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Note 24 - Share-based Payments - Weighted Average Fair Value of the Options and Assumptions (Details) - BRL (R$)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Statement Line Items [Line Items]      
Fair value of options granted [1] R$ 6.51 R$ 6.21 R$ 7.84
Share price [1] 19.80 17.18 18.41
Exercise price [1] R$ 19.80 R$ 17.18 R$ 18.41
Expected volatility [1] 26.70% 27.00% 27.50%
Vesting year [1] 5 5 5
Expected dividends [1] 5.00% 5.00% 5.00%
Risk-free interest rate [1],[2] 10.10% 12.40% 15.90%
[1] Information based on weighted average plans granted, except for the expected dividends and risk-free interest rate.
[2] The percentages include the grants of stock options and ADR's during the period, in which the risk-free interest rate of ADR's are calculated in U.S. dollar.