Commitments And Contingencies (Environmental Matters) (Detail) (USD $)	1 Months Ended	0 Months Ended	1 Months Ended	6 Months Ended		1 Months Ended
	Jul. 31, 2010	Jul. 02, 2010 Conectiv Energy Supply, Inc. [Member]	Jul. 31, 2010 Conectiv Energy Supply, Inc. [Member]	Jun. 30, 2012 Conectiv Energy Supply, Inc. [Member]	Jun. 30, 2012 Atlantic City Electric Co [Member]	Aug. 31, 2011 Potomac Electric Power Co [Member]	Jan. 31, 2011 Potomac Electric Power Co [Member] gal
Commitments And Contingencies [Line Items]
Third party maximum and seller floor for environmental remediation costs	$ 10,000,000		$ 10,000,000
Environmental remediation expense minimum		7,000,000
Environmental remediation expense maximum		18,000,000
Minimum estimated costs for closure of the operations				2,000,000
Maximum estimated costs for closure of the operations				3,000,000
Minimum estimated annual post closure operation, maintenance and monitoring costs, per year				120,000
Maximum estimated annual post closure operation, maintenance and monitoring costs, per year				193,000
Number of years that payments will be made to close coal ash landfill				30 years
EPA costs to date to clean up site					6,000,000
Estimated costs remaining to remediate the site					6,000,000
Quantity of mineral oil spill (gallons)							4,500
Penalty charges related to release of oil in U.S. waters						5,000
Civil penalty						$ 40,000