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Regulatory Matters - Narrative (Details) - USD ($) $ in Millions |  |  |  | 12 Months Ended | 36 Months Ended | 89 Months Ended |
--- | --- | --- | --- | --- | --- | --- | ---
Oct. 31, 2023 | Aug. 01, 2023 | Oct. 28, 2022 | Sep. 30, 2025 | Sep. 30, 2027 | Sep. 30, 2024 | Aug. 01, 2024
New York |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  | 8.70% |
Proposed base rate increase | $ 88.0 |  |  |  |  |  |
New York | Forecast |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Proposed rate plan period |  |  |  |  | 3 years |  |
Proposed increase in annual revenue requirement over three years |  |  |  |  | $ 86.0 |  |
Proposed increase in annual revenue requirement in first year |  |  |  | $ 57.0 |  |  |
Proposed return on equity |  |  |  |  | 9.70% |  |
Proposed common equity ratio for rate setting (as a percent) |  |  |  |  | 0.48 |  |
Pennsylvania |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Proposed base rate increase |  |  | $ 28.1 |  |  |  |
Public utilities authorized rate increase, amount |  | $ 23.0 |  |  |  |  |
Public utilities, distribution system improvement charge, plant |  |  |  |  |  | $ 785.2 |
Pennsylvania | Minimum |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Proposed public utilities distribution system improvement charge plant minimum |  |  |  |  |  |  | $ 781.3

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