Inventories, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Finished goods	$ 67,783	$ 76,981
Work in process	18,762	13,870
Raw materials and supplies	76,048	82,794
Inventories, net	162,593	173,645
Inventory valuation reserves	$ 45,800	$ 46,500