Fair Value Measurement - FV of Commodity Derivatives (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Offsetting Derivative Assets [Abstract]
Assets - gross amounts recognized	$ 919	$ 1,621
Assets - gross amounts offset	827	1,403
Assets - net amounts excluding collateral	92	218
Assets - cash collateral	6	29
Assets - net amounts subject to setoff	86	189
Offsetting Derivative Liabilities [Abstract]
Liabilities - gross amounts recognized	935	1,588
Liabilities - gross amounts offset	827	1,403
Liabilities - net amounts excluding collateral	108	185
Liabilities - cash collateral	26	16
Liabilities - net amounts subject to setoff	$ 82	$ 169

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

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Amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities.

+ References

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Fair value of liability associated with derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

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Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

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Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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The amount as of the balance sheet date of the fair value of derivative assets that in accordance with the entity's accounting policy was not offset against an obligation to return cash collateral under a master netting arrangement.

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Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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The amount as of the balance sheet date of the fair value of derivative liabilities that in accordance with the entity's accounting policy was not offset against the right to reclaim cash collateral under a master netting arrangement.

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