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Cost of sales (Details Textual) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure of cost of sales [Line Items]      
Administrative expenses $ 78,760 $ 83,597 $ 81,692
Labour [Member]      
Disclosure of cost of sales [Line Items]      
Payment of Union Agreement Bonus 69,000    
Sociedad Minera Cerro Verde S.A.A. [Member]      
Disclosure of cost of sales [Line Items]      
Increase decrease in labor costs related to profit sharing 60,200 86,400 36,800
Administrative expenses $ 0 $ 0 $ 0