Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	$ 198	$ 164	$ 411
Pension and other post retirement benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	198	161	288
Commonwealth Edison Co
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	26	60	129
Commonwealth Edison Co | Pension and other post retirement benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	26	60	129
PECO Energy Co
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	(14)	(9)	8
PECO Energy Co | Pension and other post retirement benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	(14)	(9)	8
Baltimore Gas and Electric Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	56	44	61
Baltimore Gas and Electric Company | Pension and other post retirement benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	56	44	64
Pepco Holdings LLC
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	99	53	49
Pepco Holdings LLC | Pension and other post retirement benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	99	53	49
Potomac Electric Power Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	34	9	6
Potomac Electric Power Company | Pension and other post retirement benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	34	9	6
Delmarva Power & Light Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	18	3	2
Delmarva Power & Light Company | Pension and other post retirement benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	18	3	2
Atlantic City Electric Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	13	12	11
Atlantic City Electric Company | Pension and other post retirement benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and non-pension postretirement benefit costs	$ 13	$ 12	$ 11