Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 18,683	$ 8,229
Supplies and service parts	24,283	21,841
Finished products	37,856	36,692
Inventory at FIFO cost	80,822	66,762
Excess of FIFO cost over LIFO cost	(4,483)	(4,483)
Total inventory, net	$ 76,339	$ 62,279