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Regulatory Rate Filings (Details) - USD ($) $ in Thousands				12 Months Ended
	Jul. 26, 2018	Jun. 13, 2018	Jun. 07, 2018	Dec. 31, 2018	Jan. 04, 2018
Public Utilities, General Disclosures [Line Items]
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
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 13,732	$ (14,801)
Public Utilities, Requested Rate Increase (Decrease), Percentage		3.75%	(3.89%)
Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 3,155
Public Utilities, Requested Rate Increase (Decrease), Percentage	0.83%
Scenario, Forecast [Member] | SJWTX, Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Decrease, Amount				$ 1,023

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