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Derivative Instruments (Details) - GOLDEN STATE WATER COMPANY MWh in Thousands, $ in Thousands | 3 Months Ended
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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 Number of Broker Quotes Received to Determine Fair Value of Derivative Instrument + References No definition available. + 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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- 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 + 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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