Annual report pursuant to Section 13 and 15(d)

Stockholders' equity (Details)

v2.4.0.8
Stockholders' equity (Details) (USD $)
 1 Months Ended 12 Months Ended 3 Months Ended
May 30, 2013
Nov. 30, 2012
Jun. 30, 2012
Apr. 30, 2012
Dec. 31, 2011
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Jul. 31, 2011
Mar. 24, 2014
Subsequent Event [Member]
Stockholders' equity [Abstract]                    
Common stock, shares authorized           60,000,000 30,000,000   60,000,000  
Common stock, shares authorized before increase                 30,000,000  
Stock issued during period, shares 11,500,000 1,946,000 6,100,000   267,000          
Stock issued during period, price per share $ 1.25 $ 2.10 $ 2.00   $ 6.12     $ 6.12    
Stock issued during period $ 14,400,000 $ 3,600,000 $ 12,200,000   $ 1,456,000 $ 12,969,587 $ 15,146,400 $ 1,456,065    
Costs associated with the public offering 1,405,000 445,000 1,261,000   181,000          
Placement fee percentage 7.00% 7.00% 7.00%   6.79%          
Warrants, number of shares per warrant 0.35       1     1    
Warrants, number of shares 4,025,000   305,000   267,500     267,500    
Warrants, exercise price 1.36   2.50   7.32     7.32    
Underwriter, addtional shares purchased 15.00%                  
Issuance of common stock for services, shares     4,167 4,167     8,334      
Issuance of common stock for services             29,776      
Issuance of common stock for services, price per share     $ 2.88 $ 4.26            
Subsequent Event [Line Items]                    
Shares issued for warrants exercised                   804,570
Share price                   $ 1.36
Proceeds from exercises of warrants                   $ 1,094,000