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, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation Of Revenue [Line Items]
Commissions	$ 183,317	$ 165,358	$ 368,793	$ 334,908
Investment banking	233,281	166,825	447,230	378,704
Revenue from contracts with customers	798,917	653,827	1,567,054	1,352,052
Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	101,870	78,951	196,567	139,767
Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	131,411	87,874	250,663	238,937
Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	380,757	320,264	748,233	635,833
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	1,562	1,380	2,798	2,607
Global Wealth Management [Member]
Disaggregation Of Revenue [Line Items]
Commissions	121,465	109,836	242,682	220,027
Investment banking	5,780	4,065	10,060	8,223
Revenue from contracts with customers	509,544	435,457	1,003,727	866,527
Global Wealth Management [Member] | Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	5,780	4,065	10,060	8,223
Global Wealth Management [Member] | Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	380,737	320,238	748,187	635,775
Global Wealth Management [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	1,562	1,318	2,798	2,502
Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Commissions	61,852	55,522	126,111	114,881
Investment banking	227,501	162,760	437,170	370,481
Revenue from contracts with customers	289,373	218,308	563,327	485,420
Institutional Group [Member] | Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	96,090	74,886	186,507	131,544
Institutional Group [Member] | Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	131,411	87,874	250,663	238,937
Institutional Group [Member] | Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	20	26	46	58
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers		62		105
Other [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Other		62		105
United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	743,642	577,902	1,461,275	1,219,892
United States [Member] | Global Wealth Management [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	509,544	435,457	1,003,727	866,527
United States [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	234,098	142,383	457,548	353,260
United States [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers		62		105
United Kingdom [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	33,386	45,221	61,571	68,604
United Kingdom [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	33,386	45,221	61,571	68,604
Canada [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	9,712	7,614	21,087	30,137
Canada [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	9,712	7,614	21,087	30,137
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	12,177	23,090	23,121	33,419
Other [Member] | Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	$ 12,177	$ 23,090	$ 23,121	$ 33,419