Condensed Consolidated Statements of Income (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Condensed Consolidated Statements of Income (unaudited) [Abstract]
Net sales	$ 211,350	$ 220,157	$ 768,141	$ 736,086
Cost of sales	166,212	176,896	594,724	573,890
Gross profit	45,138	43,261	173,417	162,196
Selling, general, administrative and engineering expenses	41,023	38,867	128,136	122,539
Income from operations	4,115	4,394	45,281	39,657
Interest expense	505	193	1,222	375
Other income, net of expenses	510	710	2,543	2,254
Income from operations before income taxes	4,120	4,911	46,602	41,536
Income taxes	2,162	3,145	18,070	15,734
Net income	1,958	1,766	28,532	25,802
Net loss attributable to non-controlling interest	(334)	(150)	(669)	(156)
Net income attributable to controlling interest	$ 2,292	$ 1,916	$ 29,201	$ 25,958
Net income attributable to controlling interest
Basic (in dollars per share)	$ 0.10	$ 0.08	$ 1.27	$ 1.14
Diluted (in dollars per share)	$ 0.10	$ 0.08	$ 1.26	$ 1.12
Weighted average number of common shares outstanding:
Basic (in shares)	22,943	22,830	22,930	22,813
Diluted (in shares)	23,121	23,109	23,118	23,103
Dividends declared per common share (in dollars per share)	$ 0.10	$ 0.10	$ 0.30	$ 0.30