Environmental Matters - Regulatory Deferred Assets - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022
Site Contingency [Line Items]
Regulatory Assets, Current	$ 111,819	$ 117,491	$ 92,803
Regulatory Assets, Noncurrent	$ 307,999	$ 340,432	$ 301,855
Remediation Non-recovery Percentage	3.30%	3.30%	3.30%
Annual tariff rider collection	$ 5,000
Annual insurance proceeds to apply against remediation costs	5,000
Total annual remediation expense and interest	$ 10,000
Oregon [Member]
Site Contingency [Line Items]
Remediation Recovery Percentage	96.70%
Front Street [Member] | Environmental costs [Member]
Site Contingency [Line Items]
Accrued site liabilities	$ 47	$ 43	$ 47
Northwest Natural Gas Company [Member]
Site Contingency [Line Items]
Regulatory Assets, Current	111,819	117,491	92,803
Regulatory Assets, Noncurrent	307,974	340,407	301,790
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Site Contingency [Line Items]
Deferred costs and interest	51,237	47,666	48,814
Accrued site liabilities	109,727	118,763	104,798
Insurance proceeds and interest	(56,055)	(54,784)	(60,226)
Regulatory Assets	104,909	111,645	93,386
Regulatory Assets, Current	6,749	7,392	6,975
Regulatory Assets, Noncurrent	$ 98,160	$ 104,253	$ 86,411