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Estimated Fair Value of Options on Dates of Each Grant Using Binomial Option Pricing Model (Detail)
12 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield   0.61%  
Minimum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield 0.43%   0.61%
Expected volatility 21.71% 20.13% 15.30%
Risk-free interest rate, lower range 4.99% 4.63% 5.81%
Expected term (in years) 2 years 7 months 2 days 2 years 7 months 24 days 2 years 9 months 25 days
Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield 0.46%   0.85%
Expected volatility 31.79% 28.93% 20.13%
Risk-free interest rate, upper range 6.43% 5.75% 6.70%
Expected term (in years) 5 years 4 months 9 days 5 years 5 months 4 days 5 years 5 months 1 day