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Shareholders' capital - Fair Value of Share Options Granted (Detail) - $ / shares
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Equity [Abstract]    
Risk-free interest rate 1.10% 1.20%
Expected volatility 23.00% 24.00%
Expected dividend yield 4.10% 4.10%
Expected life 5 years 6 months 5 years 6 months
Weighted average grant date fair value per option (in USD per share) $ 2.46 $ 2.72