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Debt - Additional Information (Detail) (USD $)
 3 Months Ended 12 Months Ended 0 Months Ended 1 Months Ended
Mar. 31, 2015
Sublimit
Dec. 31, 2014
Oct. 24, 2013
Apr. 30, 2015
Jan. 31, 2015
Debt Instrument [Line Items]          
Credit facility, termination date Aug. 01, 2018        
Line of credit facility maximum borrowing capacity $ 1,500,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity        
Parent company credit facility letter of credit, maximum 500,000,000pom_ParentCompanyCreditFacilityLetterOfCreditMaximum        
Same day borrowings maximum percentage amount 10.00%pom_SameDayBorrowingsMaximumPercentageAmount        
Swingline loan repayment period 14 days        
Credit facility borrowing capacity 750,000,000us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity        
Maximum amount of credit available to parent 1,250,000,000pom_CombinedMaximumAmountOfCreditFacilityAvailableToParent        
Subsidiary borrowing limit under parent's credit facility 500,000,000pom_SubsidiaryBorrowingLimitUnderParentsCreditFacility        
Maximum number of sublimit reallocations per year 8pom_MaximumNumberOfSublimitReallocationPerYear        
Debt instrument variable interest rate in addition to one month LIBOR's effective rate 1.00%pom_DebtInstrumentVariableInterestRateInAdditionToOneMonthLiborsEffectiveRate        
Borrowing capacity under the credit facility 916,000,000pom_ParentCompanyBorrowingCapacityUnderCreditFacilities 875,000,000pom_ParentCompanyBorrowingCapacityUnderCreditFacilities      
Utility subsidiaries combined cash and borrowing capacity 547,000,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount 413,000,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount      
Amended description of Change in Control The Consent amends the definition of "Change in Control" in the credit agreement to mean, following consummation of the Merger, an event or series of events by which Exelon no longer owns, directly or indirectly, 100% of the outstanding shares of voting stock of Pepco Holdings.        
Ownership percentage of outstanding voting stock for Change in Control   100.00%pom_OwnershipPercentageBasisPointForChangeInControl      
On-going commercial paper 875,000,000pom_CommercialPaperProgramMaximum        
Commercial paper outstanding 803,000,000us-gaap_ShortTermBorrowings 729,000,000us-gaap_ShortTermBorrowings      
Commercial paper weighted average maturity, in days 8 days        
Purchase price   12,000,000pom_PurchasePriceUnderAgreementToSell      
Contract payment period   9 years      
Pepco Energy Services [Member]          
Debt Instrument [Line Items]          
Purchase price     7,000,000pom_PurchasePriceUnderAgreementToSell
/ us-gaap_StatementBusinessSegmentsAxis
= pom_PepcoEnergyServicesMember		    
Contract payment period     23 years    
Federal Funds Effective Rate [Member]          
Debt Instrument [Line Items]          
Debt instrument variable interest rate in addition to the federal funds effective rate 0.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_VariableRateAxis
= us-gaap_FederalFundsEffectiveSwapRateMember		        
Commercial Paper [Member]          
Debt Instrument [Line Items]          
Commercial paper weighted average interest rate 0.74%us-gaap_ShortTermDebtWeightedAverageInterestRate
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CommercialPaperMember		        
Bonds and Debentures [Member] | Subsequent Event [Member]          
Debt Instrument [Line Items]          
Debt instrument periodical principal payments       7,000,000us-gaap_DebtInstrumentPeriodicPaymentPrincipal
/ us-gaap_LongtermDebtTypeAxis
= pom_BondsAndDebenturesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		  
Bonds and Notes [Member] | Subsequent Event [Member]          
Debt Instrument [Line Items]          
Debt instrument periodical principal payments       3,000,000us-gaap_DebtInstrumentPeriodicPaymentPrincipal
/ us-gaap_LongtermDebtTypeAxis
= pom_BondsAndNotesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		  
First Mortgage Bonds [Member] | 4.15% Due 2043 [Member]          
Debt Instrument [Line Items]          
Debt instrument, face amount 200,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= pom_FourPointOneFivePercentageNotesDueTwoThousandAndFortyThreeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		        
Debt instruments maturity date Mar. 15, 2043        
Debt instrument, interest percentage 4.15%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= pom_FourPointOneFivePercentageNotesDueTwoThousandAndFortyThreeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		        
Debt instrument, yield to maturity rate 3.90%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= pom_FourPointOneFivePercentageNotesDueTwoThousandAndFortyThreeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		        
Debt instrument, premium 8,000,000us-gaap_DebtInstrumentUnamortizedPremium
/ us-gaap_DebtInstrumentAxis
= pom_FourPointOneFivePercentageNotesDueTwoThousandAndFortyThreeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		        
Maximum [Member]          
Debt Instrument [Line Items]          
Ratio of indebtedness to total capitalization 65.00%pom_RatioOfIndebtednessToCapitalization
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		        
Ratio of deferrable interest subordinated debt to total capitalization 15.00%pom_RatioOfDeferrableInterestSubordinatedDebtToCapitalization
