Northwest Natural Holding (NWN) 10-Q 6 May 24 2024 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2024	Apr. 26, 2024
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2024
Entity Registrant Name	NORTHWEST NATURAL HOLDING COMPANY
Entity File Number	1-38681
Entity Incorporation, State or Country Code	OR
Entity Tax Identification Number	82-4710680
Entity Address, Address Line One	250 SW Taylor Street
Entity Address, City or Town	Portland
Entity Address, State or Province	OR
Entity Address, Postal Zip Code	97204
City Area Code	(503)
Local Phone Number	226-4211
Title of 12(b) Security	Common Stock
Trading Symbol	NWN
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		38,028,137
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Central Index Key	0001733998
Northwest Natural Gas Company [Member]
Document Information [Line Items]
Document Type	10-Q
Document Period End Date	Mar. 31, 2024
Entity Registrant Name	NORTHWEST NATURAL GAS COMPANY
Entity File Number	1-15973
Entity Incorporation, State or Country Code	OR
Entity Tax Identification Number	93-0256722
Entity Address, Address Line One	250 SW Taylor Street
Entity Address, City or Town	Portland
Entity Address, State or Province	OR
Entity Address, Postal Zip Code	97204
City Area Code	(503)
Local Phone Number	226-4211
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Central Index Key	0000073020

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating revenues [Abstract]
Operating revenues	$ 433,470,000	$ 462,423,000
Operating expenses:
Cost of gas	175,717,000	205,749,000
Operations and maintenance	73,614,000	71,817,000
Environmental remediation	5,746,000	5,375,000
General taxes	15,468,000	14,219,000
Revenue taxes	18,244,000	19,042,000
Depreciation	33,098,000	31,465,000
Other operating expenses	1,756,000	1,248,000
Total operating expenses	323,643,000	348,915,000
Income from operations	109,827,000	113,508,000
Other income (expense), net	(1,134,000)	1,606,000
Interest expense, net	20,531,000	18,296,000
Income (loss) before income taxes	88,162,000	96,818,000
Income tax expense	24,339,000	25,147,000
Net income	63,823,000	71,671,000
Other comprehensive income (loss):
Change in employee benefit plan liability, net of taxes	(249,000)	0
Amortization of non-qualified employee benefit plan liability, net of taxes	127,000	102,000
Derivative, Gain (Loss) on Derivative, Net	346,000	(411,000)
Comprehensive income	64,047,000	71,362,000
Supplemental Income Statement Elements [Abstract]
Change in employee benefit plan liability, tax	(66,000)
Amortization of non-qualified employee benefit plan liability, tax	46,000	37,000
Unrealized Loss on Derivative, tax	$ (124)	$ 149
Average common shares outstanding:
Basic (in shares)	37,765	35,609
Diluted (in shares)	37,796	35,708
Earnings per share of common stock:
Basic (in dollars per share)	$ 1.69	$ 2.01
Diluted (in dollars per share)	$ 1.69	$ 2.01
Northwest Natural Gas Company [Member]
Operating revenues [Abstract]
Operating revenues	$ 422,775,000	$ 454,513,000
Operating expenses:
Cost of gas	175,773,000	205,805,000
Operations and maintenance	65,509,000	65,389,000
Environmental remediation	5,746,000	5,375,000
General taxes	15,091,000	14,000,000
Revenue taxes	18,195,000	18,975,000
Depreciation	31,107,000	30,144,000
Other operating expenses	723,000	697,000
Total operating expenses	312,144,000	340,385,000
Income from operations	110,631,000	114,128,000
Other income (expense), net	(1,322,000)	2,445,000
Interest expense, net	16,078,000	14,611,000
Income (loss) before income taxes	93,231,000	101,962,000
Income tax expense	25,673,000	26,422,000
Net income	67,558,000	75,540,000
Other comprehensive income (loss):
Change in employee benefit plan liability, net of taxes	(249,000)	0
Amortization of non-qualified employee benefit plan liability, net of taxes	127,000	102,000
Comprehensive income	67,436,000	75,642,000
Supplemental Income Statement Elements [Abstract]
Amortization of non-qualified employee benefit plan liability, tax	$ 46,000	$ 37,000

