Significant Accounting Policies - Regulatory Liability Disclosure (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	$ 112,281	$ 50,362
Regulatory Liability, Noncurrent	658,332	639,663
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	982	870
Northwest Natural Gas Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	112,281	50,362
Regulatory Liability, Noncurrent	657,350	638,793
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	70	1,118
Regulatory Liability, Noncurrent	250	314
Northwest Natural Gas Company [Member] | Unrealized gain on derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	48,130	13,674
Regulatory Liability, Noncurrent	10,730	6,135
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	4,475	11,793
Regulatory Liability, Noncurrent	3,412	1,723
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	6,290	5,262
Regulatory Liability, Noncurrent	13,792	11,843
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	8,192	8,217
Regulatory Liability, Noncurrent	181,404	189,587
Northwest Natural Gas Company [Member] | Accrued asset removal costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	445,952	427,960
Northwest Natural Gas Company [Member] | Asset Optimization Revenue Sharing
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	45,124	10,298
Regulatory Liability, Noncurrent	$ 1,810	$ 1,231