Fair Value Disclosures - Summary of Primary Unobservable Inputs Used to Determine Fair Value of Level 3 Instruments and Range of Values That Could be Used for Those Inputs (Detail) (USD $) In Millions, unless otherwise specified							12 Months Ended									12 Months Ended							12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Capacity Contracts, Net [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Natural Gas Options [Member]	Dec. 31, 2012 Minimum [Member] Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Capacity Contracts, Net [Member]	Dec. 31, 2012 Minimum [Member] Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Natural Gas Options [Member] Derivative	Dec. 31, 2012 Maximum [Member] Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Capacity Contracts, Net [Member]	Dec. 31, 2012 Maximum [Member] Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Natural Gas Options [Member] Derivative	Dec. 31, 2013 Atlantic City Electric Co [Member]	Dec. 31, 2012 Atlantic City Electric Co [Member]	Dec. 31, 2013 Atlantic City Electric Co [Member] Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2012 Atlantic City Electric Co [Member] Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2012 Atlantic City Electric Co [Member] Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Capacity Contracts, Net [Member]	Dec. 31, 2012 Atlantic City Electric Co [Member] Minimum [Member] Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Capacity Contracts, Net [Member]	Dec. 31, 2012 Atlantic City Electric Co [Member] Maximum [Member] Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Capacity Contracts, Net [Member]	Dec. 31, 2013 Delmarva Power & Light Co/De [Member]	Dec. 31, 2012 Delmarva Power & Light Co/De [Member]	Dec. 31, 2013 Delmarva Power & Light Co/De [Member] Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2012 Delmarva Power & Light Co/De [Member] Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2012 Delmarva Power & Light Co/De [Member] Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Natural Gas Options [Member]	Dec. 31, 2012 Delmarva Power & Light Co/De [Member] Minimum [Member] Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Natural Gas Options [Member] Derivative	Dec. 31, 2012 Delmarva Power & Light Co/De [Member] Maximum [Member] Significant Unobservable Inputs (Level 3) [Member] Derivative [Member] Natural Gas Options [Member] Derivative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value of financial instrument	$ (5,146)	$ (5,358)	$ (573)	$ (500)	$ (3)	$ (4)					$ (1,244)	$ (1,357)	$ (215)	$ (132)	$ (3)			$ (960)	$ (990)	$ (110)	$ (113)	$ (4)
Volatility factor, range								(1.57)		2.00													1.57	2.00
Discounted cash flow, Discount rate							5.00%		9.00%							5.00%	9.00%