Consolidated Statement of Shareholders' Equity - USD ($) $ in Thousands	Total	Northwest Natural Gas Company [Member]	Common Stock Including APIC [Member]	Common Stock Including APIC [Member] Northwest Natural Gas Company [Member]	Retained Earnings [Member]	Retained Earnings [Member] Northwest Natural Gas Company [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Northwest Natural Gas Company [Member]
Beginning Balance at Dec. 31, 2020	$ 888,733	$ 835,184	$ 565,112	$ 319,506	$ 336,523	$ 528,580	$ (12,902)	$ (12,902)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contributions from parent		0		0
Net income	59,517	60,111			59,517	60,111
Dividends on common stock					(15,101)	(13,951)
Other comprehensive income	59,738	60,332					221	221
Stock-based compensation			2,030
Shares issued pursuant to equity based plans, net of shares withheld for taxes			924
Issuances of common stock, net of issuance costs			0
Ending Balance at Mar. 31, 2021	$ 936,324	881,565	568,066	319,506	380,939	574,740	(12,681)	(12,681)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4800
Beginning Balance at Dec. 31, 2021	$ 935,146	977,807	590,771	435,515	355,779	553,696	(11,404)	(11,404)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contributions from parent		527		527
Net income	56,239	57,416			56,239	57,416
Dividends on common stock					(15,249)	(14,338)
Other comprehensive income	56,436	57,613					197	197
Stock-based compensation			1,774
Shares issued pursuant to equity based plans, net of shares withheld for taxes			(76)
Issuances of common stock, net of issuance costs			9,913
Ending Balance at Mar. 31, 2022	$ 987,944	$ 1,021,609	$ 602,382	$ 436,042	$ 396,769	$ 596,774	$ (11,207)	$ (11,207)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4825