Significant Accounting Policies - Regulatory Asset Disclosure - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 108,525	$ 117,491	$ 104,830
Regulatory Assets, Noncurrent	$ 312,665	340,432	301,660
Inactive Account, Period Outstanding Prior to Write-Off	120 days
General Payment Term of NGD Receivables	15 days
Age of Closed or Inactive Accounts	120 days
Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	$ 25	25	64
Northwest Natural Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	108,525	117,491	104,830
Regulatory Assets, Noncurrent	312,640	340,407	301,596
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	46,603	28,728	19,594
Regulatory Assets, Noncurrent	21,085	20,838	18,824
Northwest Natural Gas Company [Member] | Pension balancing [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	7,131	7,131	7,131
Regulatory Assets, Noncurrent	29,450	32,997	34,928
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,208	2,208	2,399
Regulatory Assets, Noncurrent	10,540	10,943	11,168
Northwest Natural Gas Company [Member] | Pension and other postretirement benefit liabilities [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	101,413	101,413	107,722
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	7,047	7,392	9,461
Regulatory Assets, Noncurrent	108,941	104,253	82,667
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	11,361	61,223	52,115
Regulatory Assets, Noncurrent	718	22,355	3,369
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	3,480	0	114
Regulatory Assets, Noncurrent	212	0	0
Northwest Natural Gas Company [Member] | Washington Climate Commitment Act compliance
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	12,513	0	0
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	19,568	10,020	14,016
Regulatory Assets, Noncurrent	25,957	33,053	27,771
Northwest Natural Gas Company [Member] | COVID-19 Related Costs
Regulatory Assets [Line Items]
Regulatory Assets, Current	11,127	789	0
Regulatory Assets, Noncurrent	$ 1,811	$ 14,555	$ 15,147