Leases - Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lessee, Lease, Description [Line Items]
Short-term Lease, Cost	$ 925	$ 880	$ 1,220
Lessor, Operating Lease, Payments to be Received, Two Years	$ 652
Operating Lease, Weighted Average Remaining Lease Term	16 years 2 months 12 days	17 years 2 months 12 days
Lessee, Operating Lease, Liability, Payments, Due	$ 139,367
Regulatory Assets, Noncurrent	333,443	$ 340,432
Operating Lease, Expense	$ 7,420	7,034	6,917
New Headquarters Lease [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	20 years
Regulatory Assets, Noncurrent	$ 8,000	6,900
Lessee, Operating Lease, Term of Contract	20 years
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
Short Term Leases
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	12 months
Lessee, Operating Lease, Term of Contract	12 months
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	9 months
Lessee, Operating Lease, Term of Contract	9 months
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	16 years
Lessee, Operating Lease, Term of Contract	16 years
Northwest Natural Gas Company [Member]
Lessee, Lease, Description [Line Items]
Short-term Lease, Cost	$ 925	$ 880	1,220
Lessor, Operating Lease, Payments to be Received, Two Years	$ 599
Operating Lease, Weighted Average Discount Rate, Percent	7.30%	7.30%
Lessee, Operating Lease, Liability, Payments, Due	$ 138,736
Regulatory Assets, Noncurrent	333,418	$ 340,407
Operating Lease, Expense	7,244	7,003	6,859
Northwest Holdings Other [Member] | Corporate, Non-Segment [Member]
Lessee, Lease, Description [Line Items]
Short-term Lease, Cost	0	0	0
Lessee, Operating Lease, Liability, Payments, Due	631
Operating Lease, Expense	$ 176	$ 31	$ 58