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20 Accounts payable to suppliers (Tables)
 12 Months Ended
Dec. 31, 2019
Accounts Payable To Suppliers [Abstract]  
Schedule of accounts payable to suppliers
     
  12.31.2018 12.31.2017
Energy supplies  819,792  986,689
Materials and supplies  384,300  521,969
Natural gas for resale  95,478  101,026
Charges for use of grid system  169,629  117,362
   1,469,199  1,727,046
Current  1,419,243  1,683,577
Noncurrent  49,956  43,469