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Intangible Assets - Summary of Changes in Intangible Assets (Parenthetical) (Detail)
R$ in Millions
12 Months Ended
Dec. 31, 2016
BRL (R$)
Disclosure of detailed information about intangible assets [line items]  
Special obligations, write down R$ 98
Parent [member] | Luz Para Todos Program [member]  
Disclosure of detailed information about intangible assets [line items]  
Special obligations, write down R$ 98