Significant Accounting Policies - Regulatory Liability Disclosure - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	$ 111,791	$ 112,281	$ 81,314
Regulatory Liability, Noncurrent	652,977	658,332	636,384
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	982	982	869
Northwest Natural Gas Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	111,791	112,281	81,314
Regulatory Liability, Noncurrent	651,995	657,350	635,515
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	1,922	70	2,575
Regulatory Liability, Noncurrent	532	250	634
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	84,438	48,130	19,914
Regulatory Liability, Noncurrent	6,955	10,730	3,087
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	8,236	4,475	10,134
Regulatory Liability, Noncurrent	3,585	3,412	2,652
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	7,318	8,192	8,217
Regulatory Liability, Noncurrent	176,138	181,404	182,511
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	4,691	6,290	4,596
Regulatory Liability, Noncurrent	13,812	13,792	12,142
Northwest Natural Gas Company [Member] | Accrued asset removal costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	450,973	445,952	434,489
Northwest Natural Gas Company [Member] | Asset Optimization Revenue Sharing
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	5,186	45,124	35,878
Regulatory Liability, Noncurrent	$ 0	$ 1,810	$ 0