Schedule II - Valuation and Qualifying Accounts (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 34	$ 43	$ 44
Charged to Costs and Expenses	37	35	45
Charged to Other Accounts	5	8	8
Deductions	(38)	(52)	(54)
Balance at End of Period	38	34	43
Potomac Electric Power Co [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	13	18	20
Charged to Costs and Expenses	15	13	21
Charged to Other Accounts	1	2	2
Deductions	(13)	(20)	(25)
Balance at End of Period	16	13	18
Delmarva Power & Light Co/De [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	9	12	13
Charged to Costs and Expenses	11	11	11
Charged to Other Accounts	1	3	3
Deductions	(9)	(17)	(15)
Balance at End of Period	12	9	12
Atlantic City Electric Co [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	11	12	11
Charged to Costs and Expenses	11	12	13
Charged to Other Accounts	3	3	3
Deductions	(15)	(16)	(15)
Balance at End of Period	$ 10	$ 11	$ 12