Derivative Financial Instruments - Schedule of Outstanding Hedges: (Notional Amount) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Derivatives not designated as hedging instruments | Interest-rate contracts | Swap agreements and forwards
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	$ (9)	$ (336)
Derivatives not designated as hedging instruments | Interest-rate contracts | Futures
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	(11,302)	(2,621)
Derivatives not designated as hedging instruments | Foreign exchange contracts | Futures
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	(167)	0
Derivatives not designated as hedging instruments | Foreign exchange contracts | Forward, swap and spot
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	(1,419,570)	(1,274,277)
Derivatives not designated as hedging instruments | Foreign exchange contracts | Options purchased
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	0	(403)
Derivatives not designated as hedging instruments | Foreign exchange contracts | Options written
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	0	(404)
Derivatives not designated as hedging instruments | Credit derivative contracts | Credit swap agreements
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	(37)	(141)
Derivatives not designated as hedging instruments | Futures Contracts | Commodity
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	(151)	(113)
Derivatives not designated as hedging instruments | Futures Contracts | Equity
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	(103)	(87)
Derivatives not designated as hedging instruments | Other contracts | Stable value contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	(26,071)	(24,583)
Derivatives not designated as hedging instruments | Other contracts | Deferred value awards
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	(506)	(320)
Derivatives designated as hedging instruments | Interest-rate contracts | Swap agreements
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	(10,364)	(9,398)
Derivatives designated as hedging instruments | Foreign exchange contracts | Forward and swap
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	$ (4,812)	$ (4,515)