Condensed Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Sales (Note 2)	$ 90,685	$ 95,031	$ 270,282	$ 271,239
Cost of sales	71,895	75,432	215,310	213,248
Gross profit	18,790	19,599	54,972	57,991
Selling, general and administrative expenses	7,186	7,584	23,981	24,455
Operating income	11,604	12,015	30,991	33,536
Interest expense, net	(364)	(334)	(937)	(830)
Income before income taxes	11,240	11,681	30,054	32,706
Income tax expense (Note 4)	3,025	2,673	4,208	7,244
Net income	8,215	9,008	25,846	25,462
Income attributable to participating securities	54	174	171	491
Net income attributable to common shareholders and used in earnings per share calculation	$ 8,161	$ 8,834	$ 25,675	$ 24,971
Share information:
Basic and diluted weighted average common shares (in shares)	17,027,068	16,872,091	17,006,226	16,861,700
Basic and diluted earnings per common share (in dollars per share)	$ 0.48	$ 0.52	$ 1.51	$ 1.48