Fair Value Measurements - Assets and Liabilities Table (Details) - USD ($) $ in Millions	Jun. 30, 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	44	50
Short-term derivative liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current liabilities	(45)	(51)
Quoted Prices in Active Markets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability), total	(1)	(1)
Quoted Prices in Active Markets (Level 1) | Short-term derivative asset
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current assets	44	50
Quoted Prices in Active Markets (Level 1) | Short-term derivative liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current liabilities	(45)	(51)
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability), total	0	0
Significant Other Observable Inputs (Level 2) | Short-term derivative asset
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current assets	0	0
Significant Other Observable Inputs (Level 2) | Short-term derivative liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current liabilities	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability), total	0	0
Significant Unobservable Inputs (Level 3) | Short-term derivative asset
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current assets	0	0
Significant Unobservable Inputs (Level 3) | Short-term derivative liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other current liabilities	$ 0	$ 0