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22. Equity (Details) - shares | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
SummaryOfEquityLineItems [Line Items] |  |  |
Number of shares |  | 683,509,869 | 683,509,869
Percentage of shares |  | 1.0000 | 1.0000
State Department of Finance |  |  |
SummaryOfEquityLineItems [Line Items] |  |  |
Number of shares |  | 343,524,285 | 343,524,285
Percentage of shares |  | .5026 | .5026
Companhia Brasileira de Liquidacao e Custodia |  |  |
SummaryOfEquityLineItems [Line Items] |  |  |
Number of shares | [1] | 201,026,895 | 206,955,305
Percentage of shares |  | .2941 | .3028
The Bank of New York ADR Department |  |  |
SummaryOfEquityLineItems [Line Items] |  |  |
Number of shares | [1],[2] | 136,790,413 | 132,401,813
Percentage of shares |  | .2001 | .1937
Other |  |  |
SummaryOfEquityLineItems [Line Items] |  |  |
Number of shares |  | 2,168,276 | 628,466
Percentage of shares |  | .0032 | .0009
[1] | custodians
[2] | Each ADR corresponds to 1 share.

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