Regulatory Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Regulatory Assets and Liabilities
Regulatory assets	$ 401,089us-gaap_RegulatoryAssetsNoncurrent	$ 390,331us-gaap_RegulatoryAssetsNoncurrent
Regulatory liabilities	35,102us-gaap_RegulatoryLiabilityNoncurrent	36,447us-gaap_RegulatoryLiabilityNoncurrent
Short-term portion of the regulatory assets	50,016us-gaap_RegulatoryAssetsCurrent	53,199us-gaap_RegulatoryAssetsCurrent
Short-term portion of the regulatory liabilities	5,580us-gaap_RegulatoryLiabilityCurrent	6,126us-gaap_RegulatoryLiabilityCurrent
Future tax benefits due ratepayers
Regulatory Assets and Liabilities
Regulatory liabilities	26,114	26,114
Conservation program
Regulatory Assets and Liabilities
Regulatory liabilities	3,406	2,669
Pension balancing account
Regulatory Assets and Liabilities
Regulatory liabilities	3,170	4,291
Other regulatory liabilities
Regulatory Assets and Liabilities
Regulatory liabilities	2,412	3,373
Pension and retiree group health
Regulatory Assets and Liabilities
Regulatory assets	244,843	245,008
Future tax benefits due ratepayers
Regulatory Assets and Liabilities
Regulatory assets	72,350	72,350
Other accrued benefits
Regulatory Assets and Liabilities
Regulatory assets	32,684	32,959
Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory assets	19,413	14,449
Asset retirement obligations, net
Regulatory Assets and Liabilities
Regulatory assets	14,169	13,863
Interim rates long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory assets	8,996	10,627
Tank coating
Regulatory Assets and Liabilities
Regulatory assets	5,097
Health care balancing account
Regulatory Assets and Liabilities
Regulatory assets	1,875	1,075
Other regulatory assets
Regulatory Assets and Liabilities
Regulatory assets	$ 1,662

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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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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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.

+ References

+ Details

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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 405

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.24)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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