Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 57,306		$ 33,498
Work-in-process	23,691		22,040
Finished products	1,956		1,813
Total inventories	82,953		57,351
Less reserves	(3,298)		(3,204)
Total inventories, net	$ 79,655	$ 51,326	$ 54,147