Consolidated Statements of Financial Condition (Parenthetical) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Assets
Security Owned and Pledged as Collateral, Fair Value	$ 1,750,346,000	$ 1,524,136,000
Allowance for receivable from brokers	636,000	885,000
Allowance for receivable from customers	687,000	530,000
Allowance for fees receivable	886,000	3,348,000
Fixed assets, accumulated depreciation and amortization (in dollars)	50,017,000	40,670,000
Intangible assets, accumulated amortization (in dollars)	$ 33,219,000	$ 37,884,000
Stockholders' equity
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	120,750	120,750
Preferred stock, shares outstanding	120,750	120,750
Preferred Stock, Liquidation Preference, Value	$ 120,750,000	$ 120,750,000
Common stock, shares authorized	125,000,000
Portfolio Funds
Assets
Investment Owned, at Fair Value	$ 137,986,000	$ 133,454,000
Common Stock Class A
Stockholders' equity
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	62,500,000	62,500,000
Common stock, shares issued	55,826,893	49,465,491
Common stock, shares outstanding	27,778,964	26,845,628
Treasury Stock, Shares	28,047,929	22,619,863
Common Stock Class A | Restricted Stock
Stockholders' equity
Common stock, shares outstanding	901,374	334,230
Common Stock Class B
Stockholders' equity
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	62,500,000	62,500,000
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0
Convertible Preferred Stock
Stockholders' equity
Preferred Stock, Value, Issued	$ 0	$ 1,000