Quarterly report pursuant to Section 13 or 15(d)

Stock-based compensation - Narrative (Details)

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Stock-based compensation - Narrative (Details)
1 Months Ended 3 Months Ended 9 Months Ended
Aug. 11, 2016
board_member
$ / shares
shares
Oct. 31, 2013
shares
Sep. 30, 2016
USD ($)
shares
Sep. 30, 2015
USD ($)
Sep. 30, 2016
USD ($)
$ / shares
shares
Sep. 30, 2015
USD ($)
Dec. 31, 2015
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Options outstanding (in shares) | shares     1,879,012   1,879,012   1,672,578
Stock-based compensation         $ 723,433 $ 666,853  
Compensation expense         $ 160,000    
Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Options outstanding (in shares) | shares     765,000   765,000   0
Stock Options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Unrecognized compensation cost related to unvested stock-based awards     $ 1,700,000   $ 1,700,000    
Unrecognized compensation cost, recognition period         3 years 11 months 1 day    
Options granted, weighted-average grant date fair value (in dollars per share) | $ / shares         $ 1.12    
Stock Options | General and Administrative Expense              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock-based compensation     343,505 $ 162,850 $ 723,433 $ 666,853  
Immediate Vesting Awards [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Number of board members granted unrestricted vesting options | board_member 4            
Number of unrestricted immediate vesting grants (in shares) | shares 15,267            
Closing stock price | $ / shares $ 2.62            
Compensation expense     $ 160,000        
The 2013 Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Authorized shares (in shares) | shares   4,773,992          
Contractual term   10 years          
Award vesting period   5 years