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, 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		179,388		179,388
Net income	38,367	41,343			38,367	41,343
Dividends on common stock					(48,576)	(46,319)
Other comprehensive income	38,963	41,939					596	596
Stock-based compensation			2,695
Shares issued pursuant to equity based plans, net of shares withheld for taxes			1,958
Issuances of common stock, net of issuance costs			190,670
Ending Balance at Sep. 30, 2022	$ 1,120,856	1,152,815	786,094	614,903	345,570	548,720	(10,808)	(10,808)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 1.4475
Beginning Balance at Jun. 30, 2022	$ 1,138,779	1,173,676	767,826	601,032	381,963	583,654	(11,010)	(11,010)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contributions from parent				13,871
Net income	(19,587)	(18,806)			(19,587)	(18,806)
Dividends on common stock					(16,806)	(16,128)
Other comprehensive income	(19,385)	(18,604)					202	202
Stock-based compensation			463
Shares issued pursuant to equity based plans, net of shares withheld for taxes			954
Issuances of common stock, net of issuance costs			16,851
Ending Balance at Sep. 30, 2022	$ 1,120,856	1,152,815	786,094	614,903	345,570	548,720	(10,808)	(10,808)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4825
Beginning Balance at Dec. 31, 2022	$ 1,175,441	1,191,082	805,253	614,903	376,473	582,593	(6,285)	(6,414)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contributions from parent		30,000		30,000
Net income	49,228	55,837			49,228	55,837
Dividends on common stock					(52,470)	(75,123)
Other comprehensive income	50,534	56,144					1,306	307
Stock-based compensation			3,257
Shares issued pursuant to equity based plans, net of shares withheld for taxes			1,883
Issuances of common stock, net of issuance costs			40,895
Ending Balance at Sep. 30, 2023	$ 1,219,540	1,202,103	851,288	644,903	373,231	563,307	(4,979)	(6,107)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 1.4550
Beginning Balance at Jun. 30, 2023	$ 1,240,278	1,210,296	831,135	614,903	414,398	601,602	(5,255)	(6,209)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contributions from parent				30,000
Net income	(23,687)	(21,487)			(23,687)	(21,487)
Dividends on common stock					(17,480)	(16,808)
Other comprehensive income	(23,411)	(21,385)					276	102
Stock-based compensation			251
Shares issued pursuant to equity based plans, net of shares withheld for taxes			1,046
Issuances of common stock, net of issuance costs			18,856
Ending Balance at Sep. 30, 2023	$ 1,219,540	$ 1,202,103	$ 851,288	$ 644,903	$ 373,231	$ 563,307	$ (4,979)	$ (6,107)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4850