Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Other, Net [Abstract]
AFUDC - Equity	$ 63	$ 43	$ 120	$ 81
Non-service net periodic benefit cost	(11)	(13)	(21)	(26)
Commonwealth Edison Co
Other, Net [Abstract]
AFUDC - Equity	24	14	45	26
Non-service net periodic benefit cost	0	0	0	0
PECO Energy Co
Other, Net [Abstract]
AFUDC - Equity	11	10	21	17
Non-service net periodic benefit cost	0	0	0	0
Baltimore Gas and Electric Company
Other, Net [Abstract]
AFUDC - Equity	16	9	30	18
Non-service net periodic benefit cost	0	0	0	0
Pepco Holdings LLC
Other, Net [Abstract]
AFUDC - Equity	12	10	24	20
Non-service net periodic benefit cost	0	0	0	0
Potomac Electric Power Company
Other, Net [Abstract]
AFUDC - Equity	9	8	19	15
Non-service net periodic benefit cost	0	0	0	0
Delmarva Power and Light Company
Other, Net [Abstract]
AFUDC - Equity	2	1	3	3
Non-service net periodic benefit cost	0	0	0	0
Atlantic City Electric Company
Other, Net [Abstract]
AFUDC - Equity	1	1	2	2
Non-service net periodic benefit cost	$ 0	$ 0	$ 0	$ 0