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Risk and Capital Management - Maximum Exposure of Other financial assets Segregated by Business Sector (Detail) - BRL (R$) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Disclosure of credit risk exposure [line items] |  |
Other financial assets | R$ 752,920,000,000 | R$ 705,674,000,000
Other financial assets percentage | 100.00% | 100.00%
Public sector [Member] |  |
Disclosure of credit risk exposure [line items] |  |
Other financial assets | R$ 330,730,000,000 | R$ 327,932,000,000
Other financial assets percentage | 43.90% | 46.50%
Services [Member] |  |
Disclosure of credit risk exposure [line items] |  |
Other financial assets | R$ 92,562,000,000 | R$ 84,191,000,000
Other financial assets percentage | 12.30% | 11.90%
Other sectors [Member] |  |
Disclosure of credit risk exposure [line items] |  |
Other financial assets | R$ 23,072,000,000 | R$ 19,804,000,000
Other financial assets percentage | 3.10% | 2.80%
Financial [Member] |  |
Disclosure of credit risk exposure [line items] |  |
Other financial assets | R$ 306,556,000,000 | R$ 273,747,000,000
Other financial assets percentage | 40.70% | 38.80%

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