Derivatives - Schedule of Derivative Instruments in the Consolidated Balance Sheets (Details) - Not Designated as Hedges - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Asset	$ 19	$ 131
Liability	5	4
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	14	127
Commodity | Other current liabilities
Derivatives, Fair Value [Line Items]
Liability	1	0
Net Asset (Liability)	(1)
Commodity | Deferred credits and other liabilities
Derivatives, Fair Value [Line Items]
Liability	4	4
Net Asset (Liability)	(4)	(4)
Commodity | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Asset	18	131
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	18	$ 131
Commodity | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Asset	1
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 1