Condensed Consolidated Statements of Income (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net sales	$ 265,299	$ 304,802	$ 554,147	$ 630,582
Cost of sales	205,684	221,485	420,511	470,415
Gross profit	59,615	83,317	133,636	160,167
Selling, general, administrative and engineering expenses	42,762	52,792	98,929	110,951
Restructuring and asset impairment charges	5,994	44	8,705	556
Income from operations	10,859	30,481	26,002	48,660
Interest expense	(120)	(484)	(157)	(1,131)
Other income, net of expenses	434	372	668	839
Income from operations before income taxes	11,173	30,369	26,513	48,368
Income tax provision (benefit)	1,868	7,008	(3,275)	10,789
Net income	9,305	23,361	29,788	37,579
Net (income) loss attributable to non-controlling interest	(47)	16	114	72
Net income attributable to controlling interest	$ 9,258	$ 23,377	$ 29,902	$ 37,651
Net income attributable to controlling interest:
Basic (in dollars per share)	$ 0.41	$ 1.04	$ 1.33	$ 1.67
Diluted (in dollars per share)	$ 0.41	$ 1.03	$ 1.32	$ 1.66
Weighted average number of common shares outstanding:
Basic (in shares)	22,584	22,509	22,567	22,503
Diluted (in shares)	22,711	22,667	22,715	22,656
Dividends declared per common share (in dollars per share)	$ 0.11	$ 0.11	$ 0.22	$ 0.22