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Mining concessions, development costs, right-of-use assets, property, plant and equipment, net - Net assets for right in use (Details)
 12 Months Ended
Dec. 31, 2020
USD ($)
item
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2016
USD ($)
Mining concessions, development costs, property, plant and equipment, net        
After-tax discount rate applied to the pre-tax cash flows 5.25      
Pre-tax discount rate applied to the pre-tax cash flows 8.09%      
Book Value Of Assets Under Finance Lease $ 187,800,000   $ 313,300,000  
Acquisition Of Assets Under Lease   $ 0 0  
Capitalized finance costs   0 0  
Right-of-use assets 7,178,000 6,185,000    
Additions to right-of-use assets 6,200,000 3,700,000    
Disposal of right of use assets 1,300,000 10,900,000    
Reversal of Impairment loss of long-lived assets, note 11(b) 2,083,000 (2,083,000) 5,693,000  
Write-off of stripping activity asset 11,633,000 0 0  
Impairment loss       $ 0
Buildings and other constructions        
Mining concessions, development costs, property, plant and equipment, net        
Right-of-use assets 3,370,000 4,602,000    
Transportation units        
Mining concessions, development costs, property, plant and equipment, net        
Right-of-use assets 3,330,000 1,112,000    
Machinery and equipment        
Mining concessions, development costs, property, plant and equipment, net        
Right-of-use assets $ 478,000 471,000    
El Brocal        
Mining concessions, development costs, property, plant and equipment, net        
After-tax discount rate applied to the pre-tax cash flows 7.91      
Pre-tax discount rate applied to the pre-tax cash flows 12.18%      
Goodwill $ 34,000,000      
Stripping activity asset of phase 9 written off | item 1,102,117      
Write-off of stripping activity asset $ 11,633,000      
Stripping activity asset of phase 9 expected to be produced $ 3,244,000      
Stripping activity asset of phase 9 | item 307,302      
La Zanja mining unit [Member]        
Mining concessions, development costs, property, plant and equipment, net        
After-tax discount rate applied to the pre-tax cash flows 5.96      
Pre-tax discount rate applied to the pre-tax cash flows 9.19%      
Reversal of impairment loss recognised in profit or loss, property, plant and equipment   5,700,000    
Shila-Paula mining unit [Member]        
Mining concessions, development costs, property, plant and equipment, net        
Reversal of impairment loss recognised in profit or loss, property, plant and equipment     2,800,000  
Impairment Of Long Lived Asset [Member] | La Zanja mining unit [Member]        
Mining concessions, development costs, property, plant and equipment, net        
Reversal of Impairment loss of long-lived assets, note 11(b)     $ 5,700,000  
Impairment Of Long Lived Asset [Member] | Julcani Mining Unit [Member]        
Mining concessions, development costs, property, plant and equipment, net        
Provisions $ 0      
Reversal of Impairment loss of long-lived assets, note 11(b) $ 2,100,000 $ 2,100,000