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v3.25.3

Financial Instruments - Narrative (Details) | 12 Months Ended
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Sep. 30, 2025 USD ($) $ / Mcf MMcf | Sep. 30, 2024 USD ($) | Sep. 30, 2023 USD ($)
Derivative [Line Items] |  |  |
Purchase commitment volume | MMcf | 32,566 |  |
Contract netting | $ 0 | $ 0 |
Cash collateral | 0 | 0 |
Net (gain) loss on settled interest rate agreements | (20,500,000) | $ (12,800,000) | $ (2,700,000)
Net realized gains in AOCI | $ 474,800,000 |  |
Not Designated As Hedges | Gas Purchases | Commodity contracts |  |  |
Derivative [Line Items] |  |  |
Purchase commitment volume | MMcf | 24,000.0 |  |
Not Designated As Hedges | Gas Purchases | Commodity contracts | Minimum |  |  |
Derivative [Line Items] |  |  |
Hedging percent | 25.00% |  |
Not Designated As Hedges | Gas Purchases | Commodity contracts | Maximum |  |  |
Derivative [Line Items] |  |  |
Hedging percent | 50.00% |  |
Not Designated As Hedges | Gas Purchases | Commodity contracts | Weighted Average |  |  |
Derivative [Line Items] |  |  |
Derivative flow rate (USD per Mcf) | $ / Mcf | 3.83 |  |

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