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available.falsefalseUnrealized gain (loss), Derivative total98false0fe_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesfefalsedebitdurationFair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Purchases.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse00falsefalsefalsefalsefalse2truefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Purchases.No authoritative reference available.falsefalsePurchases, Derivative Asset99false0fe_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchasesfefalsecreditdurationFair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability 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Liability109false0fe_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAndLiabilitySettlementsTotalfefalsecreditdurationFair value measurement with unobservable inputs reconciliation recurring basis asset and liability settlements total.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse6000000060falsefalsefalsefalsefalse2truefalsefalse8800000088falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFair value measurement with unobservable inputs reconciliation recurring basis asset and liability settlements total.No authoritative reference available.falsefalseSettlements, Derivative Asset and Liability, total110false0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNetus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse00falsefalsefalsefalsefalse2truefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis element represents [net] transfers in to and out of assets measured at fair value on a recurring basis using unobservable inputs (Level 3) which have taken place during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 -Subparagraph c(3) falsefalseTransfers in (out) of Level 3, Derivative Asset111false0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNetus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse00falsefalsefalsefalsefalse2truefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis element represents [net] transfers in to and out of liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3) which have taken place during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 -Subparagraph c(3) falsefalseTransfers in (out) of Level 3, Derivative Liability112false0fe_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAndLiabilityTransfersNetTotalfefalsecreditdurationFair value measurement with unobservable inputs reconciliation recurring basis asset and liability transfers net total.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse00falsefalsefalsefalsefalse2truefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFair value measurement with unobservable inputs reconciliation recurring basis asset and liability transfers net total.No authoritative reference available.falsefalseTransfers in (out) of Level 3, Derivative Asset and Liability, total113false0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValueus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsetruefalseperiodendlabel1truefalsefalse112000000112falsefalsefalsefalsefalse2truefalsefalse176000000176falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 -Subparagraph c falsefalseEnding Balance, Derivative Asset114false0fe_FairValueMeasurementsWithUnobservableInputsReconciliationRecurringBasisLiabilityValuefefalsecreditinstantFair Value Measurements With Unobservable Inputs Reconciliation Recurring Basis 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available.falsefalseEnding Balance, Derivative, Total2115Fair Value of Financial Instruments (Details 6) (Non Utility Generation Contract [Member], USD $)MillionsUnKnownUnKnownUnKnownfalsetrue