Consolidated Statements Of Financial Condition (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Accounts Receivable, allowances	$ 1,964	$ 768
Furniture, Equipment and Leasehold Improvements, accumulated depreciation and amortization	13,490	11,302
Intangible Assets, accumulated amortization	$ 25,701	$ 13,337
Treasury Stock at Cost, shares	3,072,958	1,514,045
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	31,014,265	21,497,691
Common Stock, shares outstanding	27,941,307	19,983,646
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	47	48
Common Stock, shares outstanding	47	48