Investments $ in Thousands	3 Months Ended
	Sep. 30, 2023 USD ($) numberOfProjects numberOfConnections employee	Dec. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)	Jul. 31, 2022 USD ($)	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Life Insurance, Corporate or Bank Owned, Amount	$ 46,870	$ 49,358	$ 49,043
Gas reserves, noncurrent	21,439	22,970	23,770
Equity Method Investment, Aggregate Cost	36,253	23,376	23,756
Other investments	104,562	95,704	96,569
Total cumulative gas reserves investment	188,000
Deferred Taxes Related To Gas Reserves	4,400	5,200	5,500
Gas reserves, current	$ 2,400	3,400	3,700
Investments, Number of RNG Development Projects | numberOfProjects	4
Northwest Natural Gas Company [Member]
Schedule of Equity Method Investments [Line Items]
Life Insurance, Corporate or Bank Owned, Amount	$ 46,870	49,358	49,043
Gas reserves, noncurrent	21,439	22,970	23,770
Equity Method Investment, Aggregate Cost	19,444	7,782	8,058
Other investments	87,753	$ 80,110	$ 80,871
Lexington | Northwest Natural Gas Company [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Aggregate Cost	7,800
Dakota City | Northwest Natural Gas Company [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Aggregate Cost	11,600
Deconsolidation, Gain (Loss), Amount	$ 0
Other Northwest Holdings [Member] | Avion Water
Schedule of Equity Method Investments [Line Items]
Ownership percentage of Avion	43.10%	40.30%			37.30%
Investment balance in Avion		$ 14,500
Equity Method Investment, Number of Customer Connections | numberOfConnections	15,000
Equity Method Investment, Number of Employees | employee	35
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 8,800
Equity Method Investment, Additional Underlying Equity in Net Assets	$ 1,000			$ 1,000