Price Risk Management Activities, Gain (Loss) by Income Statement Location (Details) - Cost of Materials and Other [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Economic Hedges [Member] | Commodity Contracts [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	$ (86)	$ 42	$ (158)	$ (210)
Economic Hedges [Member] | Foreign Currency Contracts [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	(16)	4	(42)	5
Trading Derivatives [Member] | Commodity Contracts [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	$ 31	$ 13	$ 29	$ 51