Price Risk Management Activities, Hedging Instruments by Consolidated Balance Sheet Location (Details) (Not Designated as Hedging Instrument [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	$ 2,471	$ 3,133
Derivative liability, fair value, gross liability	2,493	2,925
Future [Member] | Commodity Contracts [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	2,438	3,096
Derivative asset, fair value, gross liability	2,455	2,886
Swap [Member] | Commodity Contracts [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	29	34
Derivative asset, fair value, gross liability	33	31
Options Held [Member] | Commodity Contracts [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	1	2
Derivative asset, fair value, gross liability	1	3
Forward Contracts [Member] | Physical Purchase Contracts [Member] | Inventories [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	0	1
Derivative asset, fair value, gross liability	4	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