Inventories (Components) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw materials	$ 61,214	$ 57,784
Work in process	3,284	5,957
Finished goods	5,391	8,163
Inventory, gross	69,889	71,904
Less: Allowance for excess and obsolete inventories	(1,209)	(1,118)	$ (1,442)	$ (1,382)
Total, net	$ 68,680	$ 70,786