Price Risk Management Activities, Hedging Instruments by Consolidated Balance Sheet Location (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	$ 258	$ 3,133
Derivative liability, fair value, gross liability	222	2,925
Future [Member] | Commodity Contracts [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	234	3,096
Derivative asset, fair value, gross liability	207	2,886
Swap [Member] | Commodity Contracts [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	12	34
Derivative asset, fair value, gross liability	12	31
Options Held [Member] | Commodity Contracts [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	2	2
Derivative asset, fair value, gross liability	0	3
Forward Contracts [Member] | Physical Purchase Contracts [Member] | Inventories [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	7	1
Derivative asset, fair value, gross liability	1	$ 5
Forward Contracts [Member] | Foreign Currency Contracts [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	3
Derivative asset, fair value, gross liability	0
Forward Contracts [Member] | Foreign Currency Contracts [Member] | Accrued Liabilities [Member]
Fair Values of Derivative Instruments
Derivative liability, fair value, gross asset	0
Derivative liability, fair value, gross liability	$ 2