Consolidated Statements of Financial Condition (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Assets
Fixed assets, accumulated depreciation and amortization (in dollars)	$ 25,968	$ 21,853
Intangible assets, accumulated amortization (in dollars)	$ 25,581	$ 26,610
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
Treasury Stock, Shares	23,507,656	15,873,549
Common stock, shares authorized	500,000,000
Common Stock Class A
Stockholders' equity
Treasury Stock, Shares	23,507,656	15,873,549
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	135,198,855	130,900,182
Common stock, shares outstanding	111,691,199	115,026,633
Common stock, restricted shares	424,479	482,522
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