Noncurrent Other Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Other Liabilities, Noncurrent [Abstract]
Asset retirement obligations	$ 14	$ 7
Deferred proceeds	46	47
Deferred revenue	6	6
Environmental (Note 12)	53	59
Income taxes payable	0	197
Insurance	43	43
Other	48	54
Total	$ 210	$ 413