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
		Mar. 31, 2022	Mar. 31, 2021
Revenues:
Revenue from contracts with customers	[1]	$ 801,478	$ 854,022
Other sources of revenue:
Interest		158,523	121,449
Principal transactions		159,270	165,006
Other		6,713	8,752
Total revenues		1,125,984	1,149,229
Commissions [Member]
Revenues:
Revenue from contracts with customers		195,909	213,614
Investment Banking [Member]
Revenues:
Revenue from contracts with customers		254,846	339,288
Asset management [Member]
Revenues:
Revenue from contracts with customers		341,636	278,147
Interest [Member]
Revenues:
Revenue from contracts with customers	[1]	6,912	6,091
Other [Member]
Revenues:
Revenue from contracts with customers	[1]	$ 2,175	$ 16,882

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