Long-Term Debt - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Mar. 31, 2023	Sep. 30, 2023	Sep. 30, 2022	Aug. 19, 2023	Aug. 04, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term Debt		$ 1,615,300	$ 1,337,620			$ 1,336,864
Other Long-Term Debt		5,800	6,300			6,200
Unamortized debt issuance costs		10,245	8,348			8,987
Long-term Debt, Gross		1,625,545	1,345,968			1,345,851
Long-term debt, Current Maturities, Gross		190,700	50,600			90,700
Long-term debt		1,424,572	1,287,006			1,246,167
Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Long-term Debt		1,404,553	1,126,471			1,125,877
Unamortized debt issuance costs		$ 10,147	$ 8,229			$ 8,823
Weighted average interest rate		4.70%	4.50%			4.50%
Long-term Debt, Gross		$ 1,414,700	$ 1,134,700			$ 1,134,700
Long-term debt		$ 1,364,556	1,076,533			1,035,935
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%
Northwest Holdings and Northwest Natural [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs		$ 10,200	$ 8,400			$ 9,000
18 Month Credit Agreement Due March 15, 2024
Debt Instrument [Line Items]
Weighted average interest rate		5.50%	4.10%			4.20%
Long-term Debt, Term		18 months
Proceeds from Issuance of Debt	$ 100,000	$ 100,000	$ 100,000
Debt Instrument Covenant Consolidated Indebtedness to Capitalization Ratio		70.00%
Derivative, Fixed Interest Rate		4.70%
18 Month Credit Agreement Due March 15, 2024 | NWN Water
Debt Instrument [Line Items]
Weighted average interest rate		5.70%	4.10%			4.20%
Long-term Debt, Term		18 months
Proceeds from Issuance of Debt	$ 50,000	$ 50,000	$ 50,000
Debt Instrument Covenant Consolidated Indebtedness to Capitalization Ratio		70.00%
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		4.80%	3.50%			2.50%
Note 5430 Series Due 2053 | Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Stated interest rate		5.43%
Proceeds from Issuance of First Mortgage Bond		$ 100,000
Note 5750 | Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Stated interest rate		5.75%
Proceeds from Issuance of Medium-term Notes		$ 100,000
Note 5180 due 2034
Debt Instrument [Line Items]
Stated interest rate					5.18%
Note 5180 due 2034 | Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Medium-term Notes		80,000
Note 5230 due 2038
Debt Instrument [Line Items]
Stated interest rate					5.23%
Note 5230 due 2038 | Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Secured Debt					$ 50,000
Note 3540 due 2023
Debt Instrument [Line Items]
Stated interest rate				3.50%
Note 3540 due 2023 | Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Repayments of First Mortgage Bond		50,000
Repayments of First Mortgage Bond		$ 50,000
Note 5620 due 2023
Debt Instrument [Line Items]
Stated interest rate		5.60%
Secured Debt, Current		$ 40,000
Secured Debt, Current		$ 40,000