Leases - Lease Asset and Liabilities - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	$ 74,416	$ 76,957	$ 75,049
Operating lease liabilities current liabilities	1,303	1,213	1,296
Operating lease liabilities noncurrent liabilities	79,162	80,414	79,468
Total operating lease liabilities	$ 80,465	$ 81,627	$ 80,764
Operating Lease, Weighted Average Remaining Lease Term	18 years	18 years 10 months 24 days	18 years 2 months 12 days
Operating Lease, Weighted Average Discount Rate, Percent	7.20%	7.20%	7.20%
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	$ 150,427
Regulatory Assets, Noncurrent	297,546	$ 338,692	$ 314,579
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	5,253
Lessee, Operating Lease, Liability, to be Paid, Year One	7,019
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,156
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,191
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,359
Lessee, Operating Lease, Liability, Payments, Due after Year Five	116,449
Lessee, Operating Lease, Liability, Payments, Due	150,427
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	69,962
Total operating lease liabilities	80,465	81,627	80,764
Operating lease liabilities current liabilities	1,303	1,213	1,296
Operating lease liabilities noncurrent liabilities	79,162	80,414	79,468
Finance Lease, Liability, Payments, Due Next Twelve Months	300
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	1,739	1,685
Finance Lease, Principal Payments	75	544
Operating leases	14	154
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	100	74
Finance Leases [Abstract]
Finance Lease, Liability	0
Finance Lease, Right-of-Use Asset	2,200	1,900	2,100
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	55	100	62
Operating lease liabilities current liabilities	17	46	23
Operating lease liabilities noncurrent liabilities	37	56	37
Total operating lease liabilities	54	102	60
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	59
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	18
Lessee, Operating Lease, Liability, to be Paid, Year One	6
Lessee, Operating Lease, Liability, Payments, Due Year Two	6
Lessee, Operating Lease, Liability, Payments, Due Year Three	6
Lessee, Operating Lease, Liability, Payments, Due Year Four	6
Lessee, Operating Lease, Liability, Payments, Due after Year Five	17
Lessee, Operating Lease, Liability, Payments, Due	59
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	5
Total operating lease liabilities	54	102	60
Operating lease liabilities current liabilities	17	46	23
Operating lease liabilities noncurrent liabilities	37	56	37
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	6	16
Northwest Natural Gas Company [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	74,361	76,857	74,987
Operating lease liabilities current liabilities	1,286	1,167	1,273
Operating lease liabilities noncurrent liabilities	79,125	80,358	79,431
Total operating lease liabilities	80,411	81,525	80,704
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	150,368
Regulatory Assets, Noncurrent	297,482	338,652	314,539
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	5,235
Lessee, Operating Lease, Liability, to be Paid, Year One	7,013
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,150
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,185
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,353
Lessee, Operating Lease, Liability, Payments, Due after Year Five	116,432
Lessee, Operating Lease, Liability, Payments, Due	150,368
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	69,957
Total operating lease liabilities	80,411	81,525	80,704
Operating lease liabilities current liabilities	1,286	1,167	1,273
Operating lease liabilities noncurrent liabilities	79,125	80,358	79,431
Leases Cash Flow [Abstract]
Operating cash flows from operating leases	1,733	1,669
Finance Lease, Principal Payments	75	544
Operating leases	14	154
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 100	74
New Headquarters Lease [Member]
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Term of Contract	20 years
Regulatory Assets, Noncurrent	$ 6,000	$ 4,600	$ 5,700
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	18 years