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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		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Disaggregation Of Revenue [Line Items]
Commissions	$ 200,756	$ 206,075	$ 630,052	$ 600,414
Investment banking	306,203	323,483	979,569	794,885
Total revenue from contracts with customers	1,000,806	962,627	3,023,102	2,644,035
Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	132,875	144,213	430,305	350,840
Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	173,328	179,270	549,264	444,045
Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	492,163	431,399	1,408,250	1,244,548
Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,684	1,670	5,231	4,188
Global Wealth Management [Member]
Disaggregation Of Revenue [Line Items]
Commissions	136,513	141,864	423,734	395,893
Investment banking	6,731	6,529	21,496	18,661
Total revenue from contracts with customers	637,051	581,270	1,858,606	1,662,987
Global Wealth Management [Member] \| Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	6,420	6,529	21,050	18,661
Global Wealth Management [Member] \| Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	311		446
Global Wealth Management [Member] \| Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	492,123	431,363	1,408,145	1,244,443
Global Wealth Management [Member] \| Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,684	1,514	5,231	3,990
Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Commissions	64,243	64,211	206,318	204,521
Investment banking	299,472	316,954	958,073	776,224
Total revenue from contracts with customers	363,755	381,201	1,164,496	980,850
Institutional Group [Member] \| Capital Raising [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	126,455	137,684	409,255	332,179
Institutional Group [Member] \| Advisory [Member]
Disaggregation Of Revenue [Line Items]
Investment banking	173,017	179,270	548,818	444,045
Institutional Group [Member] \| Asset Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	40	36	105	105
Institutional Group [Member] \| Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers			0	0
Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers		156		198
Other [Member] \| Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers		156		198
United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	935,883	895,119	2,813,029	2,464,696
United States [Member] \| Global Wealth Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	637,051	581,270	1,858,606	1,662,987
United States [Member] \| Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	298,832	313,693	954,423	801,511
United States [Member] \| Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers		156		198
United Kingdom [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	29,123	39,018	114,564	107,896
United Kingdom [Member] \| Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	29,123	39,018	114,564	107,896
Canada [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	20,991	14,749	61,408	41,407
Canada [Member] \| Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	20,991	14,749	61,408	41,407
Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	14,809	13,741	34,101	30,036
Other [Member] \| Institutional Group [Member]
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	$ 14,809	$ 13,741	$ 34,101	$ 30,036