Revenues from Contracts with Customers (Revenues from Contracts with Customers Disaggregated by Major Business Activity and Primary Geographic Regions) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation Of Revenue [Line Items]
Commissions	[1]	$ 165,358	$ 186,681	$ 334,908	$ 382,590
Investment banking	[1]	166,825	271,075	378,704	525,921
Revenue from contracts with customers	[1]	653,827	790,553	1,352,052	1,585,119
Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	78,951	71,519	139,767	144,969
Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	87,874	199,556	238,937	380,952
Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	320,264	331,264	635,833	672,900
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	1,380	1,533	2,607	3,708
Global Wealth Management [Member]
Disaggregation Of Revenue [Line Items]
Commissions	[1]	109,836	122,004	220,027	252,780
Investment banking	[1]	4,065	5,056	8,223	10,203
Revenue from contracts with customers	[1]	435,457	459,775	866,527	939,433
Global Wealth Management [Member] | Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	4,065	5,056	8,223	10,203
Global Wealth Management [Member] | Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	320,238	331,243	635,775	672,856
Global Wealth Management [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	1,318	1,472	2,502	3,594
Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Commissions	[1]	55,522	64,677	114,881	129,810
Investment banking	[1]	161,481	266,019	369,202	515,718
Revenue from contracts with customers	[1]	217,029	330,717	484,141	645,572
Institutional Group [Member] | Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	74,886	66,463	131,544	134,766
Institutional Group [Member] | Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	86,595	199,556	237,658	380,952
Institutional Group [Member] | Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	26	21	58	44
Other [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	1,279		1,279
Revenue from contracts with customers	[1]	1,341	61	1,384	114
Other [Member] | Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	1,279		1,279
Other [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Other	[1]	62	61	105	114
United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	577,902	737,311	1,219,892	1,479,608
United States [Member] | Global Wealth Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	435,457	459,775	866,527	939,433
United States [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	141,104	277,475	351,981	540,061
United States [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	1,341	61	1,384	114
United Kingdom [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	45,221	37,047	68,604	71,355
United Kingdom [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	45,221	37,047	68,604	71,355
Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	7,614	7,782	30,137	17,123
Canada [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	7,614	7,782	30,137	17,123
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	23,090	8,413	33,419	17,033
Other [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	$ 23,090	$ 8,413	$ 33,419	$ 17,033

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