Reporting Segments and Related Information - Revenue Components of Mineral Resources Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from External Customer [Line Items]
Total expenses	$ 55,873	$ 44,577	$ 50,954
Operating Segments
Revenue from External Customer [Line Items]
Total revenues	55,613	37,830	49,523
Segment profits	9,583	2,683	7,930
Mineral resources | Operating Segments
Revenue from External Customer [Line Items]
Total revenues	20,987	10,736	9,791
Total expenses	13,559	6,414	5,818
Segment profits	$ 7,428	$ 4,322	$ 3,973