Price Risk Management Activities, Effect of Derivative Instruments on Income and Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Commodity Contracts [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in other comprehensive income (loss) on derivatives	$ (21)	$ 2	$ (52)	$ 52
Commodity Contracts [Member] | Revenues [Member]
Effect of Derivative Instruments on Income
Gain (loss) reclassified from accumulated other comprehensive loss into income	(3)	(3)	(37)	42
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)	(4)	13	(3)
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	6	118	(51)	106
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)	0	2	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	19	(6)	17	43
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	$ (28)	$ 56	$ 55	$ (49)