Quarterly report pursuant to Section 13 or 15(d)

Share-Based Payment and Related Stock Option Plan - Summary of Company's Stock Options (Detail)

v3.21.2
Share-Based Payment and Related Stock Option Plan - Summary of Company's Stock Options (Detail) - $ / shares
9 Months Ended 12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2020
Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]        
Beginning balance, Number of Options 34,977 32,280 32,280  
Granted, Number of Options   5,181    
Forfeited, Number of Options   (2,484)    
Cancelled, Number of Options (34,977)      
Ending balance, Number of Options 0 34,977 34,977 32,280
Beginning balance, Weighted Average Grant Date Fair Value per Option $ 191 $ 196 $ 196  
Granted, Weighted Average Grant Date Fair Value per Option   167    
Forfeited, Weighted Average Grant Date Fair Value per Option   195    
Cancelled, Weighted Average Grant Date Fair Value per Option (191)      
Ending balance, Weighted Average Grant Date Fair Value per Option 0 191 191 $ 196
Beginning balance, Weighted Average Exercise Price 1,750 1,750 1,750  
Granted, Weighted Average Exercise Price   1,750    
Forfeited, Weighted Average Exercise Price   1,750    
Cancelled, Weighted Average Exercise Price (1,750)      
Ending balance, Weighted Average Exercise Price $ 0 $ 1,750 $ 1,750 $ 1,750
Weighted Average Remaining Contractual Term   7 years 10 months 24 days 7 years 8 months 12 days 8 years 4 months 24 days
Cancelled, Weighted Average Remaining Contractual Term 7 years 8 months 12 days