Income taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	34.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount		$ 545,000
Operating Loss Carryforwards	$ 10,100,000
Operating Loss Carryforwards Expiration	begin to expire in 202​​​​​​​0
Deferred Tax Assets, Valuation Allowance	$ 7,876,710	$ 6,372,788
Maximum [Member]
Deferred Tax Assets, Valuation Allowance	7,900,000
Minimum [Member]
Deferred Tax Assets, Valuation Allowance	$ 6,400,000