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Revenue - Summary of Revenue from Contracts with Customers (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue from contracts with customers $ 3,892.1 $ 2,967.1 $ 2,577.8
Gold [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue from contracts with customers [1] 3,748.0 2,802.0 2,408.6
Copper [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue from contracts with customers [2] $ 144.1 $ 165.1 $ 169.2
[1] All regions.
[2] Only Peru region (Cerro Corona).