Environmental Matters - Regulatory Deferred Assets - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Site Contingency [Line Items]
Regulatory Assets, Current	$ 64,481	$ 72,391	$ 47,789
Regulatory Assets, Noncurrent	$ 297,546	$ 314,579	$ 338,692
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	$ 100	$ 100	$ 100
Northwest Natural Gas Company [Member]
Site Contingency [Line Items]
Regulatory Assets, Current	64,481	72,391	47,789
Regulatory Assets, Noncurrent	297,482	314,539	338,652
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Site Contingency [Line Items]
Deferred costs and interest	45,482	45,122	46,409
Accrued site liabilities	109,061	115,773	113,456
Insurance proceeds and interest	(59,895)	(59,564)	(69,492)
Regulatory Assets	94,648	101,331	90,373
Regulatory Assets, Current	7,082	6,694	5,396
Regulatory Assets, Noncurrent	$ 87,566	$ 94,636	$ 84,977