CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Net sales	$ 936,273	$ 908,641	$ 737,084
Cost of sales	729,334	698,149	562,499
Gross profit	206,939	210,492	174,585
Selling, general and administrative expenses	136,323	132,371	109,354
Research and development expenses	20,520	20,764	15,987
Income from operations	50,096	57,357	49,244
Other income:
Interest expense	339	190	339
Interest income	1,145	883	953
Other income (expense), net	1,783	1,082	632
Income from continuing operations before income taxes	52,685	59,132	50,490
Income taxes on continuing operations	19,096	19,337	16,649
Net income from continuing operations	33,589	39,795	33,841
Discontinued operations:
Income (loss) from discontinued operations, net of tax	3,401	225	(1,269)
Gain on sale of subsidiary, net of tax	3,378	0	0
Income (loss) from discontinued operations	6,779	225	(1,269)
Net income	40,368	40,020	32,572
Net income attributable to non-controlling interest	161	102	142
Net income attributable to controlling interest	$ 40,207	$ 39,918	$ 32,430
Net income attributable to controlling interest from continuing operations:
Basic (in dollars per share)	$ 1.47	$ 1.76	$ 1.50
Diluted (in dollars per share)	$ 1.45	$ 1.73	$ 1.48
Income (loss) from discontinued operations:
Basic (in dollars per share)	$ 0.30	$ 0.01	$ (0.06)
Diluted (in dollars per share)	$ 0.29	$ 0.01	$ (0.06)
Net income attributable to controlling interest:
Basic (in dollars per share)	$ 1.77	$ 1.77	$ 1.44
Diluted (in dollars per share)	$ 1.74	$ 1.74	$ 1.42
Weighted average number of common shares outstanding:
Basic (in shares)	22,680	22,589	22,517
Diluted (in shares)	23,051	22,984	22,830