Condensed Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale, Amortized Cost	$ 117,508	$ 802,652
Accounts Receivable, Allowances	7,217	4,683
Furniture, Equipment and Leasehold Improvements, Accumulated Depreciation and Amortization	$ 194,413	$ 187,077
Treasury Stock at Cost, shares	43,491,694	41,339,113
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	81,836,929	79,686,375
Common Stock, Shares, Outstanding	38,345,235	38,347,262
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	51	50
Common Stock, Shares, Outstanding	51	50