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Subscription warrants - indemnification - Additional information (Detail) - BRL (R$)
R$ in Thousands
 12 Months Ended
Jan. 31, 2014
Dec. 31, 2018
Dec. 31, 2017
Jan. 01, 2017
Subscription warrants - indemnification [abstract]        
Subscription warrants shares issued 7   2,415,848  
Maximum number of shares to be issued - subscription warrants 3,205,622      
Subscription warrants, shares   2,412,119 2,415,848  
Subscription warrants - indemnification   R$ 123,095 R$ 171,459 R$ 153,429
Maximum number of shares available for issue - subscription warrants   2,988,158 3,035,499