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Fair Value of Financial Instruments - Additional Information (Detail) - BRL (R$) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Standby letters of credit and financial guarantees | R$ 76,852,000,000 | R$ 79,703,000,000
Short-term assumption period | 5 days |
Transfers out of Level 1 into Level 2 of fair value hierarchy, assets held at end of reporting period | R$ 0 |
Transfers out of Level 1 into Level 2 of fair value hierarchy, liabilities held at end of reporting period | 0 |
Transfers out of Level 2 into Level 1 of fair value hierarchy, assets held at end of reporting period | 0 |
Transfers out of Level 2 into Level 1 of fair value hierarchy, liabilities held at end of reporting period | 0 |
Transfers into Level 3 of fair value hierarchy, assets | 0 |
Transfers into Level 3 of fair value hierarchy, liabilities | 0 |
Transfers out of Level 3 of fair value hierarchy, assets | 0 |
Transfers out of Level 3 of fair value hierarchy, liabilities | 0 |
Fair vale of securities used to evaluate pricing service or brokers | 22,231,000,000 |
Level 2 [Member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Financial instruments classified as Level 2 | 52,849,000,000 |
Estimated fair value [Member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Standby letters of credit and financial guarantees | R$ 1,168,000,000 | R$ 935,000,000
Bottom of range [member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Purchase price of securities, percentage | 0.50% |
Top of range [member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Purchase price of securities, percentage | 0.50% |
Scenarios I [Member] | Interest rate risk [Member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Shocks basis point | 0.01% |
Scenarios I [Member] | Currency, commodities, and ratios [Member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Shocks basis point | 5.00% |
Scenarios I [Member] | Bottom of range [member] | Nonlinear [Member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Shocks basis point | 5.00% |
Scenarios I [Member] | Top of range [member] | Nonlinear [Member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Shocks basis point | 25.00% |
Scenarios II [Member] | Interest rate risk [Member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Shocks basis point | 0.25% |
Scenarios II [Member] | Currency, commodities, and ratios [Member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Shocks basis point | 10.00% |
Scenarios II [Member] | Bottom of range [member] | Nonlinear [Member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Shocks basis point | 10.00% |
Scenarios II [Member] | Top of range [member] | Nonlinear [Member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Shocks basis point | 25.00% |
Scenarios III [Member] | Interest rate risk [Member] |  |
Disclosure of fair value measurement of assets and liabilities [Line Items] |  |
Shocks basis point | 0.50% |

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