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 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

+ References

No definition available.

+ Details

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

- 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 Maturity Year

+ References

No definition available.

+ Details

Name:	pom_DebtInstrumentMaturityYear
Namespace Prefix:	pom_
Data Type:	xbrli:gYearItemType
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

Long Term Commercial Paper Program Maximum

+ References

No definition available.

+ Details

Name:	pom_LongTermCommercialPaperProgramMaximum
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Parent Company Credit Facility Letter Of Credit Maximum

+ References

No definition available.

+ Details

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

- Definition

Principal Payments

+ References

No definition available.

+ Details

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

- Definition

Ratio Of Deferrable Interest Subordinated Debt To Total Capitalization

+ References

No definition available.

+ Details

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

- Definition

Ratio Of Indebtedness To Total Capitalization

+ References

No definition available.

+ Details

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

- Definition

Same Day Borrowings Maximum Percentage Amount

+ 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

+ 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

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

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13476-108611

+ Details

Name:	us-gaap_DebtInstrumentFairValue
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

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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

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Data Type:	xbrli:dateItemType
Balance Type:	na
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

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
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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

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of the current portion of long-term unsecured obligations issued by corporations and other borrowers to investors (with maturities initially due after one year or beyond the operating cycle if longer).

+ 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 210.5-02.19,20)

-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 20

-Article 5

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19

-Article 5

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Debt (Detail) (USD $)	9 Months Ended			1 Months Ended				9 Months Ended					1 Months Ended		9 Months Ended	1 Months Ended		9 Months Ended			1 Months Ended
Debt (Detail) (USD $)	Sep. 30, 2012	Sep. 28, 2012	Dec. 31, 2011	Apr. 24, 2012 Term Loan Agreement [Member]	Sep. 30, 2012 Term Loan Agreement [Member]	Apr. 24, 2012 In Addition To Federal Funds Rate [Member]	Apr. 24, 2012 Eurodollar Rate [Member]	Sep. 30, 2012 Maximum [Member]	Sep. 30, 2012 Maximum [Member] Term Loan Agreement [Member]	Sep. 30, 2012 Potomac Electric Power Co [Member] D	Sep. 30, 2012 Delmarva Power & Light Co/De [Member] D	Aug. 06, 2012 Delmarva Power & Light Co/De [Member]	Aug. 06, 2012 Delmarva Power & Light Co/De [Member] Pollution Control Revenue Refunding Bonds [Member]	Sep. 28, 2012 Atlantic City Electric Co [Member]	Sep. 30, 2012 Atlantic City Electric Co [Member] D	Jul. 31, 2012 Atlantic City Electric Co [Member] Series 2002-1 Bonds Class A-3 [Member]	Jul. 31, 2012 Atlantic City Electric Co [Member] Series 2003-1 Bonds Class A-2 [Member]	Sep. 30, 2012 Pepco Holdings Inc [Member] D	Sep. 30, 2012 Pepco Energy Services [Member]	Dec. 31, 2011 Pepco Energy Services [Member]	Sep. 28, 2012 Pollution Control Revenue Bonds [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%
Credit facility borrowing capacity	750,000,000									250,000,000	250,000,000				250,000,000				515,000,000	283,000,000
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
Debt instrument variable interest rate in addition to the Federal Funds Effective rate	0.50%
Debt instrument variable interest rate in addition to one month LIBOR's effective rate	1.00%
Ratio of indebtedness to total capitalization								65.00%	65.00%
Ratio of deferrable interest subordinated debt to total capitalization								15.00%	15.00%
Borrowing capacity under the credit facility	1,078,000,000		994,000,000
Utility subsidiaries combined cash and borrowing capacity	563,000,000		711,000,000
Debt instrument, carrying value				200,000,000									31,000,000
Margin added to stated rate				0.875%		0.50%	1.00%
Debt instrument, interest percentage		5.60%			1.095%							5.20%	5.20%	5.60%							5.60%
Debt instrument, maturity date				Apr. 23, 2013										Dec. 31, 2025							Dec. 31, 2025
On-going commercial paper	875,000,000									500,000,000	500,000,000				250,000,000
Commercial paper outstanding	293,000,000									134,000,000	0				93,000,000
Commercial paper weighted average interest rate	0.87%									0.42%	0.43%				0.42%
Commercial paper weighted average maturity in days										4	4				3			10
Debt instrument, maturity year													2019
Debt instrument, amount outstanding												31,000,000		4,000,000							4,000,000
Cash collateral posted																			38,000,000	112,000,000
Letters of credit posted																			1,000,000	1,000,000
Debt instrument, principal payments																$ 6,000,000	$ 2,000,000