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Represents the amount of advances for construction expected to be refunded to customers after the fifth succeeding fiscal year.

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No definition available.

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Represents the amount of advances for construction expected to be refunded to customers during year five of the five succeeding fiscal years.

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No definition available.

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Represents the amount of advances for construction expected to be refunded to customers during year four of the five succeeding fiscal years.

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No definition available.

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Represents the amount of advances for construction expected to be refunded to customers during year one of the five succeeding fiscal years.

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No definition available.

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Represents the amount of advances for construction expected to be refunded to customers during year three of the five succeeding fiscal years.

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No definition available.

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Represents the amount of advances for construction expected to be refunded to customers during year two of the five succeeding fiscal years.

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No definition available.

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Represents the period over which customer advances will be refunded.

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No definition available.

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- Definition

Represents the number of non-supervisory employees who are represented by the Utility Workers Union of America, AFL-CIO.

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Number of persons employed by the Entity

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No definition available.

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Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 1A

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-Name Regulation S-X (SX)

-Number 210

-Section 03

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-Article 5

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For utilities only, represents the carrying amount of the liability as of the balance sheet date for payments received by a utility from its customers in advance of performing its obligations under terms of its construction agreements.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 210

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-Subparagraph (SX 210.5-02.24)

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-Topic 910

-SubTopic 405

-Section 50

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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-Name Accounting Standards Codification

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-SubTopic 20

-Section 50

-Paragraph 1

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

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The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period.

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-Publisher FASB

-Name Accounting Standards Codification

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The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 6) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 employee	Dec. 31, 2013	Dec. 31, 2012
Regulatory Assets and Liabilities
Regulatory Assets, Noncurrent	$ 390,331us-gaap_RegulatoryAssetsNoncurrent	$ 251,681us-gaap_RegulatoryAssetsNoncurrent
Regulatory Liability, Noncurrent	36,447us-gaap_RegulatoryLiabilityNoncurrent	34,251us-gaap_RegulatoryLiabilityNoncurrent
Short-term portion of the regulatory assets	53,199us-gaap_RegulatoryAssetsCurrent	30,887us-gaap_RegulatoryAssetsCurrent
Short-term portion of the regulatory liabilities	6,126us-gaap_RegulatoryLiabilityCurrent	1,827us-gaap_RegulatoryLiabilityCurrent
Impairment of Long-Lived Assets, Intangibles and Goodwill
Impairment of goodwill	0us-gaap_GoodwillImpairmentLoss	0us-gaap_GoodwillImpairmentLoss
Long-Term Debt Premium, Discount and Expense
Amortization expense included in interest expense	797	1,081	1,107
Advances for Construction
Advances for construction	182,284us-gaap_CustomerAdvancesForConstruction	183,393us-gaap_CustomerAdvancesForConstruction
Refund period	40 years
Estimated refunds of advances
2015	7,587
2016	7,361
2017	7,347
2018	7,330
2019	7,325
Thereafter	145,334
Collective Bargaining Agreements
Number of employees	1,105dei_EntityNumberOfEmployees
Number of non-supervisory employees represented by the Utility Workers Union of America	708
Future tax benefits due ratepayers
Regulatory Assets and Liabilities
Regulatory Liability, Noncurrent	26,114	24,195
Conservation program
Regulatory Assets and Liabilities
Regulatory Liability, Noncurrent	2,669	6,291
Pension balancing account
Regulatory Assets and Liabilities
Regulatory Liability, Noncurrent	4,291
Other Liabilities
Regulatory Assets and Liabilities
Regulatory Liability, Noncurrent	3,373	3,765
Pension and retiree group health
Regulatory Assets and Liabilities
Regulatory Assets, Noncurrent	245,008	119,868
Future tax benefits due ratepayers
Regulatory Assets and Liabilities
Regulatory Assets, Noncurrent	72,350	60,780
Other accrued benefits
Regulatory Assets and Liabilities
Regulatory Assets, Noncurrent	32,959	43,061
Interim rates long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory Assets, Noncurrent	10,627
Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory Assets, Noncurrent	14,449	15,423
Asset retirement obligations, net
Regulatory Assets and Liabilities
Regulatory Assets, Noncurrent	13,863	12,549
Health care balancing account
Regulatory Assets and Liabilities
Regulatory Assets, Noncurrent	$ 1,075