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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, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation Of Revenue [Line Items]
Commissions	$ 221,462	$ 200,669	$ 429,296	$ 394,339
Investment banking	331,954	233,460	673,366	471,402
Total revenue from contracts with customers	1,011,937	838,918	2,022,296	1,681,408
Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	174,456	106,155	297,430	206,627
Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	157,498	127,305	375,936	264,775
Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	456,630	403,608	916,087	813,149
Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,891	1,181	3,547	2,518
Global Wealth Management [Member]
Disaggregation Of Revenue [Line Items]
Commissions	147,157	128,203	287,221	254,029
Investment banking	8,693	6,224	14,765	12,132
Total revenue from contracts with customers	614,337	539,182	1,221,555	1,081,717
Global Wealth Management [Member] \| Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	8,558	6,224	14,630	12,132
Global Wealth Management [Member] \| Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	135		135
Global Wealth Management [Member] \| Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	456,596	403,574	916,022	813,080
Global Wealth Management [Member] \| Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,891	1,181	3,547	2,476
Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Commissions	74,305	72,466	142,075	140,310
Investment banking	323,261	227,236	658,601	459,270
Total revenue from contracts with customers	397,600	299,736	800,741	599,649
Institutional Group [Member] \| Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	165,898	99,931	282,800	194,495
Institutional Group [Member] \| Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	157,363	127,305	375,801	264,775
Institutional Group [Member] \| Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	34	34	65	69
Institutional Group [Member] \| Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers				0
Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers				42
Other [Member] \| Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers				42
United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	949,350	787,818	1,868,934	1,570,897
United States [Member] \| Global Wealth Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	614,337	539,182	1,221,555	1,081,717
United States [Member] \| Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	335,013	248,636	647,379	489,138
United States [Member] \| Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers				42
United Kingdom [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	33,204	32,317	85,441	67,881
United Kingdom [Member] \| Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	33,204	32,317	85,441	67,881
Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	17,295	9,786	40,417	26,658
Canada [Member] \| Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	17,295	9,786	40,417	26,658
Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	12,088	8,997	27,504	15,972
Other [Member] \| Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	$ 12,088	$ 8,997	$ 27,504	$ 15,972