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20. Employees benefits (Details 10) - BRL (R$) R$ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SummaryOfEmployeeBenefitsLineItems [Line Items]
Current interest expense and service costs	R$ 213,201
Expense to be recognize		R$ 41,627	R$ 97,011	R$ 104,656
Interest cost rate		260,409	285,227
Unfunded plan
SummaryOfEmployeeBenefitsLineItems [Line Items]
Current interest expense and service costs		262,873	282,117	248,054
Amount received from GESP (undisputed amount)		(95,191)	(96,709)	(87,232)
Expense to be recognize		R$ 167,682	R$ 185,408	R$ 160,822
Interest cost rate	232,248
Expense to be recognize	R$ 232,248

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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

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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]]

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The increase (decrease) in the net defined benefit liability (asset) resulting from the passage of time. [Refer: Interest expense; Net defined benefit liability (asset)]

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