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Mining concessions, development costs, property, plant and equipment, net (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | $ 1,949,555 | $ 1,960,025 |
Balance as of December |  | 1,847,615 | 1,949,555 | $ 1,960,025
Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 3,596,342 | 3,501,216 |
Additions |  | 172,509 | 277,824 |
Disposals |  | (9,725) |  | (18,056)
Sales |  | (9,908) | (122,906) |
Reclassifications and transfers |  | (21,815) | (41,736) |
Balance as of December |  | 3,727,403 | 3,596,342 | 3,501,216
Accumulated depreciation, amortisation and impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 1,611,982 | 1,510,809 |
Additions |  | 253,968 | 222,495 |
Disposals |  | (262) |  | (3,043)
Sales |  | (9,282) | (101,259) |
Reclassifications and transfers |  | (2,893) | (17,020) |
Balance as of December |  | 1,853,513 | 1,611,982 | 1,510,809
Accumulated impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 34,805 | 30,382 |
Additions |  | 0 | 21,620 |
Disposals |  | (8,530) |  | 0
Sales |  | 0 | (17,197) |
Reclassifications and transfers |  | 0 | 0 |
Balance as of December |  | 26,275 | 34,805 | 30,382
Land [Member] | Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 22,690 | 22,958 |
Additions |  | 783 | 0 |
Disposals |  | (462) |  | 0
Sales |  | 0 | 0 |
Reclassifications and transfers |  | (1,250) | (268) |
Balance as of December |  | 21,761 | 22,690 | 22,958
Land [Member] | Accumulated depreciation, amortisation and impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 1,249 | 0 |
Additions |  | 0 | 0 |
Disposals |  | 0 | 0 |
Sales |  | 0 | 0 |
Reclassifications and transfers |  | (1,249) | 1,249 |
Balance as of December |  | 0 | 1,249 | 0
Mining concessions [Member] | Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 151,873 | 198,009 |
Additions |  | 0 | 2 |
Disposals |  | 0 |  | 0
Sales |  | 0 | (15,000) |
Reclassifications and transfers |  | 0 | (31,138) |
Balance as of December |  | 151,873 | 151,873 | 198,009
Mining concessions [Member] | Accumulated depreciation, amortisation and impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 40,239 | 77,466 |
Additions |  | 10 | 8 |
Disposals |  | 0 |  | 0
Sales |  | 0 | (13,845) |
Reclassifications and transfers |  | 0 | (23,390) |
Balance as of December |  | 40,249 | 40,239 | 77,466
Development costs [Member] | Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 712,051 | 652,392 |
Additions |  | 32,059 | 69,335 |
Disposals |  | (2,656) |  | 0
Sales |  | 0 | (10,107) |
Reclassifications and transfers |  | 1,805 | 431 |
Balance as of December |  | 743,259 | 712,051 | 652,392
Development costs [Member] | Accumulated depreciation, amortisation and impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 263,122 | 241,636 |
Additions |  | 35,433 | 30,886 |
Disposals |  | 0 |  | 0
Sales |  | 0 | (7,910) |
Reclassifications and transfers |  | (2) | (1,490) |
Balance as of December |  | 298,553 | 263,122 | 241,636
Development costs [Member] | Accumulated impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 10,153 | 9,487 |
Additions |  | 0 | 2,864 |
Disposals |  | 0 |  | 0
Sales |  | 0 | (2,198) |
Reclassifications and transfers |  | 0 | 0 |
Balance as of December |  | 10,153 | 10,153 | 9,487
Buildings [member] | Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 1,279,251 | 1,109,167 |
Additions |  | 0 | 835 |
Disposals |  | (2,837) |  | (387)
Sales |  | 0 | (28,751) |
Reclassifications and transfers |  | 66,207 | 198,387 |
Balance as of December |  | 1,342,621 | 1,279,251 | 1,109,167
Buildings [member] | Accumulated depreciation, amortisation and impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 506,837 | 455,678 |
Additions |  | 84,244 | 73,314 |
Disposals |  | 0 |  | (115)
Sales |  | 0 | (28,208) |
Reclassifications and transfers |  | 562 | 6,168 |
Balance as of December |  | 591,643 | 506,837 | 455,678
Machinery [member] | Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 929,023 | 986,032 |
Additions |  | 0 | 2,579 |
Disposals |  | (182) |  | (3,749)
Sales |  | (9,205) | (50,097) |
Reclassifications and transfers |  | 38,830 | (5,742) |
Balance as of December |  | 958,466 | 929,023 | 986,032
Machinery [member] | Accumulated depreciation, amortisation and impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 582,449 | 558,061 |
Additions |  | 93,722 | 74,744 |
Disposals |  | (177) |  | (2,662)
