Leases - Lease Revenue (Details) - USD ($)	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Lessor, Lease, Description [Line Items]
Lessor, Sales-type Lease, Term of Contract	30 years
Lessor, Sales-type Lease, Renewal Term	50 years
Residual Value of Leased Asset	$ 4,700,000	$ 4,300,000
Lease Revenue [Abstract]
Operating Lease, Lease Income	80,000	88,000
Sales-type Lease, Lease Income	17,471,000	18,355,000
Lease Income	17,551,000	18,443,000
Operating Leases Payment to be Received [Abstract]
Lessor, Operating Lease, Payments to be Received, Next Twelve Months	627,000
Lessor, Operating Lease, Payments to be Received, Two Years	125,000
Lessor, Operating Lease, Payments to be Received, Three Years	126,000
Lessor, Operating Lease, Payments to be Received, Four Years	119,000
Lessor, Operating Lease, Payments to be Received, Five Years	92,000
Lessor, Operating Lease, Payments to be Received, Thereafter	936,000
Lessor, Operating Lease, Payments to be Received	2,025,000
Total Lease Payments to be Received [Abstract]
Lease Payments to be Received, Next twelve months	17,653,000
Lease Payments to be Received, Two Years	16,682,000
Lease Payments to be Received, Three Years	15,993,000
Lease Payments to be Received, Four Years	15,425,000
Lease Payments to be Received, Five Years	14,993,000
Lease Payments to be Received, Thereafter	237,756,000
Lease Payments to be Received	318,502,000
Northwest Natural Gas Company [Member]
Operating Leases Payment to be Received [Abstract]
Lessor, Operating Lease, Payments to be Received, Next Twelve Months	577,000
Lessor, Operating Lease, Payments to be Received, Two Years	74,000
Lessor, Operating Lease, Payments to be Received, Three Years	74,000
Lessor, Operating Lease, Payments to be Received, Four Years	66,000
Lessor, Operating Lease, Payments to be Received, Five Years	36,000
Lessor, Operating Lease, Payments to be Received, Thereafter	22,000
Lessor, Operating Lease, Payments to be Received	849,000
Total Lease Payments to be Received [Abstract]
Lease Payments to be Received, Next twelve months	17,603,000
Lease Payments to be Received, Two Years	16,631,000
Lease Payments to be Received, Three Years	15,941,000
Lease Payments to be Received, Four Years	15,372,000
Lease Payments to be Received, Five Years	14,937,000
Lease Payments to be Received, Thereafter	236,842,000
Lease Payments to be Received	317,326,000
NWN Water
Operating Leases Payment to be Received [Abstract]
Lessor, Operating Lease, Payments to be Received, Next Twelve Months	50,000
Lessor, Operating Lease, Payments to be Received, Two Years	51,000
Lessor, Operating Lease, Payments to be Received, Three Years	52,000
Lessor, Operating Lease, Payments to be Received, Four Years	53,000
Lessor, Operating Lease, Payments to be Received, Five Years	56,000
Lessor, Operating Lease, Payments to be Received, Thereafter	914,000
Lessor, Operating Lease, Payments to be Received	1,176,000
Total Lease Payments to be Received [Abstract]
Lease Payments to be Received, Next twelve months	50,000
Lease Payments to be Received, Two Years	51,000
Lease Payments to be Received, Three Years	52,000
Lease Payments to be Received, Four Years	53,000
Lease Payments to be Received, Five Years	56,000
Lease Payments to be Received, Thereafter	914,000
Lease Payments to be Received	1,176,000
Sales-type Lease [Member]
Sales-type Leases Payments to be Received [Abstract]
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Next Twelve Months	17,026,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Two Years	16,557,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Three Years	15,867,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Four Years	15,306,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Five Years	14,901,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Thereafter	236,820,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received	316,477,000
Receivable with Imputed Interest, Discount	177,160,000
Receivable with Imputed Interest, Net Amount	139,317,000
Sales-type Lease [Member] \| Northwest Natural Gas Company [Member]
Sales-type Leases Payments to be Received [Abstract]
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Next Twelve Months	17,026,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Two Years	16,557,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Three Years	15,867,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Four Years	15,306,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Five Years	14,901,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Thereafter	236,820,000
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received	316,477,000
Receivable with Imputed Interest, Net Amount	139,317,000
Sales-type Lease [Member] \| NWN Water
Sales-type Leases Payments to be Received [Abstract]
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Next Twelve Months	0
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Two Years	0
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Three Years	0
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Four Years	0
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Five Years	0
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Thereafter	0
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received	0
North Mist Lease [Member]
Lessor, Lease, Description [Line Items]
Variable Lease, Payment	0
Residual Value of Leased Asset	$ 0
Compressed Natural Gas Lease [Member]
Lessor, Lease, Description [Line Items]
Lessor, Sales-type Lease, Term of Contract	10 years
Other Nonoperating Income (Expense) [Member]
Lease Revenue [Abstract]
Lease Income	$ 500,000	$ 500,000

Lease Payments to be Received

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Lease Payments to be Received, Five Years

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Lease Payments to be Received, Four Years

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Lease Payments to be Received, Next twelve months

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Lease Payments to be Received, Thereafter

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Lease Payments to be Received, Three Years

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Lease Payments to be Received, Two Years

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Lease Revenue [Abstract]

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Operating Leases Payment to be Received [Abstract]

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Total Lease Payments to be Received [Abstract]

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Amount of lease income from operating, direct financing, and sales-type leases. Includes, but is not limited to, variable lease payments, interest income, profit (loss) recognized at commencement, and lease payments paid and payable to lessor.

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Term of lessor's sales-type lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of residual asset covered by residual value guarantee. Excludes guarantee considered to be lease payments for lessor.

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