Revenues from Contracts with Customers (Schedule of Total Revenues Broken Out by Revenues from Contracts with Customers and Other Sources of Revenues) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenues:
Revenue from contracts with customers	[1]	$ 799,285	$ 882,534	$ 1,600,763	$ 1,736,556
Other sources of revenue:
Interest		204,022	127,305	362,545	248,754
Principal transactions		125,603	152,597	284,873	317,603
Other		(3,450)	4,878	3,263	13,630
Total revenues		1,125,460	1,167,314	2,251,444	2,316,543
Commissions [Member]
Revenues:
Revenue from contracts with customers		186,681	195,579	382,590	409,193
Investment Banking [Member]
Revenues:
Revenue from contracts with customers		271,075	376,443	525,921	715,731
Asset Management [Member]
Revenues:
Revenue from contracts with customers		331,264	295,869	672,900	574,016
Interest [Member]
Revenues:
Revenue from contracts with customers	[1]	8,732	6,286	15,644	12,377
Other [Member]
Revenues:
Revenue from contracts with customers	[1]	$ 1,533	$ 8,357	$ 3,708	$ 25,239

[1] Excludes revenues not derived from contracts with customers included in the Other segment.