Advanced payment of additional taxes and related interest.

No definition available.

Name:	pom_AdvancedPaymentOfAdditionalTaxesAndRelatedInterest
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

After tax charge and interest expense from reducing carrying value of leveraged leases.

+ References

No definition available.

+ Details

Name:	pom_AfterTaxChargeAndInterestExpenseFromReducingCarryingValueOfLeveragedLeases
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Agreement with living classrooms foundation obligation fund.

+ References

No definition available.

+ Details

Name:	pom_AgreementWithLivingClassroomsFoundationObligationFund
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	pom_CommitmentsAndContingenciesLineItems
Namespace Prefix:	pom_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Donation To Foundation

+ References

No definition available.

+ Details

Name:	pom_DonationToFoundation
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

EPA costs to date to clean up site.

+ References

No definition available.

+ Details

Name:	pom_EpaCostsToDateToCleanUpSite
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Estimated costs remaining to remediate the site.

+ References

No definition available.

+ Details

Name:	pom_EstimatedCostsRemainingToRemediateSite
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Income tax examination additional tax payment.

+ References

No definition available.

+ Details

Name:	pom_IncomeTaxExaminationAdditionalTaxPayment
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Potential estimated tax liability related to disallowed tax benefits.

+ References

No definition available.

+ Details

Name:	pom_PotentialEstimatedTaxLiabilityRelatedToDisallowedTaxBenefits
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Potential interest on potential tax liability related to disallowed tax benefits.

+ References

No definition available.

+ Details

Name:	pom_PotentialInterestOnPotentialTaxLiabilityRelatedToDisallowedTaxBenefits
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Potential percentage of disallowed tax benefits associated with leases.

+ References

No definition available.

+ Details

Name:	pom_PotentialPercentageOfDisallowedTaxBenefitsAssociatedWithLeases
Namespace Prefix:	pom_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Potential percentage of penalty on amount of additional taxes due.

+ References

No definition available.

+ Details

Name:	pom_PotentialPercentageOfPenaltyOnAmountOfAdditionalTaxesDue
Namespace Prefix:	pom_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Quantity of mineral oil spill.

+ References

No definition available.

+ Details

Name:	pom_QuantityOfMineralOilSpill
Namespace Prefix:	pom_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	duration

- Definition

Total anticipated costs associated with remediation, site restoration, postclosure, monitoring commitments, or other exit costs that may occur on the sale, disposal, or abandonment of a particular property resulting from unanticipated contamination of the assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.Y.Q4)

-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section Y

-Paragraph Question 4

+ Details

Name:	us-gaap_EnvironmentalExitCostsAnticipatedCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of estimated interest recognized in the period arising from income tax examinations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

+ Details

Name:	us-gaap_IncomeTaxExaminationInterestExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of estimated penalties recognized in the period arising from income tax examinations.

+ References

+ Details

Name:	us-gaap_IncomeTaxExaminationPenaltiesExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

+ References

No definition available.

+ Details

Name:	us-gaap_LitigationSettlementExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of damages paid to the plaintiff in the legal matter.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

+ Details

Name:	us-gaap_LossContingencyDamagesPaidValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=pom_AtlanticCityElectricCoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=pom_PepcoHoldingsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=pom_PotomacElectricPowerCoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments and Contingencies - Environmental Matters - Additional Information (Detail) (USD $)	1 Months Ended			3 Months Ended
	Mar. 31, 2014	Jan. 31, 2011 gal	Nov. 30, 2008	Mar. 31, 2013	Mar. 31, 2015
Commitments and Contingencies [Line Items]
EPA costs to date to clean up site			$ 6,000,000pom_EpaCostsToDateToCleanUpSite
Estimated costs remaining to remediate the site			6,000,000
Quantity of mineral oil spill		4,500pom_QuantityOfMineralOilSpill
Cost of litigation	875,000us-gaap_LitigationSettlementExpense
Civil penalty payment	250,000us-gaap_LossContingencyDamagesPaidValue
Donation for training fund	25,000pom_DonationToFoundation
Fund provided for installation and operation of the trash collection SEP	600,000
Tax payment made		74,000,000		74,000,000
Income tax penalties		1,000,000		0
Interest expense assessed relating to disallowed deductions		28,000,000
Non-cash charge (after-tax)				377,000,000
Maximum tax penalty percentage				20.00%
Percentage of disallowed tax benefits associated with leases				100.00%
Federal income tax benefits				192,000,000
Potential interest on potential tax liability related to disallowed tax benefits				50,000,000
Deposit of additional taxes and related interest				242,000,000
PHI [Member] \| Minimum [Member]
Commitments and Contingencies [Line Items]
Cost of implementation of a closure plan and cap					3,000,000
PHI [Member] \| Maximum [Member]
Commitments and Contingencies [Line Items]
Cost of implementation of a closure plan and cap					6,000,000
Potomac Electric Power Co [Member]
Commitments and Contingencies [Line Items]
Quantity of mineral oil spill		4,500
Cost of litigation	875,000
Civil penalty payment	250,000
Donation for training fund	25,000
Fund provided for installation and operation of the trash collection SEP	600,000
Potomac Electric Power Co [Member] \| Minimum [Member]
Commitments and Contingencies [Line Items]
Cost of implementation of a closure plan and cap					3,000,000
Potomac Electric Power Co [Member] \| Maximum [Member]
Commitments and Contingencies [Line Items]
Cost of implementation of a closure plan and cap					6,000,000
Atlantic City Electric Co [Member]
Commitments and Contingencies [Line Items]
EPA costs to date to clean up site			6,000,000
Estimated costs remaining to remediate the site			$ 6,000,000