Cash and borrowing capacity available under credit facilities.

No definition available.

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

- Definition

Combined maximum amount of credit facility available to parent in the event of the adjustment of the credit sub-limits at the borrowers election.

+ References

No definition available.

+ Details

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

- Definition

Commercial paper outstanding.

+ References

No definition available.

+ Details

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

- Definition

Commercial paper program maximum.

+ References

No definition available.

+ Details

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

- Definition

Commercial paper weighted average interest rate.

+ References

No definition available.

+ Details

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

- Definition

Commercial paper weighted average maturity.

+ References

No definition available.

+ Details

Name:	pom_CommercialPaperWeightedAverageMaturity
Namespace Prefix:	pom_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument variable interest rate in addition to federal funds effective rate.

+ References

No definition available.

+ Details

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

- Definition

Debt instrument variable interest rate in addition to one month LIBOR's effective rate.

+ References

No definition available.

+ Details

Name:	pom_DebtInstrumentVariableInterestRateInAdditionToOneMonthLiborsEffectiveRate
Namespace Prefix:	pom_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line of credit facility extended expiration date.

+ References

No definition available.

+ Details

Name:	pom_LineOfCreditFacilityExtendedExpirationDate
Namespace Prefix:	pom_
Data Type:	us-types:dateStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Line Of Credit Facility Extended Maturity Period

+ References

No definition available.

+ Details

Name:	pom_LineOfCreditFacilityExtendedMaturityPeriod
Namespace Prefix:	pom_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum amount of the credit facility that the Parent Company may obtain for Letters Of Credit

+ References

No definition available.

+ Details

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

- Definition

Maximum ratio of deferrable interest subordinated debt to capitalization permitted to be excluded from the computation of total indebtedness under the credit facility and term loan agreements.

+ References

No definition available.

+ Details

Name:	pom_RatioOfDeferrableInterestSubordinatedDebtToCapitalization
Namespace Prefix:	pom_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum ratio of indebtedness to capitalization permitted under the credit facility and term loan agreements.

+ References

No definition available.

+ Details

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

- Definition

Maximum percentage of credit facility that each company may borrow under the swing-line loan sub-facility

+ References

No definition available.

+ Details

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

- Definition

Subsidiary borrowing limit under parents credit facility in the event of the adjustment of the credit sub-limits at the borrowers election

+ References

No definition available.

+ Details

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

- Definition

Utility subsidiaries combined cash and borrowings capacity.

+ References

No definition available.

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the required periodic payments applied to principal.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow for a borrowing having initial term of repayment within one year or the normal operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

