Property, Plant, Equipment and Mine Development (Details) - USD ($) $ in Millions |
Sep. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Property, Plant, and Equipment [Line Items] | ||
| Less: Accumulated depreciation, depletion and amortization | $ (2,904.4) | $ (2,673.8) |
| Property, plant, equipment and mine development, net | 3,042.2 | 3,153.3 |
| Land and coal interests | ||
| Property, Plant, and Equipment [Line Items] | ||
| Property, Plant, Equipment, and mine development, gross | 2,689.8 | 2,691.2 |
| Buildings and improvements | ||
| Property, Plant, and Equipment [Line Items] | ||
| Property, Plant, Equipment, and mine development, gross | 782.9 | 758.8 |
| Machinery and equipment | ||
| Property, Plant, and Equipment [Line Items] | ||
| Property, Plant, Equipment, and mine development, gross | $ 2,473.9 | $ 2,377.1 |
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- Definition Amount of accumulated depreciation and amortization from plant, property, and equipment and right-of-use asset from finance lease. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount, after accumulated depreciation and amortization, of property, plant, and equipment and finance lease right-of-use asset. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount, before accumulated depreciation and amortization, of property, plant, and equipment and finance lease right-of-use asset. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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