Condensed Consolidated Statements of Income (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Consolidated Statements of Income (unaudited) [Abstract]
Net sales	$ 325,453	$ 318,401
Cost of sales	247,448	242,630
Gross profit	78,005	75,771
Selling, general, administrative and engineering expenses	52,078	53,121
Income from operations	25,927	22,650
Interest expense	150	265
Other income, net of expenses	461	512
Income from operations before income taxes	26,238	22,897
Income taxes	6,022	7,817
Net income	20,216	15,080
Net loss attributable to non-controlling interest	(51)	(40)
Net income attributable to controlling interest	$ 20,267	$ 15,120
Net income attributable to controlling interest:
Basic (in dollars per share)	$ 0.88	$ 0.66
Diluted (in dollars per share)	$ 0.87	$ 0.65
Weighted average number of common shares outstanding:
Basic (in shares)	23,045	23,013
Diluted (in shares)	23,236	23,176
Dividends declared per common share (in dollars per share)	$ 0.10	$ 0.10