Business Segments - Summary of company's operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	$ 15,448	$ 12,003
Cost of goods sold, inclusive of depreciation	(10,736)	(9,930)
Gross margin (loss)	4,712	2,073
Selling, general and administrative	(2,268)	(1,927)
Interest	(42)	(27)
Total costs and expenses	(2,310)	(1,954)
Income/(loss) before income tax provision	2,402	119
Income tax provision (benefit)	504	21
Net income/(loss)	1,898	98
Capital expenditures	413	642
Operating Segments
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	15,448	12,003
Cost of goods sold, inclusive of depreciation	(10,736)	(9,930)
Gross margin (loss)	$ 4,712	$ 2,073
Gross margin %	30.50%	17.30%
Selling, general and administrative	$ (2,268)	$ (1,927)
Interest	(42)	(27)
Total costs and expenses	(13,046)	(11,884)
Income/(loss) before income tax provision	2,402	119
Income tax provision (benefit)	504	21
Net income/(loss)	1,898	98
Capital expenditures	413	511
Operating Segments | ATG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	13,814	10,595
Cost of goods sold, inclusive of depreciation	(9,366)	(8,467)
Gross margin (loss)	$ 4,448	$ 2,128
Gross margin %	32.20%	20.10%
Selling, general and administrative	$ (1,743)	$ (1,280)
Interest	(38)	(19)
Total costs and expenses	(11,147)	(9,766)
Income/(loss) before income tax provision	2,667	829
Income tax provision (benefit)	560	145
Net income/(loss)	2,107	684
Capital expenditures	413	405
Operating Segments | CPG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	1,634	1,408
Cost of goods sold, inclusive of depreciation	(1,370)	(1,463)
Gross margin (loss)	$ 264	$ (55)
Gross margin %	16.20%	(3.90%)
Selling, general and administrative	$ (525)	$ (647)
Interest	(4)	(8)
Total costs and expenses	(1,899)	(2,118)
Income/(loss) before income tax provision	(265)	(710)
Income tax provision (benefit)	(56)	(124)
Net income/(loss)	$ (209)	(586)
Capital expenditures		$ 106