Significant Accounting Policies - Credit Losses - ASU 2016-13 $ in Thousands	6 Months Ended
	Jun. 30, 2023 USD ($) numberOfLeases	Dec. 31, 2022 USD ($)	Jun. 30, 2022 USD ($)
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Number of Net Investments in Sales-Type Leases | numberOfLeases	2
Sales-type Lease, Net Investment in Lease, Allowance for Credit Loss	$ 0
Regulatory Assets, Noncurrent	307,999	$ 340,432	$ 301,855
Other Northwest Holdings [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	217	217
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	0
Accounts Receivable, Allowance for Credit Loss, Recovery	0
Northwest Holdings [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	3,297	3,296
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	1,737
Accounts Receivable, Allowance for Credit Loss, Recovery	(1,736)
Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	3,080	3,079
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	1,737
Accounts Receivable, Allowance for Credit Loss, Recovery	(1,736)
Regulatory Assets, Noncurrent	307,974	340,407	$ 301,790
Residential [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	2,331	2,155
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	1,612
Accounts Receivable, Allowance for Credit Loss, Recovery	(1,436)
Commercial [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	395	400
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	219
Accounts Receivable, Allowance for Credit Loss, Recovery	(224)
Industrial [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	90	188
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	(97)
Accounts Receivable, Allowance for Credit Loss, Recovery	(1)
Accrued unbilled and other [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	264	$ 336
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	3
Accounts Receivable, Allowance for Credit Loss, Recovery	$ (75)