Business Segments - Summary of company's operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	$ 41,444	$ 38,587
Cost of goods sold, exclusive of depreciation and amortization	(30,610)	(28,564)
Selling, general and administrative	(7,807)	(6,668)
Depreciation and amortization	(885)	(823)
Interest expense	(77)	(73)
Other income, net	10	11
Income (loss) before income tax provision (benefits)	2,075	2,470
Income tax provision (benefits)	758	717
Net income (loss)	1,317	1,753
Total assets	37,986	35,620
Capital expenditures	2,176	991
Operating Segments
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	41,444	38,587
Cost of goods sold, exclusive of depreciation and amortization	(30,610)	(28,564)
Selling, general and administrative	(7,807)	(6,668)
Depreciation and amortization	(885)	(823)
Interest expense	(77)	(73)
Other income, net	10	11
Income (loss) before income tax provision (benefits)	2,075	2,470
Income tax provision (benefits)	758	717
Net income (loss)	1,317	1,753
Total assets	37,986	35,620
Capital expenditures	2,176	991
Operating Segments | ATG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	32,414	31,059
Cost of goods sold, exclusive of depreciation and amortization	(23,094)	(21,919)
Selling, general and administrative	(5,965)	(4,808)
Depreciation and amortization	(623)	(559)
Interest expense	(45)	(43)
Other income, net	7	11
Income (loss) before income tax provision (benefits)	2,694	3,741
Income tax provision (benefits)	984	1,086
Net income (loss)	1,710	2,655
Total assets	26,331	24,037
Capital expenditures	1,998	772
Operating Segments | CPG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	9,030	7,528
Cost of goods sold, exclusive of depreciation and amortization	(7,516)	(6,645)
Selling, general and administrative	(1,842)	(1,860)
Depreciation and amortization	(262)	(264)
Interest expense	(32)	(30)
Other income, net	3	0
Income (loss) before income tax provision (benefits)	(619)	(1,271)
Income tax provision (benefits)	(226)	(369)
Net income (loss)	(393)	(902)
Total assets	11,655	11,583
Capital expenditures	$ 178	$ 219