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Stockholders' Equity - Preferred Stock (Details) - $ / shares
 3 Months Ended 12 Months Ended
Sep. 21, 2021
Sep. 20, 2021
Mar. 31, 2022
Dec. 31, 2020
Dec. 31, 2021
Class of Stock [Line Items]          
Preferred stock, shares authorized (in shares)     5,000,000   5,000,000
Preferred stock, par value (in dollars per share)     $ 0.001   $ 0.001
Preferred stock, shares outstanding (in shares)     1,952   1,952
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 A 3.6% Convertible preferred stock eliminated date Sep. 21, 2021        
Series B Convertible Preferred Stock [Member]          
Class of Stock [Line Items]          
Preferred stock, shares outstanding (in shares)     1,014   1,014
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