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v2.4.1.9

Summary of Significant Accounting Policies Narrative (Details) | 12 Months Ended
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Dec. 31, 2014
Acequia Water Supply Corporation [Member] |
Public Utilities General Disclosures [Line Items] |
Ownership percentage in Acequia Water Supply Corporation | 25.00%us-gaap_VariableInterestEntityOwnershipPercentage / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Minimum [Member] |
Public Utilities General Disclosures [Line Items] |
Service area in square miles | 240sjw_PublicUtilitiesServiceArea / us-gaap_RangeAxis = us-gaap_MinimumMember
Sales [Member] | Product Concentration Risk [Member] |
Public Utilities General Disclosures [Line Items] |
Percentage of revenue derived from sales of water to business and residential customers | 93.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_SalesMember / us-gaap_ConcentrationRiskByTypeAxis = us-gaap_ProductConcentrationRiskMember
San Jose Water Company [Member] |
Public Utilities General Disclosures [Line Items] |
Number of people served | 1,000,000sjw_PublicUtilitiesNumberOfPeopleServed / dei_LegalEntityAxis = us-gaap_SubsidiariesMember
SJWTX,Inc. dba Canyon Lake Water Supply Corporation [Member] |
Public Utilities General Disclosures [Line Items] |
Number of people served | 36,000sjw_PublicUtilitiesNumberOfPeopleServed / dei_LegalEntityAxis = sjw_SubsidiaryOneMember
444 West Santa Clara Street, L.P. [Member] |
Public Utilities General Disclosures [Line Items] |
Limited partership interest percentage | 70.00%us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest / dei_LegalEntityAxis = us-gaap_PartnershipInterestMember

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