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Income Taxes - Allocation of Tax Benefits (Details) - USD ($) $ in Millions | Sep. 30, 2024 | Sep. 30, 2023
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Commonwealth Edison Co |  |
Income Tax Contingency [Line Items] |  |
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement | $ 30 | $ 13
PECO Energy Co |  |
Income Tax Contingency [Line Items] |  |
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement | 15 | 19
Baltimore Gas and Electric Company |  |
Income Tax Contingency [Line Items] |  |
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement | 14 | 0
Pepco Holdings LLC |  |
Income Tax Contingency [Line Items] |  |
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement | 16 | 10
Potomac Electric Power Company |  |
Income Tax Contingency [Line Items] |  |
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement | 9 | 4
Delmarva Power and Light Company |  |
Income Tax Contingency [Line Items] |  |
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement | 5 | 0
Atlantic City Electric Company |  |
Income Tax Contingency [Line Items] |  |
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement | $ 2 | $ 2

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