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FINANCIAL INSTRUMENTS - Measurement of fair value (Details) - BRL (R$) R$ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
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FINANCIAL INSTRUMENTS |  |
Total financial assets | R$ 9,291,006 | R$ 12,712,924
Total financial liabilities | 22,104,962 | 25,257,075
Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Total financial assets | 9,291,006 | 12,712,924
Total financial liabilities | 22,104,962 | 25,257,075
Trade accounts payable |  |
FINANCIAL INSTRUMENTS |  |
Total financial liabilities | 3,179,954 | 2,743,818
Trade accounts payable | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial liabilities | 3,179,954 | 2,743,818
Short-term debts | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial liabilities | 2,004,341 | 4,458,220
Unrealized losses on financial instruments |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial liabilities | 1,267 |
Total financial liabilities | 1,267 | 6,584
Unrealized losses on financial instruments | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial liabilities |  | 6,584
Other current liabilities |  |
FINANCIAL INSTRUMENTS |  |
Total financial liabilities | 625,410 | 514,599
Other current liabilities | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial liabilities | 625,410 | 514,599
Long-term debt | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial liabilities | 14,457,315 | 15,959,590
Debentures |  |
FINANCIAL INSTRUMENTS |  |
Total financial liabilities | 47,928 | 165,423
Debentures | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial liabilities | 47,928 | 165,423
FIDC Obligation |  |
FINANCIAL INSTRUMENTS |  |
Total financial liabilities | 1,135,077 | 1,007,259
FIDC Obligation | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial liabilities | 1,135,077 | 1,007,259
Other non-current liabilities |  |
FINANCIAL INSTRUMENTS |  |
Total financial liabilities | 653,670 | 401,582
Other non-current liabilities | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial liabilities | 653,670 | 401,582
Cash and cash equivalents |  |
FINANCIAL INSTRUMENTS |  |
Total financial assets | 2,555,338 | 5,063,383
Cash and cash equivalents | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial assets | 2,555,338 | 5,063,383
Short-term investments |  |
FINANCIAL INSTRUMENTS |  |
Total financial assets | 821,518 | 1,024,411
Short-term investments | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial assets | 821,518 | 1,024,411
Trade accounts receivable |  |
FINANCIAL INSTRUMENTS |  |
Total financial assets | 2,798,420 | 3,576,699
Trade accounts receivable | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial assets | 2,798,420 | 3,576,699
Unrealized gains on financial instruments |  |
FINANCIAL INSTRUMENTS |  |
Total financial assets |  | 12,951
Unrealized gains on financial instruments | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial assets |  | 2,557
Other current assets |  |
FINANCIAL INSTRUMENTS |  |
Total financial assets | 469,737 | 668,895
Other current assets | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial assets | 469,737 | 668,895
Related parties |  |
FINANCIAL INSTRUMENTS |  |
Total financial assets | 51,839 | 57,541
Related parties | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial assets | 51,839 | 57,541
Unrealized gains on financial instruments, noncurrent | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial assets |  | 10,394
Judicial deposits |  |
FINANCIAL INSTRUMENTS |  |
Total financial assets | 2,051,181 | 1,861,784
Judicial deposits | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial assets | 2,051,181 | 1,861,784
Other non-current assets |  |
FINANCIAL INSTRUMENTS |  |
Total financial assets | 542,973 | 447,260
Other non-current assets | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial assets | 542,973 | 447,260
Quoted Prices Active Markets for Identical Assets (Level 1) | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Total financial assets | 238,008 | 458,639
Quoted Prices Active Markets for Identical Assets (Level 1) | Short-term investments | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial assets | 238,008 | 458,639
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Total financial assets | 9,052,998 | 12,254,285
Total financial liabilities | 22,104,962 | 25,257,075
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Trade accounts payable | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial liabilities | 3,179,954 | 2,743,818
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Short-term debts | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial liabilities | 2,004,341 | 4,458,220
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Unrealized losses on financial instruments |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial liabilities | 1,267 |
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Unrealized losses on financial instruments | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial liabilities |  | 6,584
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Other current liabilities | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial liabilities | 625,410 | 514,599
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Long-term debt | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial liabilities | 14,457,315 | 15,959,590
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Debentures | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial liabilities | 47,928 | 165,423
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | FIDC Obligation | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial liabilities | 1,135,077 | 1,007,259
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Other non-current liabilities | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial liabilities | 653,670 | 401,582
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Cash and cash equivalents | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial assets | 2,555,338 | 5,063,383
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Short-term investments | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial assets | 583,510 | 565,772
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Trade accounts receivable | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial assets | 2,798,420 | 3,576,699
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Unrealized gains on financial instruments | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial assets |  | 2,557
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Other current assets | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Current financial assets | 469,737 | 668,895
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Related parties | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial assets | 51,839 | 57,541
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Unrealized gains on financial instruments, noncurrent | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial assets |  | 10,394
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Judicial deposits | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial assets | 2,051,181 | 1,861,784
Quoted Prices in Non-Active Markets for Similar Assets (Level 2) | Other non-current assets | Measured at Fair Value on a Recurring Basis |  |
FINANCIAL INSTRUMENTS |  |
Non-current financial assets | R$ 542,973 | R$ 447,260

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