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Ownership of Coal-fired Facilities (Ownership Interests) (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2014
MW
Mar. 31, 2015
MW
Construction Work in Process   24.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
East Bend Station [Member]    
Production Capacity (MW) 186dpl_ProductionPlanCapacity
/ us-gaap_PublicUtilityAxis
= dpl_EastBendStationMember		  
DP&L [Member]    
Construction Work in Process   24.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ dei_LegalEntityAxis
= dpl_DpLMember
DP&L Share [Member] | Conesville Unit 4 [Member]    
Ownership (%)   16.50%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ us-gaap_PublicUtilityAxis
= dpl_ConesvilleUnitFourMember
Production Capacity (MW)   129dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ us-gaap_PublicUtilityAxis
= dpl_ConesvilleUnitFourMember
DP&L Share [Member] | Killen Station [Member]    
Ownership (%)   67.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ us-gaap_PublicUtilityAxis
= dpl_KillenStationMember
Production Capacity (MW)   402dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ us-gaap_PublicUtilityAxis
= dpl_KillenStationMember
DP&L Share [Member] | Miami Fort Units 7 and 8 [Member]    
Ownership (%)   36.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ us-gaap_PublicUtilityAxis
= dpl_MiamiFortUnitSevenAndEightMember
Production Capacity (MW)   368dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ us-gaap_PublicUtilityAxis
= dpl_MiamiFortUnitSevenAndEightMember
DP&L Share [Member] | Stuart Station [Member]    
Ownership (%)   35.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ us-gaap_PublicUtilityAxis
= dpl_StuartStationMember
Production Capacity (MW)   808dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ us-gaap_PublicUtilityAxis
= dpl_StuartStationMember
DP&L Share [Member] | Zimmer Station [Member]    
Ownership (%)   28.10%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ us-gaap_PublicUtilityAxis
= dpl_ZimmerStationMember
Production Capacity (MW)   371dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ us-gaap_PublicUtilityAxis
= dpl_ZimmerStationMember
DP&L Share [Member] | Total Jointly-owned Stations [Member]    
Production Capacity (MW)   2,078dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ us-gaap_PublicUtilityAxis
= dpl_TotalJointlyOwnedStationsMember
DP&L Share [Member] | DP&L [Member] | Conesville Unit 4 [Member]    
Ownership (%)   16.50%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_ConesvilleUnitFourMember
Production Capacity (MW)   129dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_ConesvilleUnitFourMember
DP&L Share [Member] | DP&L [Member] | Killen Station [Member]    
Ownership (%)   67.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_KillenStationMember
Production Capacity (MW)   402dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_KillenStationMember
DP&L Share [Member] | DP&L [Member] | Miami Fort Units 7 and 8 [Member]    
Ownership (%)   36.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_MiamiFortUnitSevenAndEightMember
Production Capacity (MW)   368dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_MiamiFortUnitSevenAndEightMember
DP&L Share [Member] | DP&L [Member] | Stuart Station [Member]    
Ownership (%)   35.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_StuartStationMember
Production Capacity (MW)   808dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_StuartStationMember
DP&L Share [Member] | DP&L [Member] | Zimmer Station [Member]    
Ownership (%)   28.10%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_ZimmerStationMember
Production Capacity (MW)   371dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_ZimmerStationMember
DP&L Share [Member] | DP&L [Member] | Total Jointly-owned Stations [Member]    
Production Capacity (MW)   2,078dpl_ProductionPlanCapacity
/ invest_InvestmentAxis
= dpl_DpandlShareMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_TotalJointlyOwnedStationsMember
DP&L Investment [Member] | Conesville Unit 4 [Member]    
Gross Plant In Service   25.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_ConesvilleUnitFourMember
Accumulated Depreciation   2.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_ConesvilleUnitFourMember
Construction Work in Process   1.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_ConesvilleUnitFourMember
SCR and FGD Equipment Installed and In Service   Yes
DP&L Investment [Member] | Killen Station [Member]    
Gross Plant In Service   308.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_KillenStationMember
Accumulated Depreciation   22.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_KillenStationMember
Construction Work in Process   4.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_KillenStationMember
SCR and FGD Equipment Installed and In Service   Yes
DP&L Investment [Member] | Miami Fort Units 7 and 8 [Member]    
Gross Plant In Service   214.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_MiamiFortUnitSevenAndEightMember
