Business Segments - Summary of company's operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers									$ 55,272	$ 47,857
Cost of goods sold, inclusive of depreciation									(43,146)	(35,772)
Gross margin									12,126	12,085
Selling, general and administrative									(9,313)	(7,743)
Interest									(125)	(107)
Total costs and expenses									(9,438)	(7,850)
Income (loss) before income tax provision									2,688	4,235
Income tax provision (benefits)									(579)	(737)
Net income/(loss)	$ 165	$ 1,132	$ 714	$ 98	$ 1,003	$ 1,457	$ 707	$ 331	2,109	3,498
Total assets	49,470				41,685				49,470	41,685
Capital expenditures									2,271	1,866
Operating Segments
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers									55,272	47,857
Cost of goods sold, inclusive of depreciation									(43,146)	(35,772)
Gross margin									$ 12,126	$ 12,085
Gross margin %									21.90%	25.30%
Selling, general and administrative									$ (9,313)	$ (7,743)
Interest									(125)	(107)
Total costs and expenses									(52,584)	(7,850)
Income (loss) before income tax provision									2,688	4,235
Income tax provision (benefits)									(579)	(737)
Net income/(loss)									2,109	3,498
Total assets	49,470				41,685				49,470	41,685
Capital expenditures									2,271	1,866
Operating Segments | ATG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers									48,519	40,415
Cost of goods sold, inclusive of depreciation									(35,632)	(28,587)
Gross margin									$ 12,887	$ 11,828
Gross margin %									26.60%	29.30%
Selling, general and administrative									$ (6,588)	$ (5,423)
Interest									(97)	(73)
Total costs and expenses									(42,317)	(34,083)
Income (loss) before income tax provision									6,203	6,332
Income tax provision (benefits)									(1,336)	(1,102)
Net income/(loss)									4,867	5,230
Total assets	39,989				31,647				39,989	31,647
Capital expenditures									1,990	1,689
Operating Segments | CPG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers									6,753	7,442
Cost of goods sold, inclusive of depreciation									(7,514)	(7,185)
Gross margin									$ (761)	$ 258
Gross margin %									(11.30%)	3.50%
Selling, general and administrative									$ (2,725)	$ (2,320)
Interest									(28)	(34)
Total costs and expenses									(10,268)	(9,539)
Income (loss) before income tax provision									(3,515)	(2,097)
Income tax provision (benefits)									757	365
Net income/(loss)									(2,758)	(1,732)
Total assets	$ 9,481				$ 10,038				9,481	10,038
Capital expenditures									$ 281	$ 177