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Risks and Uncertainties (Details) - USD ($)
$ in Thousands
3 Months Ended 16 Months Ended
Mar. 31, 2022
Mar. 31, 2022
Mar. 31, 2021
Mar. 31, 2022
Dec. 31, 2021
Jul. 15, 2019
Concentration Risk [Line Items]            
Cash and cash equivalents $ 14,736 $ 14,736   $ 14,736 $ 28,024  
Accumulated deficit 270,017 $ 270,017   $ 270,017 $ 256,796  
At-the-Market Offering            
Concentration Risk [Line Items]            
Number of shares issued in transaction (in shares)   391,652 1,672,104 7,873,071    
Consideration received on sale of stock   $ 1,298 $ 9,891 $ 37,131    
Payments for stock issuance costs   $ 62 $ 306 $ 1,826    
Remaining amount available for offering $ 36,043          
Senior Secured Notes Due 2025            
Concentration Risk [Line Items]            
Interest rate 12.50% 12.50%   12.50%    
Senior Secured Notes Due 2025 | Senior Notes            
Concentration Risk [Line Items]            
Interest rate 12.50% 12.50%   12.50%   12.50%