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Derivative Instruments (Details) - GOLDEN STATE WATER COMPANY $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Dec. 31, 2019	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) MWh	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Description of derivative activity volume | MWh				44,064
Commodity Contract
Derivative Instruments, Gain (Loss) [Line Items]
Term of derivative contract						3 years
Number of broker quotes received to determine fair value of derivative instrument		1		1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at beginning of the period		$ (336)	$ (2,625)	$ (311)	$ (2,941)
Unrealized gain on purchased power contracts		69	915	44	1,231
Fair value at end of the period		$ (267)	$ (1,710)	$ (267)	$ (1,710)	$ (2,941)
Minimum | Commodity Contract
Derivative Instruments, Gain (Loss) [Line Items]
Term of derivative contract							3 years
Maximum | Commodity Contract
Derivative Instruments, Gain (Loss) [Line Items]
Term of derivative contract							5 years
Subsequent Event [Member] | Commodity Contract
Derivative Instruments, Gain (Loss) [Line Items]
Term of derivative contract	5 years

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Derivative Activity Volume

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Number of Broker Quotes Received to Determine Fair Value of Derivative Instrument

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Amount of unrealized gain (loss) recognized in the income statement for a financial instrument classified as derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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Fair value of financial instrument classified as derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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