Price Risk Management Activities, Effect of Derivative Instruments on Income and Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Commodity Contracts [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in other comprehensive income (loss) on derivatives	$ (13)	$ 55
Commodity Contracts [Member] | Revenues [Member]
Effect of Derivative Instruments on Income
Gain (loss) reclassified from accumulated other comprehensive loss into income	(23)	26
Commodity Contracts [Member] | Revenues [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	7	(8)
Commodity Contracts [Member] | Cost of Materials and Other [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	(78)	(152)
Commodity Contracts [Member] | Operating Expenses (Excluding Depreciation and Amortization Expense) [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	1	(2)
Foreign Currency Contracts [Member] | Cost of Materials and Other [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	(8)	49
Foreign Currency Contracts [Member] | Other Income, Net [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	$ 30	$ (165)