Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Raw materials	$ 29,173	$ 25,803
Work in process	12,304	6,408
Supplies and service parts	44,592	44,323
Finished products	26,612	24,618
Inventory at FIFO cost	112,681	101,152
Excess of FIFO cost over LIFO cost	(12,328)	(12,328)
Total inventory, net	$ 100,353	$ 88,824