Segment Information - Schedule of Summarized Financial Information by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Operating revenues	$ 860,400	$ 773,679	$ 746,372
Depreciation and amortization	113,534	103,683	91,496
Income from operations	163,117	148,351	143,474
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	78,666	70,273	65,311
Capital expenditures	293,892	273,016	223,471
Total assets	4,064,604	3,756,379
Discontinued operations - total assets			15,100
Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	26,170	17,676	19,416
Depreciation and amortization	1,029	995	990
Income from operations	17,331	9,916	11,428
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	12,184	7,008	8,146
Capital expenditures	2,970	2,271	1,500
Total assets	52,260	49,468	47,652
Northwest Natural Gas Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	843,057	758,748	739,944
Depreciation and amortization	110,504	101,586	90,405
Income from operations	165,233	147,640	147,346
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	81,172	70,563	68,974
Capital expenditures	278,237	266,048	221,380
Total assets	3,898,372	3,599,336	3,321,487
Northwest Holdings Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	17,343	14,931	6,428
Depreciation and amortization	3,030	2,097	1,091
Income from operations	(2,116)	711	(3,872)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(2,506)	(290)	(3,663)
Capital expenditures	15,655	6,968	2,091
Total assets	166,232	157,043	91,833
Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	816,887	741,072	720,528
Depreciation and amortization	109,475	100,591	89,415
Income from operations	147,902	137,724	135,918
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	68,988	63,555	60,828
Capital expenditures	275,267	263,777	219,880
Total assets	3,846,112	3,549,868	3,273,835
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	843,057	758,748	739,944
Depreciation and amortization	110,504	101,586	90,405
Income from operations	165,233	147,640	147,346
Capital expenditures	278,237	266,048	221,380
Total assets	3,898,372	3,599,336
Northwest Natural Gas Company [Member] | Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	26,170	17,676
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	843,057	758,748
Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	816,887	741,072
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	860,400	773,679	746,372
Depreciation and amortization	113,534	103,683	91,496
Income from operations	163,117	148,351	143,474
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	78,666	70,273	65,311
Capital expenditures	293,892	273,016	223,471
Total assets	$ 4,064,604	$ 3,756,379	$ 3,413,320