Segment Information - Schedule of Summarized Financial Information by Segment - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Operating revenues	$ 462,423	$ 350,301
Depreciation	31,465	28,429
Income from operations	113,508	87,638
Total assets	4,592,096	4,054,634	$ 4,748,326
Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	447,770	341,398
Depreciation	29,858	27,373
Income from operations	109,159	85,663
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	71,951	55,390
Capital expenditures	63,642	64,280
Total assets	4,246,245	3,835,222	4,392,699
Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,743	5,226
Depreciation	286	264
Income from operations	4,969	2,888
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	3,589	2,026
Capital expenditures	(44)	37
Total assets	54,390	51,598	60,019
Northwest Natural Gas Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	454,513	346,624
Depreciation	30,144	27,637
Income from operations	114,128	88,551
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	75,540	57,416
Capital expenditures	63,598	64,317
Total assets	4,300,635	3,886,820	4,452,718
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	7,910	3,677
Depreciation	1,321	792
Income from operations	(620)	(913)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(3,869)	(1,177)
Capital expenditures	7,667	4,197
Total assets	291,461	167,814	295,608
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	454,513	346,624
Depreciation	30,144	27,637
Income from operations	114,128	88,551
Total assets	4,300,635	3,886,820	4,452,718
Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	447,770	341,398
Northwest Natural Gas Company [Member] | Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,743	5,226
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	454,513	346,624
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	462,423	350,301
Depreciation	31,465	28,429
Income from operations	113,508	87,638
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	71,671	56,239
Capital expenditures	71,265	68,514
Total assets	$ 4,592,096	$ 4,054,634	$ 4,748,326