Financial and Derivative Instruments (Details) - Commodity - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	$ 16	$ 22
Total Liabilities at Fair Value	84	124
Accounts and notes receivable, net
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	15	22
Long-term receivables, net
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	1	0
Accounts payable
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Liabilities at Fair Value	76	122
Deferred credits and other noncurrent obligations
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Liabilities at Fair Value	$ 8	$ 2