Condensed Consolidated Statements of Financial Condition (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Fixed assets, accumulated depreciation and amortization (in dollars)	$ 20,357	$ 17,764
Intangible assets, accumulated amortization (in dollars)	$ 9,623	$ 8,146
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Class A common stock held in treasury	499,136
Common Stock Class A
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	116,246,786	75,490,209
Common stock, shares outstanding	116,246,786	75,490,209
Common stock, restricted shares	1,110,836	1,554,124
Common Stock Class B
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0