Income taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		34.00%	34.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount		$ 545,000
Operating Loss Carryforwards		$ 16,400,000
Operating Loss Carryforwards Expiration		begin to expire in 2020
Deferred Tax Assets, Valuation Allowance		$ 6,372,788	$ 5,695,766
Scenario, Plan [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%