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Stockholders' Equity - Preferred Stock (Details) - $ / shares
3 Months Ended 12 Months Ended
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2019
Class of Stock [Line Items]      
Preferred stock, shares authorized (in shares) 5,000,000 5,000,000 5,000,000
Preferred stock, par value (in dollars per share) $ 0.001 $ 0.001 $ 0.001
Preferred stock, shares outstanding (in shares) 1,952 1,954  
Series A Convertible Preferred Stock [Member]      
Class of Stock [Line Items]      
Preferred stock, shares outstanding (in shares) 0 0  
Convertible preferred stock 3.60% 3.60%  
Series B Convertible Preferred Stock [Member]      
Class of Stock [Line Items]      
Preferred stock, shares outstanding (in shares) 1,014 1,016  
Series B Convertible Preferred Stock [Member] | 2018 Rights Offering [Member]      
Class of Stock [Line Items]      
Preferred stock, shares outstanding (in shares) 1,014    
Number of preferred stock, shares converted 5,978    
Series C Convertible Preferred Stock [Member]      
Class of Stock [Line Items]      
Preferred stock, shares outstanding (in shares) 938 938  
Series C Convertible Preferred Stock [Member] | 2018 Rights Offering [Member]      
Class of Stock [Line Items]      
Preferred stock, shares outstanding (in shares) 938    
Number of preferred stock, shares converted 416,889