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Derivative financial instruments - Embedded derivatives (Details)
item in Thousands
 12 Months Ended
Dec. 31, 2020
USD ($)
item
Dec. 31, 2019
USD ($)
item
Copper concentrate [Member] | Minimum    
Disclosure Of Embedded derivatives [Line Items]    
Forward pricing   2.793
Copper concentrate [Member] | Maximum    
Disclosure Of Embedded derivatives [Line Items]    
Forward pricing   2.804
Sociedad Minera Cerro Verde S.A.A. [Member]    
Disclosure Of Embedded derivatives [Line Items]    
Derivative financial asset liabilities $ 101,434,000 $ 36,705,000
Sociedad Minera Cerro Verde S.A.A. [Member] | Copper concentrate [Member]    
Disclosure Of Embedded derivatives [Line Items]    
Quantity of Metal | item 267,872 246,441
Embedded derivatives, maturity January 2021 to May 2021 January 2020 to May 2020
Derivative financial asset liabilities $ 98,424,000 $ 39,727,000
Sociedad Minera Cerro Verde S.A.A. [Member] | Copper concentrate [Member] | Minimum    
Disclosure Of Embedded derivatives [Line Items]    
Provisional pricing $ 2.908 2.567
Forward pricing 3.519  
Sociedad Minera Cerro Verde S.A.A. [Member] | Copper concentrate [Member] | Maximum    
Disclosure Of Embedded derivatives [Line Items]    
Provisional pricing $ 3.545 $ 2.774
Forward pricing 3.524  
Sociedad Minera Cerro Verde S.A.A. [Member] | Copper cathode [Member]    
Disclosure Of Embedded derivatives [Line Items]    
Quantity of Metal | item 3,964 4,410
Embedded derivatives, maturity January 2021 January 2020
Provisional pricing   $ 2.791
Forward pricing 3.519 2.793
Derivative financial asset liabilities $ (235,000) $ 9,000
Sociedad Minera Cerro Verde S.A.A. [Member] | Copper cathode [Member] | Minimum    
Disclosure Of Embedded derivatives [Line Items]    
Provisional pricing 3.535  
Sociedad Minera Cerro Verde S.A.A. [Member] | Copper cathode [Member] | Maximum    
Disclosure Of Embedded derivatives [Line Items]    
Provisional pricing $ 3.612  
Sociedad Minera Cerro Verde S.A.A. [Member] | Molybdenum [Member]    
Disclosure Of Embedded derivatives [Line Items]    
Quantity of Metal | item 3,382 5,370
Embedded derivatives, maturity January 2021 to February 2021 January 2020 to February 2020
Forward pricing 8.658 8.025
Derivative financial asset liabilities $ 3,245,000 $ (3,031,000)
Sociedad Minera Cerro Verde S.A.A. [Member] | Molybdenum [Member] | Minimum    
Disclosure Of Embedded derivatives [Line Items]    
Provisional pricing 7.360 7.857
Sociedad Minera Cerro Verde S.A.A. [Member] | Molybdenum [Member] | Maximum    
Disclosure Of Embedded derivatives [Line Items]    
Provisional pricing $ 7.884 $ 9.724