Borrowing capacity under the credit facilities

No definition available.

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

- Definition

Cash and borrowing capacity available under credit facilities.

+ References

No definition available.

+ Details

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

- Definition

Cash collateral paid out per agreement and will be returned at end of agreement

+ References

No definition available.

+ Details

Name:	pom_CashCollateralPaidOutPerAgreementAndWillBeReturnedAtEndOfAgreement
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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:integerItemType
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 LIBORs 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

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

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

+ References

No definition available.

+ Details

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

- Definition

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond 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 03

-Paragraph 16

-Article 9

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number APB14-1

-Paragraph 31

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

Reference 4: 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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

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

- Definition

Interest rate stated in the contractual debt agreement.

+ References

+ 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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

+ Details

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

- 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

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_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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

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

Reference 3: 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_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Debt (Detail) (USD $)	3 Months Ended		1 Months Ended				1 Months Ended	3 Months Ended				3 Months Ended				3 Months Ended				1 Months Ended				3 Months Ended
Debt (Detail) (USD $)	Mar. 31, 2013 D	Dec. 31, 2012	Mar. 28, 2013 Term Loan Agreement [Member]	Mar. 31, 2013 Term Loan Agreement [Member]	Mar. 28, 2013 In Addition To Federal Funds Rate [Member]	Mar. 28, 2013 Eurodollar Rate [Member]	Mar. 31, 2013 First Mortgage Bonds [Member]	Mar. 31, 2012 Maximum [Member]	Mar. 31, 2013 Maximum [Member] Term Loan Agreement [Member]	Mar. 31, 2013 Potomac Electric Power Co [Member] D	Dec. 31, 2012 Potomac Electric Power Co [Member]	Mar. 31, 2013 Potomac Electric Power Co [Member] First Mortgage Bonds [Member]	Mar. 31, 2012 Potomac Electric Power Co [Member] Maximum [Member]	Mar. 31, 2013 Delmarva Power & Light Co/De [Member] D	Dec. 31, 2012 Delmarva Power & Light Co/De [Member]	Mar. 31, 2012 Delmarva Power & Light Co/De [Member] Maximum [Member]	Mar. 31, 2013 Atlantic City Electric Co [Member] D	Dec. 31, 2012 Atlantic City Electric Co [Member]	Apr. 30, 2013 Atlantic City Electric Co [Member] Subsequent Event [Member]	Jan. 31, 2013 Atlantic City Electric Co [Member] Series 2002-1 Bonds, Class A-3 [Member]	Apr. 30, 2013 Atlantic City Electric Co [Member] Series 2002-1 Bonds, Class A-3 [Member] Subsequent Event [Member]	Jan. 31, 2013 Atlantic City Electric Co [Member] Series 2003-1 Bonds, Class A-2 [Member]	Apr. 30, 2013 Atlantic City Electric Co [Member] Series 2003-1 Bonds, Class A-2 [Member] Subsequent Event [Member]	Mar. 31, 2012 Atlantic City Electric Co [Member] Maximum [Member]	Mar. 31, 2013 Pepco Energy Services [Member]	Dec. 31, 2012 Pepco Energy Services [Member]	Mar. 31, 2013 Pepco Energy Services [Member] Maximum [Member] Retail Electric Supply Business [Member]	Dec. 31, 2012 Pepco Energy Services [Member] Maximum [Member] Retail Electric Supply Business [Member]
Debt Instrument [Line Items]
Line of credit facility, expiration date	Aug. 01, 2016									Aug. 01, 2016				Aug. 01, 2016			Aug. 01, 2016
Line of credit facility, extended expiration date	2017-08-01									2017-08-01				2017-08-01			2017-08-01
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%
Ratio of deferrable interest subordinated debt to total capitalization								15.00%	15.00%				15.00%			15.00%								15.00%
Borrowing capacity under the credit facility	975,000,000	861,000,000								635,000,000	477,000,000			635,000,000	477,000,000		635,000,000	477,000,000
Utility subsidiaries combined cash and borrowing capacity	635,000,000	477,000,000
Ongoing commercial paper	875,000,000									500,000,000				500,000,000			250,000,000
Commercial paper outstanding	408,000,000									0				70,000,000			185,000,000
Commercial paper weighted average interest rate	0.76%									0.38%				0.36%			0.37%
Commercial paper weighted average maturity, in days	10									7				3			7
Carrying value of instrument		200,000,000	250,000,000				250,000,000					250,000,000							4,400,000
Margin added to stated rate			0.875%		0.50%	1.00%
Debt instrument, interest percentage				1.09%			4.15%					4.15%
Debt instrument maturity date			Mar. 27, 2014				Mar. 15, 2043					Mar. 15, 2043
Debt instrument principal payment																				7,000,000	7,000,000	3,000,000	3,000,000
Cash collateral posted																									5,000,000	14,000,000
Letters of credit posted																											1,000,000	1,000,000
Borrowing capacity under PHI's credit facility																									$ 340,000,000	$ 384,000,000