Inventories - Major Classes of Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw materials	$ 133,311	$ 90,019
Work-in-process	35,807	25,166
Finished goods	153,377	99,784
Gross inventories	322,495	214,969
Excess and obsolete reserves	(25,269)	(24,561)
Net inventories	$ 297,226	$ 190,408