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

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

v3.21.2
Share-Based Payment and Related Stock Option Plan - Summary of the Company's Exercisable Stock Options (Detail) - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Share-based Payment Arrangement [Abstract]    
Range of exercise prices, Lower Range Limit $ 80.87 $ 80.87
Range of exercise prices, Upper Range Limit $ 202.18 $ 202.18
Number 153,898 85,110
Weighted average remaining contractual term (in years) 7 years 3 months 18 days 8 years 3 months 18 days
Weighted average exercise price $ 141.53 $ 141.53