Inventories (Components) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 67,519	$ 67,995
Work in process	3,131	4,060
Finished goods	5,494	6,767
Inventory, gross	76,144	78,822
Less: Allowance for excess and obsolete inventories	(1,567)	(1,210)	$ (1,209)	$ (1,118)
Total, net	$ 74,577	$ 77,612