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Regulatory Rate Filings (Details) - USD ($) $ in Thousands |  |  |  |  | 3 Months Ended | 11 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Apr. 19, 2018 | Mar. 22, 2018 | Nov. 29, 2017 | Nov. 15, 2017 | Mar. 31, 2018 | Nov. 28, 2017 | Dec. 31, 2017 | Jan. 04, 2018
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Revenue increase amount |  |  |  | $ 15,670 |  |  |  |
Revenue increase, percentage |  |  |  | 4.22% |  |  |  |
Public Utilities, Approved Reimbursement Fee, Percentage |  |  | 1.40% |  |  | 1.44% |  |
Public Utilities, Requested Equity Capital Structure, Percentage |  |  |  |  |  |  | 8.09% |
Public Utilities, Approved Equity Capital Structure, Percentage |  | 7.64% |  |  |  |  |  |
Public Utilities, Approved Equity Capital Structure, Decrease, Amount |  |  |  |  | $ 5,843 |  |  |
Public Utilities, Approved Equity Capital Structure, Decrease, Percent |  |  |  |  | 1.57% |  |  |
Regulatory Rate Filings, Requested Rate Increase, Year One |  |  |  |  |  |  |  | $ 34,288
Regulatory Rate Filings, Requested Rate Increase as Percentage of Total Revenue at Time of Request, Year One |  |  |  |  |  |  |  | 9.76%
Regulatory Rate Filings, Requested Rate Increase, Year Two |  |  |  |  |  |  |  | $ 14,232
Regulatory Rate Filings, Proposed Rate Increase, Percent of Authorized Revenue, Year Two |  |  |  |  |  |  |  | 3.70%
Regulatory Rate Filings, Requested Rate Increase, Year Three |  |  |  |  |  |  |  | $ 20,582
Regulatory Rate Filings, Requested Rate Increase, Percent of Authorized Revenue, Year Three |  |  |  |  |  |  |  | 5.17%
Memorandum Account, Authorized Recovery |  |  |  |  |  |  |  | $ 20,725
SJWTX, Inc. [Member] |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Regulatory Liability, Current |  |  |  |  | $ 139 |  |  |
Subsequent Event [Member] | SJWTX, Inc. [Member] |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount | $ (745) |  |  |  |  |  |  |

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