Price Risk Management Activities, Gain (Loss) by Income Statement Location (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Price Risk Management Activities (Textual)
Gain (loss) from components excluded from assessment of fair value hedge effectiveness, net	$ 0	$ 0
Gain (loss) from hedged firm commitment not qualifying as fair value hedge, net	0	0
Gain (loss) from components excluded from assessment of cash flow hedge effectiveness, net	0	0
Accumulated other comprehensive income, cumulative after-tax losses on cash flow hedges	(1)
Gain (loss) from cash flow hedges to be reclassified within 12 months	(1)
Amount reclassifed from accumulated OCI into income on discontinuance of cash flow hedges	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	(1)	(267)
Gain recognized in income on hedged item	0	228
Loss recognized in income on derivatives (ineffective portion)	(1)	(39)
Cash Flow Hedging [Member] \| Commodity Contract [Member]
Effect of Derivative Instruments on Income and OCI
Gain recognized in OCI on derivatives (effective portion)	1	47
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)	3	48
Loss recognized in income on derivatives (ineffective portion)	(1)	(5)
Economic Hedging [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	60	(174)
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	35	(151)
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	25	(23)
Trading Derivatives [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	(11)	(4)
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	2	(4)
Trading Derivatives [Member] \| RINs Fixed-Price Contracts [Member] \| Cost of Sales [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	$ (13)	$ 0

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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The amount of net gains and losses recognized in income during the period on derivative instruments designated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges, on derivative instruments designated and qualifying as hedging instruments in cash flow hedges, and on derivative instruments not designated as hedging instruments.

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The net gain (loss) relating to components of the gain (loss) on the cash flow hedging instrument excluded from the assessment of cash flow hedge effectiveness. Recognized in earnings.

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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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