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Provisions - Schedule of Assumption in Provision Calculation (Detail)
Dec. 31, 2021
Dec. 31, 2020
South Africa    
Disclosure of Provisions [line items]    
Inflation rate 4.50% 4.80%
Discount rate 10.60% 10.80%
Ghana    
Disclosure of Provisions [line items]    
Inflation rate 2.40% 2.20%
Australia    
Disclosure of Provisions [line items]    
Inflation rate 2.40% 2.50%
Discount rate 2.40% 2.50%
Peru    
Disclosure of Provisions [line items]    
Inflation rate 2.40% 2.20%
Discount rate 2.80% 2.20%
Chile    
Disclosure of Provisions [line items]    
Inflation rate 2.40% 2.20%
Discount rate 2.40% 2.20%
Bottom of range | Ghana    
Disclosure of Provisions [line items]    
Discount rate 6.60% 6.70%
Top of range | Ghana    
Disclosure of Provisions [line items]    
Discount rate   7.20%