Revenue from Contracts with Customers - Prior Year Contract Revenues Recognized in Current Year (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Prior Year Revenue Recognized [Line Items]
Contract with Customer, Performance Obligation Satisfied in Previous Period	$ 40	$ 27	$ 18
Pepco Holdings LLC [Member]
Prior Year Revenue Recognized [Line Items]
Contract with Customer, Performance Obligation Satisfied in Previous Period	9	0	0
Potomac Electric Power Company [Member]
Prior Year Revenue Recognized [Line Items]
Contract with Customer, Performance Obligation Satisfied in Previous Period	7	0	0
Delmarva Power & Light Company [Member]
Prior Year Revenue Recognized [Line Items]
Contract with Customer, Performance Obligation Satisfied in Previous Period	1	0	0
Atlantic City Electric Company [Member]
Prior Year Revenue Recognized [Line Items]
Contract with Customer, Performance Obligation Satisfied in Previous Period	$ 1	$ 0	$ 0