Segment Operating Results - Segment Contribution (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Net Revenues	$ 3,855,820	$ 2,979,593	$ 2,425,949
Employee Compensation and Benefits	2,500,834	1,974,036	1,656,875
Non-Compensation	565,044	471,338	407,018
Special Charges, Including Business Realignment Costs	0	7,305	2,921
Income Before Income from Equity Method Investments and Income Taxes	789,942	526,914	359,135
Income (Loss) from Equity Method Investments	3,872	6,231	6,655
Pre-Tax Income	793,814	533,145	365,790
Identifiable Segment Assets	5,358,097	4,173,971	3,703,298
Investment Banking & Equities
Segment Reporting Information [Line Items]
Net Revenues	3,767,655	2,898,489	2,355,943
Employee Compensation and Benefits	2,448,409	1,927,928	1,617,449
Non-Compensation	548,304	456,257	393,308
Special Charges, Including Business Realignment Costs	0	7,305	2,921
Income Before Income from Equity Method Investments and Income Taxes	770,942	506,999	342,265
Income (Loss) from Equity Method Investments	6	1,073	620
Pre-Tax Income	770,948	508,072	342,885
Identifiable Segment Assets	5,184,718	4,022,227	3,541,886
Investment Management
Segment Reporting Information [Line Items]
Net Revenues	88,165	81,104	70,006
Employee Compensation and Benefits	52,425	46,108	39,426
Non-Compensation	16,740	15,081	13,710
Income Before Income from Equity Method Investments and Income Taxes	19,000	19,915	16,870
Income (Loss) from Equity Method Investments	3,866	5,158	6,035
Pre-Tax Income	22,866	25,073	22,905
Identifiable Segment Assets	$ 173,379	$ 151,744	$ 161,412