Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation & Summary of Significant Accounting Policies - Additional Information (Details)

v3.21.2
Basis of Presentation & Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2020
Dec. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]            
Accumulated deficit $ (189,035)   $ (189,035)   $ (166,893)  
Net loss (7,307) $ (9,476) (22,142) $ (31,441)    
Net cash used by operating activities     14,654 30,891    
Restricted cash 393 393 393 393 393  
Cash expense for separation-related payments 400   400      
Current liabilities 5,143   5,143   6,945  
Total cash, cash equivalents, and restricted cash $ 14,913 $ 8,604 $ 14,913 $ 8,604 $ 18,289 $ 60,038
Common stock, shares issued 37,401,876   37,401,876   37,165,196  
Equipment [Member]            
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]            
Restricted cash $ 1,000   $ 1,000      
ATM Facility [Member]            
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]            
Common stock, shares issued 1,200,000   1,200,000      
Proceeds from common stock issuance     $ 3,700      
ATM Facility [Member] | Jefferies LLC [Member]            
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]            
Aggregate common stock offering value     $ 50,000