v3.26.1
Segment Information - Segment Results (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Mar. 31, 2026
Jun. 30, 2025
Mar. 31, 2025
Jun. 30, 2026
Jun. 30, 2025
Segment Reporting [Line Items]            
Coal revenues $ 491,505   $ 548,675   $ 1,015,038 $ 1,078,342
Other revenues 1,351   1,599   2,805 3,889
Total revenues 492,856   550,274   1,017,843 1,082,231
Cost of coal sales (exclusive of items shown separately below) 443,663   479,953   918,052 984,537
Depreciation, depletion and amortization 36,044   44,822   75,970 88,732
Accretion on asset retirement obligations 5,214   5,508   10,429 11,122
Amortization of acquired intangibles 876   1,357   1,752 2,714
Selling, general and administrative expenses 17,257   15,216   33,855 30,640
Interest expense 962   761   1,803 1,524
Interest income (2,919)   (4,199)   (7,125) (8,245)
Equity loss in affiliates 6,717   8,736   12,450 13,696
Income tax benefit (6,595)   (1,248)   (11,921) (12,685)
Net loss (12,252) $ (11,032) (4,954) $ (33,947) (23,284) (38,901)
Met            
Segment Reporting [Line Items]            
Coal revenues 491,505   548,675   1,015,038 1,078,342
Other revenues 1,351   1,599   2,805 3,889
Total revenues 492,856   550,274   1,017,843 1,082,231
Non-GAAP cost of coal sales 365,789   388,844   754,092 803,513
Freight and handling costs 70,220   84,589   146,434 168,513
Idled and closed mine costs 7,654   6,520   17,526 12,511
Cost of coal sales (exclusive of items shown separately below) 443,663   479,953   918,052 984,537
Depreciation, depletion and amortization 36,044   44,822   75,970 88,732
Accretion on asset retirement obligations 5,214   5,508   10,429 11,122
Amortization of acquired intangibles 876   1,357   1,752 2,714
Selling, general and administrative expenses 17,257   15,216   33,855 30,640
Interest expense 962   761   1,803 1,524
Interest income (2,919)   (4,199)   (7,125) (8,245)
Equity loss in affiliates 6,717   8,736   12,450 13,696
Other segment items 3,889   4,322   5,862 9,097
Income tax benefit (6,595)   (1,248)   (11,921) (12,685)
Total other expenses 61,445   75,275   123,075 136,595
Net loss $ (12,252)   $ (4,954)   $ (23,284) $ (38,901)