Condensed Consolidated Statements of Income (unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Condensed Consolidated Statements of Income (unaudited) [Abstract]
Net sales	$ 220,157	$ 213,177	$ 736,086	$ 709,136
Cost of sales	176,896	167,390	573,890	549,341
Gross profit	43,261	45,787	162,196	159,795
Selling, general, administrative and engineering expenses	38,867	36,635	122,539	114,797
Income from operations	4,394	9,152	39,657	44,998
Interest expense	193	269	375	417
Other income, net of expenses	710	1,100	2,254	1,885
Income from operations before income taxes	4,911	9,983	41,536	46,466
Income taxes	3,145	3,456	15,734	15,536
Net income	1,766	6,527	25,802	30,930
Net income (loss) attributable to non-controlling interest	(150)	13	(156)	154
Net income attributable to controlling interest	$ 1,916	$ 6,514	$ 25,958	$ 30,776
Net income attributable to controlling interest
Basic (in dollars per share)	$ 0.08	$ 0.29	$ 1.14	$ 1.35
Diluted (in dollars per share)	$ 0.08	$ 0.28	$ 1.12	$ 1.33
Weighted average number of common shares outstanding:
Basic (in shares)	22,830	22,756	22,813	22,744
Diluted (in shares)	23,109	23,082	23,103	23,077
Dividends declared per common share (in dollars per share)	$ 0.10	$ 0.10	$ 0.30	$ 0.20