General form of registration statement for all companies including face-amount certificate companies

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 432,500 399,151 399,151  
Granted, Number of Options   64,065 64,064 52,083
Forfeited, Number of Options   (30,716) (30,715) (67,366)
Cancelled, Number of Options (432,500)      
Ending balance, Number of Options 0 432,500 432,500 399,151
Beginning balance, Weighted Average Grant Date Fair Value per Option $ 15.45 $ 15.82 $ 15.82  
Granted, Weighted Average Grant Date Fair Value per Option   13.50 13.50 $ 15.91
Forfeited, Weighted Average Grant Date Fair Value per Option   15.80 15.80 15.80
Cancelled, Weighted Average Grant Date Fair Value per Option (15.45)      
Ending balance, Weighted Average Grant Date Fair Value per Option 0 15.45 15.45 15.82
Beginning balance, Weighted Average Exercise Price 141.53 141.53 141.53  
Granted, Weighted Average Exercise Price   141.53 141.53 141.53
Forfeited, Weighted Average Exercise Price   141.53 141.53 141.53
Cancelled, Weighted Average Exercise Price (141.53)      
Ending balance, Weighted Average Exercise Price $ 0 $ 141.53 $ 141.53 $ 141.53
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      
After Effect Of Recapitalization [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]        
Beginning balance, Number of Options 432,500 399,151 399,151 414,434
Ending balance, Number of Options     432,500 399,151
Beginning balance, Weighted Average Grant Date Fair Value per Option $ 15.45 $ 15.82 $ 15.82 $ 15.80
Ending balance, Weighted Average Grant Date Fair Value per Option     15.45 15.82
Beginning balance, Weighted Average Exercise Price $ 141.53 $ 141.53 141.53 141.53
Ending balance, Weighted Average Exercise Price     $ 141.53 $ 141.53
Weighted Average Remaining Contractual Term 7 years 8 months 12 days 8 years 4 months 24 days   9 years 3 months 18 days