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The percenage of pre-tax income from gas storage credited to a deferred regulatory account for crediting back to core utility customers when the costs of the capacity have been included in utility rates.

No definition available.

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The percenage of pre-tax income from gas storage retained when the costs of the capacity have been included in utility rates.

No definition available.

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The percenage of pre-tax income from gas storage retained when the costs of the capacity have not been included in utility rates.

No definition available.

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Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount after tax of income (loss) from continuing operations attributable to the parent.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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The net result for the period of deducting operating expenses from operating revenues.

No definition available.

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The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 45
-Paragraph 13
-Subparagraph (c)
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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
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-Section S99
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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.

No definition available.

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Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_GeographicConcentrationRiskMember
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Name:	us-gaap_StatementGeographicalAxis=stpr_OR
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Name:	dei_LegalEntityAxis=nwn_MistGasStorageFacilityMemberMember
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Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DiscontinuedOperationsHeldForSaleOrDisposedOfBySaleMember
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