Price Risk Management Activities, Hedging Instruments by Consolidated Balance Sheet Location (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Values of Derivative Instruments
Total derivatives assets, net	$ 1,215	$ 1,980
Total derivative liabilities, net	1,209	1,970
Designated as Hedging Instrument [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	94	300
Derivative liability, fair value, gross liability	79	286
Designated as Hedging Instrument [Member] | Future [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	77	264
Derivative asset, fair value, gross liability	64	240
Designated as Hedging Instrument [Member] | Swap [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	15
Derivative asset, fair value, gross liability	13
Designated as Hedging Instrument [Member] | Swap [Member] | Prepaid Expenses And Other [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	2
Derivative asset, fair value, gross liability	2
Designated as Hedging Instrument [Member] | Swap [Member] | Accrued Expenses [Member]
Fair Values of Derivative Instruments
Derivative liability, fair value, gross asset		36
Derivative liability, fair value, gross liability		46
Not Designated as Hedging Instrument [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	1,121	1,680
Derivative liability, fair value, gross liability	1,130	1,684
Not Designated as Hedging Instrument [Member] | Future [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	1,066	1,636
Derivative asset, fair value, gross liability	1,073	1,624
Not Designated as Hedging Instrument [Member] | Swap [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	9
Derivative asset, fair value, gross liability	6
Not Designated as Hedging Instrument [Member] | Swap [Member] | Prepaid Expenses And Other [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset		4
Derivative asset, fair value, gross liability		2
Not Designated as Hedging Instrument [Member] | Swap [Member] | Accrued Expenses [Member]
Fair Values of Derivative Instruments
Derivative liability, fair value, gross asset	32	38
Derivative liability, fair value, gross liability	46	51
Not Designated as Hedging Instrument [Member] | Commodity Option [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	1	2
Derivative asset, fair value, gross liability	4	0
Not Designated as Hedging Instrument [Member] | Commodity Option [Member] | Accrued Expenses [Member]
Fair Values of Derivative Instruments
Derivative liability, fair value, gross asset	1	0
Derivative liability, fair value, gross liability	0	2
Not Designated as Hedging Instrument [Member] | Forward Contracts [Member] | Inventories [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	11	0
Derivative asset, fair value, gross liability	0	2
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Trade Accounts Receivable [Member]
Fair Values of Derivative Instruments
Derivative asset, fair value, gross asset	1
Derivative asset, fair value, gross liability	0
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Accrued Expenses [Member]
Fair Values of Derivative Instruments
Derivative liability, fair value, gross asset	0	0
Derivative liability, fair value, gross liability	$ 1	$ 3