CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Net sales	$ 234,906	$ 191,157	$ 464,171	$ 389,967
Cost of sales	145,073	121,188	284,839	254,368
Gross margin	89,833	69,969	179,332	135,599
Selling, general and administrative expenses	44,959	41,694	87,372	82,024
Research and development expenses	7,492	7,295	14,664	15,100
Restructuring and impairment charges	747	0	2,253	0
Other operating (income) expense, net	890	(112)	2,105	(92)
Operating income	35,745	21,092	72,938	38,567
Equity income in unconsolidated joint ventures	1,930	1,022	4,111	2,240
Pension settlement charges	0	(55)	0	(55)
Other income (expense), net	1,239	634	4,207	(152)
Interest expense, net	(404)	(1,779)	(1,011)	(2,986)
Income before income tax expense	38,510	20,914	80,245	37,614
Income tax expense	9,855	6,394	20,372	9,835
Net income	$ 28,655	$ 14,520	$ 59,873	$ 27,779
Basic earnings per share (in dollars per share)	$ 1.53	$ 0.78	$ 3.20	$ 1.49
Diluted earnings per share (in dollars per share)	$ 1.52	$ 0.78	$ 3.18	$ 1.49
Shares used in computing:
Basic earnings per share (in shares)	18,729	18,676	18,721	18,673
Diluted earnings per share (in shares)	18,846	18,681	18,810	18,686