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Amount of gain (loss), after tax expense or benefit and not previously recognized, resulting from the sale of a business component.

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After tax income (loss) from operations of a business component (exclusive of any gain (loss) on disposal, or provision therefore) during the reporting period, until its disposal.

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Amount of sales or other form of revenues attributable to the disposal group, including a component of the entity (discontinued operation), during the reporting period.

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Amount of income (loss) from a disposal group, net of income tax before extraordinary items allocable to noncontrolling interests. Includes, net of tax, income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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Discontinued Operations - Operating Results for Retail Electric and Natural Gas Supply Businesses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended							12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement by Disposal Groups, Including Discontinued Operations [Line Items]
Income From Discontinued Operations, Net of Income Taxes	$ 8	$ (11)	$ (319)	$ 9	$ 25	$ 15	$ 18	$ (322)	$ 67	$ 35
Discontinued Operations [Member] \| Pepco Energy Services [Member]
Income Statement by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenue								84	415	954
Income from operations of discontinued operations								4	26	2
Net Gains Associated With Accelerated Disposition Of Retail Electric And Natural Gas Contracts, Net of Income Tax								1
Income From Discontinued Operations, Net of Income Taxes								$ 5	$ 26	$ 2