Revenue from contracts with customers (Schedule of Revenues by Geography) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 1,239,132	$ 1,056,765	$ 2,880,463	$ 2,862,083
Domestic [Member]
Disaggregation of Revenue [Line Items]
Total revenue	372,902	309,119	1,036,662	1,202,244
International [Member]
Disaggregation of Revenue [Line Items]
Total revenue	$ 866,230	$ 747,646	$ 1,843,801	$ 1,659,839