Description of minimum financial levels (for example, tangible net worth and working capital) and achievement of certain financial ratios (for example, working capital ratio and debt service coverage ratio), and adherence to certain clauses which generally require or restrict certain actions (for example, entering into a debt arrangement with equal or greater seniority, and selling or discontinuing a certain business segment or material subsidiary) to be in compliance with the covenant clauses of the debt agreement. May also include a discussion of the adverse consequences that would result if the entity violates or fails to satisfy the covenants.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Long-Term Debt (Details) $ in Thousands	3 Months Ended	6 Months Ended
Long-Term Debt (Details) $ in Thousands	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)
Debt Instrument [Line Items]
Long-term Debt	$ 954,164		$ 881,064	$ 736,642
Unamortized debt issuance costs	$ 7,554		5,712	5,246
Ratio of Indebtedness to Net Capital	0.625
Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 917,146		843,988	734,454
Unamortized debt issuance costs	$ 7,554		$ 5,712	$ 5,246
Weighted average interest rate	4.598%
Ratio of Indebtedness to Net Capital	0.614
Northwest Natural Gas Company [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Stated interest rate	2.822%
Northwest Natural Gas Company [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Stated interest rate	9.05%
Note 3.60 Series Due 2050 [Member] \| Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Stated interest rate	3.60%
Proceeds from Issuance of Debt	$ 150,000
Note 537 Series Due 2020 [Member] \| Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Stated interest rate	5.37%
Repayments of Debt	$ 75,000
Two-year Term Loan Due 2021 [Member]
Debt Instrument [Line Items]
Stated interest rate	1.82%
Proceeds from Issuance of Debt		$ 35,000
Debt Instrument, Covenant Description	requires NW Holdings to maintain a consolidated indebtedness to total capitalization ratio of 70% or less