Quarterly report pursuant to Section 13 or 15(d)

Summary of Unvested Stock Option Activity (Detail)

v3.21.2
Summary of Unvested Stock Option Activity (Detail) - $ / shares
shares in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Granted $ 0.49 $ 0 $ 0.72 $ 0.29
Stock Options        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Beginning Balance     1,323  
Granted     50  
Vested     (1,256)  
Ending Balance 117   117  
Beginning Balance     $ 0.34  
Granted     0.72  
Vested     0.31  
Ending Balance $ 0.73   $ 0.73