Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net sales	$ 199,685	$ 166,685	$ 365,504	$ 328,395
Cost of sales	145,831	120,023	267,069	240,163
Gross profit	53,854	46,662	98,435	88,232
Operating expenses
Selling, general and administrative expenses	18,935	17,730	36,557	40,878
Research and development expenses	21,005	16,928	40,585	34,886
Restructuring and other gain				(17,010)
Early termination charges		2,262		13,369
Total operating expenses	39,940	36,920	77,142	72,123
Operating income	13,914	9,742	21,293	16,109
Interest expense	(5,489)	(5,441)	(10,952)	(10,614)
Foreign currency gain (loss), net	(27,449)	(11,905)	(26,131)	29,881
Other income (expense), net	(960)	83	(441)	1,694
Income (loss) before income taxes	(19,984)	(7,521)	(16,231)	37,070
Income tax expenses	1,521	538	2,511	1,391
Net income (loss)	$ (21,505)	$ (8,059)	$ (18,742)	$ 35,679
Earnings (loss) per common share-
Basic	$ (0.62)	$ (0.24)	$ (0.55)	$ 1.06
Diluted	$ (0.62)	$ (0.24)	$ (0.55)	$ 0.87
Weighted average number of shares-
Basic	34,420,654	33,952,574	34,337,345	33,808,237
Diluted	34,420,654	33,952,574	34,337,345	43,772,115