Condensed Consolidated Statements of Financial Condition (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Assets
Fixed assets, accumulated depreciation and amortization (in dollars)	$ 21,853	$ 30,003
Intangible assets, accumulated amortization (in dollars)	$ 26,610	$ 22,945
Stockholders' equity
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
Common stock, shares authorized	500,000,000
Common Stock Class A
Stockholders' equity
Treasury stock, shares	15,873,549	11,292,220
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	130,900,182	123,740,112
Common stock, shares outstanding	115,026,633	112,447,892
Common stock, restricted shares	482,522	336,895
Common Stock Class B
Stockholders' equity
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