CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net sales	$ 214,611	$ 203,828
Cost of sales	138,005	123,478
Gross margin	76,606	80,350
Selling, general and administrative expenses	40,597	34,569
Research and development expenses	8,134	6,961
Restructuring and impairment charges	422	725
Other operating (income) expense, net	(3,591)	(942)
Operating income	31,044	39,037
Equity income in unconsolidated joint ventures	1,007	1,009
Other income (expense), net	66	1,119
Interest expense, net	(1,210)	(1,248)
Income before income tax expense	30,907	39,917
Income tax expense	4,771	12,885
Net income	$ 26,136	$ 27,032
Basic earnings per share (in dollars per share)	$ 1.43	$ 1.50
Diluted earnings per share (in dollars per share)	$ 1.40	$ 1.47
Shares used in computing:
Basic earnings per share (shares)	18,288	18,056
Diluted earnings per share (shares)	18,610	18,373