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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, 2013	Dec. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations, net of income taxes	$ 8	$ (11)	$ (319)	$ (322)	$ 67
Pepco Energy Services [Member] \| Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenue				84	415
Income from operations of discontinued operations, net of income taxes				4	26
Net gains associated with accelerated disposition of retail electric and natural gas contracts, net of income taxes				1
Income from discontinued operations, net of income taxes				$ 5	$ 26