Environmental Matters - Regulatory Deferred Assets - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Site Contingency [Line Items]
Regulatory Assets, Current	$ 108,525	$ 117,491	$ 104,830
Regulatory Assets, Noncurrent	$ 312,665	$ 340,432	$ 301,660
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	$ 57	$ 43	$ 34
Northwest Natural Gas Company [Member]
Site Contingency [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] | Environmental costs [Member]
Site Contingency [Line Items]
Deferred costs and interest	49,899	47,666	47,011
Accrued site liabilities	116,469	118,763	99,795
Insurance proceeds and interest	(50,380)	(54,784)	(54,678)
Regulatory Assets	115,988	111,645	92,128
Regulatory Assets, Current	7,047	7,392	9,461
Regulatory Assets, Noncurrent	$ 108,941	$ 104,253	$ 82,667