Shareholders' equity (Details) (USD $)
0 Months Ended
Jul. 30, 2013
Dec. 31, 2013
Dec. 31, 2012
Equity [Abstract]      
Issuance of Stock (in shares) 3,846,000    
Share price of IPO (in dollars per share) $ 12.00    
Gross proceeds form IPO $ 46,200,000    
Net proceeds from IPO 40,800,000    
Debt Instrument, Convertible, Conversion Ratio 1    
IPO triggered automatic exercise of warrants, number of warrants $ 8,208    
Automatic exercise of warrants, strike price of each warrant (in dollars per warrant) 0.10    
Common Stock Authorized (in shares)   100,000,000 135,715,623
Authorized Preferred Stock (in shares)   10,000,000 0
Preferred Stock, Shares Issued   0 0