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Loans, Financings and Debentures - Summary of the Currencies and Indexors Used for Monetary Updating of Loans and Financings (Detail) | Dec. 31, 2017 | Dec. 31, 2016
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US dollar [member] |  |
Disclosure of detailed information about borrowings [line items] |  |
Accumulated change | 1.50% | (16.54%)
Euro [member] |  |
Disclosure of detailed information about borrowings [line items] |  |
Accumulated change | 15.41% | (19.10%)
IPCA.[member] |  |
Disclosure of detailed information about borrowings [line items] |  |
Accumulated change | 2.95% | 6.29%
CDI [member] |  |
Disclosure of detailed information about borrowings [line items] |  |
Accumulated change | 9.93% | 14.06%

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