Leases - Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Operating Lease, Expense	$ 6,917	$ 4,506
Short-term Lease, Cost	1,220	$ 1,010
Lessor, Operating Lease, Payments to be Received, Two Years	$ 125
Operating Lease, Weighted Average Remaining Lease Term	18 years 2 months 12 days	19 years 2 months 12 days
Lessee, Operating Lease, Liability, Payments, Due	$ 152,166
Regulatory Assets, Noncurrent	314,579	$ 348,927
Finance Lease, Liability, to be Paid, Year One	$ 300
New Headquarters Lease [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	20 years
Lessee, Operating Lease, Term of Contract	20 years
New Headquarters Lease [Member]
Lessee, Lease, Description [Line Items]
Regulatory Assets, Noncurrent	$ 5,700	4,200
New Headquarters Lease [Member] \| New Headquarters Lease Renewal Term 1 of 2 [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	7 years
Lessee, Operating Lease, Term of Contract	7 years
New Headquarters Lease [Member] \| New Headquarters Lease 1st Renewal Period [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	7 years
Lessee, Operating Lease, Term of Contract	7 years
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	1 year
Lessee, Operating Lease, Term of Contract	1 year
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	18 years
Lessee, Operating Lease, Term of Contract	18 years
Northwest Natural Gas Company [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Expense	$ 6,859	4,381
Short-term Lease, Cost	1,220	$ 1,010
Lessor, Operating Lease, Payments to be Received, Two Years	$ 74
Operating Lease, Weighted Average Discount Rate, Percent	7.20%	7.20%
Lessee, Operating Lease, Liability, Payments, Due	$ 152,100
Regulatory Assets, Noncurrent	314,539	$ 348,887
Northwest Holdings Other [Member] \| Corporate, Non-Segment [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Expense	58	125
Short-term Lease, Cost	0	$ 0
Lessee, Operating Lease, Liability, Payments, Due	$ 66

Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918701-209980

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Amount of lessee's undiscounted obligation for lease payment for operating lease.

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Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of lease payment to be received by lessor for operating lease in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of operating lease expense. Excludes sublease income.

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Weighted average remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

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Amount of short-term lease cost, excluding expense for lease with term of one month or less.

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