Deferred taxes related to gas reserves

No definition available.

Name:	nwn_DeferredTaxesRelatedToGasReserves
Namespace Prefix:	nwn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

DiscontinuedOperationGainLossOnDisposalStatementOfIncomeOrComprehensiveIncomeExtensibleEnumerationNotDisclosedFlag

+ References

No definition available.

+ Details

Name:	nwn_DiscontinuedOperationGainLossOnDisposalStatementOfIncomeOrComprehensiveIncomeExtensibleEnumerationNotDisclosedFlag
Namespace Prefix:	nwn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Equity Method Investment, Additional Underlying Equity in Net Assets

+ References

No definition available.

+ Details

Name:	nwn_EquityMethodInvestmentAdditionalUnderlyingEquityInNetAssets
Namespace Prefix:	nwn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Equity Method Investment, Number of Customer Connections

+ References

No definition available.

+ Details

Name:	nwn_EquityMethodInvestmentNumberOfCustomerConnections
Namespace Prefix:	nwn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Equity Method Investment, Number of Employees

+ References

No definition available.

+ Details

Name:	nwn_EquityMethodInvestmentNumberOfEmployees
Namespace Prefix:	nwn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percent of total gas supplies that were from gas reserves.

+ References

No definition available.

+ Details

Name:	nwn_GasReservesPercentGasSuppliesYtd
Namespace Prefix:	nwn_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Investments in Unconsolidated Affiliates

+ References

No definition available.

+ Details

Name:	nwn_InvestmentsInUnconsolidatedAffiliatesAbstract
Namespace Prefix:	nwn_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of Equity Method Investment Sold

+ References

No definition available.

+ Details

Name:	nwn_PercentageOfEquityMethodInvestmentSold
Namespace Prefix:	nwn_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

RNG Development Projects

+ References

No definition available.

+ Details

Name:	nwn_RNGDevelopmentProjects
Namespace Prefix:	nwn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Total cumulative gas reserves investment

+ References

No definition available.

+ Details

Name:	nwn_TotalCumulativeGasReservesInvestment
Namespace Prefix:	nwn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of gain (loss) from deconsolidation of subsidiary and derecognition of group of assets constituting transfer of business or nonprofit activity, excluding conveyance of oil and gas mineral rights and transfer of good or service in contract with customer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1B
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=109239629&loc=SL4582445-111684

+ Details

Name:	us-gaap_DeconsolidationGainOrLossAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of capitalized gas costs of a regulated entity that are expected to be recoverable through rate adjustments within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 25
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=123417213&loc=d3e43603-110378

+ Details

Name:	us-gaap_DeferredGasCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_EquityMethodInvestmentAggregateCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI https://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of gain (loss) on sale or disposal of an equity method investment.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(b)(7)(c))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(b)(9)(a))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

+ Details

Name:	us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the entity's ownership percentage in the investee multiplied by the investee's total equity.

+ References

+ Details

Name:	us-gaap_EquityMethodInvestmentUnderlyingEquityInNetAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=109237563&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(10))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 25
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8813-108599

+ Details

Name:	us-gaap_EquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the amount that could be realized under a life insurance contract or contracts owned by the Entity as of the date of the statement of financial position. Such Entity-owned life insurance policies are commonly known as corporate-owned life insurance (COLI) or bank-owned life insurance (BOLI).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 325
-SubTopic 30
-Section 25
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6384206&loc=d3e41899-111602

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(12))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LifeInsuranceCorporateOrBankOwnedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_OtherInvestmentsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of long-term investments classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(f))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(12))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_OtherLongTermInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromDivestitureOfBusinesses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ References

