Segment Information - Schedule of Summarized Financial Information by Segment - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenues	$ 116,839	$ 101,447	$ 662,100	$ 566,310
Depreciation	29,026	28,438	85,565	84,679
Income from operations	(14,927)	(14,391)	86,250	92,939
Total assets	4,300,712	3,929,225	4,300,712	3,929,225	$ 4,064,604
Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	103,295	91,042	629,327	531,994
Depreciation	27,937	27,462	82,372	81,648
Income from operations	(20,910)	(18,288)	75,328	79,530
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(23,016)	(23,297)	32,531	29,247
Capital expenditures	79,847	72,822	235,249	197,190
Total assets	3,968,040	3,730,595	3,968,040	3,730,595	3,846,112
Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	7,131	4,994	17,974	20,971
Depreciation	264	257	794	770
Income from operations	5,616	3,203	12,054	14,642
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	4,210	2,279	8,812	10,435
Capital expenditures	431	1,410	1,218	2,209
Total assets	56,712	50,366	56,712	50,366	52,260
Northwest Natural Gas Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	110,426	96,036	647,301	552,965
Depreciation	28,201	27,719	83,166	82,418
Income from operations	(15,294)	(15,085)	87,382	94,172
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(18,806)	(21,018)	41,343	39,682
Capital expenditures	80,278	74,232	236,467	199,399
Total assets	4,024,752	3,780,961	4,024,752	3,780,961	3,898,372
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,413	5,411	14,799	13,345
Depreciation	825	719	2,399	2,261
Income from operations	367	694	(1,132)	(1,233)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(781)	363	(2,976)	(1,544)
Capital expenditures	3,868	8,036	15,375	12,977
Total assets	275,960	148,264	275,960	148,264	166,232
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	110,426	96,036	647,301	552,965
Depreciation	28,201	27,719	83,166	82,418
Income from operations	(15,294)	(15,085)	87,382	94,172
Total assets	4,024,752	3,780,961	4,024,752	3,780,961	3,898,372
Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	103,295	91,042	629,327	531,994
Northwest Natural Gas Company [Member] | Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	7,131	4,994	17,974	20,971
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	110,426	96,036	647,301	552,965
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	116,839	101,447	662,100	566,310
Depreciation	29,026	28,438	85,565	84,679
Income from operations	(14,927)	(14,391)	86,250	92,939
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(19,587)	(20,655)	38,367	38,138
Capital expenditures	84,146	82,268	251,842	212,376
Total assets	$ 4,300,712	$ 3,929,225	$ 4,300,712	$ 3,929,225	$ 4,064,604