Annual report pursuant to Section 13 and 15(d)

Property and equipment (Narrative) (Details)

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Property and equipment (Narrative) (Details) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Feb. 29, 2016
Property, Plant and Equipment [Abstract]      
Sales price of corporate headquarters, land and building to a third party     $ 4,000,000
Gain on sale of property and equipment $ 1,942,980  
Proceeds from sale of property and equipment $ 1,808,787 $ 8,110