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Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (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] |  |  |  |
Pension and Other Postretirement Benefits Costs |  |  | $ 181 | $ 152
Pension and other post retirement benefit [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs | $ 61 | $ 63 | 181 | 152
Commonwealth Edison Co |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs |  |  | 53 | 19
Commonwealth Edison Co | Pension and other post retirement benefit [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs | 17 | 6 | 53 | 19
PECO Energy Co |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs |  |  | (1) | (10)
PECO Energy Co | Pension and other post retirement benefit [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs | (1) | (3) | (1) | (10)
Baltimore Gas and Electric Company |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs |  |  | 45 | 41
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 | 14 | 45 | 42
Pepco Holdings LLC |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs |  |  | 71 | 74
Pepco Holdings LLC | Pension and other post retirement benefit [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs | 25 | 25 | 71 | 74
Potomac Electric Power Company |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs |  |  | 24 | 26
Potomac Electric Power Company | Pension and other post retirement benefit [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs | 8 | 9 | 24 | 26
Delmarva Power and Light Company |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs |  |  | 11 | 13
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 | 11 | 13
Atlantic City Electric Company |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension and Other Postretirement Benefits Costs |  |  | 10 | 10
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 | $ 10

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