Condensed Consolidated Statements of Income (unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Condensed Consolidated Statements of Income (unaudited) [Abstract]
Net sales	$ 213,177	$ 218,391	$ 709,136	$ 708,633
Cost of sales	167,390	171,094	549,341	548,993
Gross profit	45,787	47,297	159,795	159,640
Selling, general, administrative and engineering expenses	36,635	38,411	114,797	117,010
Income from operations	9,152	8,886	44,998	42,630
Interest expense	269	152	417	240
Other income, net of expenses	1,100	836	1,885	2,305
Income from continuing operations before income taxes	9,983	9,570	46,466	44,695
Income taxes on continuing operations	3,456	2,937	15,536	16,028
Net income from continuing operations	6,527	6,633	30,930	28,667
Income from discontinued operations, net of tax	0	318	0	1,400
Net income	6,527	6,951	30,930	30,067
Net income attributable to non-controlling interest	13	48	154	124
Net income attributable to controlling interest	$ 6,514	$ 6,903	$ 30,776	$ 29,943
Net income attributable to controlling interest from continuing operations:
Basic (in dollars per share)	$ 0.29	$ 0.29	$ 1.35	$ 1.26
Diluted (in dollars per share)	$ 0.28	$ 0.29	$ 1.33	$ 1.24
Income from discontinued operations, net of tax
Basic (in dollars per share)	$ 0	$ 0.01	$ 0	$ 0.06
Diluted (in dollars per share)	$ 0	$ 0.01	$ 0	$ 0.06
Net income attributable to controlling interest:
Basic (in dollars per share)	$ 0.29	$ 0.30	$ 1.35	$ 1.32
Diluted (in dollars per share)	$ 0.28	$ 0.30	$ 1.33	$ 1.30
Weighted average number of common shares outstanding:
Basic (in shares)	22,756	22,691	22,744	22,675
Diluted (in shares)	23,082	23,053	23,077	23,049
Dividends declared per common share	$ 0.10	$ 0	$ 0.20	$ 0