Income Tax - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes at statutory rates (federal and state)	$ (210)	$ (1,429)	$ 16,598	$ 11,676
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	(48)	(333)	7,260	3,344
Differences required to be flowed-through by regulatory commissions	21	173	(3,584)	(2,352)
Other, net	(40)	(83)	(30)	(213)
Total provision for income taxes on continuing operations	$ (277)	$ (1,672)	$ 20,244	$ 12,455
Effective tax rate for continuing operations	27.70%	24.60%	25.60%	22.40%
Northwest Natural Gas Company [Member]
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes at statutory rates (federal and state)	$ 184	$ (1,287)	$ 17,123	$ 12,068
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	41	(281)	7,366	3,456
Differences required to be flowed-through by regulatory commissions	21	173	(3,584)	(2,352)
Other, net	42	(24)	(65)	(173)
Total provision for income taxes on continuing operations	$ 288	$ (1,419)	$ 20,840	$ 12,999
Effective tax rate for continuing operations	32.80%	23.10%	25.60%	22.60%