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Revenue and Accounts Receivable - Narrative (Details) $ in Thousands | 3 Months Ended | 12 Months Ended | 42 Months Ended |
--- | --- | --- | --- | ---
Dec. 31, 2023 USD ($) | Sep. 30, 2025 USD ($) state | Sep. 30, 2024 USD ($) | Sep. 30, 2023 USD ($) | Sep. 30, 2025 USD ($) state | Nov. 30, 2023
Disaggregation of Revenue [Line Items] |  |  |  |  |  |
Number of states excluded due to gas cost recovery mechanisms | state |  | 6 |  |  | 6 |
Percent of customers excluded due to gas cost recovery mechanisms |  | 89.00% |  |  |  |
Reduction to bad debt expense |  | $ (30,778) | $ (24,843) | $ (22,353) |  |
Recovery of uncollectible accounts, not yet been written off |  |  | $ 4,192 |  |  |
Mississippi Public Service Commission |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |
Recovery of uncollectible accounts, term | 2 years |  |  |  |  | 1 year
Reduction to bad debt expense | $ 13,900 |  |  |  |  |
Recovery of uncollectible accounts, previously written off but not yet recovered through rates |  |  |  |  | $ 9,700 |
Recovery of uncollectible accounts, not yet been written off |  | $ 4,200 |  |  |  |
Pipeline and Storage |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |
Regulatory mechanism threshold (in percent) |  | 75.00% |  |  |  |

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