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v3.21.1

9 Restricted cash (Details Narrative) | 12 Months Ended
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Dec. 31, 2020
Agreement with the sao paulo municipal government [member] |
RestrictCashLineItems [Line Items] |
Percentage of deduction of municipal revenue | 7.50%

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- Definition Percentage of deduction of municipal revenue. + References No definition available. + Details
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Namespace Prefix: | sbs_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

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- Details
Name: | ifrs-full_ClassesOfAssetsAxis=sbs_AgreementwiththeSaoPauloMunicipalGovernmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |