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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation Of Revenue [Line Items]
Commissions	[1]	$ 186,681	$ 195,579	$ 382,590	$ 409,193
Investment banking	[1]	271,075	376,443	525,921	715,731
Revenue from contracts with customers	[1]	799,285	882,534	1,600,763	1,736,556
Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	71,519	169,778	144,969	378,584
Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	199,556	206,665	380,952	337,147
Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	331,264	295,869	672,900	574,016
Interest [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	8,732	6,286	15,644	12,377
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	1,533	8,357	3,708	25,239
Global Wealth Management [Member]
Disaggregation Of Revenue [Line Items]
Commissions	[1]	122,004	139,653	252,780	287,158
Investment banking	[1]	5,056	11,898	10,203	25,447
Revenue from contracts with customers	[1]	468,375	462,066	954,897	922,209
Global Wealth Management [Member] | Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	5,056	11,898	10,203	25,447
Global Wealth Management [Member] | Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	0	0	0	0
Global Wealth Management [Member] | Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	331,243	295,847	672,856	573,956
Global Wealth Management [Member] | Interest [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	8,600	6,246	15,464	12,302
Global Wealth Management [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	1,472	8,422	3,594	23,346
Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Commissions	[1]	64,677	55,926	129,810	122,035
Investment banking	[1]	266,019	364,545	515,718	690,284
Revenue from contracts with customers	[1]	330,849	420,533	645,752	812,454
Institutional Group [Member] | Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	66,463	157,880	134,766	353,137
Institutional Group [Member] | Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	[1]	199,556	206,665	380,952	337,147
Institutional Group [Member] | Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	21	22	44	60
Institutional Group [Member] | Interest [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	132	40	180	75
Institutional Group [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	0	0	0	0
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	61	(65)	114	1,893
Other [Member] | Interest [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	0	0	0	0
Other [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	61	(65)	114	1,893
United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	746,001	806,496	1,495,173	1,572,447
United States [Member] | Global Wealth Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	468,375	462,066	954,897	922,209
United States [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	277,565	344,495	540,162	648,345
United States [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	61	(65)	114	1,893
United Kingdom [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	37,047	45,824	71,355	91,215
United Kingdom [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	37,047	45,824	71,355	91,215
Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	7,824	21,350	17,202	51,129
Canada [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	7,824	21,350	17,202	51,129
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	8,413	8,864	17,033	21,765
Other [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	[1]	$ 8,413	$ 8,864	$ 17,033	$ 21,765

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