CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 698,437	$ 566,852	$ 524,505
Cost of sales	535,375	428,310	402,008
Gross profit	163,062	138,542	122,497
Selling, product development and administrative expenses	97,635	83,750	70,020
Operating income	65,427	54,792	52,477
Gain on sale of business	0	0	(18,647)
Interest expense	2,720	1,068	755
Other expense (income), net	1,388	(1,215)	(654)
Income before income taxes	61,319	54,939	71,023
Income tax expense	11,974	17,821	24,764
Loss (income) from equity method investment	28	(69)	0
Net income	$ 49,317	$ 37,187	$ 46,259
Earnings per common share:
Basic (USD per share)	$ 2.89	$ 2.20	$ 2.76
Diluted (USD per share)	$ 2.85	$ 2.16	$ 2.71
Weighted average common shares outstanding (shares)	17,045	16,871	16,746
Weighted average common shares and equivalents outstanding (shares)	17,317	17,241	17,084