Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Other, Net [Abstract]
AFUDC - Equity	$ 40	$ 38
Non-service net periodic benefit cost	(7)	(1)
Commonwealth Edison Co
Other, Net [Abstract]
AFUDC - Equity	10	10
Non-service net periodic benefit cost	0	0
PECO Energy Co
Other, Net [Abstract]
AFUDC - Equity	8	6
Non-service net periodic benefit cost	0	0
Baltimore Gas and Electric Company
Other, Net [Abstract]
AFUDC - Equity	7	3
Non-service net periodic benefit cost	0	0
Pepco Holdings LLC
Other, Net [Abstract]
AFUDC - Equity	15	19
Non-service net periodic benefit cost	0	0
Potomac Electric Power Company
Other, Net [Abstract]
AFUDC - Equity	12	14
Non-service net periodic benefit cost	0	0
Delmarva Power and Light Company
Other, Net [Abstract]
AFUDC - Equity	3	2
Non-service net periodic benefit cost	0	0
Atlantic City Electric Company
Other, Net [Abstract]
AFUDC - Equity	0	3
Non-service net periodic benefit cost	$ 0	$ 0