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Financial Assets at Fair Value Through Other Comprehensive Income-Securities - Additional Information (Detail) - Financial assets at fair value through other comprehensive income [Member]	12 Months Ended
	Dec. 31, 2018 BRL (R$)
Financial assets at fair value through other comprehensive income [line items]
Dividends received	R$ 0
Reclassification in stockholder's equity	R$ 0

X

- Definition

The amount of dividends received.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2017-01-01
-Paragraph B12
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2017-03-01&anchor=para_B12_a&doctype=Appendix&seq=2
-URIDate 2017-03-09

+ Details

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Balance Type:	debit
Period Type:	duration

X

- Definition

Financial assets at fair value through other comprehensive income [line items]

+ References

No definition available.

+ Details

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Namespace Prefix:	itub_
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Balance Type:	na
Period Type:	duration

X

- Definition

Reclassification of financial instruments fair value.

+ References

No definition available.

+ Details

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Namespace Prefix:	itub_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

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Namespace Prefix:
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