Property, Plant and Equipment - USD ($)	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	$ 4,041,894,000	$ 3,997,243,000	$ 3,788,283,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,137,138,000	1,125,873,000	1,091,903,000
Total property, plant, and equipment, net	2,904,756,000	2,871,370,000	2,696,380,000
Natural Gas Distribution [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	3,740,105,000	3,721,939,000	3,594,226,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	156,575,000	135,398,000	70,766,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,108,930,000	1,098,715,000	1,067,502,000
Total property, plant, and equipment, net	2,787,750,000	2,758,622,000	2,597,490,000
Other Northwest Natural [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	69,333,000	69,332,000	66,314,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	5,037,000	4,971,000	5,125,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	20,907,000	20,646,000	19,889,000
Total property, plant, and equipment, net	53,463,000	53,657,000	51,550,000
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment, net	2,841,213,000	2,812,279,000	2,649,040,000
Property, Plant, Equipment non-cash	45,964,000	37,537,000	20,969,000
Other Northwest Holdings [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	70,844,000	65,603,000	51,852,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	7,301,000	6,512,000	4,512,000
Total property, plant, and equipment, net	63,543,000	59,091,000	47,340,000
Northwest Holdings [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, Equipment non-cash	47,797,000	38,333,000	21,118,000
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	3,971,050,000	3,931,640,000	3,736,431,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,129,837,000	1,119,361,000	1,087,391,000
Total property, plant, and equipment, net	$ 2,841,213,000	$ 2,812,279,000	$ 2,649,040,000