Other Income (Expense) - net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income [Line Items]
Economic foreign currency exchange contracts	$ (261)	$ 384	$ 122
Interest income	2	3	4
Allowance for funds used during construction - equity component	16	19	14
Miscellaneous	17	6	6
Total Other Income	(226)	412	146
Other Expense [Line Items]
Charitable contributions	8	9	21
Miscellaneous	21	13	17
Total Other Expense	29	22	38
Other Income (Expense) - net	$ (255)	$ 390	$ 108