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	42,646		42,646		44,467		44,467
Dividends on common stock			(29,448)				(27,614)
Other comprehensive income	42,966			320	44,787			320
Stock-based compensation		3,626
Shares issued pursuant to equity based plans		858
Ending Balance at Jun. 30, 2020	$ 884,001	562,766	331,648	(10,413)	839,369	$ 319,557	530,225	(10,413)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.9550
Beginning Balance at Mar. 31, 2020	$ 901,741	561,264	351,050	(10,573)	857,739		548,755	(10,573)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	(4,852)		(4,852)		(4,712)		(4,712)
Dividends on common stock			(14,550)				(13,818)
Other comprehensive income	(4,692)			160	(4,552)			160
Stock-based compensation		254
Shares issued pursuant to equity based plans		1,248
Ending Balance at Jun. 30, 2020	$ 884,001	562,766	331,648	(10,413)	839,369	319,557	530,225	(10,413)
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	58,793		58,793		60,700		60,700
Dividends on common stock			(29,815)				(27,935)
Other comprehensive income	59,235			442	61,142			442
Stock-based compensation		2,446
Shares issued pursuant to equity based plans		2,227
Ending Balance at Jun. 30, 2021	$ 922,826	569,785	365,501	(12,460)	868,391	319,506	561,345	(12,460)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.9600
Beginning Balance at Mar. 31, 2021	$ 936,324	568,066	380,939	(12,681)	881,565		574,740	(12,681)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	(724)		(724)		589		589
Dividends on common stock			(14,714)				(13,984)
Other comprehensive income	(503)			221	810			221
Stock-based compensation		416
Shares issued pursuant to equity based plans		1,303
Ending Balance at Jun. 30, 2021	$ 922,826	$ 569,785	$ 365,501	$ (12,460)	$ 868,391	$ 319,506	$ 561,345	$ (12,460)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4800