XML 40 R29.htm IDEA: XBRL DOCUMENT v3.22.1
Note 3 - Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($)
$ in Thousands
Mar. 31, 2022
Dec. 31, 2021
Property, plant, and equipment    
Less: Accumulated depreciation and amortization $ (87,294) $ (80,269)
Total property, plant and equipment, net 245,930 227,077
Plant and Equipment    
Property, plant, and equipment    
Property, plant and equipment, gross 175,557 167,019
Mining Properties and Mineral Rights    
Property, plant, and equipment    
Property, plant and equipment, gross 26,953 26,064
Construction in Progress    
Property, plant, and equipment    
Property, plant and equipment, gross 19,978 9,972
Capitalized mine development cost    
Property, plant, and equipment    
Property, plant and equipment, gross 110,736 104,291
Coal Properties    
Property, plant, and equipment    
Capitalized Costs Related to Coal Reserves $ 25,900 $ 25,100