Goodwill (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Goodwill [Line Items]
Goodwill Beginning Balance, Carrying Amount	$ 1,407	$ 1,407
Goodwill Ending Balance, Carrying Amount	1,407	1,407
Delmarva Power & Light Co/De [Member]
Goodwill [Line Items]
Goodwill Beginning Balance, Carrying Amount	8	8
Goodwill Ending Balance, Carrying Amount	$ 8	$ 8

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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+ Details