Sales |  | (8,659) | (41,595) |
Reclassifications and transfers |  | (1,978) | (6,099) |
Balance as of December |  | 665,357 | 582,449 | 558,061
Transportation units [member] | Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 9,946 | 10,416 |
Additions |  | 42 | 11 |
Disposals |  | (138) |  | (190)
Sales |  | (510) | (1,079) |
Reclassifications and transfers |  | 1,545 | 788 |
Balance as of December |  | 10,885 | 9,946 | 10,416
Transportation units [member] | Accumulated depreciation, amortisation and impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 8,390 | 8,792 |
Additions |  | 745 | 837 |
Disposals |  | (85) |  | (114)
Sales |  | (436) | (1,057) |
Reclassifications and transfers |  | (15) | (68) |
Balance as of December |  | 8,599 | 8,390 | 8,792
Fixtures and fittings [member] | Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 13,902 | 14,047 |
Additions |  | 0 | 31 |
Disposals |  | 0 |  | (157)
Sales |  | (193) | (487) |
Reclassifications and transfers |  | (403) | 468 |
Balance as of December |  | 13,306 | 13,902 | 14,047
Fixtures and fittings [member] | Accumulated depreciation, amortisation and impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 9,880 | 9,172 |
Additions |  | 644 | 1,109 |
Disposals |  | 0 |  | (152)
Sales |  | (187) | (236) |
Reclassifications and transfers |  | (214) | (13) |
Balance as of December |  | 10,123 | 9,880 | 9,172
Units in transit [Member] | Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 4,749 | 30,051 |
Additions |  | 11 | 2,822 |
Disposals |  | 0 |  | 0
Sales |  | 0 | 0 |
Reclassifications and transfers |  | (2,078) | (28,124) |
Balance as of December |  | 2,682 | 4,749 | 30,051
Construction in Progress [Member] | Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 101,122 | 105,788 |
Additions |  | 67,096 | 173,333 |
Disposals |  | (3,450) |  | 0
Sales |  | 0 | (190) |
Reclassifications and transfers |  | (108,106) | (177,809) |
Balance as of December |  | 56,662 | 101,122 | 105,788
Stripping activity asset [Member] | Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance | [1] | 130,447 | 124,467 |
Additions | [1] | 11,279 | 18,282 |
Disposals | [1] | 0 |  | (13,573)
Sales | [1] | 0 | 0 |
Reclassifications and transfers | [1] | 0 | 1,271 |
Balance as of December | [1] | 141,726 | 130,447 | 124,467
Stripping activity asset [Member] | Accumulated depreciation, amortisation and impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 41,695 | 18,729 |
Additions |  | 28,820 | 16,343 |
Disposals |  | 0 |  | 0
Sales |  | 0 | 0 |
Reclassifications and transfers |  | 3 | 6,623 |
Balance as of December |  | 70,518 | 41,695 | 18,729
Mine closure costs [Member] | Gross carrying amount [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 241,288 | 247,889 |
Additions |  | 61,239 | 10,594 |
Disposals |  | 0 |  | 0
Sales |  | 0 | (17,195) |
Reclassifications and transfers |  | (18,365) | 0 |
Balance as of December |  | 284,162 | 241,288 | 247,889
Mine closure costs [Member] | Accumulated depreciation, amortisation and impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 158,121 | 141,275 |
Additions |  | 10,350 | 25,254 |
Disposals |  | 0 |  | 0
Sales |  | 0 | (8,408) |
Reclassifications and transfers |  | 0 | 0 |
Balance as of December |  | 168,471 | 158,121 | 141,275
Mine closure costs [Member] | Accumulated impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 20,121 | 10,990 |
Additions |  | 0 | 17,916 |
Disposals |  | (5,693) |  | 0
Sales |  | 0 | (8,785) |
Reclassifications and transfers |  | (1,221) | 0 |
Balance as of December |  | 13,207 | 20,121 | 10,990
Mining Concessions And Development Costs [Member] | Accumulated impairment [member] |  |  |  |
Disclosure of Mining concessions, development costs, property, plant and equipment, net [Line Items] |  |  |  |
Opening balance |  | 4,531 | 9,905 |
Additions |  | 0 | 840 |
Disposals |  | (2,837) | 0 |
Sales |  | 0 | (6,214) |
Reclassifications and transfers |  | 1,221 | 0 |
Balance as of December |  | $ 2,915 | $ 4,531 | $ 9,905
[1] | In mid-2016, a landslide occurred in the west wall of the Tajo Norte; consequently, it was decided not to mine this area due to stability and operational design issues. According to the distribution of reserves, this area (Phase 10) contained 5.5 MT of ore and 9.2 MT of waste valued at US$13,573,000, which were withdrawn from the reserves in the year 2017.

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