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Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Other, Net [Abstract] |  |  |  |
AFUDC - Equity | $ 38 | $ 40 | $ 116 | $ 113
Non-service net periodic benefit cost | (13) | (18) | (29) | (18)
Commonwealth Edison Co |  |  |  |
Other, Net [Abstract] |  |  |  |
AFUDC - Equity | 13 | 7 | 32 | 25
Non-service net periodic benefit cost | 0 | 0 | 0 | 0
PECO Energy Co |  |  |  |
Other, Net [Abstract] |  |  |  |
AFUDC - Equity | 7 | 10 | 24 | 22
Non-service net periodic benefit cost | 0 | 0 | 0 | 0
Baltimore Gas and Electric Company |  |  |  |
Other, Net [Abstract] |  |  |  |
AFUDC - Equity | 5 | 4 | 18 | 11
Non-service net periodic benefit cost | 0 | 0 | 0 | 0
Pepco Holdings LLC |  |  |  |
Other, Net [Abstract] |  |  |  |
AFUDC - Equity | 12 | 19 | 42 | 55
Non-service net periodic benefit cost | 0 | 0 | 0 | 0
Potomac Electric Power Company |  |  |  |
Other, Net [Abstract] |  |  |  |
AFUDC - Equity | 8 | 15 | 32 | 42
Non-service net periodic benefit cost | 0 | 0 | 0 | 0
Delmarva Power and Light Company |  |  |  |
Other, Net [Abstract] |  |  |  |
AFUDC - Equity | 3 | 3 | 9 | 7
Non-service net periodic benefit cost | 0 | 0 | 0 | 0
Atlantic City Electric Company |  |  |  |
Other, Net [Abstract] |  |  |  |
AFUDC - Equity | 1 | 1 | 1 | 6
Non-service net periodic benefit cost | $ 0 | $ 0 | $ 0 | $ 0

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