Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Sales	$ 92,463	$ 90,685	$ 90,501	$ 89,096	$ 104,850	$ 95,031	$ 88,252	$ 87,956	$ 362,745	$ 376,089	$ 347,448
Cost of sales	70,903	71,895	70,979	72,436	79,242	75,432	68,811	69,005	286,213	292,490	271,432
Gross profit	21,560	18,790	19,522	16,660	25,608	19,599	19,441	18,951	76,532	83,599	76,016
SG&A expenses	5,309	7,186	8,648	8,147	8,996	7,584	8,309	8,562	29,290	33,451	33,107
Operating income	16,251	11,604	10,874	8,513	16,612	12,015	11,132	10,389	47,242	50,148	42,909
Interest expense, net	(368)	(364)	(321)	(252)	(338)	(334)	(289)	(207)	(1,305)	(1,168)	(1,184)
Income before income taxes	15,883	11,240	10,553	8,261	16,274	11,681	10,843	10,182	45,937	48,980	52,758
Income tax expense (benefit)	2,936	3,025	2,642	(1,459)	4,452	2,673	3,316	1,255	7,144	11,696	10,935
Net income	$ 12,947	$ 8,215	$ 7,911	$ 9,720	$ 11,822	$ 9,008	$ 7,527	$ 8,927	$ 38,793	$ 37,284	$ 41,823
Basic and diluted EPS data (in dollars per share)	$ 0.76	$ 0.48	$ 0.46	$ 0.57	$ 0.69	$ 0.52	$ 0.44	$ 0.52	$ 2.27	$ 2.17	$ 2.44