Fair Value Measurement - Transfers (Details) - USD ($) $ in Billions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative liability | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, level 3 to level 2 transfers		$ 2.7		$ 2.9
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 3 to level 2 transfers	$ 1.9		$ 2.0
Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 3 to level 2 transfers	$ 1.3		$ 1.9
Derivative asset | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, level 3 to level 2 transfers		$ 3.0		$ 3.2