Price Risk Management Activities, Gain (Loss) by Income Statement Location (Details) - USD ($)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effect of Derivative Instruments on Income and OCI (Textual)
Accumulated other comprehensive income, cumulative after-tax gains or losses on cash flow hedges	$ 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	0	$ (42,000,000)	$ (12,000,000)
Gain recognized in income on hedged item	0	42,000,000	18,000,000
Gain (loss) recognized in income on derivatives (ineffective portion)	0	0	6,000,000
Cash Flow Hedging [Member] \| Commodity Contract [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) recognized in OCI on derivatives (effective portion)	0	(1,000,000)	(4,000,000)
Cash Flow Hedging [Member] \| Commodity Contract [Member] \| Cost of Sales [Member]
Effect of Derivative Instruments on Income and OCI
Gain (loss) reclassified from accumulated OCI into income (effective portion)	0	(2,000,000)	(2,000,000)
Gain (loss) recognized in income on derivatives (ineffective portion)	0	(1,000,000)	21,000,000
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	377,000,000	693,000,000	193,000,000
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	49,000,000	40,000,000	14,000,000
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	45,000,000	38,000,000	21,000,000
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	$ 0	$ (20,000,000)

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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