Condensed Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Investment Securities and Certificates of Deposit, amortized cost	$ 185,420	$ 744,178
Accounts Receivable, allowances	4,758	5,603
Furniture, Equipment and Leasehold Improvements, accumulated depreciation and amortization	$ 218,793	$ 212,929
Treasury Stock, Common, Shares	45,827,585	44,340,396
Class A [Member]
Common Stock, Par Value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized	1,000,000,000	1,000,000,000
Common Stock, Shares, Issued	84,342,335	82,114,009
Common Stock, Shares, Outstanding	38,514,750	37,773,613
Class B [Member]
Common Stock, Par Value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized	1,000,000	1,000,000
Common Stock, Shares, Issued	45	46
Common Stock, Shares, Outstanding	45	46