Condensed Consolidated Statements Of Financial Condition (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Class A Common Stock [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000	500,000
Common stock, shares issued	122,804	115,217
Common stock, shares outstanding	104,763	97,220
Treasury stock, shares of Class A common stock	18,041	17,997
Class B Common Stock [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000	100,000
Common stock, shares issued	34,848	34,848
Common stock, shares outstanding	34,848	34,848