Accumulated other comprehensive income (loss) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Marketable securities
Beginning balance	$ (12,563)	$ 0
Gains (losses) on available for sale securities	0	(12,563)
Less: Tax (tax benefit)	0	0
Net gains (losses) on available for sale securities	0	(12,563)
(Gains) Losses reclassified from AOCI to net income	12,563	0
Less: Tax (tax benefit)	0	0
Net gains (losses) reclassified from AOCI to net income	12,563	0
Other comprehensive income (loss), net of tax	12,563	(12,563)
Ending balance	$ 0	$ (12,563)