CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Net sales	$ 983,157	$ 975,595	$ 932,998
Cost of sales	764,314	760,279	725,879
Gross profit	218,843	215,316	207,119
Selling, general and administrative expenses	145,180	141,490	133,337
Research and development expenses	23,676	22,129	18,101
Income from operations	49,987	51,697	55,681
Other income:
Interest expense	1,611	720	423
Interest income	542	1,422	1,047
Other income (expense), net	3,055	1,207	1,937
Income before income taxes	51,973	53,606	58,242
Income taxes	20,007	19,400	19,028
Net income	31,966	34,206	39,214
Net income (loss) attributable to non-controlling interest	(831)	(252)	172
Net income attributable to controlling interest	$ 32,797	$ 34,458	$ 39,042
Net income attributable to controlling interest:
Basic (in dollars per share)	$ 1.43	$ 1.51	$ 1.72
Diluted (in dollars per share)	$ 1.42	$ 1.49	$ 1.69
Weighted average number of common shares outstanding:
Basic (in shares)	22,934	22,819	22,749
Diluted (in shares)	23,120	23,105	23,081