Regulatory Matters (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Regulatory Matters [Line Items]
Reduction of Other Post-Retirement Regulatory Liability	$ (18,533)	$ 0	$ 0
New York [Member]
Regulatory Matters [Line Items]
Approved Return on Equity	8.70%
Authorized Annual Recovery from Customers for Pension and OPEB Expense	$ 15,000
Pennsylvania [Member]
Regulatory Matters [Line Items]
Proposed Base Rate Increase	28,100
Approved Base Rate Reduction related to OPEB Expenses	(7,700)
Proposed Refund To Customers From Over-Collection Of OPEB Expenses	50,000
Reduction of Other Post-Retirement Regulatory Liability	(18,500)
Approved Refund to Customers From Over-Collection Of OPEB Expenses	$ 54,000