Business Segments - Summary of company's operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	$ 9,103	$ 8,947
Cost of goods sold, exclusive of depreciation and amortization	(7,042)	(6,716)
Selling, general and administrative	(1,832)	(1,636)
Depreciation and amortization	(210)	(207)
Interest expense	(23)	(19)
Income (loss) before income tax provision (benefit)	(4)	369
Income tax provision (benefit)	(30)	111
Net income (loss)	26	258
Capital expenditures	183	178
Operating Segments
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	9,103	8,947
Cost of goods sold, exclusive of depreciation and amortization	(7,042)	(6,716)
Selling, general and administrative	(1,832)	(1,636)
Depreciation and amortization	(210)	(207)
Interest expense	(23)	(19)
Income (loss) before income tax provision (benefit)	(4)	369
Income tax provision (benefit)	30	111
Net income (loss)	26	258
Capital expenditures	183	178
Operating Segments | ATG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	7,420	7,110
Cost of goods sold, exclusive of depreciation and amortization	(5,464)	(5,169)
Selling, general and administrative	(1,327)	(1,132)
Depreciation and amortization	(146)	(140)
Interest expense	(15)	(11)
Income (loss) before income tax provision (benefit)	468	658
Income tax provision (benefit)	112	198
Net income (loss)	356	460
Capital expenditures	181	139
Operating Segments | CPG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	1,683	1,837
Cost of goods sold, exclusive of depreciation and amortization	(1,578)	(1,547)
Selling, general and administrative	(505)	(504)
Depreciation and amortization	(64)	(67)
Interest expense	(8)	(8)
Income (loss) before income tax provision (benefit)	(472)	(289)
Income tax provision (benefit)	(142)	(87)
Net income (loss)	(330)	(202)
Capital expenditures	$ 2	$ 39