Summary of Significant Accounting Policies - Components of Other Current Assets (Details) - USD ($) $ in Thousands		Sep. 30, 2023	Sep. 30, 2022
Other Current Assets [Line Items]
Prepayments		$ 18,966	$ 17,757
Prepaid Property and Other Taxes		14,186	14,321
Regulatory Assets	[1]	36,373	21,358
Other Current Assets		100,260	59,369
Federal
Other Current Assets [Line Items]
Income Taxes Receivable		14,602	0
State
Other Current Assets [Line Items]
Income Taxes Receivable		$ 16,133	$ 5,933

[1] The Company recovers the cost of its regulatory assets but generally does not earn a return on them. There are a few exceptions to this rule. For example, the Company does earn a return on Unrecovered Purchased Gas Costs and, in the New York jurisdiction of its Utility segment, earns a return, within certain parameters, on the excess of cumulative funding to the pension plan over the cumulative amount collected in rates.