Consolidated Statements of Operations - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Income Statement [Abstract]        
Net sales $ 166,685 $ 167,106 $ 328,395 $ 315,211
Cost of sales 120,023 130,357 240,163 244,213
Gross profit 46,662 36,749 88,232 70,998
Operating expenses        
Selling, general and administrative expenses 17,730 20,403 40,878 40,355
Research and development expenses 16,928 18,178 34,886 35,993
Restructuring and other charges (gain), net   1,305 (17,010) (6,480)
Early termination charges 2,262 4,240 13,369 4,240
Total operating expenses 36,920 44,126 72,123 74,108
Operating income (loss) 9,742 (7,377) 16,109 (3,110)
Interest expense (5,441) (4,073) (10,614) (8,130)
Foreign currency gain (loss), net (11,905) (7,101) 29,881 1,094
Other income, net 83 1,007 1,694 1,542
Income (loss) before income taxes (7,521) (17,544) 37,070 (8,604)
Income tax expenses 538 272 1,391 1,087
Net income (loss) $ (8,059) $ (17,816) $ 35,679 $ (9,691)
Income (loss) per common share-        
Basic $ (0.24) $ (0.51) $ 1.06 $ (0.28)
Diluted $ (0.24) $ (0.51) $ 0.87 $ (0.28)
Weighted average number of shares-        
Basic 33,952,574 34,716,081 33,808,237 34,707,492
Diluted 33,952,574 34,716,081 43,772,115 34,707,492