Condensed Consolidated Statements of Income - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Net sales		$ 95,031	$ 86,333	$ 271,239	$ 259,255
Cost of sales	[1]	75,432	67,708	213,248	202,764
Gross profit		19,599	18,625	57,991	56,491
Selling, general and administrative expenses		7,584	8,154	24,455	24,114
Operating income		12,015	10,471	33,536	32,377
Gain on sale of equity method investment		0	11,381	0	11,381
Equity method investment loss		0	0	0	(348)
Interest expense, net		(334)	(224)	(830)	(934)
Income before income taxes		11,681	21,628	32,706	42,476
Income tax expense		2,673	7,491	7,244	13,292
Net income		9,008	14,137	25,462	29,184
Income attributable to participating securities		174	414	491	806
Net income attributable to common shareholders and used in EPS calculation		$ 8,834	$ 13,723	$ 24,971	$ 28,378
Share information:
Basic and Diluted weighted average common shares (in shares)		16,872,091	16,751,346	16,861,700	16,735,378
Basic and diluted earnings per common share (in dollars per share)		$ 0.52	$ 0.82	$ 1.48	$ 1.70
Dividends and dividend equivalents per common share (in dollars per share)		$ 0.08	$ 0.89	$ 0.24	$ 0.97

[1] Includes related party purchases of $0 and $18,425 for year to date September 30, 2018 and 2017, respectively. There were no related party purchases for the quarters ended September 30, 2018 and 2017.