Price Risk Management Activities, Hedging Instruments by Consolidated Balance Sheet Location (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair Values of Derivative Instruments
Total asset derivatives, net	$ 1,980	$ 3,343
Total liability derivatives, net	1,967	3,599
Designated as Hedging Instrument [Member]
Fair Values of Derivative Instruments
Asset derivative, fair value, gross asset	300	206
Liability derivative, fair value, gross liability	286	254
Designated as Hedging Instrument [Member] | Future [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Asset derivative, fair value, gross asset	264	120
Liability derivative, fair value, gross asset	240	183
Designated as Hedging Instrument [Member] | Swap [Member] | Prepaid Expenses And Other [Member]
Fair Values of Derivative Instruments
Asset derivative, fair value, gross asset		55
Liability derivative, fair value, gross asset		39
Designated as Hedging Instrument [Member] | Swap [Member] | Accrued Expenses [Member]
Fair Values of Derivative Instruments
Asset derivative, fair value, gross liability	36	31
Liability derivative, fair value, gross liability	46	32
Not Designated as Hedging Instrument [Member]
Fair Values of Derivative Instruments
Asset derivative, fair value, gross asset	1,680	3,137
Liability derivative, fair value, gross liability	1,681	3,345
Not Designated as Hedging Instrument [Member] | Future [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Asset derivative, fair value, gross asset	1,636	2,717
Liability derivative, fair value, gross asset	1,624	2,914
Not Designated as Hedging Instrument [Member] | Swap [Member] | Prepaid Expenses And Other [Member]
Fair Values of Derivative Instruments
Asset derivative, fair value, gross asset	4	287
Liability derivative, fair value, gross asset	2	277
Not Designated as Hedging Instrument [Member] | Swap [Member] | Accrued Expenses [Member]
Fair Values of Derivative Instruments
Asset derivative, fair value, gross liability	38	116
Liability derivative, fair value, gross liability	51	148
Not Designated as Hedging Instrument [Member] | Commodity Option [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Asset derivative, fair value, gross asset	2
Liability derivative, fair value, gross asset	0
Not Designated as Hedging Instrument [Member] | Commodity Option [Member] | Accrued Expenses [Member]
Fair Values of Derivative Instruments
Asset derivative, fair value, gross liability	0	0
Liability derivative, fair value, gross liability	2	6
Not Designated as Hedging Instrument [Member] | Forward Contracts [Member] | Inventories [Member]
Fair Values of Derivative Instruments
Asset derivative, fair value, gross liability	0	17
Liability derivative, fair value, gross liability	$ 2	$ 0