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Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands | 12 Months Ended
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Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |
Impairment of Assets | $ 141,802 | [1] | $ 519,129 | [1] | $ 0
Present Value of Contingent Consideration | California Asset Sale |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |
Value of contingent consideration from asset sale | 0 |  |  |  |
Northern Access Project |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |
Impairment of Assets |  |  | 46,100 |  |
Level 3 | Fair Value, Nonrecurring |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |
Impairment of Assets | 33,453 |  | 55,437 |  | 0
December 31, 2024 | Level 3 | Fair Value, Nonrecurring | Integrated Upstream and Gathering |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |
Impairment of Assets | 33,453 |  | 0 |  | 0
September 30, 2024 | Level 3 | Fair Value, Nonrecurring | Integrated Upstream and Gathering |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |
Impairment of Assets | $ 0 |  | $ 9,362 |  | $ 0
[1] | The Company considers this line to be a significant expense.

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