Price Risk Management Activities, Gain (Loss) by Income Statement Location (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Price Risk Management Activities (Textual)
Gain (loss) from components excluded from assessment of fair value hedge effectiveness, net	$ 0	$ 0	$ 0
Gain (loss) from hedged firm commitment not qualifying as fair value hedge, net	28	0	0
Gain (loss) from components excluded from assessment of cash flow hedge effectiveness, net	0	0	0
Accumulated other comprehensive income, cumulative after-tax gains on cash flow hedges	1
Gain (loss) from cash flow hedges to be reclassified within 12 months	1
Amount reclassified from accumulated OCI into income on discontinuance of cash flow hedges	0	0	0
Fair Value Hedging [Member] \| Commodity Contract [Member] \| Cost of Sales [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	(250)	(6)	45
Gain (loss) recognized in income on hedged item	183	(23)	(40)
Gain (loss) recognized in income on derivatives (ineffective portion)	(67)	(29)	5
Cash Flow Hedging [Member] \| Commodity Contract [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in OCI on derivatives (effective portion)	45	32	(2)
Cash Flow Hedging [Member] \| Commodity Contract [Member] \| Cost of Sales [Member]
Effect of Derivative Instruments on Income and OCI
Gain reclassified from accumulated OCI into income (effective portion)	73	3	178
Gain recognized in income on derivatives (ineffective portion)	48	5	0
Economic Hedging [Member] \| Cost of Sales [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	(37)	(302)	(234)
Economic Hedging [Member] \| Commodity Contract [Member] \| Cost of Sales [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	1	(349)	(210)
Economic Hedging [Member] \| Foreign Currency Contract [Member] \| Cost of Sales [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	(38)	18	(24)
Economic Hedging [Member] \| Other Contract [Member] \| Cost of Sales [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	0	29	0
Economic Hedging [Member] \| Future [Member] \| Commodity Contract [Member] \| Cost of Sales [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives		(542)
Trading Derivatives [Member] \| Commodity Contract [Member] \| Cost of Sales [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	$ (16)	$ 23	$ 8

Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

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The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

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Net gain (loss) relating to components of the gain (loss) on the fair value hedging instrument excluded from the assessment of fair value hedge effectiveness. Recognized in earnings.

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