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Risk and Capital Management - Summary of Position of Accounts Subject to Currency Risk (Detail) - Foreign exchange risk [member] - BRL (R$) R$ in Millions | Dec. 31, 2018 | Dec. 31, 2017
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Disclosure of position of accounts subject to currency risk [Line Items] |  |
Net exposure of financial instruments | R$ (15,125) | R$ 4,481
United States of America, Dollars |  |
Disclosure of position of accounts subject to currency risk [Line Items] |  |
Net exposure of financial instruments | (38,190) | (15,910)
Chile, Pesos |  |
Disclosure of position of accounts subject to currency risk [Line Items] |  |
Net exposure of financial instruments | 7,647 | 7,159
Other [Member] |  |
Disclosure of position of accounts subject to currency risk [Line Items] |  |
Net exposure of financial instruments | R$ 15,418 | R$ 13,232

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