Business Segments - Summary of company's operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	$ 9,616	$ 10,296	$ 18,719	$ 19,243
Cost of goods sold, exclusive of depreciation and amortization	(7,628)	(7,129)	(14,670)	(13,845)
Selling, general and administrative	(1,611)	(1,521)	(3,443)	(3,157)
Depreciation and amortization	(218)	(205)	(428)	(412)
Interest expense	(15)	(17)	(38)	(36)
Other income, net	5	10	5	10
Income (loss) before income tax provision (benefits)	149	1,434	145	1,803
Income tax provision (benefits)	44	430	14	541
Net income (loss)	105	1,004	131	1,262
Capital expenditures			571	701
Operating Segments
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	9,616	10,296	18,719	19,243
Cost of goods sold, exclusive of depreciation and amortization	(7,628)	(7,129)	(14,670)	(13,845)
Selling, general and administrative	(1,611)	(1,521)	(3,443)	(3,157)
Depreciation and amortization	(218)	(205)	(428)	(412)
Interest expense	(15)	(17)	(38)	(36)
Other income, net	5	10	5	10
Income (loss) before income tax provision (benefits)	149	1,434	145	1,803
Income tax provision (benefits)	44	430	14	541
Net income (loss)	105	1,004	131	1,262
Capital expenditures	388	523	571	701
Operating Segments | Advanced Technology Group ("ATG")
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	7,630	8,256	15,050	15,365
Cost of goods sold, exclusive of depreciation and amortization	(5,881)	(5,474)	(11,345)	(10,643)
Selling, general and administrative	(1,166)	(1,105)	(2,493)	(2,236)
Depreciation and amortization	(154)	(136)	(300)	(276)
Interest expense	(8)	(10)	(23)	(21)
Other income, net	4	10	4	10
Income (loss) before income tax provision (benefits)	425	1,541	893	2,199
Income tax provision (benefits)	127	462	239	660
Net income (loss)	298	1,079	654	1,539
Capital expenditures	314	404	495	543
Operating Segments | CPG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	1,986	2,040	3,669	3,878
Cost of goods sold, exclusive of depreciation and amortization	(1,747)	(1,655)	(3,325)	(3,202)
Selling, general and administrative	(445)	(416)	(950)	(921)
Depreciation and amortization	(64)	(69)	(128)	(136)
Interest expense	(7)	(7)	(15)	(15)
Other income, net	1		1
Income (loss) before income tax provision (benefits)	(276)	(107)	(748)	(396)
Income tax provision (benefits)	(83)	(32)	(225)	(119)
Net income (loss)	(193)	(75)	(523)	(277)
Capital expenditures	$ 74	$ 119	$ 76	$ 158