Investments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) numberOfEmployees numberOfProjects numberOfCustomerConnections	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jan. 31, 2024 USD ($)	Jun. 30, 2023 USD ($)
Schedule of Investments [Line Items]
Total Cumulative Gas Reserves Investment	$ 188,000
Other Investments [Abstract]
Life Insurance, Corporate or Bank Owned, Amount	45,713	$ 49,358
Inventory, Gas in Storage Underground, Noncurrent	20,893	22,970
Equity Method Investment, Aggregate Cost	36,345	23,376
Total Other investments	102,951	95,704
Investments in Unconsolidated Affiliates [Abstract]
Proceeds from Sale of Equity Method Investments	$ 0	0	$ 7,000
Investments, Number of RNG Development Projects | numberOfProjects	4
Northwest Holdings Other [Member] | Avion Water
Investments in Unconsolidated Affiliates [Abstract]
Ownership percentage			37.30%		43.10%
Equity Method Investment, Underlying Equity in Net Assets			$ 14,500
Equity Method Investment, Number of Customer Connections | numberOfCustomerConnections	15,000
Equity Method Investment, Number of Employees | numberOfEmployees	35
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 8,600
Equity Method Investment, Additional Underlying Equity in Net Assets					$ 1,000
Northwest Holdings Other [Member] | Avion Water | Subsequent Event [Member]
Investments in Unconsolidated Affiliates [Abstract]
Ownership percentage				45.60%
Equity Method Investment, Additional Underlying Equity in Net Assets				$ 1,000
Northwest Natural Gas Company [Member]
Other Investments [Abstract]
Total Other investments	86,145	80,110
Investments in Unconsolidated Affiliates [Abstract]
Deferred Taxes Related To Gas Reserves	$ 4,000	$ 5,200
Gas Reserves Percent Gas Supplies YTD	3.00%	3.00%
Deferred Gas Cost	$ 2,300	$ 3,400
Northwest Natural Gas Company [Member]
Other Investments [Abstract]
Life Insurance, Corporate or Bank Owned, Amount	45,713	49,358
Inventory, Gas in Storage Underground, Noncurrent	20,893	22,970
Equity Method Investment, Aggregate Cost	19,539	7,782
Total Other investments	86,145	$ 80,110
Northwest Natural Gas Company [Member] | Lexington
Other Investments [Abstract]
Equity Method Investment, Aggregate Cost	7,600
Northwest Natural Gas Company [Member] | Dakota City
Other Investments [Abstract]
Equity Method Investment, Aggregate Cost	11,900
Investments in Unconsolidated Affiliates [Abstract]
Deconsolidation, Gain (Loss), Amount	$ 0