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Pneumoconiosis ("Black Lung") Obligations (Details) - USD ($)
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Jul. 12, 2022
May 31, 2020
Feb. 21, 2020
Apr. 01, 2016
Self Insurance Reserve Disclosure [Abstract]            
Deductible amount per black lung claim $ 2,000,000     $ 500,000    
Collateral securities     $ 28,000,000   $ 39,800,000 $ 17,000,000.0
Surety Bonds 18,600,000 $ 18,600,000        
Short-term investments 14,600,000 9,000,000        
Black lung trust 1,400,000 1,800,000        
Estimated total black lung liabilities 36,600,000 28,800,000        
Black lung obligations, current 2,200,000 1,900,000        
Black lung obligations, noncurrent 34,467,000 26,966,000        
Self insurance expense (income) $ 7,300,000 $ (1,400,000)        
Self insurance reserve, adjustment to earnings (in USD per share) $ 0.14 $ (0.03)