Pension and Other Postretirement Benefits Costs - Schedule of AOCL and Changes in AOCL, Non-Qualified Employee Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 12,902
Ending balance	11,404	$ 12,902
Northwest Holdings and Northwest Natural [Member] | Non-Qualified Pension Plans, Defined Benefit [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	12,902	10,733
Amounts reclassified to AOCL	812	(3,873)
Amortization of actuarial losses	1,225	923
Total reclassifications before tax	2,037	(2,950)
Tax (benefit) expense	(539)	781
Total reclassifications for the period	1,498	(2,169)
Ending balance	(11,404)	12,902
Northwest Natural Gas Company [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	12,902
Ending balance	11,404	$ 12,902
Defined Benefit Plan Amounts That Will Be Amortized From Accumulated Other Comprehensive Income Loss In Next Fiscal Year Regulatory	11,800
Defined Benefit Plan Amortization Of Net Gains Losses Regulatory	12,100
Defined Benefit Plan Amortization Of Net Prior Service Cost Credit Regulatory	$ 300