CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Net sales	$ 160,566	$ 165,051
Cost of sales	100,058	102,626
Gross margin	60,508	62,425
Selling, general and administrative expenses	29,860	36,147
Research and development expenses	6,549	6,108
Operating income	24,099	20,170
Equity income in unconsolidated joint ventures	613	919
Other income (expense), net	(546)	(129)
Interest expense, net	(1,121)	(1,006)
Income before income tax expense	23,045	19,954
Income tax expense	8,117	6,311
Net income	$ 14,928	$ 13,643
Basic earnings per share (in dollars per share)	$ 0.83	$ 0.74
Diluted earnings per share (in dollars per share)	$ 0.82	$ 0.72
Shares used in computing:
Basic earnings per share (shares)	17,966	18,476
Diluted earnings per share (shares)	18,214	18,950