Fair Value of Financial Instruments: (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
GOLDEN STATE WATER COMPANY \| Reported Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	$ 284,892	$ 324,978
GOLDEN STATE WATER COMPANY \| Estimate of Fair Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	363,757	$ 387,889
Mutual Funds \| Fair Value, Inputs, Level 1
Financial liabilities:
Long-term debt-GSWC	17,800
Notes Payable 6.7 Percent Due 2019 [Member] \| GOLDEN STATE WATER COMPANY
Fair value of financial instruments
Debt and Capital Lease Obligations	$ 40,000
Financial liabilities:
Debt Instrument, Interest Rate, Stated Percentage	6.70%

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

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 210.9-03.13,16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

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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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Includes other investments and securities that are not at fair value as of the balance sheet date and those that are not accounted for under the equity method.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Subparagraph (SX 210.7-03(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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