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v3.25.3

Commitments and Contingencies (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Sep. 30, 2024
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Recorded Unconditional Purchase Obligation [Line Items] |  |
Estimate minimum liability for environmental remediation | $ 3,200 |
Other regulatory liabilities | 735,938 | $ 749,574
Future purchase obligation first year | 236,600 |
Future purchase obligation second year | 75,800 |
Future purchase obligation third year | 113,800 |
Future purchase obligation fourth year | 123,200 |
Future purchase obligation fifth year | 135,200 |
Future purchase obligation thereafter | 900,100 |
System Modernization and Expansion Projects |  |
Recorded Unconditional Purchase Obligation [Line Items] |  |
Contract commitments first year | 58,100 |
Contract commitments second year | 9,200 |
Contract commitments third year | 5,600 |
Contract commitments fourth year | 4,400 |
Contract commitments fifth year | 4,500 |
Contract commitments thereafter | 4,600 |
Well Development Activities |  |
Recorded Unconditional Purchase Obligation [Line Items] |  |
Contract commitments first year | 180,800 |
Contract commitments second year | 25,900 |
Environmental Site Remediation Costs |  |
Recorded Unconditional Purchase Obligation [Line Items] |  |
Other regulatory liabilities | $ 1,800 |

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