CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Net sales	$ 1,147,431	$ 983,157	$ 975,595
Cost of sales	882,162	764,314	760,279
Gross profit	265,269	218,843	215,316
Selling, general and administrative expenses	153,145	145,180	141,490
Research and development expenses	24,969	23,676	22,129
Income from operations	87,155	49,987	51,697
Other income:
Interest expense	1,395	1,611	720
Interest income	806	542	1,422
Other income (expense), net	529	3,055	1,207
Income before income taxes	87,095	51,973	53,606
Income taxes	32,107	20,007	19,400
Net income	54,988	31,966	34,206
Net loss attributable to non-controlling interest	(171)	(831)	(252)
Net income attributable to controlling interest	$ 55,159	$ 32,797	$ 34,458
Net income attributable to controlling interest:
Basic (in dollars per share)	$ 2.40	$ 1.43	$ 1.51
Diluted (in dollars per share)	$ 2.38	$ 1.42	$ 1.49
Weighted average number of common shares outstanding:
Basic (in shares)	22,992	22,934	22,819
Diluted (in shares)	23,142	23,120	23,105