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Post-Employment Benefits - Additional Information (Detail) - BRL (R$) R$ in Millions | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | --- | ---
Disclosure of defined benefit plans [line items] |  |  |
Defined benefit plan assets | R$ 18,808 | R$ 17,588 | R$ 16,520
Medical care cost [member] |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Percentage of actuarial method assumption | 8.16% |  |
Actuarial assumption of retirement age [member] |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Percentage of actuarial method assumption | 3.00% |  |
ITAU UNIBANCO HOLDING [Member] |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Defined benefit plan assets | R$ 11 | 12 |
ITAU UNIBANCO HOLDING [Member] | Real Estate [Member] |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Defined benefit plan assets | R$ 487 | R$ 531 |

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- Definition The reasonably possible percentage of the increase in the actuarial assumption used to determine the present value of defined benefit obligation. [Refer: Actuarial assumptions [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 145 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_145_a&doctype=Standard -URIDate 2017-03-09 + Details
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