Income taxes - Reconciliation of Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Tax expense at the federal statutory rate	$ (1,288,471)	$ (394,991)
Foreign taxation	(1,325,577)	198,560
Permanent Differences	1,606,144	56,768
Foreign tax differential	(203,943)	98,381
Valuation allowance	1,211,846	41,282
Net future tax asset	$ 0	$ 0