Business Segments - Summary of company's operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	$ 11,325	$ 9,465	$ 30,044	$ 28,708
Cost of goods sold, exclusive of depreciation and amortization	(8,036)	(7,043)	(22,706)	(20,888)
Selling, general and administrative	(2,080)	(1,658)	(5,523)	(4,815)
Depreciation and amortization	(209)	(198)	(637)	(610)
Interest expense	(18)	(18)	(56)	(54)
Other income, net	6	9	11	19
Income (loss) before income tax provision (benefits)	988	557	1,133	2,360
Income tax provision (benefits)	317	191	331	732
Net income (loss)	671	366	802	1,628
Capital expenditures			1,401	786
Operating Segments
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	11,325	9,465	30,044	28,708
Cost of goods sold, exclusive of depreciation and amortization	(8,036)	(7,043)	(22,706)	(20,888)
Selling, general and administrative	(2,080)	(1,658)	(5,523)	(4,815)
Depreciation and amortization	(209)	(198)	(637)	(610)
Interest expense	(18)	(18)	(56)	(54)
Other income, net	6	9	11	19
Income (loss) before income tax provision (benefits)	988	557	1,133	2,360
Income tax provision (benefits)	317	191	331	732
Net income (loss)	671	366	802	1,628
Capital expenditures	1,330	85	1,901	786
Operating Segments | Advanced Technology Group ("ATG")
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	8,918	7,658	23,968	23,023
Cost of goods sold, exclusive of depreciation and amortization	(6,062)	(5,418)	(17,407)	(16,060)
Selling, general and administrative	(1,640)	(1,240)	(4,133)	(3,477)
Depreciation and amortization	(143)	(137)	(443)	(412)
Interest expense	(9)	(11)	(32)	(32)
Other income, net	5	9	9	19
Income (loss) before income tax provision (benefits)	1,069	861	1,962	3,061
Income tax provision (benefits)	341	289	580	949
Net income (loss)	728	572	1,382	2,112
Capital expenditures	1,282	70	1,777	613
Operating Segments | CPG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	2,407	1,807	6,076	5,685
Cost of goods sold, exclusive of depreciation and amortization	(1,974)	(1,625)	(5,299)	(4,828)
Selling, general and administrative	(440)	(418)	(1,390)	(1,338)
Depreciation and amortization	(66)	(61)	(194)	(198)
Interest expense	(9)	(7)	(24)	(22)
Other income, net	1	0	2	0
Income (loss) before income tax provision (benefits)	(81)	(304)	(829)	(701)
Income tax provision (benefits)	(24)	(98)	(249)	(217)
Net income (loss)	(57)	(206)	(580)	(484)
Capital expenditures	$ 48	$ 15	$ 124	$ 173