Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Other, Net [Abstract]
AFUDC - Equity	$ 43	$ 38	$ 81	$ 78
Non-service net periodic benefit cost	(13)	(11)	(26)	(17)
Commonwealth Edison Co
Other, Net [Abstract]
AFUDC - Equity	14	9	26	19
Non-service net periodic benefit cost	0	0	0	0
PECO Energy Co
Other, Net [Abstract]
AFUDC - Equity	10	8	17	16
Non-service net periodic benefit cost	0	0	0	0
Baltimore Gas and Electric Company
Other, Net [Abstract]
AFUDC - Equity	9	6	18	13
Non-service net periodic benefit cost	0	0	0	0
Pepco Holdings LLC
Other, Net [Abstract]
AFUDC - Equity	10	15	20	30
Non-service net periodic benefit cost	0	0	0	0
Potomac Electric Power Company
Other, Net [Abstract]
AFUDC - Equity	8	12	15	23
Non-service net periodic benefit cost	0	0	0	0
Delmarva Power and Light Company
Other, Net [Abstract]
AFUDC - Equity	1	3	3	6
Non-service net periodic benefit cost	0	0	0	0
Atlantic City Electric Company
Other, Net [Abstract]
AFUDC - Equity	1	0	2	1
Non-service net periodic benefit cost	$ 0	$ 0	$ 0	$ 0