Fair Value Disclosures (Summary Of Primary Unobservable Inputs Used To Determine Fair Value Of Level 3 Instruments And Range Of Values That For Those Inputs) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value of financial instrument	5,534	5,358
Delmarva Power & Light Co/De [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value of financial instrument	968	990
Atlantic City Electric Co [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value of financial instrument	1,334	1,357
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value of financial instrument	495	500
Significant Unobservable Inputs (Level 3) [Member] | Natural Gas Options [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value of financial instrument		(4)
Significant Unobservable Inputs (Level 3) [Member] | Capacity [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value of financial instrument	(3)	(3)
Significant Unobservable Inputs (Level 3) [Member] | Delmarva Power & Light Co/De [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value of financial instrument	112	113
Significant Unobservable Inputs (Level 3) [Member] | Delmarva Power & Light Co/De [Member] | Natural Gas Options [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value of financial instrument		(4)
Significant Unobservable Inputs (Level 3) [Member] | Atlantic City Electric Co [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value of financial instrument	130	132
Significant Unobservable Inputs (Level 3) [Member] | Atlantic City Electric Co [Member] | Capacity [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value of financial instrument	(3)	(3)
Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member] | Capacity [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discounted cash flow, Discount rate	6.00%
Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member] | Capacity [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discounted cash flow, Discount rate	8.00%
Derivative [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member] | Natural Gas Options [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Volatility Factor, Range		1.57
Derivative [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member] | Capacity [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discounted cash flow, Discount rate		5.00%
Derivative [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member] | Delmarva Power & Light Co/De [Member] | Natural Gas Options [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Volatility Factor, Range		1.57
Derivative [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member] | Atlantic City Electric Co [Member] | Capacity [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discounted cash flow, Discount rate	6.00%	5.00%
Derivative [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member] | Natural Gas Options [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Volatility Factor, Range		2.00
Derivative [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member] | Capacity [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discounted cash flow, Discount rate		9.00%
Derivative [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member] | Delmarva Power & Light Co/De [Member] | Natural Gas Options [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Volatility Factor, Range		2.00
Derivative [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member] | Atlantic City Electric Co [Member] | Capacity [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discounted cash flow, Discount rate	8.00%	9.00%