Financial and Derivative Instruments - Fair Value of Derivatives (Details) - Commodity - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	$ 122	$ 74
Total Liabilities at Fair Value	231	173
Accounts and notes receivable, net
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	103	73
Long-term receivables, net
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Assets at Fair Value	19	1
Accounts payable
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Liabilities at Fair Value	221	172
Deferred credits and other noncurrent obligations
Consolidated Balance Sheet: Fair Value of Derivatives not Designated as Hedging Instruments
Total Liabilities at Fair Value	$ 10	$ 1