Goodwill and Intangibles Schedule of Goodwill by Segment (Details) (Annual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 16, 2021	Oct. 01, 2020
Goodwill [Line Items]
Goodwill, gross	$ 251,469	$ 164,548	$ 161,513
Accumulated impairment charges	(17,464)	(17,464)	(23,785)
Goodwill	234,005	147,084	137,728
Recognized goodwill	86,921	9,356
Goodwill Impairment	0	0	(4,100)
Amortization of Intangible Assets	8,000	13,000	13,100
Investment Management Reporting Unit
Goodwill [Line Items]
Goodwill, gross	0	0	0
Accumulated impairment charges	0	0	0
Goodwill	0	0	0
Recognized goodwill	0	0
Goodwill Impairment	0	0
Investment Bank Reporting Unit
Goodwill [Line Items]
Goodwill, gross	228,764	141,843	132,487
Accumulated impairment charges	(9,485)	(9,485)	(9,485)
Goodwill	219,279	132,358	123,002
Recognized goodwill	86,921	9,356
Goodwill Impairment	0	0
Cowen Investment Management Reporting Unit
Goodwill [Line Items]
Goodwill, gross	22,705	22,705	22,705
Accumulated impairment charges	(7,979)	(7,979)	(7,979)
Goodwill	14,726	14,726	14,726
Recognized goodwill	0	0
Goodwill Impairment	0	0
Asset Company Reporting Unit
Goodwill [Line Items]
Goodwill, gross	0	0	6,321
Accumulated impairment charges	0	0	(6,321)
Goodwill	0	0	0
Recognized goodwill	0	0
Goodwill Impairment	0	0	$ (4,100)
MHT Partners
Goodwill [Line Items]
Goodwill					$ 9,356
Recognized goodwill		9,400
Finite-lived Intangible Assets Acquired		$ 1,200
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		4 years 2 months 1 day
Amortization of Intangible Assets	$ 300	$ 100
MHT Partners | Minimum
Goodwill [Line Items]
Estimated average remaining useful lives	3 years
MHT Partners | Maximum
Goodwill [Line Items]
Estimated average remaining useful lives	5 years
Portico
Goodwill [Line Items]
Goodwill				$ 86,921
Recognized goodwill	$ 86,900
Finite-lived Intangible Assets Acquired	$ 19,900
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	3 years 7 days
Amortization of Intangible Assets	$ 400
Portico | Minimum
Goodwill [Line Items]
Estimated average remaining useful lives	1 year
Portico | Maximum
Goodwill [Line Items]
Estimated average remaining useful lives	4 years