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Other Long-Term Liabilities (Tables) | 9 Months Ended
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Sep. 30, 2021
Other Liabilities Disclosure [Abstract] |
Other Long-Term Liabilities | Other long-term liabilities are summarized as follows (in thousands):
| September 30, 2021 |  | December 31, 2020
Black lung obligations | $ | 34,229 |  |  | $ | 34,567 |
Other | 2,985 |  |  | 2,258 |
Total other long-term liabilities | $ | 37,214 |  |  | $ | 36,825 |

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