Name:	SBS_TradeReceivablesGross
Namespace Prefix:	SBS_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of an allowance account used to record impairments to financial assets due to credit losses. [Refer: Financial assets]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2018-01-01
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-Paragraph 16
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_16&doctype=Standard&book=B
-URIDate 2017-03-09

Name:	ifrs-full_AllowanceAccountForCreditLossesOfFinancialAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of current trade receivables. [Refer: Trade receivables]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 78
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_78_b&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 68
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_68&doctype=Standard
-URIDate 2017-03-09

Name:	ifrs-full_CurrentTradeReceivables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of non-current trade receivables. [Refer: Trade receivables]

Name:	ifrs-full_NoncurrentTradeReceivables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount due from customers for goods and services sold.

Name:	ifrs-full_TradeReceivables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Name:	SBS_TradeReceivablesAxis=SBS_UnbilledSupplyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	dei_EntitySectorIndustryClassificationsSectorAxis=SBS_PrivateSectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	SBS_TradeReceivablesAxis=SBS_GeneralAndSpecialCustomersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	SBS_TradeReceivablesAxis=SBS_AgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	dei_EntitySectorIndustryClassificationsSectorAxis=SBS_GovernmentEntitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	SBS_TradeReceivablesAxis=SBS_MunicipalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	SBS_TradeReceivablesAxis=SBS_FederalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	dei_EntitySectorIndustryClassificationsSectorAxis=SBS_WholesaleMunicipalGovernmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	SBS_TradeReceivablesAxis=SBS_GuarulhosMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	SBS_TradeReceivablesAxis=SBS_MauaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	SBS_TradeReceivablesAxis=SBS_MogiDasCruzesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	SBS_TradeReceivablesAxis=SBS_SantoAndreMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	SBS_TradeReceivablesAxis=SBS_SaoCaetanoDoSulMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: