Regulatory Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Regulatory Assets [Line Items]
Net Regulatory Assets	$ 173,445us-gaap_NetRegulatoryAssets	$ 174,863us-gaap_NetRegulatoryAssets
Less: current regulatory asset, net	15,996us-gaap_RegulatoryAssetsCurrent	16,853us-gaap_RegulatoryAssetsCurrent
Net regulatory assets, less current portion	157,449us-gaap_RegulatoryAssetsNoncurrent	158,010us-gaap_RegulatoryAssetsNoncurrent
Income tax temporary differences, net
Regulatory Assets [Line Items]
Regulatory assets:	6,731	6,731
Postretirement pensions and other medical benefits
Regulatory Assets [Line Items]
Regulatory assets:	115,494	115,494
Balancing and memorandum accounts, net
Regulatory Assets [Line Items]
Regulatory assets:	45,569	47,061
Other, net
Regulatory Assets [Line Items]
Regulatory assets:	$ 5,651	$ 5,577

The net amount of all regulatory assets less all regulatory liabilities as of the end of the period.

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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- Definition

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

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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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- Definition

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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