Business Segments - Summary of company's operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	$ 12,768	$ 11,325	$ 35,273	$ 30,044
Cost of goods sold, inclusive of depreciation and amortization	(8,828)	(8,234)	(26,359)	(23,307)
Gross Profit	$ 3,940	$ 3,091	$ 8,914	$ 6,737
Gross margin %	30.90%	27.30%	25.30%	22.40%
Selling, general and administrative	$ (2,074)	$ (2,085)	$ (5,715)	$ (5,548)
Interest expense	(28)	(18)	(80)	(56)
Income (loss) before income tax provision (benefits)	1,838	988	3,119	1,133
Income tax provision (benefits)	381	317	624	331
Net income (loss)	1,457	671	2,495	802
Capital expenditures			1,452	1,401
Operating Segments
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	12,768	11,325	35,273	30,044
Cost of goods sold, inclusive of depreciation and amortization	(8,828)	(8,234)	(26,359)	(23,307)
Gross Profit	$ 3,940	$ 3,091	$ 8,914	$ 6,737
Gross margin %	30.90%	27.30%	25.30%	22.40%
Selling, general and administrative	$ (2,074)	$ (2,085)	$ (5,715)	$ (5,548)
Interest expense	(28)	(18)	(80)	(56)
Total expenses	(10,930)	(10,337)	(32,154)	(28,911)
Income (loss) before income tax provision (benefits)	1,838	988	3,119	1,133
Income tax provision (benefits)	381	317	624	331
Net income (loss)	1,457	671	2,495	802
Capital expenditures	468	1,330	1,452	1,901
Operating Segments | ATG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	10,639	8,918	30,028	23,968
Cost of goods sold, inclusive of depreciation and amortization	(6,965)	(6,198)	(21,600)	(17,826)
Gross Profit	$ 3,674	$ 2,720	$ 8,428	$ 6,142
Gross margin %	34.50%	30.50%	28.10%	25.60%
Selling, general and administrative	$ (1,476)	$ (1,642)	$ (4,131)	$ (4,148)
Interest expense	(20)	(9)	(55)	(32)
Total expenses	(8,461)	(7,849)	(25,786)	(22,006)
Income (loss) before income tax provision (benefits)	2,178	1,069	4,242	1,962
Income tax provision (benefits)	457	341	849	580
Net income (loss)	1,721	728	3,393	1,382
Capital expenditures	432	1,282	1,277	1,777
Operating Segments | CPG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	2,129	2,407	5,245	6,076
Cost of goods sold, inclusive of depreciation and amortization	(1,863)	(2,036)	(4,759)	(5,481)
Gross Profit	$ 266	$ 371	$ 486	$ 595
Gross margin %	12.50%	15.40%	9.30%	9.80%
Selling, general and administrative	$ (598)	$ (443)	$ (1,584)	$ (1,400)
Interest expense	(8)	(9)	(25)	(24)
Total expenses	(2,469)	(2,488)	(6,368)	(6,905)
Income (loss) before income tax provision (benefits)	(340)	(81)	(1,123)	(829)
Income tax provision (benefits)	(76)	(24)	(225)	(249)
Net income (loss)	(264)	(57)	(898)	(580)
Capital expenditures	$ 36	$ 48	$ 175	$ 124