Significant Accounting Policies - Regulatory Asset Disclosure - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 124,102	$ 178,270	$ 111,819
Regulatory Assets, Noncurrent	$ 308,521	333,443	307,999
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	$ 24	0	0
Regulatory Assets, Noncurrent	106	25	25
Northwest Natural Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	124,078	178,270	111,819
Regulatory Assets, Noncurrent	308,415	333,418	307,974
Northwest Natural Gas Company [Member] \| Deferred Derivative Gain (Loss) [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	52,048	98,661	42,135
Regulatory Assets, Noncurrent	11,988	28,055	25,212
Northwest Natural Gas Company [Member] \| Pension balancing [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	7,131	7,131	7,131
Regulatory Assets, Noncurrent	24,074	27,460	29,731
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	111,502	114,010	101,413
Northwest Natural Gas Company [Member] \| Environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	9,915	9,950	6,749
Regulatory Assets, Noncurrent	112,189	118,619	98,160
Northwest Natural Gas Company [Member] \| Gas costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	7,134	9,301	24,782
Regulatory Assets, Noncurrent	853	1,917	1,122
Northwest Natural Gas Company [Member] \| Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	538	2,288	1,520
Regulatory Assets, Noncurrent	0	1,017	267
Northwest Natural Gas Company [Member] \| Washington Climate Commitment Act compliance
Regulatory Assets [Line Items]
Regulatory Assets, Current	19,655	20,537	10,379
Regulatory Assets, Noncurrent	8,983	0	1,823
Northwest Natural Gas Company [Member] \| Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	20,156	15,242	13,700
Regulatory Assets, Noncurrent	18,728	20,795	15,783
Northwest Natural Gas Company [Member] \| COVID-19 Related Costs
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,646	9,685	231
Regulatory Assets, Noncurrent	1,128	1,080	12,731
Northwest Natural Gas Company [Member] \| Security and systems improvements
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,647	3,267	2,984
Regulatory Assets, Noncurrent	$ 9,040	$ 9,734	$ 11,192