Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Other, Net [Abstract]
AFUDC - Equity	$ 40	$ 38	$ 113	$ 112
Non-service net periodic benefit cost	(18)	16	(18)	48
Commonwealth Edison Co
Other, Net [Abstract]
AFUDC - Equity	7	10	25	28
Non-service net periodic benefit cost	0	0	0	0
PECO Energy Co
Other, Net [Abstract]
AFUDC - Equity	10	7	22	22
Non-service net periodic benefit cost	0	0	0	0
Baltimore Gas and Electric Company
Other, Net [Abstract]
AFUDC - Equity	4	5	11	17
Non-service net periodic benefit cost	0	0	0	0
Pepco Holdings LLC
Other, Net [Abstract]
AFUDC - Equity	19	16	55	45
Non-service net periodic benefit cost	0	0	0	0
Potomac Electric Power Company
Other, Net [Abstract]
AFUDC - Equity	15	12	42	35
Non-service net periodic benefit cost	0	0	0	0
Delmarva Power and Light Company
Other, Net [Abstract]
AFUDC - Equity	3	2	7	5
Non-service net periodic benefit cost	0	0	0	0
Atlantic City Electric Company
Other, Net [Abstract]
AFUDC - Equity	1	2	6	5
Non-service net periodic benefit cost	$ 0	$ 0	$ 0	$ 0