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26. EQUITY AND REMUNERATION TO SHAREHOLDERS (Details) - shares | 1 Months Ended |  |  |  |
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Apr. 28, 2018 | Dec. 31, 2020 | Jul. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Number of shares issued |  | 1,518,752,601 | 60,000,000 | 1,458,752,601 | 1,458,752,601
Percentage of changes in share capital |  | 100.00% |  | 10000.00% | 100.00%
Description of capital increase | On April 23, 2018 a Shareholders’ Extraordinary General Meeting approved an increase in the Company’s capital, of R$ 999, from R$ 6,294 to R$ 7,294, through issuance of 199,910,947 new shares, each with nominal value of R$ 5.00, comprising 66,849,505 common shares and 133,061,442, preferred shares. |  |  |  |
Common Shares [member] |  |  |  |  |
Number of shares issued |  | 507,670,289 |  | 487,614,213 | 487,614,213
Percentage of changes in share capital |  | 100.00% |  | 100.00% | 100.00%
Preferred Shares [member] |  |  |  |  |
Number of shares issued |  | 1,011,082,312 | 39,943,924 | 971,138,388 | 971,138,388
Percentage of changes in share capital |  | 100.00% |  | 100.00% | 100.00%
State of minas gerais [member] |  |  |  |  |
Number of shares issued |  | 258,750,499 |  | 248,528,276 | 248,480,146
Percentage of changes in share capital |  | 17.00% |  | 17.00% | 17.00%
State of minas gerais [member] | Common Shares [member] |  |  |  |  |
Number of shares issued |  | 258,738,711 |  | 248,516,953 | 248,480,146
Percentage of changes in share capital |  | 51.00% |  | 51.00% | 51.00%
State of minas gerais [member] | Preferred Shares [member] |  |  |  |  |
Number of shares issued |  | 11,788 |  | 11,323 |
Other entities of minas gerais state [member] |  |  |  |  |
Number of shares issued |  | 7,462,750 |  | 1,431,172 | 704,350
Other entities of minas gerais state [member] | Common Shares [member] |  |  |  |  |
Number of shares issued |  | 20,713 |  | 19,896 | 56,703
Other entities of minas gerais state [member] | Preferred Shares [member] |  |  |  |  |
Number of shares issued |  | 7,442,037 |  | 1,411,276 | 647,647
Percentage of changes in share capital |  | 1.00% |  |  |
FIA Dinamica Energia S.A. [member] |  |  |  |  |
Number of shares issued |  | 158,147,949 |  | 103,833,744 | 104,105,344
Percentage of changes in share capital |  | 10.00% |  | 7.00% | 7.00%
FIA Dinamica Energia S.A. [member] | Common Shares [member] |  |  |  |  |
Number of shares issued |  | 114,172,677 |  | 48,700,000 | 48,200,000
Percentage of changes in share capital |  | 22.00% |  | 10.00% | 10.00%
FIA Dinamica Energia S.A. [member] | Preferred Shares [member] |  |  |  |  |
Number of shares issued |  | 43,975,272 |  | 55,133,744 | 55,905,344
Percentage of changes in share capital |  | 4.00% |  | 6.00% | 6.00%
BNDES Participacoes [member] |  |  |  |  |
Number of shares issued |  | 83,877,607 |  | 80,563,930 | 80,563,930
Percentage of changes in share capital |  | 6.00% |  | 6.00% | 5.00%
BNDES Participacoes [member] | Common Shares [member] |  |  |  |  |
Number of shares issued |  | 56,578,175 |  | 54,342,992 | 54,342,992
Percentage of changes in share capital |  | 11.00% |  | 11.00% | 11.00%
BNDES Participacoes [member] | Preferred Shares [member] |  |  |  |  |
Number of shares issued |  | 27,299,432 |  | 26,220,938 | 26,220,938
Percentage of changes in share capital |  | 3.00% |  | 3.00% | 3.00%
Other Shareholders In Brazil [member] |  |  |  |  |
Number of shares issued |  | 268,421,971 |  | 430,153,173 | 475,741,149
Percentage of changes in share capital |  | 18.00% |  | 29.00% | 33.00%
Other Shareholders In Brazil [member] | Common Shares [member] |  |  |  |  |
Number of shares issued |  | 55,717,246 |  | 101,170,317 | 105,402,202
Percentage of changes in share capital |  | 11.00% |  | 21.00% | 22.00%
Other Shareholders In Brazil [member] | Preferred Shares [member] |  |  |  |  |
Number of shares issued |  | 212,704,725 |  | 328,982,856 | 370,338,947
Percentage of changes in share capital |  | 21.00% |  | 34.00% | 38.00%
Foreign Shareholders [member] |  |  |  |  |
Number of shares issued |  | 588,401,855 |  | 594,242,306 | 549,157,682
Percentage of changes in share capital |  | 39.00% |  | 41.00% | 38.00%
Foreign Shareholders [member] | Common Shares [member] |  |  |  |  |
Number of shares issued |  | 22,442,767 |  | 34,864,055 | 31,132,170
Percentage of changes in share capital |  | 5.00% |  | 7.00% | 6.00%
Foreign Shareholders [member] | Preferred Shares [member] |  |  |  |  |
Number of shares issued |  | 565,959,088 |  | 559,378,251 | 518,025,512
Percentage of changes in share capital |  | 56.00% |  | 57.00% | 53.00%
BlackRock [member] |  |  |  |  |
Number of shares issued |  | 153,689,970 |  |  |
Percentage of changes in share capital |  | 10.00% |  |  |
BlackRock [member] | Preferred Shares [member] |  |  |  |  |
Number of shares issued |  | 153,689,970 |  |  |
Percentage of changes in share capital |  | 15.00% |  |  |

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