Derivative Financial Instruments - Schedule of Outstanding Hedges: (Notional Amount) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Other contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	$ 351	$ 210
Swap agreements and forwards | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	360	645
Futures | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	16,078	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	1,345,774	1,231,344
Options purchased | Foreign exchange contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	989	2,767
Options written | Foreign exchange contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	938	2,404
Credit swap agreements | Credit derivative contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	37	191
Commodity(1) | Futures Contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	138	26
Equity(1) | Futures Contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	53	2
Stable value contracts | Other contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	23,588	23,409
Swap agreements | Interest-rate contracts | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	9,407	6,077
Forward and swap | Foreign exchange contracts | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	13,052	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	1	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	$ 1	$ 7