Derivatives (Hedges of Net Investments in Foreign Operations) (Details) - Foreign Operations Hedges [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gains (Losses) Deferred in AOCI (Effective Portion)	$ (36)	$ (60)	$ (395)	$ (709)
Foreign currency forwards
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gains (Losses) Deferred in AOCI (Effective Portion)	(35)	(23)	(161)	(358)
Currency options
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gains (Losses) Deferred in AOCI (Effective Portion)	$ (1)	$ (37)	$ (234)	$ (351)