Summary of significant accounting policies (Property and Equipment) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Amount of grant awards received under The American Recovery And Reinvestment Act	$ 285,718
Rebates applied to cost of construction		$ 583,800
Minimum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	12 years
Maximum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	15 years