Condensed Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Accounts Receivable, allowances	$ 1,212	$ 1,313
Furniture, Equipment and Leasehold Improvements, accumulated depreciation and amortization	48,344	42,656
Intangible Assets, accumulated amortization	$ 28,174	$ 21,754
Treasury Stock, Shares	18,983,345	15,626,288
Class A [Member]
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	1,000,000,000	1,000,000,000
Common Stock, shares issued	57,752,977	55,249,559
Common Stock, shares outstanding	38,769,632	39,623,271
Class B [Member]
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	1,000,000	1,000,000
Common Stock, shares issued	25	25
Common Stock, shares outstanding	25	25