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

Debt - Additional Information (Detail) (USD $)	6 Months Ended		1 Months Ended		6 Months Ended					6 Months Ended				6 Months Ended					1 Months Ended		1 Months Ended						6 Months Ended				1 Months Ended
Debt - Additional Information (Detail) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Jul. 31, 2013 Series 2002-1 Bonds, Class A-3 [Member] Subsequent Event [Member]	Jul. 31, 2013 Series 2003-1 Bonds, Class A-2 [Member] Subsequent Event [Member]	Jun. 30, 2013 Maximum [Member]	Jun. 30, 2013 Maximum [Member] Term Loan Agreement [Member]	Jun. 30, 2013 Restated Agreement [Member]	Jun. 30, 2013 Potomac Electric Power Co [Member]	Dec. 31, 2012 Potomac Electric Power Co [Member]	Jun. 30, 2013 Potomac Electric Power Co [Member] Maximum [Member]	Jun. 30, 2013 Potomac Electric Power Co [Member] Restated Agreement [Member]	Jun. 30, 2013 Delmarva Power & Light Co/De [Member]	Dec. 31, 2012 Delmarva Power & Light Co/De [Member]	Jun. 30, 2013 Delmarva Power & Light Co/De [Member] Maximum [Member]	Jun. 30, 2013 Delmarva Power & Light Co/De [Member] Restated Agreement [Member]	Jun. 30, 2013 Atlantic City Electric Co [Member]	May 30, 2013 Atlantic City Electric Co [Member]	Dec. 31, 2012 Atlantic City Electric Co [Member]	May 10, 2013 Atlantic City Electric Co [Member] Term Loan Agreement [Member]	Jun. 30, 2013 Atlantic City Electric Co [Member] Term Loan Agreement [Member]	Apr. 30, 2013 Atlantic City Electric Co [Member] Series 2002-1 Bonds, Class A-3 [Member]	Jul. 31, 2013 Atlantic City Electric Co [Member] Series 2002-1 Bonds, Class A-3 [Member] Subsequent Event [Member]	Apr. 30, 2013 Atlantic City Electric Co [Member] Series 2003-1 Bonds, Class A-2 [Member]	Jul. 31, 2013 Atlantic City Electric Co [Member] Series 2003-1 Bonds, Class A-2 [Member] Subsequent Event [Member]	May 10, 2013 Atlantic City Electric Co [Member] In Addition To Federal Funds Rate [Member]	May 10, 2013 Atlantic City Electric Co [Member] Eurodollar [Member]	Jun. 30, 2013 Atlantic City Electric Co [Member] Maximum [Member]	Jun. 30, 2013 Atlantic City Electric Co [Member] Maximum [Member] Term Loan Agreement [Member]	Jun. 30, 2013 Atlantic City Electric Co [Member] Restated Agreement [Member]	Dec. 31, 2012 PHI [Member]	May 29, 2013 PHI [Member] Term Loan Agreement [Member]	Mar. 28, 2013 PHI [Member] Term Loan Agreement [Member]
Debt Instrument [Line Items]
Line of credit facility, expiration date							Aug. 01, 2018				Aug. 01, 2018				Aug. 01, 2018														Aug. 01, 2018
Line of credit facility, extended expiration date	August 1, 2017							August 1, 2017				August 1, 2017				August 1, 2017
Line of credit facility termination period							1 year				1 year				1 year	1 year
Line of credit facility maximum borrowing capacity	$ 1,500,000,000
Parent company credit facility letter of credit, maximum	500,000,000
Same day borrowings maximum percentage amount	10.00%							10.00%				10.00%				10.00%
Credit facility borrowing capacity	750,000,000							250,000,000				250,000,000				250,000,000
Maximum amount of credit available to parent	1,250,000,000
Subsidiary borrowing limit under parent's credit facility	500,000,000							500,000,000				500,000,000				500,000,000
Debt instrument variable interest rate in addition to the federal funds effective rate	0.50%							0.50%				0.50%				0.50%
Debt instrument variable interest rate in addition to one month LIBOR's effective rate	1.00%							1.00%				1.00%				1.00%
Ratio of indebtedness to total capitalization					65.00%	65.00%				65.00%				65.00%													65.00%	65.00%
Ratio of deferrable interest subordinated debt to total capitalization					15.00%	15.00%				15.00%				15.00%													15.00%	15.00%
Borrowing capacity under the credit facility	1,230,000,000	861,000,000						595,000,000	477,000,000			595,000,000	477,000,000			595,000,000		477,000,000
Utility subsidiaries combined cash and borrowing capacity	595,000,000	477,000,000
Ongoing commercial paper	875,000,000							500,000,000				500,000,000				250,000,000
Commercial paper outstanding	114,000,000							0				109,000,000				46,000,000
Commercial paper weighted average interest rate	0.71%							0.38%				0.32%				0.34%
Commercial paper weighted average maturity, in days	5 days							7 days				2 days				4 days
Debt instrument, carrying value																	4,400,000		100,000,000											200,000,000		250,000,000
Margin added to stated rate																			0.75%						0.50%	1.00%						0.875%
PHI repaid loan																															250,000,000
Debt instrument, interest percentage																			0.95%	0.95%
Debt instrument, maturity date																			Nov. 10, 2014
Debt instrument principal payment			$ 7,000,000	$ 2,000,000																	$ 7,000,000	$ 7,000,000	$ 3,000,000	$ 2,000,000