Derivatives and Financial Instruments (Summary of Commodity Balance Sheet) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Assets
Liabilities	$ (1,241)	$ (1,188)
Effect of Collateral Netting	0	0
Liabilities
Assets	1,241	1,188
Effect of Collateral Netting	168	80
Total
Effect of Collateral Netting	168	80
Not Designated as Hedging Instrument \| Commodity
Liabilities
Effect of Collateral Netting	168	80
Total
Assets	1,272	1,214
Liabilities	(1,425)	(1,282)
Effect of Collateral Netting	168	80
Net Carrying Value Presented on the Balance Sheet	15	12
Not Designated as Hedging Instrument \| Commodity \| Prepaid expenses and other current assets
Assets
Assets	56	23
Liabilities	(25)	0
Effect of Collateral Netting	0	0
Net Carrying Value Presented on the Balance Sheet	31	23
Not Designated as Hedging Instrument \| Commodity \| Other assets
Assets
Assets	0	3
Liabilities	0	0
Effect of Collateral Netting	0	0
Net Carrying Value Presented on the Balance Sheet	0	3
Not Designated as Hedging Instrument \| Commodity \| Other accruals
Liabilities
Assets	1,216	1,188
Liabilities	(1,399)	(1,281)
Effect of Collateral Netting	168	80
Net Carrying Value Presented on the Balance Sheet	(15)	(13)
Total
Effect of Collateral Netting	168	80
Not Designated as Hedging Instrument \| Commodity \| Other liabilities and deferred credits
Liabilities
Assets	0	0
Liabilities	(1)	(1)
Effect of Collateral Netting	0	0
Net Carrying Value Presented on the Balance Sheet	(1)	(1)
Total
Effect of Collateral Netting	$ 0	$ 0

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