Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Credit risk derivative liabilities, at fair value	$ 0		$ 0		$ 4
Credit risk derivative liabilities, at fair value net	0		0		4
Net settlement amount in the event of a downgrade below investment grade	0		0		2
Additional collateral that would have to be posted in the event of an investment downgrade	0		0		2
Cash plus borrowing capacity to meet future liquidity needs	595		595		477
Derivative assets (non-current assets)	4		4		8
Derivative assets (non-current liabilities)	14		14		11
Delmarva Power & Light Co/De [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Credit risk derivative liabilities, at fair value	0		0		4
Credit risk derivative liabilities, at fair value net	0		0		4
Net settlement amount in the event of a downgrade below investment grade	0		0		2
Additional collateral that would have to be posted in the event of an investment downgrade	0		0		2
Cash plus borrowing capacity to meet future liquidity needs	595		595		477
Atlantic City Electric Co [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Estimated percentage of New Jersey load			15.00%
Derivative assets (non-current assets)	4		4		8
Derivative assets (non-current liabilities)	14		14		11
Unrealized loss on derivatives	$ 7	$ 7	$ 1	$ 1
Atlantic City Electric Co [Member] | Capacity (MWs) [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Commodity forward contracts	180		180		180