Derivative Instruments And Hedging Activities (Net Outstanding Commodity Forward Contracts That Did Not Qualify For Hedge Accounting) (Detail)	12 Months Ended
Dec. 31, 2012 MW	Dec. 31, 2011
Atlantic City Electric Co [Member] \| Capacity (MW-Days) [Member]
Derivative [Line Items]
Commodity forward contracts	180
Net Position	Long	-
Delmarva Power & Light Co/De [Member] \| Natural Gas (One Million British Thermal Units (MMBtu)) [Member]
Derivative [Line Items]
Commodity forward contracts	3,838,000	6,161,200
Net Position	Long	Long

Information that would enable users to understand the volume of the entity's derivative activity.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44

-Subparagraph 2

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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