Consolidated Statement of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock Including APIC [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Northwest Natural Gas Company [Member]	Northwest Natural Gas Company [Member] Common Stock Including APIC [Member]	Northwest Natural Gas Company [Member] Retained Earnings [Member]	Northwest Natural Gas Company [Member] Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2019	$ 865,999	$ 558,282	$ 318,450	$ (10,733)	$ 822,196		$ 513,372	$ (10,733)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	47,498		47,498		49,179		49,179
Dividends on common stock			(14,898)				(13,796)
Other comprehensive income	47,658			160	49,339			160
Stock-based compensation		3,372
Shares issued pursuant to equity based plans		(390)
Ending Balance at Mar. 31, 2020	$ 901,741	561,264	351,050	(10,573)	857,739	$ 319,557	548,755	(10,573)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4775
Beginning Balance at Dec. 31, 2020	$ 888,733	565,112	336,523	(12,902)	835,184		528,580	(12,902)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	59,517		59,517		60,111		60,111
Dividends on common stock			(15,101)				(13,951)
Other comprehensive income	59,738			221	60,332			221
Stock-based compensation		2,030
Shares issued pursuant to equity based plans		924
Ending Balance at Mar. 31, 2021	$ 936,324	$ 568,066	$ 380,939	$ (12,681)	$ 881,565	$ 319,506	$ 574,740	$ (12,681)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4800