Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Raw materials	$ 30,329	$ 25,803
Work in process	9,270	6,408
Supplies and service parts	47,916	44,323
Finished products	35,773	24,618
Inventory at FIFO cost	123,288	101,152
Excess of FIFO cost over LIFO cost	(12,328)	(12,328)
Total inventory, net	$ 110,960	$ 88,824