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23. Knowledge retention program (Details)	12 Months Ended
	Dec. 31, 2018
More than 15 years
SummaryOfKnowledgeRetentionProgramLineItems [Line Items]
Percent of the Guarantee Fund for Length of Service (FGTS)	40.00%
11 - 15 years
SummaryOfKnowledgeRetentionProgramLineItems [Line Items]
Percent of the Guarantee Fund for Length of Service (FGTS)	30.00%
6 - 10 years
SummaryOfKnowledgeRetentionProgramLineItems [Line Items]
Percent of the Guarantee Fund for Length of Service (FGTS)	15.00%
0 - 5 years
SummaryOfKnowledgeRetentionProgramLineItems [Line Items]
Percent of the Guarantee Fund for Length of Service (FGTS)	5.00%

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