Significant Accounting Policies - Regulatory Asset Disclosure - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 64,481	$ 72,391	$ 47,789
Regulatory Assets, Noncurrent	297,546	314,579	338,692
Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	64	40	40
Northwest Natural Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	64,481	72,391	47,789
Regulatory Assets, Noncurrent	297,482	314,539	338,652
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	3,855	10,402	1,038
Regulatory Assets, Noncurrent	592	412	1,272
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	33,215	35,641	21,851
Regulatory Assets, Noncurrent	10,054	15,477	11,242
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	7,082	6,694	5,396
Regulatory Assets, Noncurrent	87,566	94,636	84,977
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	469	969	4
Regulatory Assets, Noncurrent	0	0	2
Northwest Natural Gas Company [Member] | Pension balancing [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	7,131	7,131	7,131
Regulatory Assets, Noncurrent	35,974	38,302	41,111
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,299	2,568	2,273
Regulatory Assets, Noncurrent	11,129	12,609	13,895
Northwest Natural Gas Company [Member] | Pension and other postretirement benefit liabilities [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	113,494	116,440	165,598
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	10,430	8,986	10,096
Regulatory Assets, Noncurrent	$ 38,673	$ 36,663	$ 20,555