CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net sales	$ 206,783	$ 165,259	$ 612,035	$ 483,314
Cost of sales	124,595	103,330	368,951	300,678
Gross margin	82,188	61,929	243,084	182,636
Selling, general and administrative expenses	38,615	31,489	112,346	95,718
Research and development expenses	7,411	7,294	21,512	20,916
Restructuring and impairment charges	962	0	2,767	0
Gain on sale of long-lived asset	(4,387)	0	(5,329)	0
Operating income	39,587	23,146	111,788	66,002
Equity income in unconsolidated joint ventures	1,384	898	3,359	2,220
Other income (expense), net	1,596	676	2,126	320
Interest expense, net	(1,639)	(811)	(4,834)	(3,047)
Income before income tax expense	40,928	23,909	112,439	65,495
Income tax expense	15,396	7,844	38,979	29,125
Net income	$ 25,532	$ 16,065	$ 73,460	$ 36,370
Basic earnings per share (in dollars per share)	$ 1.40	$ 0.89	$ 4.05	$ 2.02
Diluted earnings per share (in dollars per share)	$ 1.37	$ 0.88	$ 3.97	$ 2.00
Shares used in computing:
Basic earnings per share (shares)	18,181	17,996	18,126	17,990
Diluted earnings per share (shares)	18,588	18,183	18,503	18,217