Condensed Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Accounts Receivable, allowances	$ 1,317	$ 1,362
Furniture, Equipment and Leasehold Improvements, accumulated depreciation and amortization	40,532	33,980
Intangible Assets, accumulated amortization	$ 47,298	$ 33,735
Treasury Stock, Shares	13,124,748	10,159,116
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	49,526,315	46,414,240
Common Stock, shares outstanding	36,401,567	36,255,124
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	27
Common Stock, shares outstanding	25	27