CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales	$ 209,938	$ 197,886	$ 186,413	$ 191,660	$ 178,030	$ 180,041	$ 174,879	$ 165,487	$ 785,897	$ 698,437	$ 566,852
Cost of sales									633,252	535,078	428,048
Gross profit	41,872	35,139	36,127	39,507	39,480	40,054	43,327	40,498	152,645	163,359	138,804
Selling, product development and administrative expenses									103,457	97,159	83,359
Operating income									49,188	66,200	55,445
Interest expense									6,212	2,720	1,068
Other (income) expense, net									(289)	2,161	(562)
Income before income taxes									43,265	61,319	54,939
Income tax expense									8,453	11,974	17,821
(Income) loss from equity method investment									(132)	28	(69)
Net income	$ 7,184	$ 6,256	$ 10,450	$ 11,054	$ 13,848	$ 10,675	$ 13,125	$ 11,669	$ 34,944	$ 49,317	$ 37,187
Earnings per common share:
Basic (USD per share)	$ 0.42	$ 0.36	$ 0.61	$ 0.64	$ 0.81	$ 0.63	$ 0.77	$ 0.69	$ 2.03	$ 2.89	$ 2.20
Diluted (USD per share)	$ 0.42	$ 0.36	$ 0.60	$ 0.64	$ 0.80	$ 0.62	$ 0.76	$ 0.68	$ 2.02	$ 2.85	$ 2.16
Weighted average common shares outstanding (shares)									17,204	17,045	16,871
Weighted average common shares and equivalents outstanding (shares)									17,330	17,317	17,241