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Financial Instruments and Risk Management - Summary of Changes in Value of Options (Detail) - BRL (R$) R$ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of financial liabilities [line items]
Variation in fair value	R$ 48	R$ 187	R$ 55
Put option - SAAG [member]
Disclosure of financial liabilities [line items]
Balance	312	196	148
Variation in fair value		121
Adjustment to fair value	107		48
Reversals		(5)
Balance	R$ 419	R$ 312	R$ 196

X

- Definition

The amount of financial liabilities classified as derivative instruments. [Refer: Financial assets; Derivatives [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

+ References

No definition available.

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- Definition

The increase (decrease) in the fair value measurement of liabilities. [Refer: At fair value [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
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-IssueDate 2018-01-01
-Paragraph 93
-Subparagraph e
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- Definition

Adjustment to fair value of options.

+ References

No definition available.

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- Definition

Reversals derivative financial liabilities.

+ References

No definition available.

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