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Impairment (Charges) Reversals and Goodwill - Impairment (Charges) Reversals (Details)
Ounce in Millions
 12 Months Ended
Dec. 31, 2018
USD ($)
Ounce
Dec. 31, 2017
USD ($)
Disclosure of impairment loss and reversal of impairment loss [line items]    
Period of analyst consensus prices used for economic impairment modeling 4 years  
Impairment loss recognised in profit or loss $ 27,789,000  
Impairment charges, net of tax expense (27,800,000)  
Reversals of impairment (27,789,000) $ 61,554,000
Reversal of impairment, net of tax   53,400,000
Combined net carrying amount of Manantial Espejo mine and Joaquin and COSE development projects, net of associated closure and decommissioning liabilities 68,100,000  
Combined estimated recoverable amount $ 39,300,000  
Risk adjusted discount rate 7.25%  
Manantial Espejo mine [member]    
Disclosure of impairment loss and reversal of impairment loss [line items]    
Impairment loss recognised in profit or loss $ 27,789,000  
Reversals of impairment   0
Morococha mine [member]    
Disclosure of impairment loss and reversal of impairment loss [line items]    
Impairment loss recognised in profit or loss 0  
Reversals of impairment 60,200,000 60,237,000
Reversal of impairment, net of tax $ 52,100,000  
Increase in silver mineral reserve | Ounce 2.8  
Calcatreu project [member]    
Disclosure of impairment loss and reversal of impairment loss [line items]    
Impairment loss recognised in profit or loss $ 0  
Reversals of impairment $ 0 $ 1,317,000