Segment Information - Schedule of Summarized Financial Information by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Operating revenues	$ 1,037,353	$ 860,400	$ 773,679
Depreciation	116,707	113,534	103,683
Income (loss) from operations	167,477	163,117	148,351
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	86,303	78,666	70,273
Capital expenditures	338,602	293,892	273,016
Total assets	4,748,326	4,064,604
Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	24,587	26,170	17,676
Depreciation	1,086	1,029	995
Income (loss) from operations	16,535	17,331	9,916
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	11,874	12,184	7,008
Capital expenditures	2,707	2,970	2,271
Total assets	60,019	52,260	49,468
Northwest Natural Gas Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,014,339	843,057	758,748
Depreciation	112,957	110,504	101,586
Income (loss) from operations	169,374	165,233	147,640
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	91,564	81,172	70,563
Capital expenditures	318,686	278,237	266,048
Total assets	4,452,718	3,898,372	3,599,336
Northwest Holdings Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	23,014	17,343	14,931
Depreciation	3,750	3,030	2,097
Income (loss) from operations	(1,897)	(2,116)	711
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(5,261)	(2,506)	(290)
Capital expenditures	19,916	15,655	6,968
Total assets	295,608	166,232	157,043
Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	989,752	816,887	741,072
Depreciation	111,871	109,475	100,591
Income (loss) from operations	152,839	147,902	137,724
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	79,690	68,988	63,555
Capital expenditures	315,979	275,267	263,777
Total assets	4,392,699	3,846,112	3,549,868
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,014,339	843,057	758,748
Depreciation	112,957	110,504	101,586
Income (loss) from operations	169,374	165,233	147,640
Capital expenditures	318,686	278,237	266,048
Total assets	4,452,718	3,898,372
Northwest Natural Gas Company [Member] | Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	24,587	26,170	17,676
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,014,339	843,057	758,748
Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	989,752	816,887	741,072
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,037,353	860,400	773,679
Depreciation	116,707	113,534	103,683
Income (loss) from operations	167,477	163,117	148,351
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	86,303	78,666	70,273
Capital expenditures	338,602	293,892	273,016
Total assets	$ 4,748,326	$ 4,064,604	$ 3,756,379