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Supplemental Financial Information - Schedule of Change in Asset Retirement Obligation (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended 12 Months Ended
Mar. 31, 2024
Sep. 30, 2024
Dec. 31, 2023
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Asset retirement obligations, beginning of period $ 6,163 $ 6,163 $ 8,533
Asset retirement obligations assumed   0 1,500
Accretion   496 582
Liabilities settled   (65) (4,866)
Changes due to scope and timing of reclamation   0 414
Asset retirement obligations, end of period   6,594 6,163
Less current portion   1,259 182
Asset retirement obligations, long-term   5,335 5,981
Business Acquisition [Line Items]      
Asset retirement obligations assumed   0 1,500
Liabilities settled   $ 65 $ 4,866
Marshall Mine | Disposed of by Sale      
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Liabilities settled (4,700)    
Business Acquisition [Line Items]      
Liabilities settled 4,700    
Corbin ARO      
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Asset retirement obligations assumed 500    
Business Acquisition [Line Items]      
Asset retirement obligations assumed 500    
Mine 4 ARO      
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Asset retirement obligations assumed 1,000    
Business Acquisition [Line Items]      
Asset retirement obligations assumed $ 1,000