Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Credit risk derivative liabilities, at fair value	$ 0	$ 4
Cash collateral posted	0	0
Net settlement amount in the event of a downgrade below investment grade	0	2
Additional collateral that would have to be posted in the event of an investment downgrade	0	2
Cash plus borrowing capacity to meet future liquidity needs	332	477
Derivative assets (non-current assets)		8
Derivative Liabilities (non-current liabilities)		11
Derivatives Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative assets (non-current assets)
Derivative Liabilities (non-current liabilities)
Designated as Hedging Instrument [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net unrealized loss arising during the period	0	0	0
Designated as Hedging Instrument [Member] | Derivatives Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net realized loss recognized during the period	0	0	5
Delmarva Power & Light Co/De [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Credit risk derivative liabilities, at fair value	0	4
Cash collateral posted	0	0
Net settlement amount in the event of a downgrade below investment grade	0	2
Additional collateral that would have to be posted in the event of an investment downgrade	0	2
Cash plus borrowing capacity to meet future liquidity needs	332	477
Delmarva Power & Light Co/De [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative net unrealized gain (loss)	0	0	0
Delmarva Power & Light Co/De [Member] | Designated as Hedging Instrument [Member] | Derivatives Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net realized loss recognized during the period	0	0	5
Atlantic City Electric Co [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative net unrealized gain (loss)	3	(3)
Derivative assets (non-current assets)		8
Derivative Liabilities (non-current liabilities)		$ 11
Atlantic City Electric Co [Member] | Capacity (MWs) [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Commodity forward contracts		180