Quarterly report pursuant to Section 13 or 15(d)

Stockholders' equity (Public Offerings) (Details)

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Stockholders' equity (Public Offerings) (Details) - USD ($)
 1 Months Ended 3 Months Ended 6 Months Ended
Apr. 30, 2014
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Stockholders Equity [Line Items]        
Shares issued during period 8,335,000      
Shares issued during period, price per share $ 2.40      
Value of shares issued during period $ 20,000,000      
Cost of shares issued during period $ 1,543,000      
Placement fee percentage 6.50%      
Shares issued for warrants exercised     0 1,161,570
Exercise price of warrants   $ 1.36   $ 1.36
Value of shares issued for warrants exercised       $ 1,580,000
Incentive stock options exercised to purchase common shares   39,079    
Average exercise price   $ 2.09    
Total proceeds from stock options exercised to purchase common shares   $ 82,000    
Intrinsic value of stock options exercised to purchase common shares   $ 14,000