- Schedule of Credit Rating Downgrade Scenarios (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Collateral Posted with NW Natural Counterparties [Member]
Description Of Credit Risk Related Contingent Features [Line Items]
Collateral Already Posted, Aggregate Fair Value	$ 0	$ 0
Collateral Posted by NW Natural Counterparties [Member]
Description Of Credit Risk Related Contingent Features [Line Items]
Collateral Already Posted, Aggregate Fair Value	0	$ 0
Northwest Natural Gas Company [Member] \| Moody's, A3 Rating [Member]
Description Of Credit Risk Related Contingent Features [Line Items]
With Adequate Assurance Calls	0
Without Adequate Assurance Calls	0
Northwest Natural Gas Company [Member] \| Moody's, Baa1 Rating [Member]
Description Of Credit Risk Related Contingent Features [Line Items]
With Adequate Assurance Calls	0
Without Adequate Assurance Calls	0
Northwest Natural Gas Company [Member] \| Moody's, Baa2 Rating [Member]
Description Of Credit Risk Related Contingent Features [Line Items]
With Adequate Assurance Calls	0
Without Adequate Assurance Calls	0
Northwest Natural Gas Company [Member] \| Moody's, Baa3 Rating [Member]
Description Of Credit Risk Related Contingent Features [Line Items]
With Adequate Assurance Calls	0
Without Adequate Assurance Calls	0
Northwest Natural Gas Company [Member] \| Speculative [Member]
Description Of Credit Risk Related Contingent Features [Line Items]
With Adequate Assurance Calls	51,000
Without Adequate Assurance Calls	$ 51,000

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- Definition

Estimated level of collateral demands with adequate assurance calls

+ References

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- Definition

Estimated level of collateral demands without adequate assurance calls

+ References

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- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624258-113959

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