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Regulatory Matters - Balancing and Memorandum Accounts (Details) | Mar. 31, 2022
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Regulated Operations [Abstract] |
Authorized revenue, threshold percentage | 2.00%

X
- Definition Threshold balance of regulatory balancing or memorandum accounts as a percentage of authorized revenue to trigger an account review. + References No definition available. + Details
Name: | sjw_RegulatoryBalancingandMemorandumAccountsReviewAuthorizedRevenueThresholdPercentage
Namespace Prefix: | sjw_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

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