REPORTING SEGMENTS AND RELATED INFORMATION - Revenue Components of Mineral Resources Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenue from External Customer [Line Items]
Total expenses	$ 11,587	$ 14,113	$ 27,395	$ 26,221
Operating results	(2,318)	2,525	2,894	1,471
Operating Segments
Revenue from External Customer [Line Items]
Total revenues	9,269	16,638	30,289	27,692
Mineral resources | Operating Segments
Revenue from External Customer [Line Items]
Total revenues	4,131	7,404	16,099	14,580
Total expenses	2,445	4,253	9,602	9,300
Operating results	$ 1,686	$ 3,151	$ 6,497	$ 5,280