Property, Plant and Equipment - USD ($)	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	$ 4,468,602,000	$ 4,261,566,000	$ 4,207,328,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,189,968,000	1,147,166,000	1,166,150,000
Total property, plant, and equipment, net	3,278,634,000	3,114,400,000	3,041,178,000
Natural Gas Distribution [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	4,096,560,000	3,992,676,000	3,888,092,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	153,231,000	78,897,000	161,658,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,152,952,000	1,115,690,000	1,135,965,000
Total property, plant, and equipment, net	3,096,839,000	2,955,883,000	2,913,785,000
Other Northwest Natural [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	70,363,000	70,368,000	69,626,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	8,323,000	6,606,000	5,112,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	22,331,000	21,541,000	21,435,000
Total property, plant, and equipment, net	56,355,000	55,433,000	53,303,000
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment, net	3,153,194,000	3,011,316,000	2,967,088,000
Property, Plant, Equipment non-cash	21,402,000	24,584,000	43,954,000
Other Northwest Holdings [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	127,721,000	92,979,000	66,208,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	12,404,000	20,040,000	16,632,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	14,685,000	9,935,000	8,750,000
Total property, plant, and equipment, net	125,440,000	103,084,000	74,090,000
Northwest Holdings [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, Equipment non-cash	22,686,000	25,318,000	45,374,000
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	4,328,477,000	4,148,547,000	4,124,488,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,175,283,000	1,137,231,000	1,157,400,000
Total property, plant, and equipment, net	$ 3,153,194,000	$ 3,011,316,000	$ 2,967,088,000