Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 679,672	$ 687,969	$ 633,712
Cost of sales	491,779	531,743	498,848
Gross profit	187,893	156,226	134,864
Operating expenses
Selling, general and administrative expenses	81,775	83,549	94,378
Research and development expenses	70,523	72,180	83,420
Restructuring and other charges (gain), net	(17,010)	(6,480)
Early termination charges	13,369	4,240
Total operating expenses	148,657	153,489	177,798
Operating income (loss)	39,236	2,737	(42,934)
Interest expense	(21,559)	(16,238)	(16,268)
Foreign currency gain (loss), net	65,516	(15,360)	(42,531)
Other income, net	2,898	2,990	1,779
Income (loss) before income tax expenses	86,091	(25,871)	(99,954)
Income tax expenses (benefits)	1,155	3,744	(15,087)
Net income (loss)	$ 84,936	$ (29,615)	$ (84,867)
Earnings (loss) per common share-
Basic	$ 2.50	$ (0.85)	$ (2.47)
Diluted	$ 2.02	$ (0.85)	$ (2.47)
Weighted average number of shares-
Basic	33,943,264	34,833,967	34,380,517
Diluted	44,755,137	34,833,967	34,380,517