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Fair Value Measurements - Nonrecurring Fair Value Measures Within Level 3 (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |  |
Impairment of Assets | $ 141,802 | [1] | $ 519,129 | [1] | $ 0 |
Level 3 | Fair Value, Nonrecurring |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |  |
Impairment of Assets | 33,453 |  | 55,437 |  | 0 |
Level 3 | Fair Value, Nonrecurring | Integrated Upstream and Gathering | December 31, 2024 |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |  |
Property, plant, and equipment, fair value |  |  |  |  |  | $ 12,880
Impairment of Assets | 33,453 |  | 0 |  | 0 |
Level 3 | Fair Value, Nonrecurring | Integrated Upstream and Gathering | September 30, 2024 |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |  |
Property, plant, and equipment, fair value |  |  | 3,000 |  |  |
Impairment of Assets | 0 |  | 9,362 |  | 0 |
Level 3 | Fair Value, Nonrecurring | Pipeline and Storage |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |  |
Fair Value |  |  | 12,133 |  |  |
Impairment of Assets | $ 0 |  | $ 46,075 |  | $ 0 |
[1] | The Company considers this line to be a significant expense.

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