Condensed Consolidated Statements Of Financial Condition (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Accounts Receivable, allowances	$ 1,308	$ 768
Furniture, Equipment and Leasehold Improvements, accumulated depreciation and amortization	12,581	11,302
Intangible Assets, accumulated amortization	$ 18,113	$ 13,337
Treasury Stock at Cost, shares	2,002,624	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	28,386,422	21,497,691
Common Stock, shares outstanding	26,383,798	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	48	48
Common Stock, shares outstanding	48	48