Accumulated other comprehensive income (loss) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Marketable securities
Beginning balance	$ 0		$ (12,563)
Gains (losses) on available for sale securities	$ 0
Less: Tax (tax benefit)		$ 0
Net gains (losses) on available for sale securities			0
(Gains) Losses reclassified from accumulated other comprehensive income to net income			12,563
Less: Tax (tax benefit)			0
Net gains (losses) reclassified from accumulated other comprehensive income to net income			12,563
Other comprehensive income (loss), net of tax			$ 12,563
Ending balance		$ 0		$ 0