Allocated portion of net periodic benefit costs from parent.

No definition available.

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- Definition

Defined benefit plan prior service cost credit.

+ References

No definition available.

+ Details

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- Definition

Defined benefit plan prior service costs credits amortization period.

+ References

No definition available.

+ Details

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- Definition

Net periodic benefit cost pension and other postretirement.

+ References

No definition available.

+ Details

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- Definition

Number of amendments to other postretirement benefits plan.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Percentage of net periodic other postretirement benefit costs capitalized.

+ References

No definition available.

+ Details

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- Definition

The interest rate used to adjust for the time value of money.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(1)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

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- Definition

The amount of increase or decrease in the accumulated benefit obligation related to the effects of a change in the substantive terms of an existing defined benefit pension 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=28361610&loc=d3e1928-114920

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- 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

+ Details

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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

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Pension and Other Postretirement Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended	3 Months Ended				9 Months Ended		3 Months Ended				9 Months Ended			3 Months Ended			9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012 Other Postretirement Benefits [Member]	Jun. 30, 2013 PHI Service Company [Member]	Mar. 31, 2013 PHI Service Company [Member]	Jun. 30, 2013 PHI Service Company [Member] Other Postretirement Benefits [Member]	Sep. 30, 2013 PHI Service Company [Member] Other Postretirement Benefits [Member] Amendments	Sep. 30, 2013 Delmarva Power & Light Co/De [Member]	Mar. 31, 2013 Delmarva Power & Light Co/De [Member]	Sep. 30, 2012 Delmarva Power & Light Co/De [Member]	Mar. 31, 2012 Delmarva Power & Light Co/De [Member]	Sep. 30, 2013 Delmarva Power & Light Co/De [Member]	Sep. 30, 2012 Delmarva Power & Light Co/De [Member]	Sep. 30, 2013 Atlantic City Electric Co [Member]	Mar. 31, 2013 Atlantic City Electric Co [Member]	Sep. 30, 2012 Atlantic City Electric Co [Member]	Mar. 31, 2012 Atlantic City Electric Co [Member]	Sep. 30, 2013 Atlantic City Electric Co [Member]	Sep. 30, 2012 Atlantic City Electric Co [Member]	Sep. 30, 2013 Atlantic City Electric Co [Member] Other Postretirement Benefits [Member] Amendments	Sep. 30, 2013 Potomac Electric Power Co [Member]	Sep. 30, 2012 Potomac Electric Power Co [Member]	Mar. 31, 2012 Potomac Electric Power Co [Member]	Sep. 30, 2013 Potomac Electric Power Co [Member]	Sep. 30, 2012 Potomac Electric Power Co [Member]	Sep. 30, 2013 Potomac Electric Power Co [Member] Other Postretirement Benefits [Member] Amendments	Sep. 30, 2013 Delmarva Power Light Co Electric [Member] Other Postretirement Benefits [Member] Amendments
Defined Benefit Plan Disclosure [Line Items]
Pension contributions	$ 120	$ 200		$ 60	$ 20				$ 10		$ 85	$ 10	$ 85		$ 30		$ 30	$ 30	$ 30				$ 85		$ 85
Projected benefit obligation							124
Amortization period							10 years													10 years
Net periodic benefit cost			69				13													2						4	3
Percentage of postretirement benefit costs							30.00%													30.00%						30.00%	30.00%
Reduction of the projected benefit obligation							193
Number of amendments, PHI approved							2													2						2	2
Change in the discount rate			4.10%			4.95%
Pension and other postretirement net periodic benefit cost								20		28		74	84	20		28		74	84		20	28		74	84
Pension and other postretirement net periodic benefit cost								$ 4		$ 6		$ 14	$ 18	$ 4		$ 6		$ 14	$ 18		$ 8	$ 10		$ 27	$ 30