Income Tax - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes at statutory rates (federal and state)	$ 15,783	$ 16,808
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	6,513	7,308
Differences required to be flowed-through by regulatory commissions	(3,173)	(3,605)
Other, net	(200)	10
Total provision for income taxes on continuing operations	$ 18,923	$ 20,521
Effective tax rate for continuing operations	25.20%	25.60%
Northwest Natural Gas Company [Member]
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes at statutory rates (federal and state)	$ 16,115	$ 16,939
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	6,584	7,325
Differences required to be flowed-through by regulatory commissions	(3,173)	(3,605)
Other, net	(203)	(107)
Total provision for income taxes on continuing operations	$ 19,323	$ 20,552
Effective tax rate for continuing operations	25.20%	25.50%