CONDENSED CONSOLIDATED STATEMENTS OF INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Net sales	[1]	$ 160,366	$ 163,052	$ 488,515	$ 463,187
Cost of sales		100,836	98,504	306,041	287,583
Gross margin		59,530	64,548	182,474	175,604
Selling, general and administrative expenses		29,190	30,182	98,363	92,279
Research and development expenses		7,285	5,977	20,446	17,259
Operating income		23,055	28,389	63,665	66,066
Equity income in unconsolidated joint ventures		877	953	2,187	2,992
Other income (expense), net		(756)	(107)	(1,404)	(1,374)
Interest expense, net		(1,126)	(698)	(3,435)	(2,167)
Income before income tax expense		22,050	28,537	61,013	65,517
Income tax expense		9,595	8,149	21,392	19,647
Net income		$ 12,455	$ 20,388	$ 39,621	$ 45,870
Basic earnings per share (in dollars per share)		$ 0.68	$ 1.12	$ 2.14	$ 2.53
Diluted earnings per share (in dollars per share)		$ 0.67	$ 1.09	$ 2.10	$ 2.46
Shares used in computing:
Basic net income per share (shares)		18,430	18,259	18,511	18,123
Diluted net income per share (shares)		18,650	18,734	18,885	18,657

[1] Net sales were allocated to countries based on the location of the customer.