Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Net Regulatory Assets	$ 132,278	$ 120,417
Less: current regulatory asset, net	6,129	6,472
Total regulatory assets, net, less current portion	126,149	113,945
Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory assets:	4,829	2,433
Postretirement pensions and other medical benefits
Regulatory Assets [Line Items]
Regulatory assets:	75,434	73,525
Business combinations debt premium, net [Member]
Regulatory Assets [Line Items]
Regulatory assets:	24,385	25,020
Balancing and memorandum accounts, net
Regulatory Assets [Line Items]
Regulatory assets:	15,048	5,283
WRA [Member]
Regulatory Assets [Line Items]
Regulatory assets:	5,648	9,108
Other, net
Regulatory Assets [Line Items]
Regulatory assets:	$ 6,934	$ 5,048

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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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- Definition

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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