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Long-Term Debt - USD ($)
3 Months Ended
Mar. 31, 2022
Jun. 30, 2021
Jun. 30, 2019
Dec. 31, 2021
Mar. 31, 2021
Debt Instrument [Line Items]          
Long-term Debt $ 1,045,006,000     $ 1,044,932,000 $ 955,919,000
Unamortized debt issuance costs $ 8,171,000     8,309,000 7,364,000
Ratio of Indebtedness to Net Capital 0.582        
Northwest Natural Gas Company [Member]          
Debt Instrument [Line Items]          
Long-term Debt $ 986,627,000     986,495,000 917,336,000
Unamortized debt issuance costs $ 8,073,000     $ 8,205,000 $ 7,364,000
Weighted average interest rate 4.40%        
Long-Term Debt, Maturity, Year One $ 0        
Northwest Natural Gas Company [Member] | Minimum [Member]          
Debt Instrument [Line Items]          
Stated interest rate 2.80%        
Northwest Natural Gas Company [Member] | Maximum [Member]          
Debt Instrument [Line Items]          
Stated interest rate 7.90%        
Two-year Term Loan Due 2021 [Member]          
Debt Instrument [Line Items]          
Long-term Debt, Term 2 years        
Repayments of Debt   $ 35,000,000      
Proceeds from Issuance of Debt     $ 35,000,000    
Five-year Term Loan Due 2026          
Debt Instrument [Line Items]          
Stated interest rate 1.20%        
Long-term Debt, Term 5 years        
Proceeds from Issuance of Debt $ 55,000,000        
Debt Instrument Covenant Consolidated Indebtedness to Capitalization Ratio 70.00%