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Operating Costs And Expenses - Summary of Construction Cost (Detail) - BRL (R$)
R$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Disclosure of construction cost [Abstract]      
Personnel and managers R$ 36 R$ 58 R$ 65
Materials 550 534 521
Outsourced services 406 448 504
Others 127 153 162
Construction cost R$ 1,119 R$ 1,193 R$ 1,252