Condensed Consolidated Statements of Income (unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Condensed Consolidated Statements of Income (unaudited) [Abstract]
Net sales	$ 248,127	$ 238,275	$ 495,960	$ 490,243
Cost of sales	192,685	185,214	381,951	378,586
Gross profit	55,442	53,061	114,009	111,657
Selling, general, administrative and engineering expenses	37,795	38,456	78,162	78,599
Income from operations	17,647	14,605	35,847	33,058
Interest expense	76	42	147	88
Other income, net of expenses	32	621	784	1,469
Income from continuing operations before income taxes	17,603	15,184	36,484	34,439
Income taxes on continuing operations	6,450	5,603	12,081	12,834
Net income from continuing operations	11,153	9,581	24,403	21,605
Income from discontinued operations, net of tax	0	848	0	1,082
Net income	11,153	10,429	24,403	22,687
Net income attributable to non-controlling interest	61	63	140	76
Net income attributable to controlling interest	$ 11,092	$ 10,366	$ 24,263	$ 22,611
Net income attributable to controlling interest from continuing operations:
Basic (in dollars per share)	$ 0.49	$ 0.42	$ 1.07	$ 0.95
Diluted (in dollars per share)	$ 0.48	$ 0.41	$ 1.05	$ 0.93
Income from discontinued operations, net of tax
Basic (in dollars per share)	$ 0	$ 0.04	$ 0	$ 0.05
Diluted (in dollars per share)	$ 0	$ 0.04	$ 0	$ 0.05
Net income attributable to controlling interest:
Basic (in dollars per share)	$ 0.49	$ 0.46	$ 1.07	$ 1.00
Diluted (in dollars per share)	$ 0.48	$ 0.45	$ 1.05	$ 0.98
Weighted average number of common shares outstanding:
Basic (in shares)	22,752	22,691	22,738	22,667
Diluted (in shares)	23,069	23,041	23,075	23,047
Dividends declared per common share	$ 0.10	$ 0	$ 0.10	$ 0