PROPERTY, PLANT AND EQUIPMENT - Net Book Value of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
PROPERTY, PLANT AND EQUIPMENT
Total Property, Plant and Equipment	$ 134,040	$ 132,400
Mineral rights and properties
PROPERTY, PLANT AND EQUIPMENT
Total Property, Plant and Equipment	8,972	8,972
Other property, plant and equipment
PROPERTY, PLANT AND EQUIPMENT
Total Property, Plant and Equipment	5,803	5,863
Construction in progress
PROPERTY, PLANT AND EQUIPMENT
Total Property, Plant and Equipment	119,265	117,565
Alabama
PROPERTY, PLANT AND EQUIPMENT
Total Property, Plant and Equipment	134,023	132,382
Alabama | Mineral rights and properties
PROPERTY, PLANT AND EQUIPMENT
Total Property, Plant and Equipment	8,972	8,972
Alabama | Other property, plant and equipment
PROPERTY, PLANT AND EQUIPMENT
Total Property, Plant and Equipment	5,786	5,845
Alabama | Construction in progress
PROPERTY, PLANT AND EQUIPMENT
Total Property, Plant and Equipment	119,265	117,565
Corporate
PROPERTY, PLANT AND EQUIPMENT
Total Property, Plant and Equipment	17	18
Corporate | Other property, plant and equipment
PROPERTY, PLANT AND EQUIPMENT
Total Property, Plant and Equipment	$ 17	$ 18