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		        
Potomac Electric Power Co [Member]          
Debt Instrument [Line Items]          
Credit facility, termination date Aug. 01, 2018        
Line of credit facility maximum borrowing capacity 1,500,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		        
Parent company credit facility letter of credit, maximum 500,000,000pom_ParentCompanyCreditFacilityLetterOfCreditMaximum
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		        
Same day borrowings maximum percentage amount 10.00%pom_SameDayBorrowingsMaximumPercentageAmount
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		        
Swingline loan repayment period 14 days        
Credit facility borrowing capacity 250,000,000us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		        
Maximum amount of credit available to parent 1,250,000,000pom_CombinedMaximumAmountOfCreditFacilityAvailableToParent
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		        
Subsidiary borrowing limit under parent's credit facility 500,000,000pom_SubsidiaryBorrowingLimitUnderParentsCreditFacility
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		        
Maximum number of sublimit reallocations per year 8pom_MaximumNumberOfSublimitReallocationPerYear
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		        
Debt instrument variable interest rate in addition to one month LIBOR's effective rate 1.00%pom_DebtInstrumentVariableInterestRateInAdditionToOneMonthLiborsEffectiveRate
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		        
Utility subsidiaries combined cash and borrowing capacity 547,000,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		 413,000,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		      
Amended description of Change in Control The Consent amends the definition of "Change in Control" in the credit agreement to mean, following consummation of the Merger, an event or series of events by which Exelon no longer owns, directly or indirectly, 100% of the outstanding shares of voting stock of Pepco Holdings.        
Ownership percentage of outstanding voting stock for Change in Control   100.00%pom_OwnershipPercentageBasisPointForChangeInControl
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		      
On-going commercial paper 500,000,000pom_CommercialPaperProgramMaximum
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		        
Commercial paper outstanding   104,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		      
Commercial paper weighted average maturity, in days 5 days        
Purchase price   12,000,000pom_PurchasePriceUnderAgreementToSell
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember		      
Contract payment period   9 years      
Potomac Electric Power Co [Member] | Federal Funds Effective Rate [Member]          
Debt Instrument [Line Items]          
Debt instrument variable interest rate in addition to the federal funds effective rate 0.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember
/ us-gaap_VariableRateAxis
= us-gaap_FederalFundsEffectiveSwapRateMember		        
Potomac Electric Power Co [Member] | Commercial Paper [Member]          
Debt Instrument [Line Items]          
Commercial paper outstanding 0us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CommercialPaperMember		        
Commercial paper weighted average interest rate 0.43%us-gaap_ShortTermDebtWeightedAverageInterestRate
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CommercialPaperMember		        
Potomac Electric Power Co [Member] | First Mortgage Bonds [Member] | 4.15% Due 2043 [Member]          
Debt Instrument [Line Items]          
Debt instrument, face amount 200,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= pom_FourPointOneFivePercentageNotesDueTwoThousandAndFortyThreeMember
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		        
Debt instruments maturity date Mar. 15, 2043        
Debt instrument, interest percentage 4.15%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= pom_FourPointOneFivePercentageNotesDueTwoThousandAndFortyThreeMember
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		        
Debt instrument, yield to maturity rate 3.90%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= pom_FourPointOneFivePercentageNotesDueTwoThousandAndFortyThreeMember
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		        
Debt instrument, premium 8,000,000us-gaap_DebtInstrumentUnamortizedPremium
/ us-gaap_DebtInstrumentAxis
= pom_FourPointOneFivePercentageNotesDueTwoThousandAndFortyThreeMember
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		        
Potomac Electric Power Co [Member] | Maximum [Member]          
Debt Instrument [Line Items]          
Ratio of indebtedness to total capitalization 65.00%pom_RatioOfIndebtednessToCapitalization
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		        
Ratio of deferrable interest subordinated debt to total capitalization 15.00%pom_RatioOfDeferrableInterestSubordinatedDebtToCapitalization
/ dei_LegalEntityAxis
= pom_PotomacElectricPowerCoMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		        
Delmarva Power & Light Co/De [Member]          
Debt Instrument [Line Items]          
Credit facility, termination date Aug. 01, 2018        
Line of credit facility maximum borrowing capacity 1,500,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		        
