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Interbank Deposits and Securities Purchased Under Agreements to Resell - Summary of Interbank Deposits and Securities Purchased Under Agreements to Resell (Parenthetical) (Detail) - BRL (R$) R$ in Millions | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Disclosure of interbank deposits and securities purchased under agreements to resell [Line Items] |  |
Amounts pledged in guarantee of operations | R$ 5,120 | R$ 3,664
Losses | (10) | (8)
B3 S.A. - Brasil, Bolsa, Balco [Member] |  |
Disclosure of interbank deposits and securities purchased under agreements to resell [Line Items] |  |
Amounts pledged in guarantee of operations | 5,120 |
Amounts pledged in guarantee of repurchase agreement transactions | R$ 216,647 |
Central Bank [Member] |  |
Disclosure of interbank deposits and securities purchased under agreements to resell [Line Items] |  |
Amounts pledged in guarantee of operations |  | 3,664
Amounts pledged in guarantee of repurchase agreement transactions |  | R$ 185,296

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- Definition Disclosure of interbank deposits and securities purchased under agreements to resell. + References No definition available. + Details
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- Definition Gains losses on securities purchased sold under repurchase agreements. + References No definition available. + Details
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