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Details of Selected Financial Statement Captions - Other Non-Operating Income (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023
Balance Sheet Related Disclosures [Abstract] |  |  |
Equity component of AFUDC | $ 75,425 | $ 58,234 | $ 64,019
Performance-based rate program | 8,485 | 8,389 | 7,093
Pension and other postretirement non-service credit | 14,372 | 10,820 | 8,955
Interest income | 29,944 | 22,887 | 7,207
Community support spending | (21,114) | (20,016) | (12,027)
Unrealized gains on equity securities | 174 | 3,562 | 1,406
Miscellaneous | (17,545) | (12,830) | (6,878)
Total | $ 89,741 | $ 71,046 | $ 69,775

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