CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Stockholders' Equity
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common Stock, outstanding (in shares)	26,600,000	26,700,000
Treasury stock, shares (in shares)	8,984,349	8,843,454
Class A [Member]
Stockholders' Equity
Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, shares authorized (in shares)	100,000,000	100,000,000
Common Stock, issued (in shares)	16,543,976	16,547,476
Common Stock, outstanding (in shares)	7,559,627	7,704,022
Class B [Member]
Stockholders' Equity
Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, shares authorized (in shares)	25,000,000	25,000,000
Common Stock, issued (in shares)	24,000,000	24,000,000
Common Stock, outstanding (in shares)	19,024,117	19,024,117
Subordinated Notes [Member]
LIABILITIES AND STOCKHOLDERS' EQUITY
Debt issuance costs	$ 62	$ 75
Debt instrument, maturity date	Jun. 15, 2023
U.S. Treasury Bills [Member]
ASSETS
Cash and cash equivalents	$ 138,000	$ 123,000