SEGMENT INFORMATION - Segment Results (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Reportable segment results
Revenues	$ 2,406,511	$ 1,569,976	$ 1,328,129
Segment Adjusted EBITDA Expense	1,282,433	952,649	861,249
Segment Adjusted EBITDA	1,020,558	549,252	446,489
Total assets	2,661,473	2,159,406	2,166,016
Capital expenditures	286,394	122,984	121,101
Illinois Basin
Reportable segment results
Revenues	1,296,305	919,597	769,957
Segment Adjusted EBITDA Expense	806,080	613,303	543,264
Segment Adjusted EBITDA	420,684	265,292	213,876
Total assets	779,018	676,091	738,315
Capital expenditures	158,624	60,166	48,636
Appalachia
Reportable segment results
Revenues	928,087	545,539	500,330
Segment Adjusted EBITDA Expense	464,029	344,332	320,656
Segment Adjusted EBITDA	426,402	172,601	171,362
Total assets	431,913	420,144	440,815
Capital expenditures	76,603	47,577	70,960
Oil & Gas Royalties
Reportable segment results
Revenues	141,441	77,185	43,141
Segment Adjusted EBITDA Expense	13,950	9,943	4,106
Segment Adjusted EBITDA	131,168	68,774	39,773
Total assets	711,917	630,627	613,916
Coal Royalties
Reportable segment results
Revenues	60,680	51,471	42,217
Segment Adjusted EBITDA Expense	21,871	18,269	18,249
Segment Adjusted EBITDA	38,809	33,202	23,968
Total assets	321,587	285,943	288,525
Capital expenditures	38,276	45	12
Other, Corporate and Elimination
Reportable segment results
Revenues	(20,002)	(23,816)	(27,516)
Segment Adjusted EBITDA Expense	(23,497)	(33,198)	(25,026)
Segment Adjusted EBITDA	3,495	9,383	(2,490)
Total assets	417,038	146,601	84,445
Capital expenditures	12,891	15,196	1,493
Operating segments
Reportable segment results
Revenues	2,406,511	1,569,976	1,328,129
Operating segments | Illinois Basin
Reportable segment results
Revenues	1,296,305	919,597	769,957
Operating segments | Appalachia
Reportable segment results
Revenues	928,087	545,539	500,330
Operating segments | Oil & Gas Royalties
Reportable segment results
Revenues	141,441	77,185	43,141
Operating segments | Coal Royalties
Reportable segment results
Revenues	56	69	105
Operating segments | Other, Corporate and Elimination
Reportable segment results
Revenues	40,622	27,586	14,596
Elimination | Coal Royalties
Reportable segment results
Revenues	60,624	51,402	42,112
Elimination | Other, Corporate and Elimination
Reportable segment results
Revenues	$ (60,624)	$ (51,402)	$ (42,112)