CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financial instruments owned, at fair value, securities pledged	$ 961,479	$ 55,141
Treasury stock, shares	928,000	0
Common Class A [Member]
Class A common stock Shares authorized	1,000,000,000	0
Class A common stock, Shares issued	123,515,000	0
Class A common stock, Shares outstanding	122,587,000	0