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Overview - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2018
Itau Unibanco Participacoes SA [Member] |
Disclosure of company overview [line items] |
Percentage of common shares ownership | 51.71%
Itausa Investimentos SA [Member] |
Disclosure of company overview [line items] |
Percentage of common shares ownership | 39.21%

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