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Regulatory Matters - Narrative (Details) - USD ($) $ in Millions |  | 12 Months Ended | 36 Months Ended |
--- | --- | --- | --- | ---
Aug. 01, 2023 | Sep. 30, 2027 | Sep. 30, 2026 | Sep. 30, 2025 | Sep. 30, 2027 | Nov. 01, 2025
New York |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Increase in annual revenue requirement in first year |  |  |  | $ 57.3 |  |
Reduction to annual revenue requirement for actuarial projections of pension and other-post retirement benefit income expected to be recognized |  |  |  | 14.0 |  |
New York | Forecast |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Rate plan period |  |  |  |  | 3 years |
Approved return on equity (as a percent) |  |  |  |  | 9.70% |
Additional increase in annual revenue requirement in second year |  |  | $ 15.8 |  |  |
Additional increase in annual revenue requirement in third year |  | $ 12.7 |  |  |  |
Reduction to annual revenue requirement for actuarial projections of pension and other-post retirement benefit income expected to be recognized |  | $ 14.0 | $ 14.0 |  |  |
Pennsylvania |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Public utilities authorized rate increase, amount | $ 23.0 |  |  |  |  |
Public utilities distribution system improvement charge recovered from customers |  |  |  | $ 0.9 |  |
Empire | Forecast |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
FERC estimated annual reduction of revenue amount |  |  |  |  |  | $ 0.5

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