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21. Employees benefits (Details 10) - BRL (R$) R$ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
SummaryOfEmployeeBenefitsLineItems [Line Items] |  |  |  |
Current interest expense and service costs | R$ 233,039 |  |  |
Expense to be recognize | 8,362 | R$ 11,321 | R$ 41,627 | R$ 97,011
Interest cost rate | 224,429 | 213,201 | 260,409 |
Unfunded plan |  |  |  |
SummaryOfEmployeeBenefitsLineItems [Line Items] |  |  |  |
Current interest expense and service costs |  | 232,248 | 262,873 | 282,117
Amount received from GESP (undisputed amount) |  | (96,282) | (95,191) | (96,709)
Expense to be recognize |  | R$ 135,966 | R$ 167,682 | R$ 185,408
Unfunded plan |  |  |  |
SummaryOfEmployeeBenefitsLineItems [Line Items] |  |  |  |
Interest cost rate | 227,367 |  |  |
Expense to be recognize | R$ 227,367 |  |  |

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- Definition The decrease (increase) in the net defined benefit liability (asset) resulting from contributions to a defined benefit plan. [Refer: Net defined benefit liability (asset); Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2018-01-01 -Paragraph 141 -Subparagraph f -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_141_f&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The estimate of the expected contributions to be made to a defined benefit plan for the next annual reporting period. [Refer: Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2018-01-01 -Paragraph 147 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_147_b&doctype=Standard -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2018-01-01 -Paragraph 148 -Subparagraph d -Clause iii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_148_d_iii&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The increase (decrease) in the net defined benefit liability (asset) resulting from the passage of time. [Refer: Interest expense; Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2018-01-01 -Paragraph 141 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_141_b&doctype=Standard -URIDate 2018-03-16 + Details
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