Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Product revenues	$ 1,038,259	$ 985,683	$ 917,600
Cost of sales	743,647	674,796	622,563
Gross margin	294,612	310,887	295,037
Operating costs and expenses:
Research and development expenses	98,663	94,515	79,583
Reimbursed research and development expenses	(18,763)	(12,037)	(6,660)
Net research and development expenses	79,900	82,478	72,923
Acquisition transaction expenses		789	743
Selling, general and administrative expenses	127,152	130,522	115,252
Restructuring expenses	14,772
Total operating costs and expenses	221,824	213,789	188,918
Operating income	72,788	97,098	106,119
Interest expense	(4,942)	(4,885)	(3,257)
Foreign currency gain (loss)	622	(23,108)	7,810
Impairment loss	(11,476)
Other income (loss)	1,127	150	(109)
Earnings before income tax	58,119	69,255	110,563
Income tax expense	16,220	34,028	33,965
Net income	$ 41,899	$ 35,227	$ 76,598
Basic earnings per share	$ 1.17	$ 0.96	$ 2.10
Diluted earnings per share	$ 1.16	$ 0.96	$ 2.09
Weighted average number of shares—basic	35,920,782	36,720,749	36,448,138
Weighted average number of shares—diluted	36,177,144	36,813,719	36,600,803