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, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Revenues:
Revenue from contracts with customers	[1]	$ 695,034	$ 887,096	$ 2,295,797	$ 2,623,652
Other sources of revenue:
Interest		291,685	135,220	654,230	383,974
Principal transactions		118,379	118,977	403,252	436,580
Other		(203)	13,668	3,060	27,298
Total revenues		1,104,895	1,154,961	3,356,339	3,471,504
Commissions [Member]
Revenues:
Revenue from contracts with customers		159,054	189,239	541,644	598,432
Investment Banking [Member]
Revenues:
Revenue from contracts with customers		221,858	372,279	747,779	1,088,010
Asset Management [Member]
Revenues:
Revenue from contracts with customers		300,557	313,862	973,457	887,878
Interest [Member]
Revenues:
Revenue from contracts with customers	[1]	12,510	6,624	28,154	19,001
Other [Member]
Revenues:
Revenue from contracts with customers	[1]	$ 1,055	$ 5,092	$ 4,763	$ 30,331

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