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28 Operating revenue (Details Narrative) - BRL (R$) R$ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Operating Revenue |  |
Amount corresponding to TRCF charged from customers | R$ 72,962 | R$ 70,122

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- Definition The amount corresponding to trcf charged from customers. + References No definition available. + Details
Name: | sbs_AmountCorrespondingToTrcfChargedFromCustomers
Namespace Prefix: | sbs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
Name: | sbs_OperatingRevenueAbstract
Namespace Prefix: | sbs_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration