Inventories - Major Classes of Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 146,803	$ 133,311
Work-in-process	45,939	35,807
Finished goods	152,572	153,377
Gross inventories	345,314	322,495
Excess and obsolete reserves	(28,896)	(25,269)
Net inventories	$ 316,418	$ 297,226