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Hedge Accounting - Summary of Hedge of Net Investment in Foreign Operations (Parenthetical) (Detail) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Hedges of net investment in foreign operations [member] |  |
Disclosure of Detailed Information about Hedges [Line Items] |  |
Hedge instruments over hedge rate related to taxes | 44.65% | 44.65%

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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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Namespace Prefix: | ifrs-full_
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- Definition Hedge instruments overhedge rate related to taxes. + References No definition available. + Details
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Namespace Prefix: | itub_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |