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EQUITY - Common and preferred shares outstanding (Details) - BRL (R$) R$ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Capital |  |  |
Shares exercise period when not a public offering | 30 days |  |
Shares exercise period for public offering | 10 days |  |
Total capital | R$ 19,249,181 | R$ 19,249,181 |
Common shares |  |  |
Capital |  |  |
Authorized capital | 1,500,000,000 |  |
Shares subscribed and paid up | 573,627,483 |  |
Reconciliations of common and preferred outstanding shares |  |  |
Number of shares outstanding at beginning of the year | 571,929,945 | 571,929,945 | 571,929,945
Acquisition of Treasury shares | 0 | 0 | 0
Exercise of stock options | 0 | 0 | 0
Transfer of shares | 0 | 0 | 0
Number of shares outstanding at end of period | 571,929,945 | 571,929,945 | 571,929,945
Preferred shares |  |  |
Capital |  |  |
Authorized capital | 3,000,000,000 |  |
Shares subscribed and paid up | 1,146,031,245 |  |
Reconciliations of common and preferred outstanding shares |  |  |
Number of shares outstanding at beginning of the year | 1,137,018,570 | 1,114,744,538 | 1,132,613,562
Acquisition of Treasury shares |  | (10,000,000) | (19,923,200)
Exercise of stock options | 308,614 | 2,274,032 | 2,054,176
Transfer of shares |  | 30,000,000 |
Number of shares outstanding at end of period | 1,137,327,184 | 1,137,018,570 | 1,114,744,538

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