Income tax (Details 1) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Expected federal tax, Amount	$ 208,500	$ 161,300
Permanent differences, Amount	(1,700)	9,100
State income tax, net of federal tax benefit, Amount	22,200	30,900
Foreign tax credit, Amount	0	(3,100)
Research and Development tax credit	(29,000)	0
Other, Amount	(23,000)	54,800
Total income tax expense (benefit)	$ 177,000	$ 253,000
Expected federal tax, Percenage	21.00%	21.00%
Permanent differences, Percentage	(0.20%)	1.20%
State income tax, net of federal tax benefit, Percentage	2.20%	4.00%
Foreign tax credit, Percentage	(0.00%)	(0.40%)
Research and Development tax credit	(2.90%)	0.00%
Other, Percentage	(2.30%)	7.10%
Total, Percent	17.80%	32.90%