Derivative Instruments - Schedule of Notional Amounts (Details) - Northwest Natural Gas Company [Member] therm in Thousands, $ in Thousands	Dec. 31, 2020 USD ($) therm	Dec. 31, 2019 USD ($) therm
Natural Gas Therms [Member] \| Financial [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	784,400	651,540
Natural Gas Therms [Member] \| Physical [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	457,593	512,849
Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount \| $	$ 5,896	$ 6,650

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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- Definition

Nominal number of units used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

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