Consolidated Statements of Operations - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues
Investment banking	$ 194,341,000	$ 77,292,000	$ 503,351,000	$ 272,103,000
Brokerage	138,483,000	93,995,000	425,069,000	302,840,000
Management fees	11,954,000	7,300,000	35,211,000	21,480,000
Incentive income	127,000	701,000	127,000	724,000
Interest and dividends	37,552,000	60,707,000	127,547,000	129,846,000
Reimbursement from affiliates	269,000	238,000	777,000	780,000
Reinsurance premiums	2,505,000	8,146,000	18,943,000	29,068,000
Other revenues	1,369,000	1,237,000	4,709,000	3,228,000
Consolidated Funds
Interest and dividends	1,135,000	2,374,000	3,992,000	8,148,000
Other revenues	0	57,000	658,000	91,000
Total revenues	387,735,000	252,047,000	1,120,384,000	768,308,000
Interest and dividends expense	37,754,000	56,477,000	125,850,000	125,089,000
Total net revenues	349,981,000	195,570,000	994,534,000	643,219,000
Expenses
Employee compensation and benefits	153,427,000	120,320,000	583,137,000	388,611,000
Brokerage and trade execution costs	33,660,000	25,808,000	101,412,000	78,578,000
Underwriting expenses	4,013,000	2,846,000	16,524,000	12,383,000
Professional, advisory and other fees	15,085,000	15,535,000	40,519,000	39,396,000
Service fees	4,727,000	5,943,000	18,332,000	17,266,000
Communications	7,992,000	8,295,000	24,241,000	24,654,000
Occupancy and equipment	9,096,000	9,784,000	27,599,000	30,160,000
Depreciation and amortization	5,682,000	5,082,000	17,324,000	14,990,000
Client services and business development	2,343,000	10,364,000	16,906,000	33,549,000
Goodwill Impairment	0	0	0	4,100,000
Reinsurance claims, commissions and amortization of deferred acquisition costs	4,852,000	8,195,000	21,716,000	25,139,000
Other expenses	7,868,000	5,276,000	19,417,000	14,929,000
Consolidated Funds
Interest and dividends	0	1,153,000	2,064,000	3,376,000
Professional, advisory and other fees	334,000	857,000	1,598,000	1,375,000
Brokerage and trade execution costs	0	15,000	37,000	103,000
Other expenses	160,000	491,000	1,094,000	1,375,000
Total expenses	249,239,000	219,964,000	891,920,000	689,984,000
Other income (loss)
Net gains (losses) on securities, derivatives and other investments	(68,781,000)	18,446,000	83,738,000	61,440,000
Consolidated Funds
Net realized and unrealized gains (losses) on investments and other transactions	6,385,000	13,613,000	(31,222,000)	22,793,000
Net realized and unrealized gains (losses) on derivatives	0	293,000	1,850,000	(1,188,000)
Net gains (losses) on foreign currency transactions	0	(10,000)	(38,000)	(69,000)
Total other income (loss)	(62,396,000)	32,342,000	54,328,000	82,976,000
Income (loss) before income taxes	38,346,000	7,948,000	156,942,000	36,211,000
Income tax expense (benefit)	8,830,000	1,365,000	52,589,000	9,615,000
Net income (loss)	29,516,000	6,583,000	104,353,000	26,596,000
Net Income (Loss) Attributable to Noncontrolling Interest	9,232,000	2,770,000	(19,843,000)	7,188,000
Net income (loss) attributable to Cowen Inc.	20,284,000	3,813,000	124,196,000	19,408,000
Preferred stock dividends	1,698,000	1,698,000	5,094,000	5,094,000
Net income (loss) attributable to Cowen Inc. common stockholders	$ 18,586,000	$ 2,115,000	$ 119,102,000	$ 14,314,000
Weighted average common shares outstanding:
Basic (in shares)	27,663	29,529	28,078	29,687
Diluted (in shares)	29,970	31,264	29,646	31,381
Earnings (loss) per share:
Earnings Per Share, Basic (in dollars per share)	$ 0.67	$ 0.07	$ 4.24	$ 0.48
Earnings Per Share, Diluted (in dollars per share)	$ 0.62	$ 0.07	$ 4.02	$ 0.46