Derivative Financial Instruments - Schedule of Outstanding Hedges: (Notional Amount) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Other contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	$ 320	$ 210
Swap agreements and forwards | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	336	645
Futures | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	2,621	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	1,274,277	1,231,344
Options purchased | Foreign exchange contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	403	2,767
Options written | Foreign exchange contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	404	2,404
Credit swap agreements | Credit derivative contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	141	191
Commodity | Futures Contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	113	26
Equity | Futures Contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	87	2
Stable value contracts | Other contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	24,583	23,409
Swap agreements | Interest-rate contracts | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	9,398	6,077
Forward and swap | Foreign exchange contracts | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	4,515	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	0	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	$ 0	$ 7