Consolidated Condensed Statements of Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Product revenues	$ 259,540	$ 240,056	$ 624,214	$ 741,303
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Cost of sales	$ 176,935	$ 165,364	$ 448,807	$ 518,590
Gross margin	82,605	74,692	175,407	222,713
Operating expenses:
Net research and development expenses	18,070	18,838	51,171	56,990
Selling, general and administrative expenses	25,745	26,861	73,474	91,683
Restructuring expenses	284	8,664	3,452	11,809
Total operating expenses	44,099	54,363	128,097	160,482
Operating income	38,506	20,329	47,310	62,231
Interest expense, net	(1,259)	(1,148)	(3,368)	(3,756)
Foreign currency (loss) gain	(2,883)	4,083	(5,562)	3,482
Gain on sale of business				4,970
Impairment loss		(837)		(21,206)
Other (loss) income	(615)	231	2,531	545
Earnings before income tax	33,749	22,658	40,911	46,266
Income tax expense	9,603	6,771	15,214	19,214
Net income	$ 24,146	$ 15,887	$ 25,697	$ 27,052
Basic earnings per share	$ 0.74	$ 0.48	$ 0.79	$ 0.81
Diluted earnings per share	$ 0.73	$ 0.48	$ 0.78	$ 0.81
Weighted average number of shares – basic	32,623,532	32,838,636	32,631,423	33,282,584
Weighted average number of shares – diluted	32,958,439	32,932,679	32,924,013	33,418,555