Significant Accounting Policies - Regulatory Asset Disclosure - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 127,666	$ 178,270	$ 126,546
Regulatory Assets, Noncurrent	$ 309,173	333,443	311,419
Inactive Account, Period Outstanding Prior to Write-Off	120 days
General Payment Term of NGD Receivables	15 days
Age of Closed or Inactive Accounts	120 days
Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 25	0	0
Regulatory Assets, Noncurrent	106	25	25
Northwest Natural Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	127,641	178,270	126,546
Regulatory Assets, Noncurrent	309,067	333,418	311,394
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	52,677	98,661	44,370
Regulatory Assets, Noncurrent	12,744	28,055	15,382
Northwest Natural Gas Company [Member] | Pension balancing [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	7,131	7,131	7,131
Regulatory Assets, Noncurrent	25,016	27,460	30,613
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,208	2,208	2,208
Regulatory Assets, Noncurrent	9,930	10,731	10,540
Northwest Natural Gas Company [Member] | Pension and other postretirement benefit liabilities [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	112,791	114,010	101,413
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	9,864	9,950	6,947
Regulatory Assets, Noncurrent	112,464	118,619	99,541
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	8,279	9,301	51,296
Regulatory Assets, Noncurrent	1,319	1,917	6,546
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	958	2,288	0
Regulatory Assets, Noncurrent	0	1,017	0
Northwest Natural Gas Company [Member] | Washington Climate Commitment Act compliance
Regulatory Assets [Line Items]
Regulatory Assets, Current	19,761	20,537	0
Regulatory Assets, Noncurrent	4,223	0	6,312
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	21,965	18,509	13,807
Regulatory Assets, Noncurrent	29,452	30,529	28,232
Northwest Natural Gas Company [Member] | COVID-19 Related Costs
Regulatory Assets [Line Items]
Regulatory Assets, Current	4,798	9,685	787
Regulatory Assets, Noncurrent	$ 1,128	$ 1,080	$ 12,815