Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Raw materials	$ 16,174	$ 13,514
Supplies and service parts	22,628	21,840
Finished products	31,957	36,969
Inventory at FIFO cost	70,759	72,323
Excess of FIFO cost over LIFO cost	(3,785)	(4,072)
Total inventory, net	$ 66,974	$ 68,251