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31. FINANCIAL INSTRUMENTS AND RISK MANAGEMENT (Details 6) - BRL (R$) R$ in Millions | Dec. 31, 2020 | Dec. 31, 2019
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FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | R$ (8,191) | R$ (6,353)
Base scenario [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | (8,191) |
Probable scenario US$1=R$5.20 [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | (8,196) |
Net effect of exchange rate fluctuation | (5) |
Probable scenario appreciation 25.00% US$1= R$6.50 [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | (10,245) |
Net effect of exchange rate fluctuation | (2,054) |
Remote scenario appreciation 50.00% US$1=R$7.80 [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | (12,294) |
Net effect of exchange rate fluctuation | (4,103) |
Loans and financings [member] | Base scenario [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | (7,866) |
Loans and financings [member] | Probable scenario US$1=R$5.20 [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | (7,871) |
Loans and financings [member] | Probable scenario appreciation 25.00% US$1= R$6.50 [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | (9,838) |
Loans and financings [member] | Remote scenario appreciation 50.00% US$1=R$7.80 [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | (11,806) |
Suppliers (itaipu binacional) [member] | Base scenario [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | (325) |
Suppliers (itaipu binacional) [member] | Probable scenario US$1=R$5.20 [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | (325) |
Suppliers (itaipu binacional) [member] | Probable scenario appreciation 25.00% US$1= R$6.50 [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | (407) |
Suppliers (itaipu binacional) [member] | Remote scenario appreciation 50.00% US$1=R$7.80 [member] |  |
FinancialInstrumentsAndRiskManagementLineItems [Line Items] |  |
Net liabilities exposed | R$ (488) |

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