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Commitments and Contingencies - Restricted Cash (Details) - USD ($) $ in Thousands | Jun. 30, 2026 | Dec. 31, 2025
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Long-term Purchase Commitment [Line Items] |  |
Total long-term restricted cash | $ 128,219 | $ 126,911
Workers’ compensation and black lung obligations |  |
Long-term Purchase Commitment [Line Items] |  |
Total long-term restricted cash | 118,045 | 117,150
Reclamation-related obligations |  |
Long-term Purchase Commitment [Line Items] |  |
Total long-term restricted cash | 1,294 | 959
Financial payments and other performance obligations |  |
Long-term Purchase Commitment [Line Items] |  |
Total long-term restricted cash | $ 8,880 | $ 8,802

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