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Income and Social Contribution Taxes - Summary of Income and Social Contribution Taxes recoverable (Detail) - BRL (R$) R$ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Disclosure of income and social contribution taxes [Abstract] |  |
Income tax | R$ 224 | R$ 436
Social contribution tax | 116 | 154
Income and social contribution tax credits current | 340 | 590
Income tax | 7 | 98
Social contribution tax | 14 | 14
Income and social contribution tax credits noncurrent | 21 | 112
Income and social contribution tax credits | R$ 361 | R$ 702

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