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Retirement Benefits - Defined Contribution Savings Plans (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Savings Plan Employer Contributions | $ 25 | $ 27 | $ 76 | $ 74
Commonwealth Edison Co |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Savings Plan Employer Contributions | 12 | 12 | 32 | 31
PECO Energy Co |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Savings Plan Employer Contributions | 3 | 3 | 11 | 10
Baltimore Gas and Electric Company |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Savings Plan Employer Contributions | 2 | 3 | 8 | 8
Pepco Holdings LLC |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Savings Plan Employer Contributions | 4 | 5 | 12 | 13
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

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