Segment Information - Schedule of Summarized Financial Information by Segment - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Operating revenues	$ 237,859	$ 194,960	$ 700,282	$ 545,261
Depreciation	31,293	28,110	62,758	56,539
Income from operations	13,843	13,539	127,351	101,177
Total assets	4,536,705	4,100,518	4,536,705	4,100,518	$ 4,748,326
Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	223,714	184,634	671,484	526,032
Depreciation	29,623	27,062	59,481	54,435
Income from operations	10,390	10,575	119,549	96,238
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(271)	157	71,680	55,547
Capital expenditures	65,215	91,122	128,857	155,402
Total assets	4,176,376	3,875,237	4,176,376	3,875,237	4,392,699
Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,634	5,617	11,377	10,843
Depreciation	257	266	543	530
Income from operations	2,912	3,550	7,881	6,438
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	2,055	2,576	5,644	4,602
Capital expenditures	485	750	441	787
Total assets	53,538	54,760	53,538	54,760	60,019
Northwest Natural Gas Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	228,348	190,251	682,861	536,875
Depreciation	29,880	27,328	60,024	54,965
Income from operations	13,302	14,125	127,430	102,676
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	1,784	2,733	77,324	60,149
Capital expenditures	65,700	91,872	129,298	156,189
Total assets	4,229,914	3,929,997	4,229,914	3,929,997	4,452,718
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	9,511	4,709	17,421	8,386
Depreciation	1,413	782	2,734	1,574
Income from operations	541	(586)	(79)	(1,499)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(540)	(1,018)	(4,409)	(2,195)
Capital expenditures	7,898	7,310	15,565	11,507
Total assets	306,791	170,521	306,791	170,521	295,608
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	228,348	190,251	682,861	536,875
Depreciation	29,880	27,328	60,024	54,965
Income from operations	13,302	14,125	127,430	102,676
Total assets	4,229,914	3,929,997	4,229,914	3,929,997	4,452,718
Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	223,713	184,634	671,483	526,032
Northwest Natural Gas Company [Member] | Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,635	5,617	11,378	10,843
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	228,348	190,251	682,861	536,875
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	237,859	194,960	700,282	545,261
Depreciation	31,293	28,110	62,758	56,539
Income from operations	13,843	13,539	127,351	101,177
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	1,244	1,715	72,915	57,954
Capital expenditures	73,598	99,182	144,863	167,696
Total assets	$ 4,536,705	$ 4,100,518	$ 4,536,705	$ 4,100,518	$ 4,748,326