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Pensions and Post-Employment Benefits - Summary of Significant Assumptions Used in the Determination of the Benefit Obligation (Detail) - Defined Benefit Obligation [Member]
Dec. 31, 2020
Dec. 31, 2019
Mexico [member]    
Disclosure of defined benefit plans [line items]    
Discount rates 7.80% 8.75%
Rate of return on plan assets 7.80% 8.75%
Rate of salary increases 4.50% 4.00%
United States [member]    
Disclosure of defined benefit plans [line items]    
Discount rates 2.60% 3.60%
Rate of return on plan assets 2.60% 3.60%
United Kingdom [member]    
Disclosure of defined benefit plans [line items]    
Discount rates 1.50% 2.10%
Rate of return on plan assets 1.50% 2.10%
Rate of salary increases 3.00% 3.00%
Top of range [member] | Other countries [member]    
Disclosure of defined benefit plans [line items]    
Discount rates 9.00% 8.80%
Rate of return on plan assets 9.00% 8.80%
Rate of salary increases 6.80% 6.80%
Bottom of range [member] | Other countries [member]    
Disclosure of defined benefit plans [line items]    
Discount rates 0.20% 0.40%
Rate of return on plan assets 0.20% 0.40%
Rate of salary increases 2.30% 2.30%