Allocated portion of net periodic benefit costs from parent.

No definition available.

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

- Definition

Net periodic benefit cost pension and other postretirement.

+ References

No definition available.

+ Details

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

- Definition

Number of amendments to other postretirement benefits plan.

+ References

No definition available.

+ Details

Name:	pom_NumberOfAmendmentsToOtherPostretirementBenefitsPlan
Namespace Prefix:	pom_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of net periodic other postretirement benefit costs capitalized.

+ References

No definition available.

+ Details

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

- Details

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

- Definition

The amount of increase or decrease in net periodic benefit cost related to the effects of a change in the substantive terms of an existing defined benefit plan or the initiation of a new plan. A plan amendment may increase or decrease benefits, including those attributed to years of service already rendered.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Glossary Plan Amendment

-URI http://asc.fasb.org/extlink&oid=6520743

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Plan Amendment

-URI http://asc.fasb.org/extlink&oid=6520782

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (r)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

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

- Definition

The amount of cash or cash equivalents contributed by the entity to fund its pension plans.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585

+ Details

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

Pension and Other Postretirement Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended			3 Months Ended			9 Months Ended				3 Months Ended			9 Months Ended				3 Months Ended			9 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Sep. 30, 2014 Other Postretirement Benefits [Member]	Dec. 31, 2013 Other Postretirement Benefits [Member] Amendments	Sep. 30, 2014 Potomac Electric Power Co [Member]	Sep. 30, 2013 Potomac Electric Power Co [Member]	Mar. 31, 2013 Potomac Electric Power Co [Member]	Sep. 30, 2014 Potomac Electric Power Co [Member]	Sep. 30, 2013 Potomac Electric Power Co [Member]	Sep. 30, 2014 Potomac Electric Power Co [Member] Other Postretirement Benefits [Member]	Dec. 31, 2013 Potomac Electric Power Co [Member] Other Postretirement Benefits [Member] Amendments	Sep. 30, 2014 Delmarva Power & Light Co/De [Member]	Sep. 30, 2013 Delmarva Power & Light Co/De [Member]	Mar. 31, 2013 Delmarva Power & Light Co/De [Member]	Sep. 30, 2014 Delmarva Power & Light Co/De [Member]	Sep. 30, 2013 Delmarva Power & Light Co/De [Member]	Sep. 30, 2014 Delmarva Power & Light Co/De [Member] Other Postretirement Benefits [Member]	Dec. 31, 2013 Delmarva Power & Light Co/De [Member] Other Postretirement Benefits [Member] Amendments	Sep. 30, 2014 Atlantic City Electric Co [Member]	Sep. 30, 2013 Atlantic City Electric Co [Member]	Mar. 31, 2013 Atlantic City Electric Co [Member]	Sep. 30, 2014 Atlantic City Electric Co [Member]	Sep. 30, 2013 Atlantic City Electric Co [Member]	Sep. 30, 2014 Atlantic City Electric Co [Member] Other Postretirement Benefits [Member]	Dec. 31, 2013 Atlantic City Electric Co [Member] Other Postretirement Benefits [Member] Amendments
Defined Benefit Plan Disclosure [Line Items]
Percentage of postretirement benefit costs				37.00%							37.00%							37.00%							37.00%
Pension contributions	$ 60	$ 20	$ 120					$ 0	$ 0	$ 0					$ 10	$ 0	$ 10					$ 30	$ 0	$ 30
Number of amendments, PHI approved					2							2							2							2
Reduction in net periodic benefit cost				17							6							4							2
Pension and other postretirement net periodic benefit cost						16	20		44	74			16	20		44	74			16	20		44	74
Pension and other postretirement net periodic benefit cost, allocated portion						$ 5	$ 8		$ 16	$ 27			$ 1	$ 4		$ 5	$ 14			$ 4	$ 4		$ 10	$ 14