Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 32,920	$ 29,270
Accounts receivable	121,341	168,906
Accrued unbilled revenue	$ 83,138	89,048
Receivables from affiliates - Affiliated Entity [Extensible Enumeration]	Affiliated Entity [Member]
Allowance for uncollectible accounts	$ (3,455)	(3,296)
Regulatory assets	178,270	117,491
Derivative instruments	11,380	194,412
Inventories	112,571	87,096
Other current assets	65,275	61,286
Total current assets	601,440	744,213
Non-current assets:
Property, plant, and equipment	4,556,609	4,261,566
Less: Accumulated depreciation	1,198,555	1,147,166
Total property, plant, and equipment, net	3,358,054	3,114,400
Regulatory Assets, Noncurrent	333,443	340,432
Derivative instruments	431	5,045
Other investments	102,951	95,704
Operating lease right of use asset, net	71,308	73,429
Assets under sales-type leases	129,882	134,302
Goodwill	163,344	149,283
Other non-current assets	106,239	91,518
Total non-current assets	4,265,652	4,004,113
Total assets	4,867,092	4,748,326
Current liabilities:
Short-term debt	89,780	258,200
Current maturities of long-term debt	150,865	90,697
Accounts payable	$ 145,361	180,667
Payables to affiliates - Affiliated Entity [Extensible Enumeration]	Affiliated Entity [Member]
Taxes accrued	$ 15,454	15,625
Interest accrued	15,836	10,169
Regulatory liabilities	84,962	248,582
Derivative instruments	98,661	28,728
Operating lease liabilities	2,333	1,514
Other current liabilities	93,626	64,552
Total current liabilities	696,878	898,734
Long-term debt	1,425,435	1,246,167
Deferred credits and other non-current liabilities:
Deferred Income Tax Liabilities, Net	382,673	366,022
Regulatory liabilities	695,896	689,578
Pension and other postretirement benefit liabilities	158,116	149,143
Derivative instruments	28,055	20,838
Operating lease liabilities	77,167	78,965
Other non-current liabilities	119,034	123,438
Total deferred credits and other non-current liabilities	1,460,941	1,427,984
Commitments and contingencies (see Note 16 and Note 17)
Equity:
Common stock - no par value	890,976	805,253
Retained earnings	399,911	376,473
Accumulated other comprehensive loss	(7,049)	(6,285)
Total equity	1,283,838	1,175,441
Total liabilities and equity	$ 4,867,092	$ 4,748,326
Par Value (in dollars per share)	$ 0	$ 0
Shares Authorized (in shares)	100,000,000	100,000,000
Shares issued (in shares)	37,631,212	35,524,590
Shares outstanding (in shares)	37,631,212	35,524,590
Northwest Natural Gas Company [Member]
Current assets:
Cash and cash equivalents	$ 19,841	$ 12,977
Accounts receivable	117,216	165,607
Accrued unbilled revenue	$ 81,524	87,482
Receivables from affiliates - Affiliated Entity [Extensible Enumeration]	Affiliated Entity [Member]
Receivables from affiliates	$ 824	634
Allowance for uncollectible accounts	(3,228)	(3,079)
Regulatory assets	178,270	117,491
Derivative instruments	11,184	194,236
Inventories	110,855	86,207
Other current assets	60,138	57,269
Total current assets	576,624	718,824
Non-current assets:
Property, plant, and equipment	4,393,759	4,148,547
Less: Accumulated depreciation	1,181,962	1,137,231
Total property, plant, and equipment, net	3,211,797	3,011,316
Regulatory Assets, Noncurrent	333,418	340,407
Derivative instruments	373	5,045
Other investments	86,145	80,110
Operating lease right of use asset, net	70,728	72,720
Assets under sales-type leases	129,882	134,302
Other non-current assets	102,410	89,994
Total non-current assets	3,934,753	3,733,894
Total assets	4,511,377	4,452,718
Current liabilities:
Short-term debt	16,780	170,200
Current maturities of long-term debt	0	89,942
Accounts payable	138,111	177,590
Payables to affiliates	$ 14,850	9,175
Payables to affiliates - Affiliated Entity [Extensible Enumeration]	Affiliated Entity [Member]
Taxes accrued	$ 15,293	15,426
Interest accrued	15,111	8,900
Regulatory liabilities	84,912	248,553
Derivative instruments	98,661	28,728
Operating lease liabilities	2,128	1,363
Other current liabilities	89,371	62,019
Total current liabilities	475,217	811,896
Long-term debt	1,364,732	1,035,935
Deferred credits and other non-current liabilities:
Deferred Income Tax Liabilities, Net	371,867	362,353
Regulatory liabilities	694,947	688,599
Pension and other postretirement benefit liabilities	158,116	149,143
Derivative instruments	28,055	20,838
Operating lease liabilities	76,757	78,345
Other non-current liabilities	109,066	114,527
Total deferred credits and other non-current liabilities	1,438,808	1,413,805
Commitments and contingencies (see Note 16 and Note 17)
Equity:
Common stock - no par value	644,903	614,903
Retained earnings	594,954	582,593
Accumulated other comprehensive loss	(7,237)	(6,414)
Total equity	1,232,620	1,191,082
Total liabilities and equity	$ 4,511,377	$ 4,452,718