Leases - Lease Asset and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Lease Asset and Liabilities [Abstract]
Operating Lease, Right-of-Use Asset	$ 71,308	$ 73,429
Operating Lease, Liability, Current	2,333	1,514
Operating Lease, Liability, Noncurrent	77,167	78,965
Operating Lease, Liability	$ 79,500	$ 80,479
Operating Lease, Weighted Average Remaining Lease Term	16 years 2 months 12 days	17 years 2 months 12 days
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	$ 7,667
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,538
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,514
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,645
Lessee, Operating Lease, Liability, Payments, Due Year Five	7,725
Lessee, Operating Lease, Liability, Payments, Due after Year Five	101,278
Lessee, Operating Lease, Liability, Payments, Due	139,367
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	59,867
Operating Lease, Liability	79,500	$ 80,479
Operating Lease, Liability, Current	2,333	1,514
Operating Lease, Liability, Noncurrent	77,167	78,965
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	139,367
Leases Cash Flow [Abstract]
Operating Lease, Payments	7,610	7,057	$ 6,898
Finance Lease, Principal Payments	369	524	801
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	659	977	223
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 470	$ 270	314
Finance Leases [Abstract]
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Total property, plant, and equipment, net	Total property, plant, and equipment, net
Prior Period Disclosures [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	$ 7,667
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,538
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,514
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,645
Lessee, Operating Lease, Liability, Payments, Due Year Five	7,725
Lessee, Operating Lease, Liability, Payments, Due after Year Five	101,278
Lessee, Operating Lease, Liability, Payments, Due	139,367
Regulatory Assets, Noncurrent	333,443	$ 340,432
Finance Lease, Liability, to be Paid	0
Northwest Natural Gas Company [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating Lease, Right-of-Use Asset	70,728	72,720
Operating Lease, Liability, Current	2,128	1,363
Operating Lease, Liability, Noncurrent	76,757	78,345
Operating Lease, Liability	$ 78,885	$ 79,708
Operating Lease, Weighted Average Discount Rate, Percent	7.30%	7.30%
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	$ 7,484
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,362
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,361
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,538
Lessee, Operating Lease, Liability, Payments, Due Year Five	7,719
Lessee, Operating Lease, Liability, Payments, Due after Year Five	101,272
Lessee, Operating Lease, Liability, Payments, Due	138,736
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	59,851
Operating Lease, Liability	78,885	$ 79,708
Operating Lease, Liability, Current	2,128	1,363
Operating Lease, Liability, Noncurrent	76,757	78,345
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	138,736
Leases Cash Flow [Abstract]
Operating Lease, Payments	7,434	6,993	6,840
Finance Lease, Principal Payments	369	524	801
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	659	309	223
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	369	270	314
Prior Period Disclosures [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	7,484
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,362
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,361
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,538
Lessee, Operating Lease, Liability, Payments, Due Year Five	7,719
Lessee, Operating Lease, Liability, Payments, Due after Year Five	101,272
Lessee, Operating Lease, Liability, Payments, Due	138,736
Regulatory Assets, Noncurrent	333,418	340,407
Corporate, Non-Segment [Member] | Northwest Holdings Other [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating Lease, Right-of-Use Asset	580	709
Operating Lease, Liability, Current	205	151
Operating Lease, Liability, Noncurrent	410	620
Operating Lease, Liability	615	771
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	183
Lessee, Operating Lease, Liability, Payments, Due Year Two	176
Lessee, Operating Lease, Liability, Payments, Due Year Three	153
Lessee, Operating Lease, Liability, Payments, Due Year Four	107
Lessee, Operating Lease, Liability, Payments, Due Year Five	6
Lessee, Operating Lease, Liability, Payments, Due after Year Five	6
Lessee, Operating Lease, Liability, Payments, Due	631
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	16
Operating Lease, Liability	615	771
Operating Lease, Liability, Current	205	151
Operating Lease, Liability, Noncurrent	410	620
Lease Not Yet Commenced [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	631
Leases Cash Flow [Abstract]
Operating Lease, Payments	176	64	58
Finance Lease, Principal Payments	0	0	0
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	0	668	0
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	101	$ 0	$ 0
Prior Period Disclosures [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	183
Lessee, Operating Lease, Liability, Payments, Due Year Two	176
Lessee, Operating Lease, Liability, Payments, Due Year Three	153
Lessee, Operating Lease, Liability, Payments, Due Year Four	107
Lessee, Operating Lease, Liability, Payments, Due Year Five	6
Lessee, Operating Lease, Liability, Payments, Due after Year Five	6
Lessee, Operating Lease, Liability, Payments, Due	$ 631
Maximum [Member]
Prior Period Disclosures [Abstract]
Lessee, Operating Lease, Term of Contract	16 years