Derivative Instruments (Details) (GOLDEN STATE WATER COMPANY, USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Description of derivative activity volume	554,000awr_DerivativeActivityVolume
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]
Balance, at beginning of the period	$ (3,339)	$ 0
Unrealized loss on purchased power contracts	(2,837)	0
Balance, at end of the period	$ (6,176)	$ 0
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

Derivative Activity Volume

No definition available.

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- Definition

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

+ References

No definition available.

+ Details

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- Details

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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

No definition available.

+ Details

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- Details

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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

+ Details

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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

+ Details

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