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Pension and Other Postretirement Benefit Costs - Narrative - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Defined benefit pension plan cash contributions			$ 3,400	$ 0
Estimated future employer contributions in next fiscal year	$ 17,200		17,200
Employer contributions			5,800	5,900
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive loss	(6,500)	$ (5,255)	(6,500)	(5,255)		$ (7,049)
Northwest Natural Gas Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive loss	(7,092)	(6,209)	(7,092)	(6,209)		(7,237)
Non-Qualified Pension Plans, Defined Benefit \| Northwest Natural Gas Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive loss	(7,092)	(6,209)	(7,092)	(6,209)	$ (7,359)	$ (7,237)	$ (6,312)	$ (6,414)
Amortization of actuarial losses	207	140	380	279
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	207	140	197	279
Tax expense (benefit)	60	(37)	(52)	(74)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	$ 267	$ 103	$ 145	$ 205