Equity Method Investments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Retained earnings related to undistributed earnings of equity method investees	$ 68
Difference between the carrying value of an equity method investment and the underlying net assets of the investee	13
Equity Method Investments	$ 286	$ 305
Advantage Pipeline
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments	50.00%
Equity Method Investments	$ 73	70
Atlantic Methanol Production Company
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments	45.00%
Alba Plant
Schedule of Equity Method Investments [Line Items]
Ownership interest in equity method investments	28.00%
Equity Method Investments	$ 58	$ 80