Significant Accounting Policies - Regulatory Asset Disclosure (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 178,270	$ 117,491
Regulatory Assets, Noncurrent	333,443	340,432
Sales-type Lease, Net Investment in Lease, Allowance for Credit Loss	0
Inventory, Emissions Allowances	39,300
Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	25	25
Northwest Natural Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	178,270	117,491
Regulatory Assets, Noncurrent	$ 333,418	340,407
Regulatory Asset, Amortization Period	12 months
Accounts Receivable, Allowance for Credit Loss	$ 3,228	3,079
Accounts Receivable, Allowance for Credit Loss, Recovery	2,973
Northwest Natural Gas Company [Member] | Residential
Regulatory Assets [Line Items]
Accounts Receivable, Allowance for Credit Loss	2,397	2,155
Accounts Receivable, Allowance for Credit Loss, Recovery	2,501
Northwest Natural Gas Company [Member] | Unrealized loss on derivatives [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	98,661	28,728
Regulatory Assets, Noncurrent	28,055	20,838
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	9,301	61,223
Regulatory Assets, Noncurrent	1,917	22,355
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	9,950	7,392
Regulatory Assets, Noncurrent	118,619	104,253
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,288	0
Regulatory Assets, Noncurrent	1,017	0
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,208	2,208
Regulatory Assets, Noncurrent	10,731	10,943
Northwest Natural Gas Company [Member] | Pension balancing [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	7,131	7,131
Regulatory Assets, Noncurrent	27,460	32,997
Northwest Natural Gas Company [Member] | Pension and other postretirement benefit liabilities [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	114,010	101,413
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	18,509	10,020
Regulatory Assets, Noncurrent	30,529	33,053
Northwest Natural Gas Company [Member] | COVID-19 Related Costs
Regulatory Assets [Line Items]
Regulatory Assets, Current	9,685	789
Regulatory Assets, Noncurrent	1,080	14,555
Northwest Natural Gas Company [Member] | Washington Climate Commitment Act compliance
Regulatory Assets [Line Items]
Regulatory Assets, Current	20,537	0
Northwest Holdings Other [Member]
Regulatory Assets [Line Items]
Accounts Receivable, Allowance for Credit Loss	227	217
Accounts Receivable, Allowance for Credit Loss, Recovery	0
Northwest Holdings [Member]
Regulatory Assets [Line Items]
Accounts Receivable, Allowance for Credit Loss	3,455	$ 3,296
Accounts Receivable, Allowance for Credit Loss, Recovery	$ 2,973