Condensed Consolidated Statements of Financial Condition (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accounts Receivable, allowances	$ 1,362	$ 2,436
Furniture, Equipment and Leasehold Improvements, accumulated depreciation and amortization	33,980	25,992
Intangible Assets, accumulated amortization	$ 33,735	$ 27,538
Treasury Stock, Shares	10,159,116	7,702,900
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	46,414,240	40,772,434
Common Stock, shares outstanding	36,255,124	33,069,534
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	27	42
Common Stock, shares outstanding	27	42