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Stock-Based Compensation - Summary of Restricted Stock Awards (Details) - $ / shares
9 Months Ended 12 Months Ended
Sep. 30, 2021
Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Number of shares, Granted   21,750
Restricted Stock [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Number of shares, Unvested 66,681  
Number of shares, Granted 297,724  
Number of shares, Vested (15,766)  
Number of shares, Unvested 348,639  
Unvested, weighted average grant date fair value per share, beginning balance $ 1.00  
Granted, weighted average grant date fair value 8.55  
Vested, weighted average grant date fair value per share 1.42  
Unvested, weighted average grant date fair value per share, ending balance $ 7.03