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Financial instruments and concentration of credit risks - Additional Information (Detail) - Foreign Exchange Forward Contract - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Fair Value Measurements Disclosure [Line Items]    
Maturity period limit of foreign currency exchange instruments (in months) 3 months  
Notional amount of foreign exchange forward contracts not designated as hedging instruments $ 588.5 $ 437.0