Business Segments - Summary of company's operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	$ 49,844	$ 55,272
Cost of goods sold, inclusive of depreciation	(41,604)	(43,146)
Gross margin (loss)	8,240	12,126
Selling, general and administrative	(7,998)	(8,883)
Interest	(180)	(125)
Total costs and expenses	(8,178)	(9,008)
Income (loss) before income tax provision	62	3,118
Income tax provision (benefit)	(38)	671
Net income/(loss)	100	2,447
Total Assets	50,328	49,470
Capital expenditures	729	2,271
Operating Segments
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	49,844	55,272
Cost of goods sold, inclusive of depreciation	(41,604)	(43,146)
Gross margin (loss)	$ 8,240	$ 12,126
Gross margin %	16.50%	21.90%
Selling, general and administrative	$ (7,998)	$ (8,883)
Interest	(180)	(125)
Total costs and expenses	(49,782)	(52,154)
Income (loss) before income tax provision	62	3,118
Income tax provision (benefit)	(38)	671
Net income/(loss)	100	2,447
Total Assets	50,328	49,470
Capital expenditures	729	2,271
Operating Segments | ATG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	40,782	48,519
Cost of goods sold, inclusive of depreciation	(33,440)	(35,632)
Gross margin (loss)	$ 7,342	$ 12,887
Gross margin %	18.00%	26.60%
Selling, general and administrative	$ (6,245)	$ (6,158)
Interest	(170)	(97)
Total costs and expenses	(39,855)	(41,887)
Income (loss) before income tax provision	927	6,633
Income tax provision (benefit)	492	1,428
Net income/(loss)	435	5,205
Total Assets	40,826	39,989
Capital expenditures	661	1,990
Operating Segments | CPG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	9,062	6,753
Cost of goods sold, inclusive of depreciation	(8,164)	(7,514)
Gross margin (loss)	$ 898	$ (761)
Gross margin %	9.90%	(11.30%)
Selling, general and administrative	$ (1,753)	$ (2,725)
Interest	(10)	(28)
Total costs and expenses	(9,927)	(10,268)
Income (loss) before income tax provision	(865)	(3,515)
Income tax provision (benefit)	(530)	(757)
Net income/(loss)	(335)	(2,758)
Total Assets	9,502	9,481
Capital expenditures	$ 68	$ 281