Consolidated Condensed Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Product revenues	$ 263,779	$ 243,378	$ 525,668	$ 492,645
Cost of sales	189,308	165,060	372,652	329,176
Gross margin	74,471	78,318	153,016	163,469
Operating expenses:
Net research and development expenses	21,022	21,407	44,326	40,912
Selling, general and administrative expenses	31,641	31,775	65,368	62,581
Restructuring expenses	6,215		7,080
Total operating expenses	58,878	53,182	116,774	103,493
Operating income	15,593	25,136	36,242	59,976
Interest expense	(1,240)	(1,261)	(2,420)	(2,383)
Foreign currency gain (loss)	5,174	(13,251)	596	(14,580)
Other income	215	260	1,326	505
Earnings before income tax	19,742	10,884	35,744	43,518
Income tax expense	3,083	2,371	6,119	9,603
Net income	$ 16,659	$ 8,513	$ 29,625	$ 33,915
Basic earnings per share	$ 0.46	$ 0.23	$ 0.81	$ 0.92
Diluted earnings per share	$ 0.45	$ 0.23	$ 0.81	$ 0.92
Weighted average number of shares – basic	36,523,742	36,776,545	36,560,193	36,698,618
Weighted average number of shares – diluted	36,666,999	36,840,371	36,663,226	36,796,168