CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net sales	$ 239,798	$ 214,611
Cost of sales	154,404	138,005
Gross margin	85,394	76,606
Selling, general and administrative expenses	43,252	40,597
Research and development expenses	7,609	8,134
Restructuring and impairment charges	822	422
Other operating (income) expense, net	911	(3,591)
Operating income	32,800	31,044
Equity income in unconsolidated joint ventures	837	1,007
Other income (expense), net	1,404	66
Interest expense, net	(1,938)	(1,210)
Income before income tax expense	33,103	30,907
Income tax expense	4,704	4,771
Net income	$ 28,399	$ 26,136
Basic earnings per share (in dollars per share)	$ 1.53	$ 1.43
Diluted earnings per share (in dollars per share)	$ 1.52	$ 1.40
Shares used in computing:
Basic earnings per share (in shares)	18,557	18,288
Diluted earnings per share (in shares)	18,692	18,610