Leases - Lease Asset and Liabilities - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	$ 69,813	$ 72,096	$ 71,308
Operating lease liabilities current liabilities	1,851	1,732	2,333
Operating lease liabilities noncurrent liabilities	76,692	77,951	77,167
Total operating lease liabilities	$ 78,543	$ 79,683	$ 79,500
Operating Lease, Weighted Average Remaining Lease Term	15 years 9 months 18 days	16 years 9 months 18 days	16 years 2 months 12 days
Operating Lease, Weighted Average Discount Rate, Percent	7.30%	7.30%	7.30%
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	$ 135,628
Regulatory Assets, Noncurrent	308,521	$ 307,999	$ 333,443
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	3,928
Lessee, Operating Lease, Liability, to be Paid, Year One	7,538
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,514
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,645
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,725
Lessee, Operating Lease, Liability, Payments, Due after Year Five	101,278
Lessee, Operating Lease, Liability, Payments, Due	135,628
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	57,085
Total operating lease liabilities	78,543	79,683	79,500
Operating lease liabilities current liabilities	1,851	1,732	2,333
Operating lease liabilities noncurrent liabilities	76,692	77,951	77,167
Leases Cash Flow [Abstract]
Operating Lease, Payments	3,738	3,643
Finance Lease, Principal Payments	277	173
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	0	81
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	277	263
Finance Leases [Abstract]
Finance Lease, Liability	0
Finance Lease, Right-of-Use Asset	2,800	2,400	2,600
Other Northwest Holdings [Member] \| Corporate, Non-Segment [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	496	588	580
Operating lease liabilities current liabilities	160	134	205
Operating lease liabilities noncurrent liabilities	337	461	410
Total operating lease liabilities	497	595	615
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	542
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	94
Lessee, Operating Lease, Liability, to be Paid, Year One	176
Lessee, Operating Lease, Liability, Payments, Due Year Two	153
Lessee, Operating Lease, Liability, Payments, Due Year Three	107
Lessee, Operating Lease, Liability, Payments, Due Year Four	6
Lessee, Operating Lease, Liability, Payments, Due after Year Five	6
Lessee, Operating Lease, Liability, Payments, Due	542
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	45
Total operating lease liabilities	497	595	615
Operating lease liabilities current liabilities	160	134	205
Operating lease liabilities noncurrent liabilities	337	461	410
Leases Cash Flow [Abstract]
Operating Lease, Payments	88	78
Northwest Natural Gas Company [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	69,317	71,508	70,728
Operating lease liabilities current liabilities	1,691	1,598	2,128
Operating lease liabilities noncurrent liabilities	76,355	77,490	76,757
Total operating lease liabilities	78,046	79,088	78,885
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	135,086
Regulatory Assets, Noncurrent	308,415	307,974	333,418
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	3,834
Lessee, Operating Lease, Liability, to be Paid, Year One	7,362
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,361
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,538
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,719
Lessee, Operating Lease, Liability, Payments, Due after Year Five	101,272
Lessee, Operating Lease, Liability, Payments, Due	135,086
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	57,040
Total operating lease liabilities	78,046	79,088	78,885
Operating lease liabilities current liabilities	1,691	1,598	2,128
Operating lease liabilities noncurrent liabilities	76,355	77,490	76,757
Leases Cash Flow [Abstract]
Operating Lease, Payments	3,650	3,565
Finance Lease, Principal Payments	277	173
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	0	81
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	277	173
Other Northwest Holdings [Member] \| Corporate, Non-Segment [Member]
Leases Cash Flow [Abstract]
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 0	90
New Headquarters Lease [Member]
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Term of Contract	20 years
Regulatory Assets, Noncurrent	$ 8,600	$ 7,500	$ 8,000
New Headquarters Lease Renewal Term 2 of 2 [Member] \| New Headquarters Lease [Member]
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Renewal Term	7 years
New Headquarters Lease Renewal Term 1 of 2 [Member] \| New Headquarters Lease [Member]
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Renewal Term	7 years
Maximum [Member]
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Term of Contract	16 years

Finance Leases [Abstract]

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Lease Not Yet Commenced [Abstract]

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Leases Cash Flow [Abstract]

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Maturity of Operating Lease Liabilities [Abstract]

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Operating Lease Asset and Liabilities [Abstract]

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Present value of lessee's discounted obligation for lease payments from finance lease.

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Amount of cash outflow for principal payment on finance lease.

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Amount, after accumulated amortization, of right-of-use asset from finance lease.

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

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Amount of lessee's undiscounted obligation for lease payment for operating lease due after fifth 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 lessee's undiscounted obligation for lease payment for operating 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).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fourth 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 lessee's undiscounted obligation for lease payment for operating lease to be paid in third 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 lessee's undiscounted obligation for lease payment for operating lease to be paid 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 lessee's undiscounted obligation for lease payment for operating lease having initial or remaining lease term in excess of one year to be paid in remainder of current fiscal year.

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Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for operating lease.

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

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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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Present value of lessee's discounted obligation for lease payments from operating lease.

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.

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Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.

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Amount of lessee's right to use underlying asset under operating lease.

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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 increase in right-of-use asset obtained in exchange for finance lease liability.

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Amount of increase in right-of-use asset obtained in exchange for operating lease liability.

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