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21. Employees benefits (Details 9) - BRL (R$) R$ in Thousands | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
SummaryOfEmployeeBenefitsLineItems [Line Items] |  |  |  |
Defined benefit obligation, beginning of the year | R$ 2,532,338 | R$ 2,319,841 | R$ 2,465,721 |
Current interest expense and service costs | R$ 233,039 |  |  |
Actuarial (gains)/losses recorded as other comprehensive income |  | (10,994) | 287,547 | R$ (472,266)
Benefits paid |  | (128,797) | (118,360) |
Defined benefit obligation, end of the year |  | 2,532,338 | 2,319,841 | 2,465,721
Unfunded plan |  |  |  |
SummaryOfEmployeeBenefitsLineItems [Line Items] |  |  |  |
Current interest expense and service costs |  | 232,248 | 262,873 | R$ 282,117
Actuarial (gains)/losses recorded as other comprehensive income |  | (10,783) | (51,535) |
Benefits paid |  | R$ (180,801) | R$ (179,541) |

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- Definition The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in financial assumptions that result in remeasurements of the net defined benefit liability (asset). Financial assumptions deal with items such as: (a) the discount rate; (b) benefit levels, excluding any cost of the benefits to be met by employees, and future salary; (c) in the case of medical benefits, future medical costs, including claim handling costs (ie the costs that will be incurred in processing and resolving claims, including legal and adjuster's fees); and (d) taxes payable by the plan on contributions relating to service before the reporting date or on benefits resulting from that service. [Refer: 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 c -Clause iii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_141_c_iii&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The present value, without deducting any plan assets, of expected future payments required to settle the obligation resulting from employee service in the current and prior periods. [Refer: Plan assets, at fair value] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2018-01-01 -Paragraph 57 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_57_a&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 decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan. [Refer: 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 g -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_141_g&doctype=Standard -URIDate 2018-03-16 + Details
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