Supplementary Information Foreign Currency Exchange Gain (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Foreign Currency Exchange Gain (Loss) [Line Items]
Exchange losses - net	$ (32)	$ (1)	$ (59)	$ (116)	[1]
Foreign Currency Transaction Gain (Loss) Tax (Expense) Benefit	18	(44)	12	26
Foreign Currency Transaction Gain (Loss) After Tax	(14)	(45)	(47)	(90)
Subsidiary Monetary Position
Foreign Currency Exchange Gain (Loss) [Line Items]
Exchange losses - net	17	(178)	7	(112)
Foreign Currency Transaction Gain (Loss) Tax (Expense) Benefit	7	(3)	(3)	25
Foreign Currency Transaction Gain (Loss) After Tax	24	(181)	4	(87)
Hedging Program [Member]
Foreign Currency Exchange Gain (Loss) [Line Items]
Exchange losses - net	(49)	177	(66)	(4)	[2]
Foreign Currency Transaction Gain (Loss) Tax (Expense) Benefit	11	(41)	15	1
Foreign Currency Transaction Gain (Loss) After Tax	$ (38)	$ 136	$ (51)	$ (3)

[1] Includes a $(50) million foreign exchange loss for the six months ended June 30, 2018 related to adjustments to foreign currency exchange contracts as a result of U.S. tax reform, which is included within significant items.

[2] Includes a $(50) million foreign exchange loss for the six months ended June 30, 2018 related to adjustments to foreign currency exchange contracts as a result of U.S. tax reform.