Long-Term Debt Narrative (Details)	12 Months Ended
Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Long-term debt	$ 384,316,000	$ 384,949,000
Significant Observable Inputs (Level 2)
Fair value of long-term debt	500,035,000	460,171,000
Senior Notes [Member]
Long-term debt	$ 315,000,000	315,000,000
San Jose Water Company [Member] \| Senior Notes [Member]
Ratio of indebtedness to total capital	0.6666
Ratio of net income available for interest charges for the trailing 12-month calendar period to interest charges	1.75
San Jose Water Company [Member] \| Senior Notes [Member] \| Series A [Member]
Long-term debt	$ 20,000,000	20,000,000
Stated interest rates	8.58%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series L [Member]
Long-term debt	$ 50,000,000	50,000,000
Stated interest rates	5.14%
SJWTX,Inc. dba Canyon Lake Water Supply Corporation [Member] \| Senior Notes [Member] \| Series A [Member]
Long-term debt	$ 15,000,000	15,000,000
Stated interest rates	6.27%
Ratio of indebtedness to total capital	0.6666
Ratio of net income available for interest charges for the trailing 12-month calendar period to interest charges	1.75
SJW Corp. [Member] \| Senior Notes [Member] \| Series A [Member]
Long-term debt	$ 50,000,000	$ 50,000,000
Stated interest rates	4.35%
Ratio of indebtedness to total capital	0.6666
Minimum net worth required for compliance	$ 175,000,000
Cumulative net income, percentage included in net worth for compliance	30.00%
SJW Corp. [Member] \| Senior Notes [Member] \| Series A [Member] \| Financial Guarantee [Member]
Ratio of indebtedness to total capital	0.6666
Minimum net worth required for compliance	$ 125,000,000
SJW Corp. [Member] \| Senior Notes [Member] \| Series A [Member] \| Financial Guarantee [Member] \| Minimum [Member]
Cumulative net income, percentage included in net worth for compliance	30.00%

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Ratio of Income to Interest Charges

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Ratio of Indebtedness to Total Capital

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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The lowest amount of net worth (total assets minus total liabilities) required by secondary market investors or state-imposed regulatory mandates.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)(a)
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