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LONG-TERM INCENTIVE PLANS - Stock option activity (Details) - Stock options | 12 Months Ended
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Dec. 31, 2018 BRL (R$) Options | Dec. 31, 2017 BRL (R$) Options | Dec. 31, 2016 BRL (R$) Options
Number of shares |  |  |
Balance, beginning of year | Options | 292,391 | 569,115 | 1,074,246
Options Exercised | Options | (33,499) |  |
Options Forfeited | Options | (243,412) | (276,724) | (505,131)
Balance, end of year | Options | 15,480 | 292,391 | 569,115
Average exercise price in the year |  |  |
Beginning of year | R$ 17.91 | R$ 16.64 | R$ 18.36
Options Exercised | 14.86 |  |
Options Forfeited | 18.62 | 15.11 | 20.49
End of year | 16.72 | 17.91 | 16.64
Average market price of the share | R$ 15.70 | R$ 11.19 | R$ 11.68

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