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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

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