Segment Operating Results - Segment Expense Footnotes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Occupancy and Equipment Rental	$ 25,731	$ 21,944
Professional Fees	32,613	31,219
Travel and Related Expenses	22,018	19,222
Communications and Information Services	23,144	19,167
Depreciation and Amortization	5,976	6,293
Execution, Clearing and Custody Fees	3,346	3,341
Other Operating Expenses	10,992	7,804
Non-Compensation	123,820	108,990
Investment Banking & Equities
Segment Reporting Information [Line Items]
Occupancy and Equipment Rental	25,103	21,403
Professional Fees	31,094	30,063
Travel and Related Expenses	21,811	18,973
Communications and Information Services	22,302	18,464
Depreciation and Amortization	5,893	6,209
Execution, Clearing and Custody Fees	2,883	2,923
Other Operating Expenses	10,688	7,516
Non-Compensation	119,774	105,551
Investment Management
Segment Reporting Information [Line Items]
Occupancy and Equipment Rental	628	541
Professional Fees	1,519	1,156
Travel and Related Expenses	207	249
Communications and Information Services	842	703
Depreciation and Amortization	83	84
Execution, Clearing and Custody Fees	463	418
Other Operating Expenses	304	288
Non-Compensation	$ 4,046	$ 3,439