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Financial Instruments and Risk Management - Summary of Changes in Value of Options - The Difference Between Esimated Fair Value for Assets and Corresponding Exercise Price (Detail) - BRL (R$) R$ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure of financial liabilities [abstract] |  |  |
Balance | R$ 1,150 | R$ 1,245 | R$ 166
Variation in fair value | 187 |  |
Variation in fair value |  | 55 | 1,079
Written down, due to exercise of Put | (830) |  |
Reversals |  | (150) |
Balance | R$ 507 | R$ 1,150 | R$ 1,245

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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 -Number 13 -IssueDate 2017-01-01 -Paragraph 93 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=13&date=2017-03-01&anchor=para_93_e&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition Reversals in fair value of options. + References No definition available. + Details
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- Definition Written down, due to exercise of Put in fair value of options. + References No definition available. + Details
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