Fair Value Measurements - Assets and Liabilities Table (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability), total	$ (1)	$ (1)
Short-term derivative asset
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current assets	43	50
Short-term derivative liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current liabilities	(44)	(51)
Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability), total	(1)	(1)
Fair Value, Inputs, Level 1 | Short-term derivative asset
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current assets	43	50
Fair Value, Inputs, Level 1 | Short-term derivative liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current liabilities	(44)	(51)
Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability), total	0	0
Fair Value, Inputs, Level 2 | Short-term derivative asset
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current assets	0	0
Fair Value, Inputs, Level 2 | Short-term derivative liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current liabilities	0	0
Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability), total	0	0
Fair Value, Inputs, Level 3 | Short-term derivative asset
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current assets	0	0
Fair Value, Inputs, Level 3 | Short-term derivative liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current liabilities	$ 0	$ 0