Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Other, Net [Abstract]
AFUDC - Equity	$ 34	$ 38	$ 71	$ 74
Non-service net periodic benefit cost	(1)	16	(2)	33
Commonwealth Edison Co [Member]
Other, Net [Abstract]
AFUDC - Equity	7	9	17	17
Non-service net periodic benefit cost	0	0	0	0
PECO Energy Co [Member]
Other, Net [Abstract]
AFUDC - Equity	6	8	12	15
Non-service net periodic benefit cost	0	0	0	0
Baltimore Gas and Electric Company [Member]
Other, Net [Abstract]
AFUDC - Equity	4	6	7	12
Non-service net periodic benefit cost	0	0	0	0
Pepco Holdings LLC [Member]
Other, Net [Abstract]
AFUDC - Equity	17	15	35	30
Non-service net periodic benefit cost	0	0	0	0
Potomac Electric Power Company [Member]
Other, Net [Abstract]
AFUDC - Equity	13	11	27	22
Non-service net periodic benefit cost	0	0	0	0
Delmarva Power and Light Company [Member]
Other, Net [Abstract]
AFUDC - Equity	2	2	4	4
Non-service net periodic benefit cost	0	0	0	0
Atlantic City Electric Company [Member]
Other, Net [Abstract]
AFUDC - Equity	2	2	4	4
Non-service net periodic benefit cost	$ 0	$ 0	$ 0	$ 0