Inventories, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Finished goods	$ 68,876	$ 76,981
Work in process	14,060	13,870
Raw materials and supplies	79,816	82,794
Inventories, net	162,752	173,645
Inventory valuation reserves	$ 48,500	$ 46,500