Regulatory Matters (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
NEW YORK | Forecast
Regulatory Matters [Line Items]
Rate plan period					3 years
Approved Return on Equity (as a percent)					9.70%
Increase in annual revenue requirement in first year				$ 57.3
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	$ 14.0
PENNSYLVANIA
Regulatory Matters [Line Items]
Public utilities authorized rate increase, amount	$ 23.0