Intangible Assets - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Nov. 01, 2018	Mar. 24, 2016
Goodwill [Line Items]
Goodwill	$ 6,677	$ 6,677
Commonwealth Edison Co [Member]
Goodwill [Line Items]
Goodwill	2,625	2,625
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount			30.00%
Pepco Holdings LLC [Member]
Goodwill [Line Items]
Goodwill	4,005	4,005
Potomac Electric Power Company [Member]
Goodwill [Line Items]
Goodwill				$ 2,100
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount			30.00%
Delmarva Power & Light Company [Member]
Goodwill [Line Items]
Goodwill	$ 8	$ 8		1,400
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount			20.00%
Atlantic City Electric Company [Member]
Goodwill [Line Items]
Goodwill				$ 500
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount			30.00%