Consolidated Statements of Financial Condition (Parenthetical) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Security Owned and Pledged as Collateral, Fair Value	$ 224,264,000	$ 57,583,000
Allowance for receivable from customers	563,000	516,000
Allowance for fees receivable	915,000	1,569,000
Allowance for receivable from brokers	780,000	472,000
Other investments fair value	146,133,000	141,236,000
Other assets, Allowance for Notes	11,000	0
Assets
Fixed assets, accumulated depreciation and amortization (in dollars)	29,684,000	31,630,000
Intangible assets, accumulated amortization (in dollars)	$ 44,633,000	$ 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	16,664,613	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	46,144,900	43,774,371
Common stock, shares outstanding	29,480,287.000	28,437,860
Common stock, restricted shares	174,285	253,772
Treasury Stock, Shares	16,664,613	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