XML 110 R103.htm IDEA: XBRL DOCUMENT v3.19.1
Customers, Traders and Power Transport Concession Holders - Summary of Advances from Customers (Detail) - BRL (R$)
R$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Disclosure Of Advances From Customers [line items]    
Beginning balance R$ 233  
Ending Balance 79 R$ 233
Cemig GT [member]    
Disclosure Of Advances From Customers [line items]    
Beginning balance 233 181
Additions 50 325
Disposals (215) (318)
Inflation adjustment 11 45
Ending Balance R$ 79 R$ 233