Income Tax (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Unrecognized Tax Benefits	$ 0	$ 0	$ 0
Regulatory Settlement	0	0	(1,129,000)
Deferred Tax Liabilities, Property, Plant and Equipment	310,471,000	297,078,000
Deferred Tax Liabilities, Leasing Arrangements	38,123,000	39,396,000
Deferred Tax Liabilities, Lease Right of Use Assets	21,362,000	21,613,000
Deferred Tax Liabilities Non Regulated Liabilities	7,793,000	0
Deferred Tax Liabilities, Net	340,231,000	319,292,000
Deferred Tax Assets, Lease Liabilities	21,376,000	21,622,000
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	100,000
Deferred Tax Assets, Tax Credit Carryforwards, Other	126,000	861,000
Deferred Tax Assets, Net of Valuation Allowance	75,433,000	80,965,000
Regulatory Liability, Noncurrent	658,332,000	639,663,000
Deferred Tax Assets, Goodwill and Intangible Assets	3,484,000	4,485,000
Deferred Tax Liabilities, Gross	415,664,000	400,257,000
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate	22,275,000	19,185,000	16,370,000
Income Tax Reconciliation, State and Local Income Taxes, net of federal tax benefit	9,962,000	6,389,000	4,422,000
Income Tax Reconciliation, Differences Regulatory Commission	(4,655,000)	(3,960,000)	(5,772,000)
Income Tax Reconciliation, Other Adjustments	(176,000)	(532,000)	(1,249,000)
Income Tax Expense (Benefit)	$ 27,406,000	$ 21,082,000	$ 12,642,000
Effective Income Tax Rate	25.80%	23.10%	16.20%
Tax Provision Current And Deferred [Abstract]
Current Federal Tax Expense (Benefit)	$ 6,508,000	$ 10,106,000	$ 5,530,000
Current State and Local Tax Expense (Benefit)	6,281,000	5,971,000	1,667,000
Current Income Tax Expense (Benefit)	12,789,000	16,077,000	7,197,000
Deferred Federal Income Tax Expense (Benefit)	8,289,000	2,888,000	1,515,000
Deferred State and Local Income Tax Expense (Benefit)	6,328,000	2,117,000	3,930,000
Deferred Income Tax Expense (Benefit)	14,617,000	5,005,000	5,445,000
Income Tax Expense (Benefit)	27,406,000	21,082,000	12,642,000
Tax Provision Regulated And Nonutility [Abstract]
Income Tax Expense (Benefit)	27,406,000	21,082,000	12,642,000
Deferred Tax Assets, Other	0	1,407,000
Pension Plan [Member]
Regulatory Assets [Line Items]
Deferred Tax Liabilities, Regulatory Assets	23,097,000	25,066,000
Income taxes [Member]
Regulatory Assets [Line Items]
Deferred Tax Liabilities, Regulatory Assets	14,818,000	17,104,000
Deferred Tax Assets, Regulatory Assets and Liabilities	50,447,000	52,590,000
Tax Provision Regulated And Nonutility [Abstract]
Deferred Tax Assets, Regulatory Assets and Liabilities	50,447,000	52,590,000
Northwest Natural Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory Settlement	0	0	(1,129,000)
Deferred Tax Liabilities, Property, Plant and Equipment	303,928,000	290,105,000
Deferred Tax Liabilities, Leasing Arrangements	38,123,000	39,396,000
Deferred Tax Liabilities, Lease Right of Use Assets	21,350,000	21,596,000
Deferred Tax Liabilities Non Regulated Liabilities	8,003,000	0
Deferred Tax Liabilities, Net	337,717,000	318,034,000
Deferred Tax Assets, Lease Liabilities	21,365,000	21,606,000
Deferred Tax Assets, Tax Credit Carryforwards, Other	44,000	80,000
Deferred Tax Assets, Net of Valuation Allowance	71,602,000	75,233,000
Regulatory Liability, Noncurrent	657,350,000	638,793,000
Deferred Tax Assets, Goodwill and Intangible Assets	0	0
Deferred Tax Liabilities, Gross	409,319,000	393,267,000
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate	22,996,000	19,248,000	17,438,000
Income Tax Reconciliation, State and Local Income Taxes, net of federal tax benefit	10,150,000	6,385,000	4,716,000
Income Tax Reconciliation, Differences Regulatory Commission	(4,738,000)	(3,960,000)	(5,772,000)
Income Tax Reconciliation, Other Adjustments	(75,000)	(578,000)	(1,188,000)
Income Tax Expense (Benefit)	$ 28,333,000	$ 21,095,000	$ 14,065,000
Effective Income Tax Rate	25.90%	23.00%	16.90%
Tax Provision Current And Deferred [Abstract]
Current Federal Tax Expense (Benefit)	$ 7,570,000	$ 11,092,000	$ 6,755,000
Current State and Local Tax Expense (Benefit)	7,540,000	5,357,000	2,101,000
Current Income Tax Expense (Benefit)	15,110,000	16,449,000	8,856,000
Deferred Federal Income Tax Expense (Benefit)	7,915,000	1,921,000	1,340,000
Deferred State and Local Income Tax Expense (Benefit)	5,308,000	2,725,000	3,869,000
Deferred Income Tax Expense (Benefit)	13,223,000	4,646,000	5,209,000
Income Tax Expense (Benefit)	28,333,000	21,095,000	14,065,000
Tax Provision Regulated And Nonutility [Abstract]
Income Tax Expense (Benefit)	28,333,000	21,095,000	$ 14,065,000
Deferred Tax Assets, Other	0	1,181,000
Northwest Natural Gas Company [Member] | Income taxes [Member] | Equity Portion, AFUDC
Regulatory Assets [Line Items]
Regulatory Assets	2,400,000	2,500,000
Northwest Natural Gas Company [Member] | Income taxes [Member] | Oregon Corporate Activity Tax
Regulatory Assets [Line Items]
Regulatory Assets	400,000	1,700,000
Northwest Natural Gas Company [Member] | Pension Plan [Member]
Regulatory Assets [Line Items]
Deferred Tax Liabilities, Regulatory Assets	23,097,000	25,066,000
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Assets [Line Items]
Deferred Tax Liabilities, Regulatory Assets	14,818,000	17,104,000
Deferred Tax Assets, Regulatory Assets and Liabilities	50,193,000	52,366,000
Regulatory Liabilities	189,600,000	197,800,000
Regulatory Liability, Noncurrent	181,404,000	189,587,000
Tax Provision Regulated And Nonutility [Abstract]
Deferred Tax Assets, Regulatory Assets and Liabilities	50,193,000	52,366,000
Excluding AFUDC [Member] | Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets	12,400,000	$ 14,600,000
Domestic Tax Authority [Member]
Regulatory Assets [Line Items]
Operating Loss Carryforwards	200,000
State and Local Jurisdiction [Member]
Regulatory Assets [Line Items]
Operating Loss Carryforwards	$ 200,000