CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
ASSETS
Cash and cash equivalents	$ 123,000	$ 15,000
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, shares outstanding (in shares)	26.7	27.5
Treasury stock, shares (in shares)	8,843,454	8,142,732
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, shares issued (in shares)	16,547,476	16,621,426
Common stock, shares outstanding (in shares)	7,704,022	8,478,694
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	100,000,000
Common stock, shares issued (in shares)	24,000,000	24,000,000
Common stock, shares outstanding (in shares)	19,024,117	19,024,117
Subordinated Notes [Member]
LIABILITIES AND STOCKHOLDERS' EQUITY
Debt issuance costs	$ 75
Debt instrument, maturity date	Jun. 15, 2023
5.875% Senior Notes [Member]
LIABILITIES AND STOCKHOLDERS' EQUITY
Debt instrument, interest rate	5.875%	5.875%
Debt issuance costs		$ 10
Debt instrument, maturity date	Jun. 01, 2021