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Revenue - Summary of Revenue from Contracts with Customers (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue from contracts with customers $ 2,967.1 $ 2,577.8 $ 2,761.8
Gold [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue from contracts with customers [1] 2,802.0 2,408.6 2,584.0
Copper [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue from contracts with customers [2] $ 165.1 $ 169.2 $ 177.8
[1] All regions.
[2] Only Peru region (Cerro Corona).