Fair Value of Financial Instruments: (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
GOLDEN STATE WATER COMPANY \| Reported Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	$ 284,489	$ 284,699
GOLDEN STATE WATER COMPANY \| Estimate of Fair Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	386,284	$ 376,467
Mutual Funds \| Fair Value, Inputs, Level 1
Financial liabilities:
Long-term debt-GSWC	$ 21,600

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(5))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(12))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

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