Significant Accounting Policies - Credit Losses - ASU 2016-13	3 Months Ended
	Mar. 31, 2023 USD ($) numberOfLeases	Dec. 31, 2022 USD ($)	Mar. 31, 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	311,419,000	$ 340,432,000	$ 297,546,000
Settlement Agreement
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	2,600,000
Other Receivables	3,250,000
Proceeds from Collection of Other Receivables	0
Other Northwest Holdings [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	2,823,000	217,000
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	2,606,000
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	6,760,000	3,296,000
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	3,807,000
Accounts Receivable, Allowance for Credit Loss, Recovery	(343,000)
Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	3,937,000	3,079,000
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	1,201,000
Accounts Receivable, Allowance for Credit Loss, Recovery	(343,000)
Regulatory Assets, Noncurrent	311,394,000	340,407,000	$ 297,482,000
Residential [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	2,953,000	2,155,000
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	1,063,000
Accounts Receivable, Allowance for Credit Loss, Recovery	(265,000)
Commercial [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	481,000	400,000
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	114,000
Accounts Receivable, Allowance for Credit Loss, Recovery	(33,000)
Industrial [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	201,000	188,000
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	14,000
Accounts Receivable, Allowance for Credit Loss, Recovery	(1,000)
Accrued unbilled and other [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	302,000	$ 336,000
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	10,000
Accounts Receivable, Allowance for Credit Loss, Recovery	$ (44,000)