Organization and operations (Details)	3 Months Ended				6 Months Ended
	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Jun. 30, 2019 USD ($) segment	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments | segment					2
Net loss	$ 1,384,777	$ 2,230,430	$ 9,051,872	$ 8,223,227	$ 3,615,207	$ 17,275,099
Retained earnings (accumulated deficit)	(136,576,482)				(136,576,482)		$ (132,961,275)
Cash and cash equivalents	$ 6,514,215				$ 6,514,215		$ 9,829,624