Consolidated Statements of Financial Condition (Parenthetical) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Security Owned and Pledged as Collateral, Fair Value	$ 132,555,000	$ 57,583,000
Allowance for receivable from customers	623,000	516,000
Allowance for fees receivable	1,399,000	1,569,000
Allowance for receivable from brokers	719,000	472,000
Assets
Fixed assets, accumulated depreciation and amortization (in dollars)	31,007,000	31,630,000
Intangible assets, accumulated amortization (in dollars)	$ 47,878,000	$ 38,093,000
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
Treasury Stock, Shares	17,462,976	15,336,871
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	46,476,113	43,774,371
Common stock, shares outstanding	29,013,137	28,437,860
Common stock, restricted shares	216,912	253,772
Treasury Stock, Shares	17,462,976	15,336,871
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