Business Segments - Summary of company's operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	$ 47,857	$ 41,444
Cost of goods sold, inclusive of depreciation	(35,772)	(31,447)
Gross margin	12,085	9,997
Selling, general and administrative	(7,743)	(7,845)
Interest	(107)	(77)
Total costs and expenses	(7,850)	(7,922)
Income (loss) before income tax provision	4,235	2,075
Income tax provision (benefits)	737	758
Net income/(loss)	3,498	1,317
Total assets	41,685	37,986
Capital expenditures	1,866	2,176
Operating Segments
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	47,857	41,444
Cost of goods sold, inclusive of depreciation	(35,772)	(31,447)
Gross margin	$ 12,085	$ 9,997
Gross margin %	25.30%	24.10%
Selling, general and administrative	$ (7,743)	$ (7,845)
Interest	(107)	(77)
Income (loss) before income tax provision	4,235	2,075
Income tax provision (benefits)	737	758
Net income/(loss)	3,498	1,317
Total assets	41,685	37,986
Capital expenditures	1,866	2,176
Operating Segments | ATG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	40,415	32,414
Cost of goods sold, inclusive of depreciation	(28,587)	(23,683)
Gross margin	$ 11,828	$ 8,731
Gross margin %	29.30%	26.90%
Selling, general and administrative	$ (5,423)	$ (5,992)
Interest	(73)	(45)
Income (loss) before income tax provision	6,332	2,694
Income tax provision (benefits)	1,102	984
Net income/(loss)	5,230	1,710
Total assets	31,647	26,331
Capital expenditures	1,689	1,998
Operating Segments | CPG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	7,442	9,030
Cost of goods sold, inclusive of depreciation	(7,185)	(7,764)
Gross margin	$ 258	$ 1,266
Gross margin %	3.50%	14.00%
Selling, general and administrative	$ (2,320)	$ (1,853)
Interest	(34)	(32)
Income (loss) before income tax provision	(2,097)	(619)
Income tax provision (benefits)	(365)	(226)
Net income/(loss)	(1,732)	(393)
Total assets	10,038	11,655
Capital expenditures	$ 177	$ 178