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Derivative Instruments (Details) - GOLDEN STATE WATER COMPANY MWh in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) MWh	Mar. 31, 2016 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Description of derivative activity volume | MWh	306
Commodity Contract
Derivative Instruments, Gain (Loss) [Line Items]
Number of broker quotes received to determine fair value of derivative instrument	1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at end of the period	$ (4,901)	$ (7,053)
Unrealized loss on purchased power contracts	(559)	(192)
Fair value at end of the period	$ (5,460)	$ (7,245)
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

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- Definition

Derivative Activity Volume

+ References

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- Definition

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

+ References

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- Definition

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.

+ References

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.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19279-110258

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