Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Other, Net [Abstract]
AFUDC - Equity	$ 38	$ 36
Non-service net periodic benefit cost	(1)	17
Commonwealth Edison Co [Member]
Other, Net [Abstract]
AFUDC - Equity	10	8
Non-service net periodic benefit cost	0	0
PECO Energy Co [Member]
Other, Net [Abstract]
AFUDC - Equity	6	7
Non-service net periodic benefit cost	0	0
Baltimore Gas and Electric Company [Member]
Other, Net [Abstract]
AFUDC - Equity	3	6
Non-service net periodic benefit cost	0	0
Pepco Holdings LLC [Member]
Other, Net [Abstract]
AFUDC - Equity	19	15
Non-service net periodic benefit cost	0	0
Potomac Electric Power Company [Member]
Other, Net [Abstract]
AFUDC - Equity	14	11
Non-service net periodic benefit cost	0	0
Delmarva Power and Light Company [Member]
Other, Net [Abstract]
AFUDC - Equity	2	2
Non-service net periodic benefit cost	0	0
Atlantic City Electric Company [Member]
Other, Net [Abstract]
AFUDC - Equity	3	2
Non-service net periodic benefit cost	$ 0	$ 0