Condensed Consolidated Statements of Income (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Condensed Consolidated Statements of Income (unaudited) [Abstract]
Net sales	$ 247,752	$ 211,350	$ 820,868	$ 768,141
Cost of sales	192,363	166,212	620,071	594,724
Gross profit	55,389	45,138	200,797	173,417
Selling, general, administrative and engineering expenses	43,950	41,023	132,716	128,136
Income from operations	11,439	4,115	68,081	45,281
Interest expense	264	505	1,057	1,222
Other income, net of expenses	505	510	1,324	2,543
Income from operations before income taxes	11,680	4,120	68,348	46,602
Income taxes	4,845	2,162	25,694	18,070
Net income	6,835	1,958	42,654	28,532
Net loss attributable to non-controlling interest	(3)	(334)	(119)	(669)
Net income attributable to controlling interest	$ 6,838	$ 2,292	$ 42,773	$ 29,201
Net income attributable to controlling interest:
Basic (in dollars per share)	$ 0.30	$ 0.10	$ 1.86	$ 1.27
Diluted (in dollars per share)	$ 0.30	$ 0.10	$ 1.85	$ 1.26
Weighted average number of common shares outstanding:
Basic (in shares)	23,001	22,943	22,989	22,930
Diluted (in shares)	23,145	23,121	23,138	23,118
Dividends declared per common share (in dollars per share)	$ 0.10	$ 0.10	$ 0.30	$ 0.30