Price Risk Management Activities, Gain (Loss) by Income Statement Location (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Price Risk Management Activities (Textual)
Accumulated other comprehensive income, cumulative after-tax gains on cash flow hedges	$ 3
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	(31)	(1)
Gain recognized in income on hedged item	30	0
Loss recognized in income on derivatives (ineffective portion)	(1)	(1)
Cash Flow Hedging [Member] \| Commodity Contract [Member]
Effect of Derivative Instruments on Income and OCI
Gain recognized in OCI on derivatives (effective portion)	7	1
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	3
Loss recognized in income on derivatives (ineffective portion)	(4)	(1)
Economic Hedging [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	13	60
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	4	35
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	9	25
Trading Derivatives [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in income on derivatives	(1)	(11)
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	(1)	2
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	$ 0	$ (13)

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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Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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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 effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

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The net gain (loss) recognized in earnings during the reporting period representing the amount of the cash flow hedges' ineffectiveness.

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Amount of gain (loss)recognized in the income statement from the hedging ineffectiveness of a fair value hedge.

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