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Interest and similar income and expense and net gain (loss) on investment securities and derivatives - Summary of Interest, Similar Income of Financial Assets at Amortized Cost and at Fair Value Through Other Comprehensive Income (Detail) - BRL (R$) R$ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Disclosure Of Interest Income [Line Items] |  |  |
Interest and similar income | R$ 117,523 | R$ 110,324 | R$ 122,703
Central Bank compulsory deposits [member] |  |  |
Disclosure Of Interest Income [Line Items] |  |  |
Interest and similar income | 4,734 | 5,063 | 7,201
Interbank deposits [member] |  |  |
Disclosure Of Interest Income [Line Items] |  |  |
Interest and similar income | 1,173 | 1,080 | 744
Securities purchased under agreements to resell [member] |  |  |
Disclosure Of Interest Income [Line Items] |  |  |
Interest and similar income | 16,197 | 17,365 | 25,711
Financial assets at fair value through other comprehensive income [member] |  |  |
Disclosure Of Interest Income [Line Items] |  |  |
Interest and similar income | 10,758 | 9,194 | 8,886
Financial assets at amortised cost, category [member] |  |  |
Disclosure Of Interest Income [Line Items] |  |  |
Interest and similar income | 2,582 | 2,614 | 3,017
Loans [member] |  |  |
Disclosure Of Interest Income [Line Items] |  |  |
Interest and similar income | 81,046 | 73,640 | 75,568
Other financial asset [member] |  |  |
Disclosure Of Interest Income [Line Items] |  |  |
Interest and similar income | R$ 1,033 | R$ 1,368 | R$ 1,576

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