Basis of Presentation - Narrative (Details) - USD ($)		3 Months Ended
	Mar. 31, 2016	Mar. 31, 2016	Mar. 23, 2016	Mar. 31, 2015	Jan. 01, 2014
Pepco Holdings, LLC [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Interest		$ 1,000,000		$ 1,000,000
Pepco Holdings, LLC [Member] | Predecessor [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Interest			$ 1,000,000
Pepco Holdings, LLC [Member] | Successor [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Interest	$ 1,000,000
Potomac Electric Power Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Interest				1,000,000
Delmarva Power and Light Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Interest				1
Atlantic City Electric Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Interest		1		1
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets					$ 12,000,000
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income		$ 1,000,000		$ 5,000,000