Long-Term Debt Long-term Debt Schedule (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term debt	$ 437,717	$ 384,316
Unamortized Debt Issuance Expense	4,257	3,638
Current portion	125	3,491
Long-term debt, less current portion	433,335	377,187
Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt	$ 315,000	315,000
Mortgages [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Stated interest rates	5.61%
Mortgages [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Stated interest rates	6.09%
Mortgages [Member] \| Mortgage loans due 2016 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 0	2,997
Mortgages [Member] \| Mortgage loans due 2017 [Member]
Debt Instrument [Line Items]
Long-term debt	0	11,634
Mortgages [Member] \| 444 West Santa Clara Street, L.P. [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,717	2,836
Stated interest rates	5.68%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series A [Member]
Debt Instrument [Line Items]
Long-term debt	$ 20,000	20,000
Stated interest rates	8.58%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series B [Member]
Debt Instrument [Line Items]
Long-term debt	$ 30,000	30,000
Stated interest rates	7.37%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series C [Member]
Debt Instrument [Line Items]
Long-term debt	$ 10,000	10,000
Stated interest rates	9.45%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series D [Member]
Debt Instrument [Line Items]
Long-term debt	$ 15,000	15,000
Stated interest rates	7.15%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series E [Member]
Debt Instrument [Line Items]
Long-term debt	$ 15,000	15,000
Stated interest rates	6.81%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series F [Member]
Debt Instrument [Line Items]
Long-term debt	$ 20,000	20,000
Stated interest rates	7.20%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series G [Member]
Debt Instrument [Line Items]
Long-term debt	$ 20,000	20,000
Stated interest rates	5.93%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series H [Member]
Debt Instrument [Line Items]
Long-term debt	$ 20,000	20,000
Stated interest rates	5.71%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series I [Member]
Debt Instrument [Line Items]
Long-term debt	$ 20,000	20,000
Stated interest rates	5.93%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series J [Member]
Debt Instrument [Line Items]
Long-term debt	$ 10,000	10,000
Stated interest rates	6.54%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series K [Member]
Debt Instrument [Line Items]
Long-term debt	$ 20,000	20,000
Stated interest rates	6.75%
San Jose Water Company [Member] \| Senior Notes [Member] \| Series L [Member]
Debt Instrument [Line Items]
Long-term debt	$ 50,000	50,000
Stated interest rates	5.14%
San Jose Water Company [Member] \| Public Utility, Bonds [Member] \| California Pollution Control Financing Authority Revenue Bonds [Member]
Debt Instrument [Line Items]
Long-term debt	$ 50,000	50,000
Stated interest rates	5.10%
San Jose Water Company [Member] \| Public Utility, Bonds [Member] \| California Pollution Control Financing Authority Revenue Bonds Two [Member]
Debt Instrument [Line Items]
Long-term debt	$ 70,000	0
Stated interest rates	4.75%
San Jose Water Company [Member] \| SDWSRF loans [Member]
Debt Instrument [Line Items]
Long-term debt	$ 0	1,849
San Jose Water Company [Member] \| SDWSRF loans [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Stated interest rates	2.39%
San Jose Water Company [Member] \| SDWSRF loans [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Stated interest rates	2.60%
SJWTX,Inc. dba Canyon Lake Water Supply Corporation [Member] \| Senior Notes [Member] \| Series A [Member]
Debt Instrument [Line Items]
Long-term debt	$ 15,000	15,000
Stated interest rates	6.27%
SJW Group [Member] \| Senior Notes [Member] \| Series A [Member]
Debt Instrument [Line Items]
Long-term debt	$ 50,000	$ 50,000
Stated interest rates	4.35%

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

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

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. 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 FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: 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))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: 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))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. 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 FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. 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 FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ 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 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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