Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Narrative (Details)

v3.19.1
Stockholders' Equity - Narrative (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended 12 Months Ended
Jan. 30, 2019
$ / shares
shares
Feb. 28, 2018
USD ($)
$ / shares
shares
Jun. 30, 2016
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
shares
Dec. 31, 2017
USD ($)
$ / shares
shares
Class of Stock [Line Items]          
Cash proceeds from option exercises | $       $ 986 $ 781
Cash proceeds from exercise of warrants | $       $ 314 $ 3,309
Number of shares per unit (shares)     1    
Warrant exercise period     5 years    
Par value of preferred stock (USD per share) | $ / shares       $ 0.001 $ 0.001
Shares of preferred stock issued (shares)       2,907 4,963
Series A Convertible Preferred Stock          
Class of Stock [Line Items]          
Price per unit issued (USD per share) | $ / shares     $ 2.015    
Number of shares per unit (shares)     1    
Shares issued upon conversion of convertible preferred stock (shares)     1,000    
Proportion of beneficial ownership (as a percent)     9.99%    
Par value of preferred stock (USD per share) | $ / shares     $ 0.001    
Series B Convertible Preferred Stock | Subsequent Event          
Class of Stock [Line Items]          
Par value of preferred stock (USD per share) | $ / shares $ 0.001        
Tranche A Warrants          
Class of Stock [Line Items]          
Number of shares called by warrants (shares)     0.4    
Number of warrants     1    
Exercise price (USD per share) | $ / shares     $ 2.00    
Tranche B Warrants          
Class of Stock [Line Items]          
Number of shares called by warrants (shares)     0.2    
Number of warrants     1    
Exercise price (USD per share) | $ / shares     $ 3.00    
Common Stock          
Class of Stock [Line Items]          
Issuance of common stock resulting from exercise of stock options (shares)         453,209
Stock options to purchase shares of common stock (shares)         182,471
Cash proceeds from option exercises | $         $ 800
Issuance of common stock resulting from exercise convertible securities (shares)         1,505,026
Cash proceeds from exercise of warrants | $         $ 3,300
Cashless Exercise | Common Stock          
Class of Stock [Line Items]          
Issuance of common stock resulting from exercise of stock options (shares)         83,491
Net exercise of common stock shares underlying warrants (shares)         89,330
Issuance of shares of common stock from exercise (shares)         49,127
Cash-Based Awards | Common Stock          
Class of Stock [Line Items]          
Issuance of common stock resulting from exercise of stock options (shares)         369,718
Number of shares called by warrants (shares)         1,455,899
Common Shares          
Class of Stock [Line Items]          
Issuance of common stock resulting from exercise of stock options (shares)       596,000 453,000
Issuance of common stock resulting from exercise convertible securities (shares)       157,000 1,505,000
Preferred Stock | Series A Convertible Preferred Stock | Subsequent Event          
Class of Stock [Line Items]          
Beneficial ownership blocker provision (as a percent) 9.99%        
Public Offering | Common Stock          
Class of Stock [Line Items]          
Shares of common stock issued (shares)   6,325,000      
Issue price per share (USD per share) | $ / shares   $ 8      
Net proceeds from underwritten public offering | $   $ 47,600      
Stock issuance costs | $   $ 400      
Over-Allotment Option | Common Stock          
Class of Stock [Line Items]          
Shares of common stock issued (shares)   825,000      
Securities Purchase Agreement          
Class of Stock [Line Items]          
Issue price per share (USD per share) | $ / shares     $ 2.015    
Number of capital units sold in private placement transaction (units)     8,188,804    
Gross proceeds from private placement units sold | $     $ 16,500    
Net proceeds from private placement units sold | $     $ 15,300    
2016 PIPE          
Class of Stock [Line Items]          
Shares of common stock issued (shares)     3,225,804    
Stock Exchange, Shares from Existing Shareholders | Common Shares | Common Stock | Subsequent Event          
Class of Stock [Line Items]          
Shares of common stock issued (shares) 5,000,000        
Preferred Share Exchange | Preferred Stock | Series A Convertible Preferred Stock | Subsequent Event          
Class of Stock [Line Items]          
Shares of common stock issued (shares) 5,000        
Biotechnology Value Fund | Common Stock | Subsequent Event          
Class of Stock [Line Items]          
Stock owned by party (shares) 7,457,921        
Proportion of common stock owned (as a percent) 13.77%        
2016 PIPE | Private Placement | Series A Convertible Preferred Stock          
Class of Stock [Line Items]          
Shares of preferred stock issued (shares)     4,963