Significant Accounting Policies - Regulatory Liability Disclosure (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	$ 84,962		$ 248,582
Regulatory Liability, Noncurrent	695,896		689,578
CCI Deferred Costs	20,500
Oregon [Member]
Regulatory Liabilities [Line Items]
CCI Credits Liability	19,900
Washington Climate Commitment Act Allowances
Regulatory Liabilities [Line Items]
Proceeds from Other Operating Activities	7,100	$ 10,000
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	50		29
Regulatory Liability, Noncurrent	949		979
Accrued asset removal costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	496,200		467,700
Northwest Natural Gas Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	84,912		248,553
Regulatory Liability, Noncurrent	694,947		688,599
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	6,375		4,121
Regulatory Liability, Noncurrent	8,556		12,644
Northwest Natural Gas Company [Member] | Unrealized gain on derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	11,184		194,236
Regulatory Liability, Noncurrent	373		5,045
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	7,612		14,026
Regulatory Liability, Noncurrent	2,118		3,814
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	6,233		2,636
Regulatory Liability, Noncurrent	15,855		16,741
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	4,726		7,166
Regulatory Liability, Noncurrent	169,485		174,212
Regulatory Liabilities	174,200		181,400
Northwest Natural Gas Company [Member] | Accrued asset removal costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	496,235		467,742
Northwest Natural Gas Company [Member] | Asset Optimization Revenue Sharing
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	31,583		26,368
Regulatory Liability, Noncurrent	2,325		8,401
Northwest Natural Gas Company [Member] | Washington Climate Commitment Act compliance
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	17,199		$ 0
Regulatory Liabilities	$ 7,100	$ 10,000