Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Computation of earnings per share:
Net income (loss)	$ 65,855	$ 303,991	$ 207,064
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	(10,603)	8,380	(9,299)
Net income (loss) attributable to Cowen Inc.	76,458	295,611	216,363
Preferred stock dividends	6,792	6,792	6,792
Net income (loss) attributable to Cowen Inc. common stockholders	69,666	288,819	209,571
Dilutive Securities, Effect on Basic Earnings Per Share	55	0	0
Net Income (Loss) Available to Common Stockholders, Diluted	$ 69,721	$ 288,819	$ 209,571
Shares for basic and diluted calculations:
Weighted average shares used in basic computation, shares	28,183,000	27,721,000	27,790,000
Weighted average shares used in diluted computation, shares	31,544,000	32,628,000	29,519,000
Earnings (loss) per share:
Earnings Per Share, Basic (in dollars per share)	$ 2.47	$ 10.42	$ 7.54
Earnings Per Share, Diluted (in dollars per share)	$ 2.21	$ 8.85	$ 7.10
Convertible Debt
Shares for basic and diluted calculations:
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	0	1,404,000	0
Convertible Preferred Stock
Shares for basic and diluted calculations:
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	949,000	0	0
Restricted Stock
Shares for basic and diluted calculations:
Shares attributable to share-based payment awards, shares	1,932,000	2,748,000	1,644,000
Restricted Stock | Quarton
Shares for basic and diluted calculations:
Shares attributable to share-based payment awards, shares	50,000	0	85,000
Restricted Stock Units (RSUs) | Equity Plans
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Share-based compensation arrangement by share-based payment award, non-option equity instruments, outstanding, number		972,732
Performance based restricted stock
Shares for basic and diluted calculations:
Shares attributable to share-based payment awards, shares	430,000	755,000	0
Common Stock Class A
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares outstanding, shares	28,234,289	27,778,964
Common stock, restricted shares, shares	310,426
Common Stock Class A | Restricted Stock
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares outstanding, shares	950,919	901,374