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Pension and Other Postretirement Benefits Costs - Schedule of Future Employer Contributions and Benefit Payments (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Dec. 22, 2013
Defined Benefit Plan Disclosure [Line Items]        
Payment for Pension and Other Postretirement Benefits $ 0      
Expected future employer contributions 20,600      
Northwest Natural Gas Company [Member]        
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]        
Defined Contribution Plan, Cost 10,400 $ 9,600 $ 8,800  
Northwest Natural Gas Company [Member] | Western States Office and Professional Employees Union Pension Fund [Member]        
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]        
Multiemployer Plan, Employer Contribution, Cost 600 $ 600 $ 400  
Multiemployer Plan, Pension, Insignificant, Plan Contribution 600      
Multiemployer Plans, Withdrawal Obligation 5,000     $ 8,300
Northwest Natural Gas Company [Member] | Western States Office and Professional Employees Union Pension Fund [Member] | Maximum [Member]        
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]        
Multiemployer Plan, Pension, Insignificant, Employer Contribution under Collective-Bargaining Arrangement to All Participating Employer Contributions, Percentage   4.00% 4.00%  
Northwest Natural Gas Company [Member] | Western States Office and Professional Employees Union Pension Fund [Member] | Minimum [Member]        
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]        
Multiemployer Plan, Pension, Insignificant, Employer Contribution under Collective-Bargaining Arrangement to All Participating Employer Contributions, Percentage   1.00% 1.00%  
Northwest Natural Gas Company [Member] | Pension Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Payment for Pension and Other Postretirement Benefits 2,269 $ 2,353    
Expected future employer contributions 22,850      
Benefits paid 27,970 27,563 $ 25,371  
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]        
Year 1 27,288      
Year 2 36,313      
Year 3 27,979      
Year 4 28,300      
Year 6 28,604      
Thereafter 145,652      
Northwest Natural Gas Company [Member] | Other Postretirement Benefits Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Payment for Pension and Other Postretirement Benefits 1,793 2,026    
Expected future employer contributions 3,233      
Benefits paid 1,793 $ 2,026 $ 2,050  
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]        
Year 1 3,233      
Year 2 1,652      
Year 3 1,620      
Year 4 1,608      
Year 6 1,583      
Thereafter $ 7,440