v3.26.1
Business Segments (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Segment Reporting Information [Line Items]      
Revenues $ 62,775 $ 65,571  
Cost of sales 48,484 55,917  
Earnings of unconsolidated operations 16,571 15,986  
Operating expenses (income) 19,846 17,958  
Operating profit (loss) 11,016 7,682  
Expenditures for property, plant and equipment and acquisition of mineral interests 33,430 8,808  
Depreciation, depletion and amortization 5,507 6,793  
 Total assets 685,656   $ 661,228
Operating segments | Utility Coal Mining      
Segment Reporting Information [Line Items]      
Revenues 16,691 19,239  
Cost of sales 15,950 22,570  
Earnings of unconsolidated operations 14,108 14,463  
Operating expenses (income) 7,425 7,341  
Operating profit (loss) 7,424 3,791  
Expenditures for property, plant and equipment and acquisition of mineral interests 533 617  
Depreciation, depletion and amortization 2,312 2,018  
 Total assets 118,954   125,715
Operating segments | Contract Mining      
Segment Reporting Information [Line Items]      
Revenues 32,639 31,526  
Cost of sales 27,744 28,378  
Earnings of unconsolidated operations 1,502 969  
Operating expenses (income) 2,409 2,147  
Operating profit (loss) 3,988 1,970  
Expenditures for property, plant and equipment and acquisition of mineral interests 11,832 6,754  
Depreciation, depletion and amortization 1,998 2,702  
 Total assets 222,644   213,571
Operating segments | Minerals and Royalties      
Segment Reporting Information [Line Items]      
Revenues 9,546 10,902  
Cost of sales 1,121 2,244  
Earnings of unconsolidated operations 961 554  
Operating expenses (income) 1,650 1,305  
Operating profit (loss) 7,736 7,907  
Expenditures for property, plant and equipment and acquisition of mineral interests 69 807  
Depreciation, depletion and amortization 887 1,908  
 Total assets 115,999   115,545
Unallocated Items      
Segment Reporting Information [Line Items]      
Revenues 4,831 4,400  
Cost of sales 4,612 3,237  
Operating expenses (income) 8,362 7,165  
Operating profit (loss) (8,143) (6,002)  
Expenditures for property, plant and equipment and acquisition of mineral interests 20,996 630  
Depreciation, depletion and amortization 310 165  
 Total assets 228,059   $ 206,397
Eliminations      
Segment Reporting Information [Line Items]      
Revenues (932) (496)  
Cost of sales (943) (512)  
Operating profit (loss) $ 11 $ 16