Price Risk Management Activities, Hedging Instruments by Consolidated Balance Sheet Location (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	$ 600	$ 685
Derivative liability, fair value, gross liability	650	563
Commodity Future [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	562	648
Derivative asset, fair value, gross liability	604	522
Commodity Swap [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	23	30
Derivative asset, fair value, gross liability	22	33
Commodity Option [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	10	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	0	0
Derivative asset, fair value, gross liability	19	6
Foreign Currency Contracts [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	5	3
Derivative asset, fair value, gross liability	$ 0	$ 0