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Risk and Capital Management - Summary of Sensitivity Analysis Impact in Results and Stockholder's Equity (Detail) - BRL (R$) R$ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Private Pension | R$ 20,136 | R$ 22,177 | R$ 19,490
5% increase in mortality rates [Member] |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Private Pension | 15 | 24 |
Insurance | (1) |  |
5% decrease in mortality rates [Member] |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Private Pension | (16) | (25) |
Insurance | (1) | (1) |
0.1% increase in risk-free interest rates [Member] |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Private Pension | 30 | 26 |
Insurance | 8 | 5 |
0.1% decrease in risk-free interest rates [Member] |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Private Pension | (44) | (27) |
Insurance | (8) | (5) |
5% increase in conversion in income rates [Member] |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Private Pension | (14) | (13) |
5% decrease in conversion in income rates [Member] |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Private Pension | 14 | 13 |
5% increase in claims [Member] |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Insurance | (37) | (36) |
5% decrease in claims [Member] |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Insurance | R$ 37 | R$ 36 |

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