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Net sales (Details) - USD ($)
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure Of Net Sales [Line Items]      
Revenue from sale of goods $ 1,122,995,000 $ 1,223,942,000 $ 1,015,670,000
Revenue from rendering of services 24,001,000 29,697,000 28,782,000
Gold 411,926,000 511,434,000 440,603,000
Silver 369,167,000 409,775,000 385,989,000
Copper 274,761,000 268,527,000 2,390,840,000
Zinc 174,048,000 188,023,000 142,425,000
Lead 89,059,000 94,955,000 58,690,000
Manganese sulfate 6,655,000 6,317,000 5,982,000
Revenue from sale of goods before commercial deductions 1,325,616,000 1,479,097,000 1,258,338,000
Commercial deductions (195,865,000) (253,939,000) (244,414,000)
Indium 0 66,000 0
Royalty income 20,385,000 20,739,000 24,339,000
Revenue from contracts with customers 1,174,137,000 1,275,594,000 1,067,045,000
America [member]      
Disclosure Of Net Sales [Line Items]      
Revenue from sale of goods 370,624,000 471,863,000 397,795,000
Revenue from rendering of services 289,000 14,794,000 0
Peru [Member]      
Disclosure Of Net Sales [Line Items]      
Revenue from sale of goods 537,816,000 551,243,000 396,733,000
Revenue from rendering of services 23,712,000 14,903,000 28,782,000
Royalty income 20,385 20,739 24,339
Europe [Member]      
Disclosure Of Net Sales [Line Items]      
Revenue from sale of goods 100,792,000 81,333,000 121,929,000
Asia [Member]      
Disclosure Of Net Sales [Line Items]      
Revenue from sale of goods $ 120,519,000 $ 120,719,000 $ 97,467,000