Acquisition (Preliminary Purchase Price Allocation) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 16, 2021	Feb. 26, 2021	Dec. 31, 2020	Oct. 01, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 234,005			$ 147,084		$ 137,728
Portico
Business Acquisition [Line Items]
Cash		$ 5,089
Operating lease right-of-use assets		2,707
Fixed assets		8
Intangible assets		19,900
Other assets		514
Operating lease liabilities		(2,707)
Other liabilities		(401)
Total net identifiable assets acquired and liabilities assumed		25,110
Goodwill		86,921
Total estimated purchase price		$ 112,031
Cowen Insurance
Business Acquisition [Line Items]
Cash			$ 14,844
Securities owned, at fair value			1,571
Fixed assets			30
Intangible assets			4,794
Other assets			12,828
Compensation payable			(17)
Other liabilities			(16,099)
Total net identifiable assets acquired and liabilities assumed			17,951
Bargain purchase gain			(5,216)
Total estimated purchase price			$ 12,735
MHT Partners
Business Acquisition [Line Items]
Operating lease right-of-use assets					$ 1,120
Fixed assets					101
Intangible assets					1,224
Other assets					43
Operating lease liabilities					(1,446)
Compensation payable					(533)
Total net identifiable assets acquired and liabilities assumed					509
Goodwill					9,356
Total estimated purchase price					$ 9,865