Price Risk Management Activities, Hedging Instruments by Consolidated Balance Sheet Location (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	$ 780	$ 685
Derivative liability, fair value, gross liability	735	563
Commodity Future [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	749	648
Derivative asset, fair value, gross liability	702	522
Commodity Swap [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	21	30
Derivative asset, fair value, gross liability	17	33
Commodity Option [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	8	4
Derivative asset, fair value, gross liability	5	2
Physical Purchase Contracts [Member] | Inventories [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	1	0
Derivative asset, fair value, gross liability	11	6
Foreign Currency Contracts [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	1	3
Derivative asset, fair value, gross liability	$ 0	$ 0