Condensed Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Sales (Note 2)	$ 90,501	$ 88,252	$ 179,597	$ 176,208
Cost of sales	70,979	68,811	143,415	137,816
Gross profit	19,522	19,441	36,182	38,392
Selling, general and administrative expenses	8,648	8,309	16,795	16,871
Operating income	10,874	11,132	19,387	21,521
Interest expense, net	(321)	(289)	(573)	(496)
Income before income taxes	10,553	10,843	18,814	21,025
Income tax expense (Note 4)	2,642	3,316	1,183	4,571
Net income	7,911	7,527	17,631	16,454
Income attributable to participating securities	51	148	117	323
Net income attributable to common shareholders and used in earnings per share calculation	$ 7,860	$ 7,379	$ 17,514	$ 16,131
Share information:
Basic and diluted weighted average common shares (in shares)	17,021,599	16,869,481	16,994,864	16,856,423
Basic and diluted earnings per common share (in dollars per share)	$ 0.46	$ 0.44	$ 1.03	$ 0.96