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, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Revenues:
Revenue from contracts with customers	[1]	$ 653,827	$ 790,553	$ 1,352,052	$ 1,585,119
Other sources of revenue:
Interest		482,770	212,754	934,334	378,189
Principal transactions		105,700	125,603	221,222	284,873
Other		(486)	(3,450)	(4,006)	3,263
Total revenues		1,241,811	1,125,460	2,503,602	2,251,444
Commissions [Member]
Revenues:
Revenue from contracts with customers		165,358	186,681	334,908	382,590
Investment Banking [Member]
Revenues:
Revenue from contracts with customers		166,825	271,075	378,704	525,921
Asset Management [Member]
Revenues:
Revenue from contracts with customers		320,264	331,264	635,833	672,900
Other [Member]
Revenues:
Revenue from contracts with customers	[1]	$ 1,380	$ 1,533	$ 2,607	$ 3,708

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