v3.24.2.u1
Long-Term Debt - USD ($)
$ in Thousands
 6 Months Ended 12 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Dec. 31, 2023
Debt Instrument [Line Items]      
Long-term Debt $ 1,575,617 $ 1,535,292 $ 1,576,300
Other Long-Term Debt 6,300 5,900 6,600
Unamortized debt issuance costs 10,369 10,261 10,044
Long-term Debt, Gross 1,585,986 1,545,553 1,586,344
Long-term debt, Current Maturities, Gross 900 240,700 150,900
Long-term debt 1,574,751 1,294,578 1,425,435
Current maturities of long-term debt 866 240,714 150,865
Northwest Natural Gas Company [Member]      
Debt Instrument [Line Items]      
Long-term Debt 1,365,066 1,324,559 1,364,732
Unamortized debt issuance costs $ 9,634 $ 10,141 $ 9,968
Weighted average interest rate 4.60% 4.70% 4.70%
Long-term Debt, Gross $ 1,374,700 $ 1,334,700 $ 1,374,700
Long-term debt 1,365,066 1,234,577 1,364,732
Current maturities of long-term debt $ 0 89,982 0
Northwest Natural Gas Company [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Stated interest rate 2.82%    
Northwest Natural Gas Company [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Stated interest rate 7.85%    
Northwest Holdings and Northwest Natural [Member]      
Debt Instrument [Line Items]      
Unamortized debt issuance costs $ 10,400 10,300 10,000
Northwest Holdings [Member]      
Debt Instrument [Line Items]      
Long-term debt $ 1,574,700 $ 1,294,600 $ 1,425,400
18 Month Credit Agreement Due March 15, 2024      
Debt Instrument [Line Items]      
Weighted average interest rate 0.00% 5.50% 5.50%
Proceeds from Issuance of Debt $ 0 $ 100,000 $ 100,000
Repayments of Debt $ 100,000    
18 Month Credit Agreement Due March 15, 2024 | NWN Water      
Debt Instrument [Line Items]      
Weighted average interest rate 0.00% 5.50% 5.80%
Proceeds from Issuance of Debt $ 0 $ 50,000 $ 50,000
Repayments of Debt $ 50,000    
NWN Water Term Loan Due 2026      
Debt Instrument [Line Items]      
Derivative, Fixed Interest Rate 3.80%    
NWN Water Term Loan Due 2026 | Corporate, Non-Segment [Member] | Other Northwest Holdings [Member]      
Debt Instrument [Line Items]      
Long-term Debt $ 55,000    
NWN Water Term Loan Due 2026 | NWN Water      
Debt Instrument [Line Items]      
Long-term Debt $ 55,000 $ 55,000 $ 55,000
Weighted average interest rate 4.70% 4.80% 4.70%
Note 5780 Series due 2028      
Debt Instrument [Line Items]      
Stated interest rate 5.78%    
Proceeds from Issuance of Debt $ 100,000    
Note 5840 Series due 2029      
Debt Instrument [Line Items]      
Stated interest rate 5.84%    
Proceeds from Issuance of Debt $ 50,000    
NW Holdings Unsecured Senior Bonds      
Debt Instrument [Line Items]      
Weighted average interest rate 5.80% 0.00% 0.00%
Proceeds from Issuance of Debt $ 150,000 $ 0 $ 0