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v3.5.0.2

General - Additional Information (Details) | 1 Months Ended | 9 Months Ended
--- | --- | ---
Jun. 30, 2016 | Dec. 31, 2015
Regulatory Liabilities [Line Items] |  |
Water reduction target goal (percent) | 20.00% | 30.00%

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- Definition Water Reduction Target Goal, Percentage + References No definition available. + Details
Name: | sjw_WaterReductionTargetGoalPercentage
Namespace Prefix: | sjw_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_RegulatoryLiabilitiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration