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Risk and Capital Management - Summary of Assessing Minimum Capital Requirements (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2018
Disclosure of regulatory capital [Abstract]
Capital required for market risk standardized model, percentage	80.00%

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- Definition

Capital required for market risk standardized model, percentage.

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No definition available.

+ Details

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- Definition

Disclosure of regulatory capital [Abstract]

+ References

No definition available.

+ Details

Name:	itub_DisclosureOfRegulatoryCapitalAbstract
Namespace Prefix:	itub_
Data Type:	xbrli:stringItemType
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Period Type:	duration