Accumulated Depreciation   26.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_MiamiFortUnitSevenAndEightMember
Construction Work in Process   3.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_MiamiFortUnitSevenAndEightMember
SCR and FGD Equipment Installed and In Service   Yes
DP&L Investment [Member] | Stuart Station [Member]    
Gross Plant In Service   220.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_StuartStationMember
Accumulated Depreciation   17.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_StuartStationMember
Construction Work in Process   12.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_StuartStationMember
SCR and FGD Equipment Installed and In Service   Yes
DP&L Investment [Member] | Zimmer Station [Member]    
Gross Plant In Service   185.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_ZimmerStationMember
Accumulated Depreciation   37.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_ZimmerStationMember
Construction Work in Process   4.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_ZimmerStationMember
SCR and FGD Equipment Installed and In Service   Yes
DP&L Investment [Member] | Total Jointly-owned Stations [Member]    
Gross Plant In Service   994.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_TotalJointlyOwnedStationsMember
Accumulated Depreciation   110.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_TotalJointlyOwnedStationsMember
Construction Work in Process   24.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= dpl_TotalJointlyOwnedStationsMember
DP&L Investment [Member] | Transmission (At Varying Percentages) [Member]    
Gross Plant In Service   42.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricTransmissionMember
Accumulated Depreciation   6.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricTransmissionMember
DP&L Investment [Member] | DP&L [Member] | Conesville Unit 4 [Member]    
Gross Plant In Service   24.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_ConesvilleUnitFourMember
Accumulated Depreciation   5.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_ConesvilleUnitFourMember
Construction Work in Process   1.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_ConesvilleUnitFourMember
SCR and FGD Equipment Installed and In Service   Yes
DP&L Investment [Member] | DP&L [Member] | Killen Station [Member]    
Gross Plant In Service   624.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_KillenStationMember
Accumulated Depreciation   317.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_KillenStationMember
Construction Work in Process   4.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_KillenStationMember
SCR and FGD Equipment Installed and In Service   Yes
DP&L Investment [Member] | DP&L [Member] | Miami Fort Units 7 and 8 [Member]    
Gross Plant In Service   361.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_MiamiFortUnitSevenAndEightMember
Accumulated Depreciation   164.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_MiamiFortUnitSevenAndEightMember
Construction Work in Process   3.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_MiamiFortUnitSevenAndEightMember
SCR and FGD Equipment Installed and In Service   Yes
DP&L Investment [Member] | DP&L [Member] | Stuart Station [Member]    
Gross Plant In Service   758.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_StuartStationMember
Accumulated Depreciation   327.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_StuartStationMember
Construction Work in Process   12.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_StuartStationMember
SCR and FGD Equipment Installed and In Service   Yes
DP&L Investment [Member] | DP&L [Member] | Zimmer Station [Member]    
Gross Plant In Service   1,104.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_ZimmerStationMember
Accumulated Depreciation   679.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_ZimmerStationMember
Construction Work in Process   4.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_ZimmerStationMember
SCR and FGD Equipment Installed and In Service   Yes
DP&L Investment [Member] | DP&L [Member] | Total Jointly-owned Stations [Member]    
Gross Plant In Service   2,969.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_TotalJointlyOwnedStationsMember
Accumulated Depreciation   1,555.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_TotalJointlyOwnedStationsMember
Construction Work in Process   24.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= dpl_TotalJointlyOwnedStationsMember
DP&L Investment [Member] | DP&L [Member] | Transmission (At Varying Percentages) [Member]    
Gross Plant In Service   98.0us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricTransmissionMember
Accumulated Depreciation   63.0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ invest_InvestmentAxis
= dpl_DpandlInvestmentMember
/ dei_LegalEntityAxis
= dpl_DpLMember
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricTransmissionMember