Long-Term Debt Narrative (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Long-term debt	$ 384,949,000us-gaap_LongTermDebt	$ 335,551,000us-gaap_LongTermDebt
Significant Observable Inputs (Level 2)
Fair value of long-term debt	460,171,000	395,684,000
Senior Notes [Member]
Long-term debt	315,000,000	265,000,000
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	0
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
SJW Corp. [Member] \| Senior Notes [Member] \| Series A [Member] \| Financial Guarantee [Member] \| Minimum [Member]
Minimum net worth required for compliance	$ 125,000,000
Cumulative net income, percentage included in net worth for compliance	30.00%

Cumulative Net Income, Percentage Included in Net Worth for Compliance

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- Definition

Ratio of Income to Interest Charges

+ References

No definition available.

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- Definition

Ratio of Indebtedness to Total Capital

+ References

No definition available.

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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 SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: 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))

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

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Reference 3: 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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Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20, 22

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

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- Definition

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.

+ References

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47304-110998

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (c)(a)

-URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47080-110998

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