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Fair Value Measurements (Reconciliation of Assets and Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Investments    
Beginning balance $ 155us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue $ 111us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Total pretax gains (losses) included in earnings 24us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1 18us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
Purchases 9us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases 1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
Sales (1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales (1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
Settlements (10)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements (39)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
Transfers in and/or out of level 3   (5)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
Total gains (losses) included on the Condensed Consolidated Balance Sheet as regulatory assets or liabilities 6duk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisDeferredGainsOrLossesAsRegulatoryAssetsAndLiabilitiesNet  
Ending balance 183us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue 85us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Beginning balance (1)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs 13us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
Total pretax gains (losses) included in earnings 24us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings 18us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings
Settlements (10)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSettlements (39)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSettlements
Transfers out of level 3   (5)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationTransfersOutOfLevel3
Total gains (losses) included on the Condensed Consolidated Balance Sheet as regulatory assets or liabilities 1duk_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsGainsOrLossesAsRegulatoryAssetOrLiability (1)duk_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsGainsOrLossesAsRegulatoryAssetOrLiability
Ending balance 14us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs (14)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
Pretax amounts included in the Condensed Consolidated Statements of Comprehensive Income related to Level 3 measurements outstanding   7us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
Derivative [Member]    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Pretax amounts included in the Condensed Consolidated Statements of Comprehensive Income related to Level 3 measurements outstanding   7us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_DerivativeMember
Investments [Member]    
Investments    
Beginning balance 156us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
98us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
Purchases 9us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
Sales (1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
(1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
Total gains (losses) included on the Condensed Consolidated Balance Sheet as regulatory assets or liabilities 5duk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisDeferredGainsOrLossesAsRegulatoryAssetsAndLiabilitiesNet
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
1duk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisDeferredGainsOrLossesAsRegulatoryAssetsAndLiabilitiesNet
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
Ending balance 169us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
99us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
Duke Energy Carolinas [Member]    
Investments    
Beginning balance 154us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
79us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Purchases 9us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Sales   (1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Issuances (1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
 
Settlements   (2)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Total gains (losses) included on the Condensed Consolidated Balance Sheet as regulatory assets or liabilities 5duk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisDeferredGainsOrLossesAsRegulatoryAssetsAndLiabilitiesNet
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
1duk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisDeferredGainsOrLossesAsRegulatoryAssetsAndLiabilitiesNet
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Ending balance 167us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
78us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Beginning balance   (2)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Settlements   (2)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSettlements
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Ending balance   (4)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Duke Energy Carolinas [Member] | Investments [Member]    
Investments    
Beginning balance 154us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
81us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Purchases 9us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Sales   (1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Issuances (1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
 
Total gains (losses) included on the Condensed Consolidated Balance Sheet as regulatory assets or liabilities 5duk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisDeferredGainsOrLossesAsRegulatoryAssetsAndLiabilitiesNet
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
1duk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisDeferredGainsOrLossesAsRegulatoryAssetsAndLiabilitiesNet
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Ending balance 167us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
82us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
/ dei_LegalEntityAxis
= duk_DukeEnergyCarolinasMember
Progress Energy [Member]    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Total pretax gains (losses) included in earnings   (3)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings
/ dei_LegalEntityAxis
= duk_ProgressEnergyMember
Ending balance   (3)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_ProgressEnergyMember
Progress Energy [Member] | Derivative [Member]    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Pretax amounts included in the Condensed Consolidated Statements of Comprehensive Income related to Level 3 measurements outstanding   (3)us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_DerivativeMember
/ dei_LegalEntityAxis
= duk_ProgressEnergyMember
Duke Energy Progress [Member]    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Total pretax gains (losses) included in earnings   (3)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings
/ dei_LegalEntityAxis
= duk_DukeEnergyProgressMember
Ending balance   (3)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_DukeEnergyProgressMember
Duke Energy Progress [Member] | Derivative [Member]    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Pretax amounts included in the Condensed Consolidated Statements of Comprehensive Income related to Level 3 measurements outstanding   (3)us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_DerivativeMember
/ dei_LegalEntityAxis
= duk_DukeEnergyProgressMember
Duke Energy Ohio [Member]    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Beginning balance (18)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
(4)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
Total pretax gains (losses) included in earnings 25us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
(6)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
Settlements   (4)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSettlements
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
Transfers out of level 3   (5)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationTransfersOutOfLevel3
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
Ending balance 7us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
(19)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
Duke Energy Ohio [Member] | Derivative [Member]    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Pretax amounts included in the Condensed Consolidated Statements of Comprehensive Income related to Level 3 measurements outstanding   (7)us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_DerivativeMember
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
Duke Energy Indiana [Member]    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Beginning balance 14us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_DukeEnergyIndianaMember
12us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_DukeEnergyIndianaMember
Total pretax gains (losses) included in earnings (3)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings
/ dei_LegalEntityAxis
= duk_DukeEnergyIndianaMember
27us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings
/ dei_LegalEntityAxis
= duk_DukeEnergyIndianaMember
Settlements (9)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSettlements
/ dei_LegalEntityAxis
= duk_DukeEnergyIndianaMember
(31)us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSettlements
/ dei_LegalEntityAxis
= duk_DukeEnergyIndianaMember
Total gains (losses) included on the Condensed Consolidated Balance Sheet as regulatory assets or liabilities 1duk_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsGainsOrLossesAsRegulatoryAssetOrLiability
/ dei_LegalEntityAxis
= duk_DukeEnergyIndianaMember
(1)duk_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsGainsOrLossesAsRegulatoryAssetOrLiability
/ dei_LegalEntityAxis
= duk_DukeEnergyIndianaMember
Ending balance $ 3us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_DukeEnergyIndianaMember
$ 7us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs
/ dei_LegalEntityAxis
= duk_DukeEnergyIndianaMember