Price Risk Management Activities, Effect of Derivative Instruments on Income (Details) - Derivatives Not Designated as Hedging Instruments [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Commodity Contracts [Member] | Revenues [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	$ 5	$ 0	$ 5	$ 0
Commodity Contracts [Member] | Cost of Materials and Other [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	72	(15)	1	(27)
Foreign Currency Contracts [Member] | Cost of Materials and Other [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	2	17	(7)	14
Foreign Currency Contracts [Member] | Other Income, Net [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	$ 48	$ (17)	$ 55	$ (17)