Significant Accounting Policies - Regulatory Asset Disclosure (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 72,391	$ 31,745
Regulatory Assets, Noncurrent	314,579	348,927
Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	40	40
Northwest Natural Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	72,391	31,745
Regulatory Assets, Noncurrent	314,539	348,887
Northwest Natural Gas Company [Member] | Unrealized loss on derivatives [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	10,402	4,198
Regulatory Assets, Noncurrent	412	2,852
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	35,641	1,979
Regulatory Assets, Noncurrent	15,477	3,925
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	6,694	4,992
Regulatory Assets, Noncurrent	94,636	90,623
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	969	361
Regulatory Assets, Noncurrent	0	1,031
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,568	3,484
Regulatory Assets, Noncurrent	12,609	15,368
Northwest Natural Gas Company [Member] | Pension balancing [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	7,131	7,131
Regulatory Assets, Noncurrent	38,302	43,383
Northwest Natural Gas Company [Member] | Pension and other postretirement benefit liabilities [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	116,440	170,812
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	8,986	9,600
Regulatory Assets, Noncurrent	$ 36,663	$ 20,893