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Revenues - Summary of Deductions from Revenue (Detail) - BRL (R$) R$ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure of revenue [Line Items] |  |  |
Taxes on revenues | R$ 8,547 | R$ 7,702 | R$ 7,247
Charges to the consumer | 2,604 | 2,795 | 4,302
Deductions from revenue | 11,151 | 10,497 | 11,549
ICMS [member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Taxes on revenues | 5,847 | 5,211 | 4,487
Cofins [member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Taxes on revenues | 2,237 | 2,041 | 2,263
PIS and Pasep [member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Taxes on revenues | 455 | 443 | 491
Other [Member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Taxes on revenues | 8 | 7 | 6
Global Reversion Reserve - RGR [Member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Charges to the consumer | 17 | (18) | 36
Energy Efficiency Program (P.E.E.) [Member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Charges to the consumer | 56 | 58 | 45
Energy Development Account - CDE [Member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Charges to the consumer | 1,822 | 2,074 | 2,870
Research and Development - P&D [Member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Charges to the consumer | 38 | 48 | 47
National Scientific and Technological Development Fund - FNDCT [Member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Charges to the consumer | 38 | 48 | 47
Energy System Expansion Research - EPE [Member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Charges to the consumer | 19 | 24 | 24
Customer charges - Proinfa alternative sources program [Member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Charges to the consumer | 39 | 43 | 27
Energy Services Inspection Charge [Member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Charges to the consumer | 29 | 35 | 37
Royalties for use of water resources [Member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Charges to the consumer | 92 | 123 | 102
Customer Charges - Tariff Flag Amounts [member] |  |  |
Disclosure of revenue [Line Items] |  |  |
Charges to the consumer | R$ 454 | R$ 360 | R$ 1,067

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