CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Net sales	$ 975,595	$ 932,998	$ 936,273
Cost of sales	760,279	725,879	728,322
Gross profit	215,316	207,119	207,951
Selling, general and administrative expenses	141,490	133,337	136,323
Research and development expenses	22,129	18,101	20,520
Income from operations	51,697	55,681	51,108
Other income:
Interest expense	720	423	339
Interest income	1,422	1,047	1,145
Other income (expense), net	1,207	1,937	1,783
Income from continuing operations before income taxes	53,606	58,242	53,697
Income taxes on continuing operations	19,400	19,028	19,487
Net income from continuing operations	34,206	39,214	34,210
Discontinued operations:
Income from discontinued operations, net of tax	0	0	3,401
Gain on sale of subsidiary, net of tax	0	0	3,378
Income from discontinued operations	0	0	6,779
Net income	34,206	39,214	40,989
Net income (loss) attributable to non-controlling interest	(252)	172	161
Net income attributable to controlling interest	$ 34,458	$ 39,042	$ 40,828
Net income attributable to controlling interest from continuing operations:
Basic (in dollars per share)	$ 1.51	$ 1.72	$ 1.50
Diluted (in dollars per share)	$ 1.49	$ 1.69	$ 1.48
Income from discontinued operations:
Basic (in dollars per share)	$ 0	$ 0	$ 0.30
Diluted (in dollars per share)	$ 0	$ 0	$ 0.29
Net income attributable to controlling interest:
Basic (in dollars per share)	$ 1.51	$ 1.72	$ 1.80
Diluted (in dollars per share)	$ 1.49	$ 1.69	$ 1.77
Weighted average number of common shares outstanding:
Basic (in shares)	22,819	22,749	22,680
Diluted (in shares)	23,105	23,081	23,051