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Financial Instruments and Risk Management - Summary of Put Option (Detail) - BRL (R$) R$ in Millions | Dec. 31, 2017 | Dec. 31, 2016
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Disclosure of detailed information about financial instruments [line items] |  |
Put option | R$ 815 | R$ 1,341
Put option for shares in RME and Lepsa [member] | Put Option 1 [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Put option | 507 | 1,150
Put option - SAAG [member] | Put Option 1 [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Put option | 312 | 196
Put / call options - Ativas and Sonda [member] | Put Option 1 [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Put option | R$ (4) | R$ (5)

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- Details
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