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Concession Financial Assets and Liabilities - Summary of Generation Indemnity Receivable (Parenthetical) (Detail) - BRL (R$) R$ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016
Disclosure Of Financial Assets and Liabilities Of The Concession [Line Items] |  |
Monetary updating | R$ 317 | R$ 352
Miranda and Sao Simao hydroelectric plants [member] |  |
Disclosure Of Financial Assets and Liabilities Of The Concession [Line Items] |  |
Monetary updating | 56 |
Adjustment of MME of transmission assets | R$ 271 |

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