Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Current assets:
Cash and cash equivalents	$ 72,375	$ 32,920	$ 140,821
Accounts receivable	128,433	121,341	164,157
Accrued unbilled revenue	57,905	83,138	59,542
Allowance for uncollectible accounts	(4,181)	(3,455)	(6,760)
Regulatory assets	127,666	178,270	126,546
Derivative instruments	5,746	11,380	8,507
Inventories	99,874	112,571	41,392
Other current assets	49,896	65,275	41,968
Total current assets	537,714	601,440	576,173
Non-current assets:
Property, plant, and equipment	4,660,104	4,556,609	4,320,476
Less: Accumulated depreciation	1,218,580	1,198,555	1,164,498
Total property, plant, and equipment, net	3,441,524	3,358,054	3,155,978
Regulatory assets	309,173	333,443	311,419
Derivative instruments	3,099	431	1,432
Other investments	84,081	102,951	93,611
Operating lease right of use asset, net	70,547	71,308	72,699
Assets under sales-type leases	128,840	129,882	133,159
Goodwill	162,966	163,344	149,836
Other non-current assets	111,122	106,239	97,789
Total non-current assets	4,311,352	4,265,652	4,015,923
Total assets	4,849,066	4,867,092	4,592,096
Current liabilities:
Short-term debt	94,700	89,780	72,500
Current maturities of long-term debt	869	150,865	240,712
Accounts payable	107,888	145,361	111,152
Taxes accrued	27,031	15,454	31,372
Interest accrued	16,360	15,836	13,089
Regulatory liabilities	77,659	84,962	57,523
Derivative instruments	52,677	98,661	44,370
Operating lease liabilities	2,053	2,333	1,700
Other current liabilities	89,107	93,626	71,662
Total current liabilities	468,344	696,878	644,080
Long-term debt	1,574,735	1,425,435	1,294,590
Deferred credits and other non-current liabilities:
Deferred tax liabilities	394,068	382,673	376,237
Regulatory liabilities	700,703	695,896	669,328
Pension and other postretirement benefit liabilities	157,812	158,116	147,890
Derivative instruments	12,743	28,055	15,382
Operating lease liabilities	77,051	77,167	78,302
Other non-current liabilities	120,224	119,034	117,980
Total deferred credits and other non-current liabilities	1,462,601	1,460,941	1,405,119
Commitments and contingencies (Note 16)
Equity:
Common stock	$ 905,153	$ 890,976	$ 824,304
Shares Authorized (in shares)	100,000,000	100,000,000	100,000,000
Shares outstanding (in shares)	38,027,266	37,631,212	35,929,228
Shares issued (in shares)	38,027,266	37,631,212	35,929,228
Par Value (in dollars per share)	$ 0	$ 0	$ 0
Retained earnings	$ 445,058	$ 399,911	$ 430,597
Accumulated other comprehensive loss	(6,825)	(7,049)	(6,594)
Total equity	1,343,386	1,283,838	1,248,307
Total liabilities and equity	$ 4,849,066	4,867,092	4,592,096
Accounts Payable, Related Party, Type [Extensible Enumeration]	Affiliated Entity [Member]
Other Receivable, after Allowance for Credit Loss, Related Party, Type [Extensible Enumeration]	Affiliated Entity [Member]
Northwest Natural Gas Company [Member]
Current assets:
Cash and cash equivalents	$ 61,906	19,841	129,731
Accounts receivable	124,827	117,216	158,675
Accrued unbilled revenue	56,213	81,524	57,855
Other Receivables, Net, Current	2,409	824	2,388
Allowance for uncollectible accounts	(3,946)	(3,228)	(3,937)
Regulatory assets	127,641	178,270	126,546
Derivative instruments	5,420	11,184	8,890
Inventories	97,979	110,855	39,835
Other current assets	48,769	60,138	40,950
Total current assets	521,218	576,624	560,933
Non-current assets:
Property, plant, and equipment	4,488,931	4,393,759	4,200,299
Less: Accumulated depreciation	1,199,866	1,181,962	1,153,060
Total property, plant, and equipment, net	3,289,065	3,211,797	3,047,239
Regulatory assets	309,067	333,418	311,394
Derivative instruments	2,700	373	1,432
Other investments	66,343	86,145	78,102
Operating lease right of use asset, net	70,019	70,728	72,077
Assets under sales-type leases	128,840	129,882	133,158
Other non-current assets	107,390	102,410	96,300
Total non-current assets	3,973,424	3,934,753	3,739,702
Total assets	4,494,642	4,511,377	4,300,635
Current liabilities:
Short-term debt	31,700	16,780	0
Current maturities of long-term debt	0	0	89,962
Accounts payable	103,283	138,111	107,986
Accounts Payable, Other, Current	26,872	14,850	24,806
Taxes accrued	14,745	15,293	15,120
Interest accrued	15,487	15,111	12,535
Regulatory liabilities	77,463	84,912	57,494
Derivative instruments	52,677	98,661	44,370
Operating lease liabilities	1,863	2,128	1,538
Other current liabilities	84,700	89,371	69,114
Total current liabilities	408,790	475,217	422,925
Long-term debt	1,364,899	1,364,732	1,234,460
Deferred credits and other non-current liabilities:
Deferred tax liabilities	381,568	371,867	374,092
Regulatory liabilities	699,753	694,947	668,348
Pension and other postretirement benefit liabilities	157,812	158,116	147,890
Derivative instruments	12,743	28,055	15,382
Operating lease liabilities	76,624	76,757	77,840
Other non-current liabilities	110,091	109,066	109,518
Total deferred credits and other non-current liabilities	1,438,591	1,438,808	1,393,070
Commitments and contingencies (Note 16)
Equity:
Common stock	644,903	644,903	614,911
Retained earnings	644,818	594,954	641,581
Accumulated other comprehensive loss	(7,359)	(7,237)	(6,312)
Total equity	1,282,362	1,232,620	1,250,180
Total liabilities and equity	$ 4,494,642	$ 4,511,377	$ 4,300,635