Condensed Consolidated Statements of Financial Condition (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts Receivable, allowances	$ 2,097	$ 1,949
Furniture, Equipment and Leasehold Improvements, accumulated depreciation and amortization	21,143	19,880
Intangible Assets, accumulated amortization	$ 21,996	$ 20,002
Treasury Stock at Cost, shares	6,244,468	5,463,515
Class A
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	1,000,000,000	1,000,000,000
Common Stock, shares issued	38,049,288	35,040,501
Common Stock, shares outstanding	31,804,820	29,576,986
Class B
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	1,000,000	1,000,000
Common Stock, shares issued	42	43
Common Stock, shares outstanding	42	43