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