v3.26.1
Segment Information (Disaggregation of Revenue) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Disaggregation of Revenue [Line Items]        
Total coal revenues $ 506,371 $ 459,337 $ 966,862 $ 900,788
Other 7,758 8,542 14,459 16,339
Total revenues 514,129 467,879 981,321 917,127
Metallurgical Coal [Member]        
Disaggregation of Revenue [Line Items]        
Total coal revenues 479,628 427,328 887,901 848,831
Thermal Coal [Member]        
Disaggregation of Revenue [Line Items]        
Total coal revenues 26,743 32,009 78,961 51,957
Australia Segment [Member] | Operating Segments [Member]        
Disaggregation of Revenue [Line Items]        
Total coal revenues 318,908 251,537 571,313 517,561
Other 7,706 8,308 14,388 15,561
Total revenues 326,614 259,845 585,701 533,122
Australia Segment [Member] | Metallurgical Coal [Member] | Operating Segments [Member]        
Disaggregation of Revenue [Line Items]        
Total coal revenues 296,354 230,624 506,345 480,690
Australia Segment [Member] | Thermal Coal [Member] | Operating Segments [Member]        
Disaggregation of Revenue [Line Items]        
Total coal revenues 22,554 20,913 64,968 36,871
United States Segment [Member] | Operating Segments [Member]        
Disaggregation of Revenue [Line Items]        
Total coal revenues 187,463 207,800 395,549 383,227
Other 52 234 71 778
Total revenues 187,515 208,034 395,620 384,005
United States Segment [Member] | Metallurgical Coal [Member] | Operating Segments [Member]        
Disaggregation of Revenue [Line Items]        
Total coal revenues 183,274 196,704 381,556 368,141
United States Segment [Member] | Thermal Coal [Member] | Operating Segments [Member]        
Disaggregation of Revenue [Line Items]        
Total coal revenues $ 4,189 $ 11,096 $ 13,993 $ 15,086