Other Items (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Interest and Other Financing [Abstract]
Interest income	$ 32	$ 34	$ 14
Interest expense(a)	(280)	(380)	(398)
Income on interest rate swaps	0	53	13
Interest capitalized	0	3	18
Total interest	(248)	(290)	(353)
Net foreign currency gains (losses)	9	8	6
Other	13	12	15
Total other	22	20	21
Net interest and other	(226)	(270)	(332)
Aggregate foreign currency gains losses [Abstract]
Net interest and other	9	8	6
Provision for income taxes	10	57	(32)
Aggregate foreign currency gains (losses)	$ 19	$ 65	$ (26)