Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Schedule of Income Tax [Line Items]
Consolidated effective income tax rates from continuing operations	38.00%	250.00%
Change in estimates and interest related to uncertain tax positions		$ 51
Establishment of valuation allowance on deferred tax assets		101
PCI Future Deferred Tax Asset		101
After-tax effect of revised lease rerun		377
Potomac Electric Power Co [Member]
Schedule of Income Tax [Line Items]
Consolidated effective income tax rates from continuing operations	33.30%	8.00%
Additional interest income		5
After-tax effect of revised lease rerun		377
Potomac Electric Power Co [Member] | Interest Expense [Member]
Schedule of Income Tax [Line Items]
After-tax non-cash charge		54
Delmarva Power & Light Co/De [Member]
Schedule of Income Tax [Line Items]
Consolidated effective income tax rates from continuing operations	40.30%	38.10%
Additional interest income		1
After-tax effect of revised lease rerun		377
Delmarva Power & Light Co/De [Member] | Interest Expense [Member]
Schedule of Income Tax [Line Items]
After-tax non-cash charge		54
Atlantic City Electric Co [Member]
Schedule of Income Tax [Line Items]
Consolidated effective income tax rates from continuing operations	37.50%	(50.30%)
Additional interest income		6
After-tax effect of revised lease rerun		377
Atlantic City Electric Co [Member] | Interest Expense [Member]
Schedule of Income Tax [Line Items]
After-tax non-cash charge		$ 54