Condensed Consolidated Statements of Income - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net sales		$ 87,956	$ 87,169
Cost of sales	[1]	69,005	68,128
Gross profit		18,951	19,041
Selling, general and administrative expenses (SG&A)		8,562	7,649
Operating income		10,389	11,392
Equity method investment earnings		0	471
Interest expense, net		(207)	(331)
Income before income taxes		10,182	11,532
Income tax expense		1,255	2,854
Net income		8,927	8,678
Income attributable to participating securities		175	250
Net income attributable to common shareholders and used in EPS calculation		$ 8,752	$ 8,428
Share information:
Basic and diluted weighted average common shares (in shares)		16,843,255	16,712,578
Basic and diluted earnings per common share (in dollars per share)		$ 0.52	$ 0.50
Dividends and dividend equivalents per common share (in dollars per share)		$ 0.08	$ 0.04

[1] Includes related party purchases of $0 and $9,245 for the quarters ended March 31, 2018 and 2017, respectively.