Price Risk Management Activities, Gain (Loss) by Income Statement Location (Details) - Economic Hedges [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commodity Contracts [Member] | Cost of Materials and Other [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	$ (165)	$ (278)	$ (86)
Commodity Contracts [Member] | Operating Expenses (Excluding Depreciation and Amortization Expense) [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	7	0	0
Foreign Currency Contracts [Member] | Cost of Materials and Other [Member]
Effect of Derivative Instruments on Income
Gain (loss) recognized in income on derivatives	$ 56	$ (40)	$ 16