Segment Information - Schedule of Summarized Financial Information by Segment - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Operating revenues	$ 141,479	$ 116,839	$ 841,761	$ 662,100
Depreciation	30,061	29,026	92,819	85,565
Income from operations	(17,577)	(14,927)	109,774	86,250
Total assets	4,665,118	4,300,712	4,665,118	4,300,712	$ 4,748,326
Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	124,624	103,295	796,108	629,327
Depreciation	28,169	27,937	87,650	82,372
Income from operations	(22,192)	(20,910)	97,357	75,328
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(24,160)	(23,016)	47,520	32,531
Capital expenditures	86,017	79,847	214,874	235,249
Total assets	4,285,309	3,968,040	4,285,309	3,968,040	4,392,699
Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,318	7,131	16,695	17,974
Depreciation	277	264	820	794
Income from operations	3,777	5,616	11,658	12,054
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	2,673	4,210	8,317	8,812
Capital expenditures	1,053	431	1,494	1,218
Total assets	52,894	56,712	52,894	56,712	60,019
Northwest Natural Gas Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	129,942	110,426	812,803	647,301
Depreciation	28,446	28,201	88,470	83,166
Income from operations	(18,415)	(15,294)	109,015	87,382
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(21,487)	(18,806)	55,837	41,343
Capital expenditures	87,070	80,278	216,368	236,467
Total assets	4,338,203	4,024,752	4,338,203	4,024,752	4,452,718
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	11,537	6,413	28,958	14,799
Depreciation	1,615	825	4,349	2,399
Income from operations	838	367	759	(1,132)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(2,200)	(781)	(6,609)	(2,976)
Capital expenditures	10,814	3,868	26,379	15,375
Total assets	326,915	275,960	326,915	275,960	295,608
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	129,942	110,426	812,803	647,301
Depreciation	28,446	28,201	88,470	83,166
Income from operations	(18,415)	(15,294)	109,015	87,382
Total assets	4,338,203	4,024,752	4,338,203	4,024,752	4,452,718
Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	124,625	103,295	796,108	629,327
Northwest Natural Gas Company [Member] | Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,317	7,131	16,695	17,974
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	129,942	110,426	812,803	647,301
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	141,479	116,839	841,761	662,100
Depreciation	30,061	29,026	92,819	85,565
Income from operations	(17,577)	(14,927)	109,774	86,250
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(23,687)	(19,587)	49,228	38,367
Capital expenditures	97,884	84,146	242,747	251,842
Total assets	$ 4,665,118	$ 4,300,712	$ 4,665,118	$ 4,300,712	$ 4,748,326