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Accounting Policies - Narrative (Details) $ in Millions |  | 3 Months Ended | 6 Months Ended |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 31, 2026 USD ($) | Mar. 31, 2026 USD ($) | Jun. 30, 2026 USD ($) | Dec. 31, 2025 USD ($) | Dec. 31, 2024 | Sep. 30, 2024 | Apr. 30, 2024 | Mar. 31, 2024 | Oct. 31, 2021 | Mar. 31, 2021
Inventories |  |  |  |  |  |  |  |  |  |
Materials and supplies inventory |  |  | $ 132.4 | $ 144.9 |  |  |  |  |  |
Hydrocarbons inventory |  |  | 7.5 | $ 27.7 |  |  |  |  |  |
Facility |  |  |  |  |  |  |  |  |  |
Cash, Cash Equivalents and Restricted Cash |  |  |  |  |  |  |  |  |  |
Debt cover ratio | 2.50 | 2.50 |  |  |  |  | 2.50 |  |  |
Restricted cash required |  | $ 23.5 |  |  |  |  |  |  |  |
Debt service reserve account | $ 23.5 |  | $ 23.5 |  |  |  |  |  |  |
Facility Interest or Senior Notes |  |  |  |  |  |  |  |  |  |
Cash, Cash Equivalents and Restricted Cash |  |  |  |  |  |  |  |  |  |
Period for contractual future interest payments |  |  | 6 months |  |  |  |  |  |  |
7.750% Senior Notes | Senior Notes |  |  |  |  |  |  |  |  |  |
Cash, Cash Equivalents and Restricted Cash |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  |  |  | 7.75% |
7.500% Senior Notes | Senior Notes |  |  |  |  |  |  |  |  |  |
Cash, Cash Equivalents and Restricted Cash |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  |  |  |  | 7.50%
8.750% Senior Notes | Senior Notes |  |  |  |  |  |  |  |  |  |
Cash, Cash Equivalents and Restricted Cash |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  | 8.75% |  |  |  |
3.125% Convertible Senior Notes | Senior Notes |  |  |  |  |  |  |  |  |  |
Cash, Cash Equivalents and Restricted Cash |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  | 3.125% | 3.125% | 3.125% |  |  | 3.125% |  |

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