503
Net gains (losses) on foreign currency transactions	191	(411)	97
Total other income (loss)	123,742	105,779	44,066
Income (loss) before income taxes	98,936	6,962	(31,487)
Income tax expense (benefit)	15,719	44,053	(19,092)
Net income (loss)	83,217	(37,091)	(12,395)
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds	(40,398)	(23,791)	(6,882)
Net income (loss) attributable to Cowen Inc.	42,819	(60,882)	(19,277)
Preferred stock dividends	6,792	6,792	6,792
Net income (loss) attributable to Cowen Inc. common stockholders	$ 36,027	$ (67,674)	$ (26,069)
Weighted average common shares outstanding:
Basic (in shares)	29,545	29,492	26,857
Diluted (in shares)	30,735	29,492	26,857
Earnings (loss) per share:
Earnings Per Share, Basic (in dollars per share)	$ 1.22	$ (2.29)	$ (0.97)
Earnings Per Share, Diluted (in dollars per share)	$ 1.17	$ (2.29)	$ (0.97)