Derivative Financial Instruments - Schedule of Outstanding Hedges: (Notional Amount) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Other contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	$ 386	$ 210
Swap agreements and forwards | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	266	645
Futures | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	12,225	3,939
Forward, swap and spot | Foreign exchange contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	1,331,780	1,231,344
Options purchased | Foreign exchange contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	2,433	2,767
Options written | Foreign exchange contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	2,309	2,404
Credit swap agreements | Credit derivative contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	229	191
Commodity(1) | Futures Contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	77	26
Equity(1) | Futures Contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	52	2
Stable value contracts | Other contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	23,280	23,409
Swap agreements | Interest-rate contracts | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	6,961	6,077
Forward and swap | Foreign exchange contracts | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	9,570	2,705
Long | Options and caps purchased | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	2	7
Short | Options and caps purchased | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	$ 2	$ 7