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

Commercial paper outstanding.

No definition available.

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

Commercial paper program maximum.

No definition available.

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

Commercial paper weighted average interest rate.

No definition available.

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

Commercial paper weighted average maturity.

No definition available.

Name:	pom_CommercialPaperWeightedAverageMaturity
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Contractual Obligation Payments Period

No definition available.

Name:	pom_ContractualObligationPaymentsPeriod
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

Debt instrument carrying value.

No definition available.

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

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

No definition available.

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

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

No definition available.

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

Line of credit facility extended expiration date.

No definition available.

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

Parent Company Borrowing Capacity Under Credit Facilities

No definition available.

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

The maximum amount of the credit facility that the parent company may obtain for letters of credit.

No definition available.

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

Payments for Retirement of Debt

No definition available.

Name:	pom_PaymentsForRetirementOfDebt
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Balance Type:	credit
Period Type:	duration

Purchase Price Under Agreement To Sell

No definition available.

Name:	pom_PurchasePriceUnderAgreementToSell
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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.

No definition available.

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

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

No definition available.

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

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

No definition available.

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

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

No definition available.

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

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

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
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Data Type:	num:percentItemType
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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.

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

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Period Type:	instant

Face (par) amount of debt instrument at time of issuance.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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Balance Type:	credit
Period Type:	instant

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

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

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-Name Accounting Standards Codification

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- Details

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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

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Amount of the required periodic payments applied to principal.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

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

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-Name Accounting Standards Codification

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Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

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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.

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

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-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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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.

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

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-Name Regulation S-X (SX)

-Number 210

-Section 02

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The cash outflow from the repayment of a long-term debt instrument issued, secured by a first mortgage deed of trust, containing a pledge of real property. The lender has the highest claim on the property in case of default.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

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-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

Name:	us-gaap_RepaymentsOfFirstMortgageBond
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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

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

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

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