Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			$ 152	$ 124
Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	$ 63	$ 40	152	122
Commonwealth Edison Co
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			19	45
Commonwealth Edison Co | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	6	15	19	45
PECO Energy Co
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			(10)	(6)
PECO Energy Co | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	(3)	(2)	(10)	(6)
Baltimore Gas and Electric Company
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			41	34
Baltimore Gas and Electric Company | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	14	11	42	33
Pepco Holdings LLC
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			74	39
Pepco Holdings LLC | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	25	13	74	39
Potomac Electric Power Company
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			26	6
Potomac Electric Power Company | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	9	2	26	6
Delmarva Power and Light Company
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			13	3
Delmarva Power and Light Company | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	4	1	13	3
Atlantic City Electric Company
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			10	9
Atlantic City Electric Company | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	$ 3	$ 3	$ 10	$ 9