Segment Information - Schedule of Summarized Financial Information by Segment - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenues	$ 350,301	$ 315,946
Depreciation	28,429	28,097
Income from operations	87,638	94,706
Total assets	4,054,634	3,758,625	$ 4,064,604
Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	341,398	301,338
Depreciation	27,373	26,913
Income from operations	85,663	86,487
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	55,390	53,925
Capital expenditures	64,280	63,992
Total assets	3,835,222	3,570,153	3,846,112
Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,226	11,012
Depreciation	264	256
Income from operations	2,888	8,631
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	2,026	6,186
Capital expenditures	37	106
Total assets	51,598	49,415	52,260
Northwest Natural Gas Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	346,624	312,350
Depreciation	27,637	27,169
Income from operations	88,551	95,118
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	57,416	60,111
Capital expenditures	64,317	64,098
Total assets	3,886,820	3,619,568	3,898,372
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	3,677	3,596
Depreciation	792	928
Income from operations	(913)	(412)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(1,177)	(594)
Capital expenditures	4,197	1,604
Total assets	167,814	139,057	166,232
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	346,624	312,350
Depreciation	27,637	27,169
Income from operations	88,551	95,118
Total assets	3,886,820	3,619,568	3,898,372
Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	341,398	301,338
Northwest Natural Gas Company [Member] | Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,226	11,012
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	346,624	312,350
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	350,301	315,946
Depreciation	28,429	28,097
Income from operations	87,638	94,706
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	56,239	59,517
Capital expenditures	68,514	65,702
Total assets	$ 4,054,634	$ 3,758,625	$ 4,064,604