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)	Retained Earnings/(Accumulated deficit) Cumulative Effect, Period of Adoption, Adjustment	Parent	Nonredeemable Noncontrolling Interests
Common stock outstanding, beginning balance (in shares) at Dec. 31, 2018		28,437,860
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock awards issued (in shares)		2,407,857
Common stock issuance for purchase of investment		0
Common stock issuance upon acquisition (in shares)		1,033,350
Purchase of treasury stock, at cost (in shares)		(3,268,710)
Share settlement of convertible notes (in shares)		0
Common stock outstanding, ending balance (in shares) at Dec. 31, 2019		28,610,357
Preferred stock outstanding, beginning balance (in shares) at Dec. 31, 2018			120,750
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Modification of Series A Convertible Preferred Stock (in shares)			0
Preferred stock outstanding, ending balance (in shares) at Dec. 31, 2019			120,750
Balance, start at Dec. 31, 2018		$ 324	$ 1	$ (234,142)	$ 1,062,877	$ (5)	$ (34,648)	$ 0	$ 794,407	$ 64,880
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuance upon acquisition	$ 14,446	10			14,436
Reclassification of Series A Convertible Preferred Stock			0		0
Purchase of treasury stock, at cost				(50,159)
Common stock issuance for purchase of investment					0
Embedded cash conversion option, net of tax					(596)
Equity portion of convertible note extinguishment					0
Amortization of share based awards					33,918
Foreign currency translation						0
Net income (loss) attributable to Cowen Inc.	24,631						24,631
Preferred dividends paid							(6,792)
Cash dividends to common stockholders	0						0
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds										22,797
Capital contributions										11,655
Capital withdrawals										(5,012)
Consolidation of entity										0
Deconsolidation of entity										0
Balance, end at Dec. 31, 2019	$ 904,175	$ 334	$ 1	(284,301)	1,110,635	(5)	(16,809)	(10)	809,855	94,320
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock awards issued (in shares)		2,174,859
Common stock issuance for purchase of investment		0
Common stock issuance upon acquisition (in shares)		74,694
Purchase of treasury stock, at cost (in shares)		(4,014,282)
Share settlement of convertible notes (in shares)		0
Common stock outstanding, ending balance (in shares) at Dec. 31, 2020		26,845,628
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Modification of Series A Convertible Preferred Stock (in shares)			0
Preferred stock outstanding, ending balance (in shares) at Dec. 31, 2020	120,750		120,750
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuance upon acquisition	$ 926	$ 0			926
Reclassification of Series A Convertible Preferred Stock			$ 0		0
Purchase of treasury stock, at cost				(62,569)
Common stock issuance for purchase of investment					0
Embedded cash conversion option, net of tax					0
Equity portion of convertible note extinguishment					(29,645)
Amortization of share based awards					48,222
Foreign currency translation						(2)
Net income (loss) attributable to Cowen Inc.	216,363						216,363
Preferred dividends paid							(6,792)
Cash dividends to common stockholders	(6,851)						(6,851)
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds										23,625
Capital contributions										201,223
Capital withdrawals										(78,251)
Consolidation of entity										48,596
Deconsolidation of entity										(89,889)
Balance, end at Dec. 31, 2020	$ 1,169,121	$ 334	$ 1	(346,870)	1,130,138	(7)	185,901	$ 0	969,497	199,624
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock awards issued (in shares)		2,710,719
Common stock issuance for purchase of investment		68,980
Common stock issuance upon acquisition (in shares)		642,862
Purchase of treasury stock, at cost (in shares)		(5,428,066)
Share settlement of convertible notes (in shares)		2,938,841
Common stock outstanding, ending balance (in shares) at Dec. 31, 2021		27,778,964
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Modification of Series A Convertible Preferred Stock (in shares)			(120,750)
Preferred stock outstanding, ending balance (in shares) at Dec. 31, 2021	120,750		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuance upon acquisition	$ 23,060	$ 0			23,060
Reclassification of Series A Convertible Preferred Stock			$ (1)		(120,749)
Purchase of treasury stock, at cost				(200,242)
Common stock issuance for purchase of investment					2,500
Embedded cash conversion option, net of tax					0
Equity portion of convertible note extinguishment					0
Amortization of share based awards					65,718
Foreign currency translation						5
Net income (loss) attributable to Cowen Inc.	295,611						295,611
Preferred dividends paid							(6,792)
Cash dividends to common stockholders	(12,738)						(12,738)
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds										8,380
Capital contributions										55,556
Capital withdrawals										(29,012)
Consolidation of entity										0
Deconsolidation of entity										(74,813)
Balance, end at Dec. 31, 2021	$ 1,175,604	$ 334	$ 0	$ (547,112)	$ 1,100,667	$ (2)	$ 461,982		$ 1,015,869	$ 159,735