CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Accounts Receivable, allowances	$ 2,035	$ 1,964
Furniture, Equipment and Leasehold Improvements,accumulated depreciation and amortization	18,447	13,490
Intangible Assets, accumulated amortization	$ 34,360	$ 25,701
Treasury Stock at Cost, shares	5,406,472	3,072,958
Common 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	34,448,133	31,014,265
Common Stock, shares outstanding	29,041,661	27,941,307
Common 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	45	47
Common Stock, shares outstanding	45	47