Derivative Instruments (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative Assets
Fair Value	$ 213us-gaap_DerivativeAssets	$ 239us-gaap_DerivativeAssets
Amounts Not Offset in Consolidated Balance Sheet, Derivative Instruments	(140)	(110)
Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral (Received)/Pledged	0	(9)
Net Fair Value	73	120
Derivative Liabilities
Fair Value	(334)us-gaap_DerivativeLiabilities	(347)us-gaap_DerivativeLiabilities
Amounts Not Offset in Consolidated Balance Sheet, Derivative Instruments	140	110
Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral (Received)/Pledged	35	12
Net Fair Value	(159)	(225)
Commodity contracts
Derivative Assets
Fair Value	172	215
Amounts Not Offset in Consolidated Balance Sheet, Derivative Instruments	(126)	(106)
Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral (Received)/Pledged	0	(9)
Net Fair Value	46	100
Derivative Liabilities
Fair Value	(167)	(113)
Amounts Not Offset in Consolidated Balance Sheet, Derivative Instruments	126	106
Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral (Received)/Pledged	35	7
Net Fair Value	(6)	0
FTRs
Derivative Assets
Fair Value	39	4
Amounts Not Offset in Consolidated Balance Sheet, Derivative Instruments	(14)	(4)
Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral (Received)/Pledged	0	0
Net Fair Value	25	0
Derivative Liabilities
Fair Value	(14)	(12)
Amounts Not Offset in Consolidated Balance Sheet, Derivative Instruments	14	4
Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral (Received)/Pledged	0	5
Net Fair Value	0	(3)
NUGs
Derivative Assets
Fair Value	2	20
Amounts Not Offset in Consolidated Balance Sheet, Derivative Instruments	0	0
Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral (Received)/Pledged	0	0
Net Fair Value	2	20
Derivative Liabilities
Fair Value	(153)	(222)
Amounts Not Offset in Consolidated Balance Sheet, Derivative Instruments	0	0
Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral (Received)/Pledged	0	0
Net Fair Value	$ (153)	$ (222)

Derivative Assets, Fair Value, Amounts Offset Against Derivative Liabilities

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Derivative Liabilities, Fair Value, Amounts Offset Against Derivative Assets

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

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-Publisher FASB

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Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

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Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

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Fair value, after effects of master netting arrangements, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset offset against an obligation to return collateral. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after effects of master netting arrangements, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset offset against the right to receive collateral. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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