Leases - Lease Asset and Liabilities - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	$ 71,477	$ 73,145	$ 71,477	$ 73,145	$ 73,429
Operating lease liabilities current liabilities	1,815	1,361	1,815	1,361	1,514
Operating lease liabilities noncurrent liabilities	77,475	78,469	77,475	78,469	78,965
Total operating lease liabilities	$ 79,290	$ 79,830	$ 79,290	$ 79,830	$ 80,479
Operating Lease, Weighted Average Remaining Lease Term	16 years 6 months	17 years 6 months	16 years 6 months	17 years 6 months	17 years 2 months 12 days
Operating Lease, Weighted Average Discount Rate, Percent	7.30%	7.30%	7.30%	7.30%	7.30%
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	$ 140,866		$ 140,866
Regulatory Assets, Noncurrent	312,665	$ 301,660	312,665	$ 301,660	$ 340,432
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	1,845		1,845
Lessee, Operating Lease, Liability, to be Paid, Year One	7,490		7,490
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,369		7,369
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,514		7,514
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,645		7,645
Lessee, Operating Lease, Liability, Payments, Due after Year Five	109,003		109,003
Lessee, Operating Lease, Liability, Payments, Due	140,866		140,866
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	61,576		61,576
Total operating lease liabilities	79,290	79,830	79,290	79,830	80,479
Operating lease liabilities current liabilities	1,815	1,361	1,815	1,361	1,514
Operating lease liabilities noncurrent liabilities	77,475	78,469	77,475	78,469	78,965
Finance Lease, Liability, Payments, Due Next Twelve Months	0		0		0
Leases Cash Flow [Abstract]
Operating Lease, Payments	1,863	1,771	5,506	5,249
Finance Lease, Principal Payments	196	92	369	474
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	0	61	81	61
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	207	6	470	226
Finance Leases [Abstract]
Finance Lease, Liability	0		0
Finance Lease, Right-of-Use Asset	2,600	2,300	2,600	2,300	2,300
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	625	99	625	99	709
Operating lease liabilities current liabilities	157	63	157	63	151
Operating lease liabilities noncurrent liabilities	434	33	434	33	620
Total operating lease liabilities	591	96	591	96	771
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	675		675
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	44		44
Lessee, Operating Lease, Liability, to be Paid, Year One	183		183
Lessee, Operating Lease, Liability, Payments, Due Year Two	176		176
Lessee, Operating Lease, Liability, Payments, Due Year Three	153		153
Lessee, Operating Lease, Liability, Payments, Due Year Four	107		107
Lessee, Operating Lease, Liability, Payments, Due after Year Five	12		12
Lessee, Operating Lease, Liability, Payments, Due	675		675
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	84		84
Total operating lease liabilities	591	96	591	96	771
Operating lease liabilities current liabilities	157	63	157	63	151
Operating lease liabilities noncurrent liabilities	434	33	434	33	620
Leases Cash Flow [Abstract]
Operating Lease, Payments	54	12	132	24
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	0	61	0	61
Northwest Natural Gas Company [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	70,852	73,046	70,852	73,046	72,720
Operating lease liabilities current liabilities	1,658	1,298	1,658	1,298	1,363
Operating lease liabilities noncurrent liabilities	77,041	78,436	77,041	78,436	78,345
Total operating lease liabilities	78,699	79,734	78,699	79,734	79,708
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	140,191		140,191
Regulatory Assets, Noncurrent	312,640	301,596	312,640	301,596	340,407
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	1,801		1,801
Lessee, Operating Lease, Liability, to be Paid, Year One	7,307		7,307
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,193		7,193
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,361		7,361
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,538		7,538
Lessee, Operating Lease, Liability, Payments, Due after Year Five	108,991		108,991
Lessee, Operating Lease, Liability, Payments, Due	140,191		140,191
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	61,492		61,492
Total operating lease liabilities	78,699	79,734	78,699	79,734	79,708
Operating lease liabilities current liabilities	1,658	1,298	1,658	1,298	1,363
Operating lease liabilities noncurrent liabilities	77,041	78,436	77,041	78,436	78,345
Leases Cash Flow [Abstract]
Operating Lease, Payments	1,809	1,759	5,374	5,225
Finance Lease, Principal Payments	196	92	369	474
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	0	0	81	0
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	196	6	369	226
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Leases Cash Flow [Abstract]
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 11		$ 101	0
New Headquarters Lease [Member]
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Term of Contract	20 years		20 years
Regulatory Assets, Noncurrent	$ 7,800	$ 6,600	$ 7,800	$ 6,600	$ 6,900
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		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		7 years
Maximum [Member]
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Term of Contract	17 years		17 years