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Interest and similar income and expense and net gain (loss) on investment securities and derivatives - Schedule of Adjustments to Fair Value of Financial Assets and Liabilities (Detail) - BRL (R$) R$ in Millions | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Disclosure of financial assets and liabilities measured at fair value [Line Items] |  |  |
Adjustments to Fair Value of Financial Assets and Liabilities | R$ (4,834) | R$ 4,181 | R$ 7,066
Derivatives [member] |  |  |
Disclosure of financial assets and liabilities measured at fair value [Line Items] |  |  |
Adjustments to Fair Value of Financial Assets and Liabilities | (260) | 2,028 | 7,332
Financial Assets Designated At Fair Value Through Profit Or Loss Equity Securities [Member] |  |  |
Disclosure of financial assets and liabilities measured at fair value [Line Items] |  |  |
Adjustments to Fair Value of Financial Assets and Liabilities | (218) | 180 | 48
Financial assets designated at fair value through profit or loss [member] |  |  |
Disclosure of financial assets and liabilities measured at fair value [Line Items] |  |  |
Adjustments to Fair Value of Financial Assets and Liabilities | (4,110) | 2,138 | 684
Financial assets at fair value through other comprehensive income [Member] |  |  |
Disclosure of financial assets and liabilities measured at fair value [Line Items] |  |  |
Adjustments to Fair Value of Financial Assets and Liabilities | (254) | (128) | (851)
Financial liabilities at fair value through profit or loss, category [member] |  |  |
Disclosure of financial assets and liabilities measured at fair value [Line Items] |  |  |
Adjustments to Fair Value of Financial Assets and Liabilities | R$ 8 | R$ (37) | R$ (147)

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- Definition Adjustments for gains (losses) on changes in the fair value of derivatives to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: At fair value [member]; Derivatives [member]; Profit (loss)] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 7 -IssueDate 2017-01-01 -Paragraph 20 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2017-03-01&anchor=para_20&doctype=Standard -URIDate 2017-03-09 + Details
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