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v3.20.1

Significant Accounting Policies - Additional Information (Detail) - Segment | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Disclosure of accounting policies [line items] |  |
Percentage of variation in total assets due to transition to IFRS 16 | 10.00% |
Number of reportable segments | 3 |
Bottom of range [member] |  |
Disclosure of accounting policies [line items] |  |
Consolidated companies percentage as total consolidated assets, as well as interests in their voting capital | 95.00% | 95.00%

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- Definition Aggregate percentage of consolidated companies to consolidated assets + 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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- Definition Disclosure of accounting policies [line items] + References No definition available. + Details
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Namespace Prefix: | itub_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Number of Reportable Segments1 + References No definition available. + Details
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Namespace Prefix: | itub_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition Percentage of variation in total assets due to transition to IFRS 16. + 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: |