+ Details

Name:	us-gaap_ProceedsFromSaleOfEquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DiscontinuedOperationsHeldforsaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=nwn_GillRanchMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=nwn_AvionWaterMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=nwn_TrailWestHoldingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=nwn_BioCarbNPartnershipMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=nwn_OtherNorthwestHoldingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=nwn_NorthwestNaturalGasCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_CashAndCashEquivalentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_NotesReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=nwn_NorthwestNaturalGasCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=nwn_LexingtonMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Investments (Details) $ in Thousands	6 Months Ended	12 Months Ended
Investments (Details) $ in Thousands	Dec. 31, 2022 USD ($) numberOfCustomerConnections projects numberOfEmployees	Dec. 31, 2022 USD ($) numberOfCustomerConnections projects numberOfEmployees	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jul. 31, 2022 USD ($)
Schedule of Investments [Line Items]
Total Cumulative Gas Reserves Investment	$ 188,000	$ 188,000
Other Investments [Abstract]
Life Insurance, Corporate or Bank Owned, Amount	49,358	49,358	$ 48,178
Equity Method Investments	22,970	22,970	26,608
Equity Method Investment, Aggregate Cost	23,376	23,376	14,492
Total Other investments	95,704	95,704	89,278
Investments in Unconsolidated Affiliates [Abstract]
Equity Method Investment, Underlying Equity in Net Assets	$ 23,400	23,400	14,500
Proceeds from Sale of Equity Method Investments		0	7,000	$ 7,000
Proceeds from sale of discontinued operations		$ 0	0	12,500
Discontinued Operations, Held-for-sale [Member] \| Gill Ranch [Member]
Investments in Unconsolidated Affiliates [Abstract]
Proceeds from sale of discontinued operations				$ 13,500	$ 1,000
DiscontinuedOperationGainLossOnDisposalStatementOfIncomeOrComprehensiveIncomeExtensibleEnumerationNotDisclosedFlag			$ 5,900
Avion Water
Investments in Unconsolidated Affiliates [Abstract]
Ownership percentage	37.30%	37.30%
Equity Method Investment, Underlying Equity in Net Assets	$ 14,500	$ 14,500
Equity Method Investment, Number of Customer Connections \| numberOfCustomerConnections	15,000	15,000
Equity Method Investment, Number of Employees \| numberOfEmployees	35	35
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 9,400	$ 9,400
Trail West Holdings [Member]
Investments in Unconsolidated Affiliates [Abstract]
Percentage of Equity Method Investment Sold			10000.00%
Equity Method Investment, Realized Gain (Loss) on Disposal			$ 500
BioCarbN Partnership \| Maximum [Member]
Investments in Unconsolidated Affiliates [Abstract]
RNG Development Projects \| projects	4	4
Northwest Holdings Other [Member] \| Avion Water
Investments in Unconsolidated Affiliates [Abstract]
Ownership percentage	40.30%	40.30%
Equity Method Investment, Additional Underlying Equity in Net Assets						$ 1,000
Northwest Holdings Other [Member] \| Trail West Holdings [Member]
Investments in Unconsolidated Affiliates [Abstract]
Proceeds from Sale of Equity Method Investments		$ 14,000
Northwest Natural Gas Company [Member]
Other Investments [Abstract]
Total Other investments	$ 80,110	80,110	74,786
Investments in Unconsolidated Affiliates [Abstract]
Deferred Taxes Related To Gas Reserves	5,200	$ 5,200	$ 6,900
Gas Reserves Percent Gas Supplies YTD		3.00%	4.00%
Deferred Gas Cost	3,400	$ 3,400	$ 5,400
Cash and Cash Equivalents [Member] \| Trail West Holdings [Member]
Investments in Unconsolidated Affiliates [Abstract]
Proceeds from Sale of Equity Method Investments			7,000
Notes Receivable [Member] \| Trail West Holdings [Member]
Investments in Unconsolidated Affiliates [Abstract]
Proceeds from Sale of Equity Method Investments		7,000
Northwest Natural Gas Company [Member]
Other Investments [Abstract]
Life Insurance, Corporate or Bank Owned, Amount	49,358	49,358	48,178
Equity Method Investments	22,970	22,970	26,608
Equity Method Investment, Aggregate Cost	7,782	7,782	0
Total Other investments	80,110	$ 80,110	$ 74,786
Northwest Natural Gas Company [Member] \| Lexington
Investments in Unconsolidated Affiliates [Abstract]
Deconsolidation, Gain (Loss), Amount	$ 0