v3.25.2
Business Segments (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2024
Segment Reporting Information [Line Items]          
Revenues $ 68,235 $ 52,345 $ 133,806 $ 105,634  
Cost of sales 61,415 45,327 117,332 91,598  
Earnings of unconsolidated operations 13,138 13,592 29,124 26,899  
Operating expenses (income) 20,009 13,244 37,967 28,812  
Operating (loss) profit (51) 7,366 7,631 12,123  
Expenditures for property, plant and equipment and acquisition of mineral interests 3,142 7,918 11,950 22,401  
Depreciation, depletion and amortization 6,091 7,007 12,884 12,699  
 Total assets 631,312   631,312   $ 631,687
Operating segments | Utility Coal Mining          
Segment Reporting Information [Line Items]          
Revenues 28,626 14,996 47,865 30,541  
Cost of sales 30,327 16,138 52,897 37,081  
Earnings of unconsolidated operations 11,656 12,006 26,119 24,013  
Operating expenses (income) 8,733 8,097 16,074 15,123  
Operating (loss) profit 1,222 2,767 5,013 2,350  
Expenditures for property, plant and equipment and acquisition of mineral interests 1,433 1,913 2,050 3,707  
Depreciation, depletion and amortization 2,132 2,896 4,150 5,110  
 Total assets 117,201   117,201   125,301
Operating segments | Contract Mining          
Segment Reporting Information [Line Items]          
Revenues 30,723 27,920 62,249 52,403  
Cost of sales 28,659 24,254 57,037 45,925  
Earnings of unconsolidated operations 1,232 1,448 2,201 2,813  
Operating expenses (income) 2,286 2,029 4,433 3,851  
Operating (loss) profit 1,010 3,085 2,980 5,440  
Expenditures for property, plant and equipment and acquisition of mineral interests 1,032 5,168 7,786 10,986  
Depreciation, depletion and amortization 2,917 2,434 5,619 4,690  
 Total assets 212,254   212,254   204,889
Operating segments | Minerals and Royalties          
Segment Reporting Information [Line Items]          
Revenues 7,268 5,593 18,170 15,994  
Cost of sales 986 1,501 3,230 2,865  
Earnings of unconsolidated operations 251 138 805 73  
Operating expenses (income) 1,328 (3,361) 2,633 (2,319)  
Operating (loss) profit 5,205 7,591 13,112 15,521  
Expenditures for property, plant and equipment and acquisition of mineral interests 0 10 807 146  
Depreciation, depletion and amortization 845 1,323 2,753 2,316  
 Total assets 96,247   96,247   99,905
Unallocated Items          
Segment Reporting Information [Line Items]          
Revenues 2,223 4,566 6,623 7,828  
Cost of sales 2,051 4,167 5,288 6,879  
Earnings of unconsolidated operations (1) 0 (1) 0  
Operating expenses (income) 7,662 6,479 14,827 12,157  
Operating (loss) profit (7,491) (6,080) (13,493) (11,208)  
Expenditures for property, plant and equipment and acquisition of mineral interests 677 827 1,307 7,562  
Depreciation, depletion and amortization 197 354 362 583  
 Total assets 205,610   205,610   $ 201,592
Eliminations          
Segment Reporting Information [Line Items]          
Revenues (605) (730) (1,101) (1,132)  
Cost of sales (608) (733) (1,120) (1,152)  
Operating (loss) profit $ 3 $ 3 $ 19 $ 20