Leasing Activities (Income Recognized From Cross-Border Energy Lease Investments) (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013
Leases [Abstract]
Interest expense on uncertain tax positions	$ 16

Income Tax Interest Expense On Uncertain Tax Positions

No definition available.

Name:	pom_IncomeTaxInterestExpenseOnUncertainTaxPositions
Namespace Prefix:	pom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration