Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Other, Net [Abstract]
AFUDC - Equity	$ 66	$ 49	$ 186	$ 130
Non-service net periodic benefit cost	(12)	(13)	(33)	(39)
Commonwealth Edison Co
Other, Net [Abstract]
AFUDC - Equity	25	19	71	45
Non-service net periodic benefit cost	0	0	0	0
PECO Energy Co
Other, Net [Abstract]
AFUDC - Equity	12	9	33	26
Non-service net periodic benefit cost	0	0	0	0
Baltimore Gas and Electric Company
Other, Net [Abstract]
AFUDC - Equity	17	11	47	29
Non-service net periodic benefit cost	0	0	0	0
Pepco Holdings LLC
Other, Net [Abstract]
AFUDC - Equity	12	10	35	30
Non-service net periodic benefit cost	0	0	0	0
Potomac Electric Power Company
Other, Net [Abstract]
AFUDC - Equity	9	8	27	23
Non-service net periodic benefit cost	0	0	0	0
Delmarva Power and Light Company
Other, Net [Abstract]
AFUDC - Equity	2	1	5	4
Non-service net periodic benefit cost	0	0	0	0
Atlantic City Electric Company
Other, Net [Abstract]
AFUDC - Equity	1	1	3	3
Non-service net periodic benefit cost	$ 0	$ 0	$ 0	$ 0