Quarterly report pursuant to Section 13 or 15(d)

Convertible preferred stock (Details)

v3.21.1
Convertible preferred stock (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended 3 Months Ended
Oct. 23, 2020
shares
Oct. 12, 2020
shares
Oct. 01, 2020
USD ($)
shares
Oct. 31, 2020
USD ($)
$ / shares
shares
Mar. 31, 2021
USD ($)
$ / shares
shares
Mar. 31, 2020
USD ($)
Dec. 31, 2020
$ / shares
shares
Sep. 30, 2020
$ / shares
Jun. 30, 2020
$ / shares
Mar. 17, 2020
$ / shares
Dec. 19, 2019
$ / shares
Nov. 04, 2019
$ / shares
Dec. 12, 2018
shares
Subsidiary, Sale of Stock [Line Items]                          
Stated value (in dollars per share) | $ / shares         $ 0.001   $ 0.001            
Common stock, par value (in dollars per share) | $ / shares         $ 0.001   $ 0.001            
Number of warrants included in each unit (in shares) | shares                         1
Term of warrants                     24 months 24 months  
Warrants, exercise price (in dollars per share) | $ / shares               $ 0.65 $ 0.75 $ 1.62 $ 5.00 $ 5.00  
Preferred stock, authorized (in shares) | shares         30,000   30,000            
Issued pursuant to a private placement | $         $ 4,072 $ 500              
Liquidation preference (in dollars per share) | $ / shares         $ 1,000                
Conversion ratio         0.50                
Series F Unit                          
Subsidiary, Sale of Stock [Line Items]                          
Shares and warrants issued pursuant to a private placement (in shares) | shares     14,264                    
Series F Unit | Cavalry                          
Subsidiary, Sale of Stock [Line Items]                          
Shares and warrants issued pursuant to a private placement (in shares) | shares     3,500                    
Series F Convertible Preferred Stock                          
Subsidiary, Sale of Stock [Line Items]                          
Preferred stock, authorized (in shares) | shares     30,000                    
Shares and warrants issued pursuant to a private placement (in shares) | shares 100                        
Series F Convertible Preferred Stock | Retained Earnings [Member]                          
Subsidiary, Sale of Stock [Line Items]                          
Issued pursuant to a private placement | $     $ 5,400                    
Series F private placement                          
Subsidiary, Sale of Stock [Line Items]                          
Common stock, par value (in dollars per share) | $ / shares       $ 0.001                  
Value per share (in dollars per share) | $ / shares       $ 0.50                  
Number of warrants included in each unit (in shares) | shares       1                  
Term of warrants       6 years                  
Warrants, exercise price (in dollars per share) | $ / shares       $ 0.75                  
Gross cash proceeds | $       $ 18,200                  
Series F private placement | Officers and directors                          
Subsidiary, Sale of Stock [Line Items]                          
Gross cash proceeds | $       $ 6,500                  
Series F private placement | Series F Unit                          
Subsidiary, Sale of Stock [Line Items]                          
Purchase price (in dollars per share) | $ / shares       $ 1,000                  
Shares and warrants issued pursuant to a private placement (in shares) | shares 2,832 1,106                      
Series F private placement | Series F Convertible Preferred Stock                          
Subsidiary, Sale of Stock [Line Items]                          
Number of shares of stock included in each unit (in shares) | shares       1                  
Stated value (in dollars per share) | $ / shares       $ 0.001