Price Risk Management Activities, Hedging Instruments by Consolidated Balance Sheet Location (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	$ 2,084	$ 894
Derivative liability, fair value, gross liability	2,133	982
Commodity Future [Member] | Receivable, Net [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	2,072	875
Derivative asset, fair value, gross liability	2,108	955
Commodity Swap [Member] | Receivable, Net [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	11	11
Derivative asset, fair value, gross liability	10	11
Commodity Option [Member] | Receivable, Net [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	1	8
Derivative asset, fair value, gross liability	1	3
Physical Purchase Contracts [Member] | Inventories [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	0	0
Derivative asset, fair value, gross liability	11	6
Foreign Currency Contracts [Member] | Accrued Expenses [Member]
Fair Values of Derivative Instruments
Derivative liability, fair value, gross asset	0	0
Derivative liability, fair value, gross liability	$ 3	$ 7