Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Inventory Disclosure [Abstract]
Raw materials and work in process	$ 36,804	$ 37,175
Supplies and service parts	45,179	33,760
Finished products	32,445	26,992
Inventory at FIFO cost	114,428	97,927
Excess of FIFO cost over LIFO cost	(13,356)	(13,100)
Total inventory, net	$ 101,072	$ 84,827