v2.4.0.6

Fair Value Measurement - FV of Commodity Derivatives (Details 1) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Offsetting Derivative Assets [Abstract]
Assets - gross amounts recognized	$ 1,475	$ 1,621
Assets - gross amounts offset	1,304	1,403
Assets - net amounts excluding collateral	171	218
Assets - cash collateral	29	29
Asssets - net amounts subject to setoff	142	189
Offsetting Derivative Liabilities [Abstract]
Liabilities - gross amounts recognized	1,523	1,588
Liabilities - gross amounts offset	1,304	1,403
Liabilities - net amounts excluding collateral	219	185
Liabilities - cash collateral	56	16
Liabilities - net amounts subject to setoff	$ 163	$ 169

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