Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw materials	$ 35,499	$ 28,541
Work in process	5,994	6,498
Supplies and service parts	49,729	45,152
Finished products	36,559	24,678
Inventory at FIFO cost	127,781	104,869
Excess of FIFO cost over LIFO cost	(12,143)	(12,143)
Total inventory, net	$ 115,638	$ 92,726