Restructuring charges (Details) (USD $)
3 Months Ended 12 Months Ended
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Restructuring Charges [Abstract]              
Restructuring and related cost, expected expense reduction         $ 6,000,000    
Severance costs         324,615    
Restructuring costs and asset impairment charges         (188,329)    
Restructuring charges 513,000 0 0 0 512,944 0 0
Payments for restructuring         (206,385)    
Accrued severance charges $ 118,230       $ 118,230