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INTANGIBLE ASSETS - Changes in intangible assets by type (Details) - BRL (R$) R$ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
INTANGIBLE ASSETS |  |  |
Other intangible assets at beginning of period | R$ 1,319,941 | R$ 1,835,761 | R$ 1,547,098
Foreign exchange effect | 7,666 | (208,785) | 464,966
Acquisition | 37,939 | 54,044 | 126,428
Disposal | (27,652) | (15,195) | (5,390)
Amortization | (285,197) | (318,135) | (297,341)
Effect of selling of subsidiary |  | (27,749) |
Assets held for sale | (80,608) |  |
Other intangible assets at end of period | 972,089 | 1,319,941 | 1,835,761
Supplier relationships |  |  |
INTANGIBLE ASSETS |  |  |
Other intangible assets at beginning of period | 39,726 | 47,571 | 56,654
Amortization | (6,940) | (7,845) | (9,083)
Other intangible assets at end of period | 32,786 | 39,726 | 47,571
Software development |  |  |
INTANGIBLE ASSETS |  |  |
Other intangible assets at beginning of period | 636,605 | 808,482 | 688,061
Foreign exchange effect | 2,947 | (60,464) | 123,167
Acquisition | 37,939 | 40,643 | 118,933
Disposal |  | (2,145) | (1,182)
Amortization | (149,150) | (149,911) | (120,497)
Assets held for sale | (37,512) |  |
Other intangible assets at end of period | R$ 490,829 | 636,605 | 808,482
Estimated useful lives | 7 years |  |
Customers contracts and relationships |  |  |
INTANGIBLE ASSETS |  |  |
Other intangible assets at beginning of period | R$ 615,608 | 911,483 | 749,027
Foreign exchange effect | 3,835 | (140,812) | 327,424
Disposal | (27,652) |  |
Amortization | (125,621) | (155,063) | (164,968)
Assets held for sale | (25,396) |  |
Other intangible assets at end of period | 440,774 | 615,608 | 911,483
Others |  |  |
INTANGIBLE ASSETS |  |  |
Other intangible assets at beginning of period | 28,002 | 68,225 | 53,356
Foreign exchange effect | 884 | (7,509) | 14,375
Acquisition |  | 13,401 | 7,495
Disposal |  | (13,050) | (4,208)
Amortization | (3,486) | (5,316) | (2,793)
Effect of selling of subsidiary |  | (27,749) |
Assets held for sale | (17,700) |  |
Other intangible assets at end of period | R$ 7,700 | R$ 28,002 | R$ 68,225
Estimated useful lives | 5 years |  |
Minimum | Supplier relationships |  |  |
INTANGIBLE ASSETS |  |  |
Estimated useful lives | 5 years |  |
Minimum | Customers contracts and relationships |  |  |
INTANGIBLE ASSETS |  |  |
Estimated useful lives | 5 years |  |
Maximum | Supplier relationships |  |  |
INTANGIBLE ASSETS |  |  |
Estimated useful lives | 20 years |  |
Maximum | Customers contracts and relationships |  |  |
INTANGIBLE ASSETS |  |  |
Estimated useful lives | 20 years |  |

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