Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Raw materials	$ 20,021	$ 13,514
Supplies and service parts	22,787	21,840
Finished products	34,681	36,969
Inventory at FIFO cost	77,489	72,323
Excess of FIFO cost over LIFO cost	(3,836)	(4,072)
Total inventory, net	$ 73,653	$ 68,251