Noncurrent Other Liabilities (Schedule of Noncurrent Other Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other Liabilities, Noncurrent [Abstract]
Asset retirement obligations	$ 7	$ 20
Deferred proceeds	47	41
Deferred revenue	6	9
Environmental (Note 16)	59	50
Income taxes payable (Note 19)	197	6
Insurance	43	46
Other	54	43
Total	$ 413	$ 215