Annual report pursuant to Section 13 and 15(d)

Capitalization and Equity Structure - Narrative (Details)

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Capitalization and Equity Structure - Narrative (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended 2 Months Ended 12 Months Ended
Feb. 11, 2021
$ / shares
Mar. 24, 2020
Oct. 31, 2020
USD ($)
$ / shares
Jun. 30, 2020
USD ($)
$ / shares
shares
Dec. 31, 2019
$ / shares
shares
Feb. 28, 2021
USD ($)
$ / shares
shares
Dec. 31, 2021
USD ($)
$ / shares
shares
Dec. 31, 2020
USD ($)
$ / shares
shares
Dec. 31, 2019
$ / shares
shares
May 31, 2019
shares
Class of Warrant or Right [Line Items]                    
Common stock, shares authorized (in shares) | shares             141,429,000 141,429,000    
Preferred stock, shares authorized (in shares) | shares             10,000,000 10,000,000    
Common stock, shares issued (in shares) | shares             12,693,000 8,349,000    
Common stock, shares outstanding (in shares) | shares             12,693,000 8,349,000    
Preferred stock, shares issued (in shares) | shares             0 0    
Preferred stock, shares outstanding (in shares) | shares             0 0    
Proceeds from exercise of common stock warrants | $             $ 1,417 $ 3,334    
Aggregate proceeds | $             $ 1,417 1,436    
Exercise price (in dollars per share) | $ / shares             $ 8.06      
Warrants issued (in shares) | shares             273,000      
Warrant expense | $             $ 0 329    
Reverse stock split   0.067                
Proceeds from issuance of common stock and warrants, net | $             37,295 7,082    
Exercise of warrants | $             $ 3,878 $ 7,310    
Warrants expired (in shares) | shares             0      
June 2020 Warrants                    
Class of Warrant or Right [Line Items]                    
Class of warrant or right expiration period             5 years 6 months      
June 2020 Investor Warrants                    
Class of Warrant or Right [Line Items]                    
Exercise price (in dollars per share) | $ / shares       $ 5.18       $ 5.18    
Class of warrant or right expiration period             5 years 6 months      
June 2020 Placement Agent Warrants                    
Class of Warrant or Right [Line Items]                    
Exercise price (in dollars per share) | $ / shares       $ 5.64       $ 5.64    
Class of warrant or right cash fee percentage       7.00%            
Class of warrant or right cash fee | $       $ 552            
Class of warrant or right management fee percentage       1.00%            
Class of warrant or right management fee | $       $ 79            
Percentage of warrants issued to purchase shares of common stock       7.00%            
Warrants issued (in shares) | shares       122,000            
Warrant expense | $       $ 98            
Issuance costs | $       808            
Fair value of warrants | $       $ 309            
Class of warrant or right expiration period               5 years    
December 2019 warrants                    
Class of Warrant or Right [Line Items]                    
Exercise price (in dollars per share) | $ / shares         $ 8.10       $ 8.10  
Class of warrant or right expiration period         5 years   6 months 1 day      
Duration of put option                 30 days  
Put option pay period                 5 days  
December 2019 Placement Agent Warrants                    
Class of Warrant or Right [Line Items]                    
Exercise price (in dollars per share) | $ / shares             $ 8.44      
Warrants issued (in shares) | shares             0      
Warrants expired (in shares) | shares             0      
Class of warrant or right expiration period             5 years      
December 2019 Placement Agent Warrants | Conversion price                    
Class of Warrant or Right [Line Items]                    
Conversion price (in dollars per share) | $ / shares             $ 8.44 $ 8.44    
May 2019 Warrants                    
Class of Warrant or Right [Line Items]                    
Exercise price (in dollars per share) | $ / shares             $ 3.52      
Warrants issued (in shares) | shares             0      
Shares issued (in dollars per share) | $ / shares       $ 4.51            
Warrants expired (in shares) | shares             0      
Class of warrant or right expiration period             3 years      
May 2019 Warrants | Conversion price                    
Class of Warrant or Right [Line Items]                    
Conversion price (in dollars per share) | $ / shares             $ 3.52 $ 3.52    
February 2021 Offering                    
Class of Warrant or Right [Line Items]                    
Exercise price (in dollars per share) | $ / shares           $ 12.81        
Percentage of warrants issued to purchase shares of common stock           7.00%        
2021 Warrants                    
Class of Warrant or Right [Line Items]                    
Exercise price (in dollars per share) | $ / shares           $ 12.81        
Warrants issued (in shares) | shares           273,000 273,000      
Class of warrant or right expiration period           5 years        
Duration of put option           30 days        
Put option pay period           5 days        
2021 Warrants | Conversion price                    
Class of Warrant or Right [Line Items]                    
Conversion price (in dollars per share) | $ / shares $ 12.81           $ 12.81      
Direct offering                    
Class of Warrant or Right [Line Items]                    
Aggregate proceeds | $       $ 7,890            
Issuance costs | $       1,117            
Direct offering | June 2020 Warrants                    
Class of Warrant or Right [Line Items]                    
Aggregate proceeds | $       2,650            
Issuance costs | $       $ 329            
At-the-market offering                    
Class of Warrant or Right [Line Items]                    
Number of shares sold (in shares) | shares             78,000      
Sale of shares (in dollars per share) | $ / shares     $ 6.75       $ 10.72      
Value of shares sold | $     $ 7,500              
Proceeds from debt | $             $ 791      
Over-allotment option | February 2021 Offering                    
Class of Warrant or Right [Line Items]                    
Number of shares sold (in shares) | shares           3,902,000        
Sale of shares (in dollars per share) | $ / shares           $ 10.25        
Value of shares sold | $           $ 40,000        
Proceeds from issuance of common stock and warrants, net | $           $ 36,504        
Expected term           5 years        
Common stock                    
Class of Warrant or Right [Line Items]                    
Exercise of warrants | $             $ 1      
Warrants expired (in shares) | shares             (358,000)      
Exercise of warrants (in shares) | shares             300,000 723,000    
Common stock | Direct offering                    
Class of Warrant or Right [Line Items]                    
Number of shares sold (in shares) | shares       1,748,000            
Number warrants called (in shares) | shares         556,000       556,000  
Aggregate proceeds | $       $ 5,240            
Issuance costs | $       $ 479            
Common stock | Direct offering | June 2020 Investor Warrants                    
Class of Warrant or Right [Line Items]                    
Number warrants called (in shares) | shares       874,000       874,000    
Common stock | Direct offering | May 2019 Warrants                    
Class of Warrant or Right [Line Items]                    
Number warrants called (in shares) | shares                   444,000
Common stock | At-the-market offering                    
Class of Warrant or Right [Line Items]                    
Sale of stock, stock available for issuance, value | $             $ 6,668