v3.26.1
Segment Information - Results (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Reportable segment results          
Revenues $ 551,560 $ 547,463 $ 1,067,577 $ 1,087,931  
Segment Adjusted EBITDA Expense 347,432 354,371 685,558 697,019  
Other segment items 1,291 1,060 2,504 2,368  
Segment Adjusted EBITDA 204,386 185,354 376,644 366,397  
Total assets 2,941,792 2,869,446 2,941,792 2,869,446 $ 2,853,788
Capital expenditures 50,014 67,017 145,704 153,793  
Coal royalties          
Reportable segment results          
Revenues 0 0 0 0  
Transportation revenues          
Reportable segment results          
Revenues 7,510 8,558 16,153 18,758  
Transportation expenses 7,510 8,558 16,153 18,758  
Other revenues          
Reportable segment results          
Revenues 28,213 17,963 50,964 43,636  
Operating Segments, Excluding Corporate and Elimination          
Reportable segment results          
Revenues 536,312 531,731 1,037,452 1,051,135  
Operating Segments, Excluding Corporate and Elimination | Illinois Basin Coal          
Reportable segment results          
Revenues 337,888 350,247 656,850 693,242  
Operating Segments, Excluding Corporate and Elimination | Appalachia Coal          
Reportable segment results          
Revenues 151,897 145,983 292,000 285,479  
Operating Segments, Excluding Corporate and Elimination | Oil & Gas Royalties          
Reportable segment results          
Revenues 46,527 35,501 88,311 72,414  
Operating Segments, Excluding Corporate and Elimination | Coal Royalties          
Reportable segment results          
Revenues 0 0 291 0  
Operating Segments          
Reportable segment results          
Revenues 560,619 549,343 1,080,859 1,084,542  
Segment Adjusted EBITDA 204,386 185,354 376,644 366,397  
Total assets 2,720,710 2,705,035 2,720,710 2,705,035  
Capital expenditures 47,045 65,400 140,987 148,858  
Operating Segments | Illinois Basin Coal          
Reportable segment results          
Revenues 339,472 350,247 658,434 693,242  
Segment Adjusted EBITDA Expense 229,177 231,189 442,763 441,148  
Other segment items 0 0 0 0  
Segment Adjusted EBITDA 104,212 114,229 203,411 240,402  
Total assets 1,070,838 1,076,634 1,070,838 1,076,634  
Capital expenditures 37,466 50,072 94,360 102,657  
Operating Segments | Illinois Basin Coal | Coal royalties          
Reportable segment results          
Revenues 0 0 0 0  
Operating Segments | Illinois Basin Coal | Transportation revenues          
Reportable segment results          
Revenues 6,083 4,829 12,260 11,692  
Transportation expenses 6,083 4,829 12,260 11,692  
Operating Segments | Illinois Basin Coal | Other revenues          
Reportable segment results          
Revenues 3,117 1,577 6,147 4,475  
Operating Segments | Appalachia Coal          
Reportable segment results          
Revenues 151,897 145,983 292,000 285,479  
Segment Adjusted EBITDA Expense 101,277 112,829 212,729 233,397  
Other segment items 0 0 0 0  
Segment Adjusted EBITDA 49,193 29,425 75,378 45,016  
Total assets 420,593 472,142 420,593 472,142  
Capital expenditures 9,579 15,226 31,127 46,054  
Operating Segments | Appalachia Coal | Coal royalties          
Reportable segment results          
Revenues 0 0 0 0  
Operating Segments | Appalachia Coal | Transportation revenues          
Reportable segment results          
Revenues 1,427 3,729 3,893 7,066  
Transportation expenses 1,427 3,729 3,893 7,066  
Operating Segments | Appalachia Coal | Other revenues          
Reportable segment results          
Revenues 11,198 626 15,308 1,508  
Operating Segments | Oil & Gas Royalties          
Reportable segment results          
Revenues 46,527 35,501 88,311 72,414  
Segment Adjusted EBITDA Expense 7,224 4,558 13,188 10,279  
Other segment items 1,291 1,060 2,504 2,368  
Segment Adjusted EBITDA 38,012 29,883 72,619 59,767  
Total assets 920,383 847,300 920,383 847,300  
Capital expenditures 0 0 0 0  
Operating Segments | Oil & Gas Royalties | Coal royalties          
Reportable segment results          
Revenues 0 0 0 0  
Operating Segments | Oil & Gas Royalties | Transportation revenues          
Reportable segment results          
Revenues 0 0 0 0  
Transportation expenses 0 0 0 0  
Operating Segments | Oil & Gas Royalties | Other revenues          
Reportable segment results          
Revenues 234 28 677 857  
Operating Segments | Coal Royalties          
Reportable segment results          
Revenues 22,723 17,612 42,114 33,407  
Segment Adjusted EBITDA Expense 9,754 5,795 16,878 12,195  
Other segment items 0 0 0 0  
Segment Adjusted EBITDA 12,969 11,817 25,236 21,212  
Total assets 308,896 308,959 308,896 308,959  
Capital expenditures 0 102 15,500 147  
Operating Segments | Coal Royalties | Coal royalties          
Reportable segment results          
Revenues 22,723 17,612 41,823 33,407  
Operating Segments | Coal Royalties | Transportation revenues          
Reportable segment results          
Revenues 0 0 0 0  
Transportation expenses 0 0 0 0  
Operating Segments | Coal Royalties | Other revenues          
Reportable segment results          
Revenues 0 0 291 0  
Elimination          
Reportable segment results          
Revenues 24,307 17,612 43,407 33,407  
Elimination | Illinois Basin Coal          
Reportable segment results          
Revenues 1,584 0 1,584 0  
Elimination | Appalachia Coal          
Reportable segment results          
Revenues 0 0 0 0  
Elimination | Oil & Gas Royalties          
Reportable segment results          
Revenues 0 0 0 0  
Elimination | Coal Royalties          
Reportable segment results          
Revenues 22,723 17,612 41,823 33,407  
Other, Corporate and Elimination          
Reportable segment results          
Revenues (24,307) (17,612) (43,407) (33,407)  
Total assets 221,082 164,411 221,082 164,411  
Capital expenditures 2,969 1,617 4,717 4,935  
Other, Corporate and Elimination | Other revenues          
Reportable segment results          
Revenues $ 15,248 $ 15,732 $ 30,125 $ 36,796