Retirement Benefits - Defined Contribution Savings Plans (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]
Savings Plan Employer Contributions	$ 27	$ 23	$ 74	$ 66
Commonwealth Edison Co
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Employer Contributions	12	11	31	29
PECO Energy Co
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Employer Contributions	3	3	10	9
Baltimore Gas and Electric Company
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Employer Contributions	3	2	8	7
Pepco Holdings LLC
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Employer Contributions	5	4	13	11
Potomac Electric Power Company
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Employer Contributions	1	1	3	3
Delmarva Power and Light Company
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Employer Contributions	1	1	3	3
Atlantic City Electric Company
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Employer Contributions	$ 1	$ 1	$ 2	$ 2