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Net employee defined benefit - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disclosure of net defined benefit asset (liability) [line items]      
Employer contributions $ 2.8 $ 4.4 $ 4.8
Retirement of interest earned 1.1 2.5 0.0
Actuarial loss recognized in other comprehensive income $ 15.5 $ 4.4 $ 0.3
Duration of defined benefit plan obligation 9 years    
Indemnity plan [member]      
Disclosure of net defined benefit asset (liability) [line items]      
Percentage of eligible earnings accumulated as benefit 6.54%