v2.4.0.8
Collateralized Transactions (Financial instruments owned and pledged where the counterparty has the right to repledge) (Details) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2014
Dec. 31, 2013
Disclosure Collateralized Transactions [Abstract]    
Stocks $ 759.7 $ 1,097.8
Warrants 0.3 0.2
U.S. and foreign government securities 78.0 64.4
Corporate and municipal bonds 1.5 1.1
Financial Instruments Owned and Pledged as Collateral - Eligible to be Repledged by Counterparty $ 839.5 $ 1,163.5