Inventories, Net and Significant Suppliers - Inventory Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Reserve for Excess and Obsolete Inventory
Balance at beginning of period	$ 4,205	$ 3,045	$ 2,539
Additions charged to costs and expenses	3,685	3,464	3,070
Sell through	(1,242)	(1,116)	(1,108)
(Write-offs)/Foreign exchange effects	(2,360)	(1,188)	(1,456)
Balance at end of period	4,288	4,205	3,045
Inventory scrapped during production	$ 400	$ 300	$ 300