Price Risk Management Activities, Effect of Derivative Instruments on Income and Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Effect of Derivative Instruments on Income (Textual)
Estimated deferred after-tax gain expected to be reclassified into income over next 12 months	$ 18
Commodity Contracts [Member]
Effect of Derivative Instruments on Income
Gain recognized in other comprehensive income (loss) on derivatives	55	$ 0
Commodity Contracts [Member] \| Revenues [Member]
Effect of Derivative Instruments on Income
Gain reclassified from accumulated other comprehensive loss into income	26	0
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	(8)	0
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	(152)	(71)
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	(2)	0
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	49	(9)
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	$ (165)	$ 7

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

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