Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Shares	Preferred Shares	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings/(Accumulated deficit)	Cowen Inc Equity	Nonredeemable Noncontrolling Interests
Common stock outstanding, beginning balance (in shares) at Dec. 31, 2020		26,845,628
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock awards issued (in shares)		705,512
Common stock issuance upon acquisition (in shares)		56,801
Purchase of treasury stock, at cost (in shares)		(755,610)
Common stock outstanding, ending balance (in shares) at Mar. 31, 2021		26,852,331
Preferred stock outstanding, beginning balance (in shares) at Dec. 31, 2020			120,750
Preferred stock outstanding, ending balance (in shares) at Mar. 31, 2021			120,750
Balance, start at Dec. 31, 2020		$ 334	$ 1	$ (346,870)	$ 1,130,138	$ (7)	$ 185,901	$ 969,497	$ 199,624
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury stock, at cost				(26,904)
Common stock issuance upon acquisition	$ 2,202				2,202
Amortization of share based awards					19,037
Foreign currency translation						4
Net income (loss) attributable to Cowen Inc.	147,504						147,504
Preferred dividends paid							(1,698)
Cash dividends declared	(2,777)						(2,777)
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds									4,562
Capital contributions									22,515
Capital withdrawals									(18,773)
Deconsolidation of entity									(74,813)
Balance, end at Mar. 31, 2021	1,239,980	$ 334	$ 1	(373,774)	1,151,377	(3)	328,930	1,106,865	133,115
Common stock outstanding, beginning balance (in shares) at Dec. 31, 2021		27,778,964
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock awards issued (in shares)		949,803
Common stock issuance upon acquisition (in shares)		58,587
Purchase of treasury stock, at cost (in shares)		(1,172,451)
Common stock outstanding, ending balance (in shares) at Mar. 31, 2022		27,614,903
Preferred stock outstanding, beginning balance (in shares) at Dec. 31, 2021			0
Preferred stock outstanding, ending balance (in shares) at Mar. 31, 2022			0
Balance, start at Dec. 31, 2021	1,175,604	$ 334	$ 0	(547,112)	1,100,667	(2)	461,982	1,015,869	159,735
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury stock, at cost				(36,423)
Common stock issuance upon acquisition	1,881				1,881
Amortization of share based awards					24,612
Foreign currency translation						2
Net income (loss) attributable to Cowen Inc.	35,016						35,016
Preferred dividends paid							(1,698)
Cash dividends declared	(4,111)						(4,111)
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds									20,131
Capital contributions									1,610
Capital withdrawals									(5,901)
Deconsolidation of entity									0
Balance, end at Mar. 31, 2022	$ 1,210,723	$ 334	$ 0	$ (583,535)	$ 1,127,160	$ 0	$ 491,189	$ 1,035,148	$ 175,575