Price Risk Management Activities, Hedging Instruments by Consolidated Balance Sheet Location (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	$ 1,029	$ 894
Derivative liability, fair value, gross liability	1,048	982
Commodity Future [Member] | Receivable, net [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	1,009	875
Derivative asset, fair value, gross liability	1,029	955
Commodity Swap [Member] | Receivable, net [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	6	11
Derivative asset, fair value, gross liability	12	11
Commodity Option [Member] | Receivable, net [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	11	8
Derivative asset, fair value, gross liability	5	3
Physical Purchase Contracts [Member] | Inventories [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	2	0
Derivative asset, fair value, gross liability	2	6
Foreign Currency Contracts [Member] | Receivable, net [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	1
Derivative asset, fair value, gross liability	$ 0
Foreign Currency Contracts [Member] | Accrued expenses [Member]
Fair Values of Derivative Instruments
Derivative liability, fair value, gross asset		0
Derivative liability, fair value, gross liability		$ 7