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Financial Investments - Additional Information (Detail) - Cash and Cash Equivalent and Financial Investments [member]
Dec. 31, 2018
Dec. 31, 2017
Brazil, Brazil Real [member]    
Disclosure of financial assets [line items]    
Weighted average interest rate 6.56% 10.18%
United States of America, Dollars [member]    
Disclosure of financial assets [line items]    
Weighted average interest rate 2.40% 1.70%