TargetHedgeAchieved

No definition available.

Name:	nwn_TargetHedgeAchieved
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Data Type:	num:percentItemType
Balance Type:	na
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- 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_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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=109980867&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=109980867&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmount
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Balance Type:	na
Period Type:	instant

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

+ Details

Name:	us-gaap_DerivativeNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=nwn_NorthwestNaturalGasCompanyMember
Namespace Prefix:
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Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=nwn_FinancialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	nwn_GasYearAxis=nwn_GasYear20192020Member
Namespace Prefix:
Data Type:	na
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- Details

Name:	nwn_GasYearAxis=nwn_GasYear20182019Member
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Data Type:	na
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=nwn_PhysicalMember
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- Details

Name:	us-gaap_UnderlyingAssetClassAxis=nwn_NaturalGasThermsMember
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- Details

Name:	us-gaap_UnderlyingAssetClassAxis=us-gaap_ForeignExchangeContractMember
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Derivative Instruments Notional Amounts (Details) - Northwest Natural Gas Company [Member] therm in Thousands, $ in Thousands	Jun. 30, 2020 USD ($) therm	Dec. 31, 2019 USD ($) therm	Jun. 30, 2019 USD ($) therm
Financial [Member] \| Gas Year 2019 - 2020 [Member]
Derivative [Line Items]
TargetHedgeAchieved	52.00%
Financial [Member] \| Gas Year 2018 - 2019 [Member]
Derivative [Line Items]
TargetHedgeAchieved	48.00%
Physical [Member] \| Gas Year 2019 - 2020 [Member]
Derivative [Line Items]
TargetHedgeAchieved	19.00%
Physical [Member] \| Gas Year 2018 - 2019 [Member]
Derivative [Line Items]
TargetHedgeAchieved	24.00%
Natural Gas Therms [Member] \| Financial [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	654,145	651,540	466,280
Natural Gas Therms [Member] \| Physical [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	570,600	512,849	564,500
Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount \| $	$ 7,176	$ 6,650	$ 7,552