Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Inventory [Line Items]
Raw materials	$ 35,225	$ 33,185
Finished goods	88,178	81,369
Spare parts	13,969	13,741
Inventory, Net	137,372	128,295
Inventory Valuation Reserves	$ 12,574	$ 13,422