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INTANGIBLE ASSETS - Changes in intangible assets by type (Details) - BRL (R$) R$ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
INTANGIBLE ASSETS |  |  |
Other intangible assets at beginning of period | R$ 972,089 | R$ 1,319,941 | R$ 1,835,761
Foreign exchange effect | 107,434 | 7,666 | (208,785)
Acquisition | 67,388 | 37,939 | 54,044
Disposal | (3,879) | (27,652) | (15,195)
Amortization | (306,936) | (285,197) | (318,135)
Effect of selling of subsidiary |  |  | (27,749)
Assets held for sale |  | (80,608) |
Other intangible assets at end of period | 836,096 | 972,089 | 1,319,941
Supplier relationships |  |  |
INTANGIBLE ASSETS |  |  |
Other intangible assets at beginning of period | 32,786 | 39,726 | 47,571
Amortization | (6,067) | (6,940) | (7,845)
Other intangible assets at end of period | 26,719 | 32,786 | 39,726
Software development |  |  |
INTANGIBLE ASSETS |  |  |
Other intangible assets at beginning of period | 490,829 | 636,605 | 808,482
Foreign exchange effect | 28,598 | 2,947 | (60,464)
Acquisition | 67,388 | 37,939 | 40,643
Disposal | (3,791) |  | (2,145)
Amortization | (167,384) | (149,150) | (149,911)
Assets held for sale |  | (37,512) |
Other intangible assets at end of period | R$ 415,640 | 490,829 | 636,605
Estimated useful lives | 7 years |  |
Customers contracts and relationships |  |  |
INTANGIBLE ASSETS |  |  |
Other intangible assets at beginning of period | R$ 440,774 | 615,608 | 911,483
Foreign exchange effect | 77,593 | 3,835 | (140,812)
Disposal | (88) | (27,652) |
Amortization | (130,980) | (125,621) | (155,063)
Assets held for sale |  | (25,396) |
Other intangible assets at end of period | 387,299 | 440,774 | 615,608
Others |  |  |
INTANGIBLE ASSETS |  |  |
Other intangible assets at beginning of period | 7,700 | 28,002 | 68,225
Foreign exchange effect | 1,243 | 884 | (7,509)
Acquisition |  |  | 13,401
Disposal |  |  | (13,050)
Amortization | (2,505) | (3,486) | (5,316)
Effect of selling of subsidiary |  |  | (27,749)
Assets held for sale |  | (17,700) |
Other intangible assets at end of period | R$ 6,438 | R$ 7,700 | R$ 28,002
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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