Condensed Consolidated Statements of Operations (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed Consolidated Statements of Operations (unaudited) [Abstract]
Net sales	$ 255,807	$ 256,613	$ 886,389	$ 854,595
Cost of sales	203,947	198,329	674,362	717,197
Gross profit	51,860	58,284	212,027	137,398
Selling, general, administrative and engineering expenses	47,643	51,054	158,594	154,396
Restructuring and asset impairment charges	875	0	1,431	0
Income (loss) from operations	3,342	7,230	52,002	(16,998)
Interest expense	(167)	(170)	(1,299)	(488)
Other income, net of expenses	412	23	1,252	1,536
Income (loss) from operations before income taxes	3,587	7,083	51,955	(15,950)
Income tax provision (benefit)	632	180	11,420	(2,301)
Net income (loss)	2,955	6,903	40,535	(13,649)
Net loss attributable to non-controlling interest	55	92	127	238
Net income (loss) attributable to controlling interest	$ 3,010	$ 6,995	$ 40,662	$ (13,411)
Net income (loss) attributable to controlling interest:
Basic (in dollars per share)	$ 0.13	$ 0.31	$ 1.81	$ (0.58)
Diluted (in dollars per share)	$ 0.13	$ 0.30	$ 1.79	$ (0.58)
Weighted average number of common shares outstanding:
Basic (in shares)	22,523	22,923	22,510	23,009
Diluted (in shares)	22,684	23,084	22,666	23,009
Dividends declared per common share (in dollars per share)	$ 0.11	$ 0.11	$ 0.33	$ 0.31