Parent company credit facility letter of credit, maximum 500,000,000pom_ParentCompanyCreditFacilityLetterOfCreditMaximum
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		        
Same day borrowings maximum percentage amount 10.00%pom_SameDayBorrowingsMaximumPercentageAmount
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		        
Swingline loan repayment period 14 days        
Credit facility borrowing capacity 250,000,000us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		        
Maximum amount of credit available to parent 1,250,000,000pom_CombinedMaximumAmountOfCreditFacilityAvailableToParent
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		        
Subsidiary borrowing limit under parent's credit facility 500,000,000pom_SubsidiaryBorrowingLimitUnderParentsCreditFacility
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		        
Maximum number of sublimit reallocations per year 8pom_MaximumNumberOfSublimitReallocationPerYear
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		        
Debt instrument variable interest rate in addition to one month LIBOR's effective rate 1.00%pom_DebtInstrumentVariableInterestRateInAdditionToOneMonthLiborsEffectiveRate
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		        
Utility subsidiaries combined cash and borrowing capacity 547,000,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		 413,000,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		      
Amended description of Change in Control The Consent amends the definition of "Change in Control" in the credit agreement to mean, following consummation of the Merger, an event or series of events by which Exelon no longer owns, directly or indirectly, 100% of the outstanding shares of voting stock of Pepco Holdings.        
Ownership percentage of outstanding voting stock for Change in Control   100.00%pom_OwnershipPercentageBasisPointForChangeInControl
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		      
On-going commercial paper 500,000,000pom_CommercialPaperProgramMaximum
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		        
Commercial paper outstanding 280,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		 211,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember		      
Commercial paper weighted average maturity, in days 5 days        
Delmarva Power & Light Co/De [Member] | Federal Funds Effective Rate [Member]          
Debt Instrument [Line Items]          
Debt instrument variable interest rate in addition to the federal funds effective rate 0.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember
/ us-gaap_VariableRateAxis
= us-gaap_FederalFundsEffectiveSwapRateMember		        
Delmarva Power & Light Co/De [Member] | Commercial Paper [Member]          
Debt Instrument [Line Items]          
Commercial paper outstanding 175,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CommercialPaperMember		        
Commercial paper weighted average interest rate 0.45%us-gaap_ShortTermDebtWeightedAverageInterestRate
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CommercialPaperMember		        
Delmarva Power & Light Co/De [Member] | Maximum [Member]          
Debt Instrument [Line Items]          
Ratio of indebtedness to total capitalization 65.00%pom_RatioOfIndebtednessToCapitalization
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		        
Ratio of deferrable interest subordinated debt to total capitalization 15.00%pom_RatioOfDeferrableInterestSubordinatedDebtToCapitalization
/ dei_LegalEntityAxis
= pom_DelmarvaPowerLightCoMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		        
Atlantic City Electric Co [Member]          
Debt Instrument [Line Items]          
Credit facility, termination date Aug. 01, 2018        
Line of credit facility maximum borrowing capacity 1,500,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		        
Parent company credit facility letter of credit, maximum 500,000,000pom_ParentCompanyCreditFacilityLetterOfCreditMaximum
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		        
Same day borrowings maximum percentage amount 10.00%pom_SameDayBorrowingsMaximumPercentageAmount
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		        
Swingline loan repayment period 14 days        
Credit facility borrowing capacity 250,000,000us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		        
Maximum amount of credit available to parent 1,250,000,000pom_CombinedMaximumAmountOfCreditFacilityAvailableToParent
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		        
Subsidiary borrowing limit under parent's credit facility 500,000,000pom_SubsidiaryBorrowingLimitUnderParentsCreditFacility
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		        
Maximum number of sublimit reallocations per year 8pom_MaximumNumberOfSublimitReallocationPerYear
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		        
Utility subsidiaries combined cash and borrowing capacity 547,000,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		 413,000,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		      
Amended description of Change in Control The Consent amends the definition of "Change in Control" in the credit agreement to mean, following consummation of the Merger, an event or series of events by which Exelon no longer owns, directly or indirectly, 100% of the outstanding shares of voting stock of Pepco Holdings.        
