Summary of Significant Accounting Policies - Components of Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Summary of Significant Accounting Policies [Line Items]
Prepayments	$ 16,477	$ 18,463
Prepaid Property and Other Taxes	13,920	14,187
Regulatory Assets	35,362	38,264
Other Current Assets	80,759	92,229
Federal
Summary of Significant Accounting Policies [Line Items]
Income Taxes Receivable	14,511	8,154
State
Summary of Significant Accounting Policies [Line Items]
Income Taxes Receivable	$ 489	$ 13,161