Debt Short-term Debt - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Short-term Debt [Line Items]
Short-term debt	$ 236,225	$ 304,525	$ 550,000
Ratio of Indebtedness to Net Capital	0.560
Commercial Paper Maximum Maturity	76 days
Commercial Paper Average Maturity	20 days
Northwest Natural Gas Company [Member]
Short-term Debt [Line Items]
Short-term debt	$ 175,225	$ 231,525	$ 450,000
Line of Credit [Member]
Short-term Debt [Line Items]
Short-term debt	$ 61,000
Debt, Weighted Average Interest Rate	1.19%
Commercial Paper [Member] | Northwest Natural Gas Company [Member]
Short-term Debt [Line Items]
Short-term debt	$ 175,200
Debt, Weighted Average Interest Rate	0.43%