Property, Plant and Equipment - USD ($)	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	$ 4,207,328,000	$ 3,997,243,000	$ 3,919,096,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,166,150,000	1,125,873,000	1,112,734,000
Total property, plant, and equipment, net	3,041,178,000	2,871,370,000	2,806,362,000
Natural Gas Distribution [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	3,888,092,000	3,721,939,000	3,663,699,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	161,658,000	135,398,000	120,412,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,135,965,000	1,098,715,000	1,086,510,000
Total property, plant, and equipment, net	2,913,785,000	2,758,622,000	2,697,601,000
Other Northwest Natural [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	69,626,000	69,332,000	66,314,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	5,112,000	4,971,000	7,228,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	21,435,000	20,646,000	20,392,000
Total property, plant, and equipment, net	53,303,000	53,657,000	53,150,000
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment, net	2,967,088,000	2,812,279,000	2,750,751,000
Property, Plant, Equipment non-cash	43,954,000	37,537,000	33,968,000
Other Northwest Holdings [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	66,208,000	57,184,000	53,175,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	16,632,000	8,419,000	8,268,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	8,750,000	6,512,000	5,832,000
Total property, plant, and equipment, net	74,090,000	59,091,000	55,611,000
Northwest Holdings [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, Equipment non-cash	45,374,000	38,333,000	35,955,000
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	4,124,488,000	3,931,640,000	3,857,652,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,157,400,000	1,119,361,000	1,106,901,000
Total property, plant, and equipment, net	$ 2,967,088,000	$ 2,812,279,000	$ 2,750,751,000