Organization - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended	0 Months Ended
	Apr. 29, 2014	Dec. 31, 2013	Dec. 31, 2014	Oct. 27, 2014	Jul. 29, 2014	Apr. 30, 2014	Jan. 26, 2015	Mar. 31, 2013
Reorganization [Line Items]
Common stock, par value	$ 0.01	$ 0.01	$ 0.01
Right to receive cash under cancellation of shares	$ 27.25
Non-voting Series A Preferred Stock, maximum number of shares issued				1,800	1,800
Amount Of Non Voting Series A Preferred Stock Purchase price			$ 126,000,000
Non-voting Series A Preferred Stock, maximum aggregate consideration	180,000,000
Termination fee	259,000,000
Reimbursement of termination related expenses	40,000,000
Redemption of preferred stock at purchase price			$ 10,000
PCI recorded deferred tax asset in prior years		101,000,000						101,000,000
Establishment of valuation allowances on deferred tax assets		101,000,000						101,000,000
Deferred tax assets valuation allowances charged off		101,000,000
Potomac Electric Power Co [Member]
Reorganization [Line Items]
Common stock, par value	$ 0.01	$ 0.01	$ 0.01
Right to receive cash under cancellation of shares	$ 27.25
Non-voting Series A Preferred Stock, maximum number of shares issued				1,800	1,800
Non-voting Series A Preferred Stock, maximum aggregate consideration	180,000,000
Termination fee	259,000,000
Reimbursement of termination related expenses	40,000,000
Redemption of preferred stock at purchase price			$ 10,000
Delmarva Power & Light Co/De [Member]
Reorganization [Line Items]
Common stock, par value	$ 0.01	$ 2.25	$ 2.25
Right to receive cash under cancellation of shares	$ 27.25
Non-voting Series A Preferred Stock, maximum number of shares issued				1,800	1,800
Non-voting Series A Preferred Stock, maximum aggregate consideration	180,000,000
Termination fee	259,000,000
Reimbursement of termination related expenses	40,000,000
Redemption of preferred stock at purchase price			$ 10,000
Atlantic City Electric Co [Member]
Reorganization [Line Items]
Common stock, par value	$ 0.01	$ 3.00	$ 3.00
Right to receive cash under cancellation of shares	$ 27.25
Non-voting Series A Preferred Stock, maximum number of shares issued				1,800	1,800
Non-voting Series A Preferred Stock, maximum aggregate consideration	180,000,000
Termination fee	259,000,000
Reimbursement of termination related expenses	40,000,000
Redemption of preferred stock at purchase price			$ 10,000
Non-Voting Series A Preferred Stock [Member]
Reorganization [Line Items]
Issuance of non-voting Series A Preferred Stock, shares issued						9,000
Non-voting Series A Preferred Stock, par value						$ 0.01
Non-voting Series A Preferred Stock, shares purchased price						90,000,000
Amount Of Non Voting Series A Preferred Stock Purchase price				18,000,000	18,000,000
Non-voting Series A Preferred Stock, cumulative, non-participating cash dividend						0.10%
Non-Voting Series A Preferred Stock [Member] | Potomac Electric Power Co [Member]
Reorganization [Line Items]
Issuance of non-voting Series A Preferred Stock, shares issued						9,000
Non-voting Series A Preferred Stock, par value						$ 0.01
Non-voting Series A Preferred Stock, shares purchased price						90,000,000
Amount Of Non Voting Series A Preferred Stock Purchase price				18,000,000	18,000,000
Non-voting Series A Preferred Stock, cumulative, non-participating cash dividend						0.10%
Non-Voting Series A Preferred Stock [Member] | Delmarva Power & Light Co/De [Member]
Reorganization [Line Items]
Issuance of non-voting Series A Preferred Stock, shares issued						9,000
Non-voting Series A Preferred Stock, par value						$ 0.01
Non-voting Series A Preferred Stock, shares purchased price						90,000,000
Amount Of Non Voting Series A Preferred Stock Purchase price				18,000,000	18,000,000
Non-voting Series A Preferred Stock, cumulative, non-participating cash dividend						0.10%
Non-Voting Series A Preferred Stock [Member] | Atlantic City Electric Co [Member]
Reorganization [Line Items]
Issuance of non-voting Series A Preferred Stock, shares issued						9,000
Non-voting Series A Preferred Stock, par value						$ 0.01
Non-voting Series A Preferred Stock, shares purchased price						90,000,000
Amount Of Non Voting Series A Preferred Stock Purchase price				18,000,000	18,000,000
Non-voting Series A Preferred Stock, cumulative, non-participating cash dividend						0.10%
Terminations Due to New Acquisition Proposal [Member]
Reorganization [Line Items]
Termination fee	293,000,000
Terminations Due to New Acquisition Proposal [Member] | Potomac Electric Power Co [Member]
Reorganization [Line Items]
Termination fee	293,000,000
Terminations Due to New Acquisition Proposal [Member] | Delmarva Power & Light Co/De [Member]
Reorganization [Line Items]
Termination fee	293,000,000
Terminations Due to New Acquisition Proposal [Member] | Atlantic City Electric Co [Member]
Reorganization [Line Items]
Termination fee	293,000,000
Subsequent Event [Member]
Reorganization [Line Items]
Non-voting Series A Preferred Stock, maximum number of shares issued							1,800
Subsequent Event [Member] | Potomac Electric Power Co [Member]
Reorganization [Line Items]
Non-voting Series A Preferred Stock, maximum number of shares issued							1,800
Subsequent Event [Member] | Delmarva Power & Light Co/De [Member]
Reorganization [Line Items]
Non-voting Series A Preferred Stock, maximum number of shares issued							1,800
Subsequent Event [Member] | Atlantic City Electric Co [Member]
Reorganization [Line Items]
Non-voting Series A Preferred Stock, maximum number of shares issued							1,800
Subsequent Event [Member] | Non-Voting Series A Preferred Stock [Member]
Reorganization [Line Items]
Amount Of Non Voting Series A Preferred Stock Purchase price							18,000,000
Subsequent Event [Member] | Non-Voting Series A Preferred Stock [Member] | Potomac Electric Power Co [Member]
Reorganization [Line Items]
Amount Of Non Voting Series A Preferred Stock Purchase price							18,000,000
Subsequent Event [Member] | Non-Voting Series A Preferred Stock [Member] | Delmarva Power & Light Co/De [Member]
Reorganization [Line Items]
Amount Of Non Voting Series A Preferred Stock Purchase price							18,000,000
Subsequent Event [Member] | Non-Voting Series A Preferred Stock [Member] | Atlantic City Electric Co [Member]
Reorganization [Line Items]
Amount Of Non Voting Series A Preferred Stock Purchase price							$ 18,000,000
Maximum [Member]
Reorganization [Line Items]
Non-voting Series A Preferred Stock, maximum number of shares issued	18,000
Maximum [Member] | Potomac Electric Power Co [Member]
Reorganization [Line Items]
Non-voting Series A Preferred Stock, maximum number of shares issued	18,000
Maximum [Member] | Delmarva Power & Light Co/De [Member]
Reorganization [Line Items]
Non-voting Series A Preferred Stock, maximum number of shares issued	18,000
Maximum [Member] | Atlantic City Electric Co [Member]
Reorganization [Line Items]
Non-voting Series A Preferred Stock, maximum number of shares issued	18,000