XML 97 R90.htm IDEA: XBRL DOCUMENT v3.8.0.1
Customers, Traders and Power Transport Concession Holders - Summary of Changes in Provision for Doubtful Accounts (Detail) - BRL (R$)
R$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Changes in allowance account for credit losses of financial assets [abstract]      
Beginning balance R$ 660 R$ 625 R$ 650
Additions, net 248 382 175
Written off (340) (347) (200)
Ending balance R$ 568 R$ 660 R$ 625