Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	$ 61	$ 45
Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	61	45
Commonwealth Edison Co
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	17	6
Commonwealth Edison Co | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	17	6
PECO Energy Co
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	0	(3)
PECO Energy Co | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	0	(3)
Baltimore Gas and Electric Company
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	15	14
Baltimore Gas and Electric Company | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	15	14
Pepco Holdings LLC
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	23	24
Pepco Holdings LLC | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	23	24
Potomac Electric Power Company
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	9	8
Potomac Electric Power Company | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	9	8
Delmarva Power and Light Company
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	4	4
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	4
Atlantic City Electric Company
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	3	4
Atlantic City Electric Company | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	$ 3	$ 4