Ownership percentage of outstanding voting stock for Change in Control   100.00%pom_OwnershipPercentageBasisPointForChangeInControl
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		      
On-going commercial paper 350,000,000pom_CommercialPaperProgramMaximum
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		        
Commercial paper outstanding 143,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		 127,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember		      
Commercial paper weighted average maturity, in days 5 days        
Atlantic City Electric Co [Member] | Commercial Paper [Member]          
Debt Instrument [Line Items]          
Commercial paper outstanding 143,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CommercialPaperMember		        
Commercial paper weighted average interest rate 0.44%us-gaap_ShortTermDebtWeightedAverageInterestRate
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CommercialPaperMember		        
Atlantic City Electric Co [Member] | Bonds and Debentures [Member]          
Debt Instrument [Line Items]          
Debt instrument periodical principal payments         8,000,000us-gaap_DebtInstrumentPeriodicPaymentPrincipal
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember
/ us-gaap_LongtermDebtTypeAxis
= pom_BondsAndDebenturesMember
Atlantic City Electric Co [Member] | Bonds and Debentures [Member] | Subsequent Event [Member]          
Debt Instrument [Line Items]          
Debt instrument periodical principal payments       7,000,000us-gaap_DebtInstrumentPeriodicPaymentPrincipal
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember
/ us-gaap_LongtermDebtTypeAxis
= pom_BondsAndDebenturesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		  
Atlantic City Electric Co [Member] | Bonds and Notes [Member]          
Debt Instrument [Line Items]          
Debt instrument periodical principal payments         3,000,000us-gaap_DebtInstrumentPeriodicPaymentPrincipal
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember
/ us-gaap_LongtermDebtTypeAxis
= pom_BondsAndNotesMember
Atlantic City Electric Co [Member] | Bonds and Notes [Member] | Subsequent Event [Member]          
Debt Instrument [Line Items]          
Debt instrument periodical principal payments       3,000,000us-gaap_DebtInstrumentPeriodicPaymentPrincipal
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember
/ us-gaap_LongtermDebtTypeAxis
= pom_BondsAndNotesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		  
Atlantic City Electric Co [Member] | Maximum [Member]          
Debt Instrument [Line Items]          
Debt instrument variable interest rate in addition to one month LIBOR's effective rate 1.00%pom_DebtInstrumentVariableInterestRateInAdditionToOneMonthLiborsEffectiveRate
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		        
Ratio of indebtedness to total capitalization 65.00%pom_RatioOfIndebtednessToCapitalization
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		        
Ratio of deferrable interest subordinated debt to total capitalization 15.00%pom_RatioOfDeferrableInterestSubordinatedDebtToCapitalization
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		        
Atlantic City Electric Co [Member] | Maximum [Member] | Federal Funds Effective Rate [Member]          
Debt Instrument [Line Items]          
Debt instrument variable interest rate in addition to the federal funds effective rate 0.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ dei_LegalEntityAxis
= pom_AtlanticCityElectricCoMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_FederalFundsEffectiveSwapRateMember		        
PHI [Member] | Commercial Paper [Member]          
Debt Instrument [Line Items]          
Commercial paper outstanding $ 380,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= pom_PepcoHoldingsIncMember
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CommercialPaperMember