Summary of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
Dec. 31, 2015 mi² people_served
Acequia Water Supply Corporation [Member]
Public Utilities General Disclosures [Line Items]
Ownership percentage in Acequia Water Supply Corporation	25.00%
Minimum [Member]
Public Utilities General Disclosures [Line Items]
Service area in square miles \| mi²	243
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%
San Jose Water Company [Member]
Public Utilities General Disclosures [Line Items]
Number of people served	1,000,000
SJWTX,Inc. dba Canyon Lake Water Supply Corporation [Member]
Public Utilities General Disclosures [Line Items]
Number of people served	37,000
444 West Santa Clara Street, L.P. [Member]
Public Utilities General Disclosures [Line Items]
Limited partership interest percentage	70.00%

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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The number of units or percentage investment held by one or more members or limited partners of the LLC or LP.

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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.

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Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

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