CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Net sales	$ 197,886	$ 180,041	$ 575,959	$ 520,407
Cost of sales	162,747	139,987	465,186	396,528
Gross profit	35,139	40,054	110,773	123,879
Selling, product development and administrative expenses	25,406	24,700	74,755	73,339
Operating income	9,733	15,354	36,018	50,540
Interest expense	1,505	705	2,617	2,106
Other (income) expense, net	(40)	601	(93)	1,727
Income before income taxes	8,268	14,048	33,494	46,707
Income tax expense	2,076	3,404	5,854	11,201
Income from equity method investment	(64)	(31)	(120)	37
Net income	$ 6,256	$ 10,675	$ 27,760	$ 35,469
Earnings per share:
Basic (USD per share)	$ 0.36	$ 0.63	$ 1.61	$ 2.08
Diluted (USD per share)	$ 0.36	$ 0.62	$ 1.60	$ 2.05
Weighted average number of common shares outstanding:
Basic (shares)	17,216	17,055	17,189	17,028
Diluted (shares)	17,349	17,267	17,339	17,270