v3.26.1
Property, Plant and Equipment (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Jun. 30, 2025
Property, Plant, and Equipment [Line Items]      
Property, plant, and equipment $ 5,844,802 $ 5,640,435 $ 5,415,697
Less: Accumulated depreciation 1,318,811 1,288,422 1,269,274
Total property, plant, and equipment, net 4,525,991 4,352,013 4,146,423
NW Natural      
Property, Plant, and Equipment [Line Items]      
Property, plant, and equipment 5,130,446 5,000,329 4,860,664
Less: Accumulated depreciation 1,269,895 1,256,289 1,236,148
Total property, plant, and equipment, net 3,860,551 3,744,040 3,624,516
Parent Company      
Property, Plant, and Equipment [Line Items]      
Less: Accumulated depreciation 1,318,811 1,288,422 1,269,274
Total property, plant, and equipment, net 4,525,991 4,352,013 4,146,423
Capital expenditures in accrued liabilities 68,873 57,762 40,588
Parent Company | Plant in service      
Property, Plant, and Equipment [Line Items]      
Property, plant, and equipment 5,592,574 5,468,170 5,204,265
Parent Company | Construction work in progress      
Property, Plant, and Equipment [Line Items]      
Construction work in progress 252,228 172,265 211,432
Subsidiaries | NW Natural      
Property, Plant, and Equipment [Line Items]      
Less: Accumulated depreciation 1,269,895 1,256,289 1,236,148
Total property, plant, and equipment, net 3,860,551 3,744,040 3,624,516
Capital expenditures in accrued liabilities 44,947 33,582 28,586
Subsidiaries | NW Natural | Plant in service      
Property, Plant, and Equipment [Line Items]      
Property, plant, and equipment 4,945,768 4,879,816 4,677,407
Subsidiaries | NW Natural | Construction work in progress      
Property, Plant, and Equipment [Line Items]      
Construction work in progress $ 184,678 $ 120,513 $ 183,257