Derivative Financial Instruments - Schedule of Outstanding Hedges: (Notional Amount) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Additional compensation and employee benefits expense due to accelerated vesting	$ 249
Derivatives not designated as hedging instruments | Interest-rate contracts | Swap agreements and forwards
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	0	$ 336
Derivatives not designated as hedging instruments | Interest-rate contracts | Futures
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	13,455	2,621
Derivatives not designated as hedging instruments | Foreign exchange contracts | Forward, swap and spot
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	1,414,765	1,274,277
Derivatives not designated as hedging instruments | Foreign exchange contracts | Options purchased
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	337	403
Derivatives not designated as hedging instruments | Foreign exchange contracts | Options written
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	202	404
Derivatives not designated as hedging instruments | Credit derivative contracts | Credit swap agreements
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	0	141
Derivatives not designated as hedging instruments | Commodity and Equity Contracts | Commodity
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	0	113
Derivatives not designated as hedging instruments | Commodity and Equity Contracts | Equity
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	0	87
Derivatives not designated as hedging instruments | Other contracts | Stable value contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	27,182	24,583
Derivatives not designated as hedging instruments | Other contracts | Deferred value awards
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	409	320
Derivatives designated as hedging instruments | Interest-rate contracts | Swap agreements
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	10,169	9,398
Derivatives designated as hedging instruments | Foreign exchange contracts | Forward and swap
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	$ 8,564	$ 4,515