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Securities Sold Under Repurchase Agreements and Interbank and Institutional Market Debts - Summary of Breakdown of Funds Obtained in Institutional Markets (Parenthetical) (Detail) - BRL (R$) R$ in Millions | Dec. 31, 2018 | Dec. 31, 2017 | Jan. 01, 2017
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Disclosure Of Repurchase Agreements [Line Items] |  |  |
Institutional market debt | R$ 93,974 | R$ 98,482 | R$ 96,239
Structured Operations Certificates [Member] |  |  |
Disclosure Of Repurchase Agreements [Line Items] |  |  |
Institutional market debt | 2,798 | 4,386 |
Market value of fund | 2,902 | 4,605 |
Reference Equity [Member] |  |  |
Disclosure Of Repurchase Agreements [Line Items] |  |  |
Institutional market debt | R$ 32,205 | R$ 42,687 |

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