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		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues:
Revenue from contracts with customers	[1]	$ 646,469	$ 682,524	$ 1,998,521	$ 2,267,643
Other sources of revenue:
Interest		505,198	304,195	1,439,532	682,384
Principal transactions		114,841	118,379	336,063	403,252
Other		(921)	(203)	(4,927)	3,060
Total revenues		1,265,587	1,104,895	3,769,189	3,356,339
Commissions [Member]
Revenues:
Revenue from contracts with customers		165,075	159,054	499,983	541,644
Investment Banking [Member]
Revenues:
Revenue from contracts with customers		146,887	221,858	525,591	747,779
Asset Management [Member]
Revenues:
Revenue from contracts with customers		333,127	300,557	968,960	973,457
Other [Member]
Revenues:
Revenue from contracts with customers	[1]	$ 1,380	$ 1,055	$ 3,987	$ 4,763

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