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v3.19.1

Taxes - Summary of Calculation of Tax Rates (Detail) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Disclosure of effective income tax rate [Abstract] |  |
Income tax | 15.00% |
Additional income tax | 10.00% |
Social contribution | 20.00% | 15.00%

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- Definition Additional income tax rate. + 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 effective income tax rate. + References No definition available. + Details
Name: | itub_DisclosureOfEffectiveIncomeTaxRateAbstract
Namespace Prefix: | itub_
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Balance Type: | na
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- Definition Income tax rate. + References No definition available. + Details
Name: | itub_IncomeTaxRate
Namespace Prefix: | itub_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Social contribution tax rate. + References No definition available. + Details
Name: | itub_SocialContributionTaxRate
Namespace Prefix: | itub_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration