Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Raw materials	$ 16,570	$ 13,514
Supplies and service parts	24,061	21,840
Finished products	30,849	36,969
Inventory at FIFO cost, net	71,480	72,323
Excess of FIFO cost over LIFO cost	(5,635)	(4,072)
Total inventory, net	$ 65,845	$ 68,251