Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Equity Offerings (Details)

v3.20.1
Stockholders' Equity - Equity Offerings (Details)
1 Months Ended 12 Months Ended
Jan. 29, 2019
USD ($)
Institution
$ / shares
shares
Jan. 28, 2019
USD ($)
$ / shares
shares
Dec. 14, 2015
USD ($)
Jun. 30, 2018
USD ($)
Dec. 31, 2019
USD ($)
shares
Dec. 31, 2018
USD ($)
shares
Dec. 31, 2017
USD ($)
Stockholders' Equity              
Common stock authorized (in shares) | shares         200,000,000 200,000,000  
Preferred stock authorized (in shares) | shares         5,000,000 5,000,000  
Net proceeds from the offering         $ 10,312,000 $ 33,195,000 $ 20,712,000
Offering price (in dollars per share) | $ / shares $ 1.00            
Issuance of common stock, net of issuance costs         9,965,000 $ 33,194,000 $ 20,712,000
Wainwright              
Stockholders' Equity              
Percentage of aggregate gross proceeds paid   7.00%          
Expenses paid   $ 50,000          
Warrants to purchase shares of common stock | shares   500,000          
Warrants term   5 years          
Exercise price (in dollars per share) | $ / shares   $ 1.25          
At-the-market sales facility - December 14, 2015 agreement              
Stockholders' Equity              
Offering amount         0    
Issuance of common stock (in shares) | shares           11,400,000  
Issuance of common stock, net of issuance costs           $ 20,000,000  
At-the-market sales facility - December 14, 2015 agreement | Maximum              
Stockholders' Equity              
Offering amount     $ 75,000,000        
Commission (as a percent)     3.00%        
At-the-market sales facility - June 2018 agreement              
Stockholders' Equity              
Offering amount       $ 50,000,000 0    
Shelf registration       $ 175,000,000      
Issuance of common stock (in shares) | shares           8,500,000  
Issuance of common stock, net of issuance costs           $ 13,200,000  
At-the-market sales facility - April 17, 2019 agreement | Maximum              
Stockholders' Equity              
Offering amount         $ 50,000,000    
Private Placement              
Stockholders' Equity              
Issuance of common stock (in shares) | shares 10,000,000            
Issuance of common stock, net of issuance costs $ 9,200,000            
Number of institutional investors | Institution 2            
CW ATM Program              
Stockholders' Equity              
Issuance of common stock (in shares) | shares         1,400,000    
Net proceeds from the offering         $ 1,100,000    
Stock available for further issuance         $ 48,900,000