Subsequent Events - Narrative (Details) - Sale of transmission tower attachment agreements [Member] - Subsequent Event [Member] $ in Millions	Jul. 01, 2020 USD ($)
Potomac Electric Power Company [Member]
Subsequent Event [Line Items]
Agreement Liabilities Recorded	$ 98
Delmarva Power and Light Company [Member]
Subsequent Event [Line Items]
Undivided Interest Sold	60.00%
Agreement Liabilities Recorded	$ 13
Atlantic City Electric Company [Member]
Subsequent Event [Line Items]
Undivided Interest Sold	60.00%
Agreement Liabilities Recorded	$ 13