Condensed Consolidated Statements of Income (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Condensed Consolidated Statements of Income (unaudited) [Abstract]
Net sales	$ 294,394	$ 268,042	$ 573,116	$ 556,791
Cost of sales	220,942	205,809	427,708	428,512
Gross profit	73,452	62,233	145,408	128,279
Selling, general, administrative and engineering expenses	44,961	43,308	88,766	87,112
Income from operations	28,491	18,925	56,642	41,167
Interest expense	326	420	793	717
Other income, net of expenses	276	273	819	2,033
Income from operations before income taxes	28,441	18,778	56,668	42,483
Income taxes	10,300	7,120	20,849	15,909
Net income	18,141	11,658	35,819	26,574
Net loss attributable to non-controlling interest	(51)	(147)	(116)	(335)
Net income attributable to controlling interest	$ 18,192	$ 11,805	$ 35,935	$ 26,909
Net income attributable to controlling interest:
Basic (in dollars per share)	$ 0.79	$ 0.51	$ 1.56	$ 1.17
Diluted (in dollars per share)	$ 0.79	$ 0.51	$ 1.55	$ 1.16
Weighted average number of common shares outstanding:
Basic (in shares)	22,999	22,942	22,982	22,923
Diluted (in shares)	23,135	23,119	23,135	23,117
Dividends declared per common share (in dollars per share)	$ 0.10	$ 0.10	$ 0.20	$ 0.20