Debt Short-term Debt $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	0.568
Short-term debt	$ 240,000	$ 304,525	$ 233,000
Commercial Paper Maximum Maturity	29 days
Commercial Paper Average Maturity	15 days
Northwest Natural Gas Company [Member]
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	0.562
Short-term debt	$ 198,000	$ 231,525	$ 153,000
Line of Credit [Member]
Short-term Debt [Line Items]
Short-term debt	$ 42,000
Debt, Weighted Average Interest Rate	1.10%
Commercial Paper [Member] | Northwest Natural Gas Company [Member]
Short-term Debt [Line Items]
Short-term debt	$ 98,000
Debt, Weighted Average Interest Rate	0.20%
364-Day Term Loan, Due 2022 | Northwest Natural Gas Company [Member]
Short-term Debt [Line Items]
Proceeds from Issuance of Debt	$ 100,000
Debt, Weighted Average Interest Rate	0.60%