Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Regulatory Assets [Line Items]
Net Regulatory Assets	$ 159,324	$ 168,563
Less: current regulatory asset, net	25,661	16,542
Net regulatory assets, less current portion	133,663	152,021
Income tax temporary differences, net
Regulatory Assets [Line Items]
Regulatory assets:	8,184	8,184
Postretirement pensions and other medical benefits
Regulatory Assets [Line Items]
Regulatory assets:	109,168	109,168
Balancing and memorandum accounts, net
Regulatory Assets [Line Items]
Regulatory assets:	35,967	45,206
Other, net
Regulatory Assets [Line Items]
Regulatory assets:	$ 6,005	$ 6,005

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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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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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