XML 45 R33.htm IDEA: XBRL DOCUMENT v3.21.2
Inventories, net (Details) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Inventory Disclosure [Abstract]    
Coal $ 53,161 $ 86,272
Raw materials, parts, supplies and other, net 40,865 32,441
Total inventories, net $ 94,026 $ 118,713