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Risk and Capital Management - Summary of Exposure Weighted by Credit Risk Amount and Ratio Required and Current (Detail) - BRL (R$) R$ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017
Disclosure of credit risk exposure [line items] |  |
Common Equity Tier I, Required | R$ 36,813 | R$ 34,052
Additional Tier I Capital, Required | 0 | 0
Tier I (Common Equity Tier I + Additional Tier I Capital), Required | 49,084 | 45,402
Tier II, Required | 0 | 0
Referential Equity (Tier I + Tier II), Required | 70,559 | 69,995
Common Equity Tier I | 123,358 | 122,396
Additional Tier I Capital | 7,796 | 57
Tier I (Common Equity Tier I + Additional Tier I Capital) | 131,154 | 122,453
Tier II | 15,874 | 19,799
Referential Equity (Tier I + Tier II) | R$ 147,028 | R$ 142,252
Common Equity Tier I | 4.50% | 4.50%
Tier I (Common Equity Tier I + Additional Tier I Capital) | 6.00% | 6.00%
Referential Equity (Tier I + Tier II) | 8.625% | 9.25%
Amount Required for Additional Common Equity Tier I (ACP) | R$ 19,429 | R$ 11,351
Additional Common Equity Tier I (ACP) | 2.375% | 1.50%
Required ratio [Member] |  |
Disclosure of credit risk exposure [line items] |  |
Common Equity Tier I | 4.50% | 4.50%
Additional Tier I Capital | 0.00% | 0.00%
Tier I (Common Equity Tier I + Additional Tier I Capital) | 6.00% | 6.00%
Tier II | 0.00% | 0.00%
Referential Equity (Tier I + Tier II) | 8.625% | 9.25%
Current ratio [Member] |  |
Disclosure of credit risk exposure [line items] |  |
Common Equity Tier I | 15.10% | 16.20%
Additional Tier I Capital | 0.00% | 0.00%
Tier I (Common Equity Tier I + Additional Tier I Capital) | 16.00% | 16.20%
Tier II | 0.00% | 0.00%
Referential Equity (Tier I + Tier II) | 18.00% | 18.80%

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