Price Risk Management Activities, Effect of Derivative Instruments on Income (Details) - Derivatives Not Designated as Hedging Instruments [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Commodity Contracts [Member] | Revenues [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	$ (1)	$ 0	$ 4	$ 0
Commodity Contracts [Member] | Cost of Materials and Other [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	(26)	(98)	(25)	(125)
Foreign Currency Contracts [Member] | Cost of Materials and Other [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	9	(7)	2	7
Foreign Currency Contracts [Member] | Other Income, Net [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	$ (19)	$ 11	$ 36	$ (6)