Consolidated Balance Sheets

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

Consolidated Statement of Share

Consolidated Statement of Shareholders' Equity - USD ($) $ in Thousands	Total	Northwest Natural Gas Company [Member]	Common Stock Including APIC [Member]	Common Stock Including APIC [Member] Northwest Natural Gas Company [Member]	Retained Earnings [Member]	Retained Earnings [Member] Northwest Natural Gas Company [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Northwest Natural Gas Company [Member]
Beginning Balance at Dec. 31, 2022	$ 1,175,441	$ 1,191,082	$ 805,253	$ 614,903	$ 376,473	$ 582,593	$ (6,285)	$ (6,414)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contributions from parent		8		8
Net income	71,671	75,540			71,671	75,540
Dividends on common stock					(17,547)	(16,552)
Other comprehensive income (loss)	71,362	75,642					(309)	102
Stock-based compensation			2,580
Shares issued pursuant to equity based plans, net of shares withheld for taxes			(174)
Issuances of common stock, net of issuance costs			16,645
Ending Balance at Mar. 31, 2023	$ 1,248,307	1,250,180	824,304	614,911	430,597	641,581	(6,594)	(6,312)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4850
Beginning Balance at Dec. 31, 2023	$ 1,283,838	1,232,620	890,976	644,903	399,911	594,954	(7,049)	(7,237)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contributions from parent		0		0
Net income	63,823	67,558			63,823	67,558
Dividends on common stock					(18,676)	(17,694)
Other comprehensive income (loss)	64,047	67,436					224	(122)
Stock-based compensation			1,728
Shares issued pursuant to equity based plans, net of shares withheld for taxes			231
Issuances of common stock, net of issuance costs			12,218
Ending Balance at Mar. 31, 2024	$ 1,343,386	$ 1,282,362	$ 905,153	$ 644,903	$ 445,058	$ 644,818	$ (6,825)	$ (7,359)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4875

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating activities:
Net income	$ 63,823	$ 71,671
Adjustments to reconcile net income to cash provided by operations:
Depreciation	33,098	31,465
Regulatory amortization of gas reserves	546	833
Deferred income taxes	8,041	5,228
Qualified defined benefit pension plan expense (benefit)	1,082	(791)
Deferred environmental expenditures, net	(6,264)	(4,113)
Environmental remediation expense	5,746	5,375
Asset optimization revenue sharing bill credits	(20,608)	(10,471)
Other	8,905	8,509
Changes in assets and liabilities:
Receivables, net	17,839	38,727
Inventories	13,070	46,129
Income and other taxes	21,796	25,567
Accounts payable	(30,930)	(47,773)
Deferred gas costs	(8,808)	(11,300)
Increase (Decrease) in Asset Optimization Revenue Sharing	108	(7,769)
Decoupling mechanism	6,427	(1,303)
Change in Cloud-based software Assets	(6,485)	(3,673)
Asset optimization revenue sharing	13,335	958
Other, net	4,534	14,054
Cash provided by operating activities	125,039	176,861
Investing activities:
Payments to Acquire Property, Plant, and Equipment	(82,217)	(71,265)
Acquisitions, net of cash acquired	0	(468)
Purchase of equity method investment	(1,000)	0
Other	729	(1,285)
Cash used in investing activities	(82,488)	(73,018)
Financing activities:
Proceeds from common stock issued, net	12,218	16,669
Long-term debt issued	150,000	200,000
Long-term debt retired	(150,000)	0
Changes in other short-term debt, net	4,920	(185,700)
Cash dividend payments on common stock	(17,746)	(16,532)
Payment of financing fees	(748)	(1,498)
Shares withheld for tax purposes	(1,314)	(1,312)
Other	(247)	(440)
Cash used in financing activities	(2,917)	11,187
Cash, cash equivalents and restricted cash	89,258	155,994
Increase (decrease) in cash, cash equivalents and restricted cash	39,634	115,030
Supplemental disclosure of cash flow information:
Income taxes paid, net of refunds	1,000	1,300
Interest paid, net of capitalization	18,044	14,904
Northwest Natural Gas Company [Member]
Operating activities:
Net income	67,558	75,540
Adjustments to reconcile net income to cash provided by operations:
Depreciation	31,107	30,144
Regulatory amortization of gas reserves	546	833
Deferred income taxes	6,624	6,495
Qualified defined benefit pension plan expense (benefit)	1,082	(791)
Deferred environmental expenditures, net	(6,264)	(4,113)
Environmental remediation expense	5,746	5,375
Asset optimization revenue sharing bill credits	(20,608)	(10,471)
Other	8,189	7,851
Changes in assets and liabilities:
Receivables, net	17,636	36,671
Inventories	13,249	46,509
Income and other taxes	15,279	20,310
Accounts payable	(31,563)	(48,531)
Deferred gas costs	(8,808)	(11,299)
Increase (Decrease) in Asset Optimization Revenue Sharing	108	(7,769)
Decoupling mechanism	6,427	(1,303)
Change in Cloud-based software Assets	(6,485)	(3,673)
Asset optimization revenue sharing	13,335	958
Other, net	5,041	16,557
Cash provided by operating activities	117,983	174,831
Investing activities:
Payments to Acquire Property, Plant, and Equipment	(72,037)	(63,598)
Other	483	(1,284)
Cash used in investing activities	(71,554)	(64,882)
Financing activities:
Capital contributions from parent	0	8
Long-term debt issued	0	200,000
Changes in other short-term debt, net	14,920	(170,200)
Cash dividend payments on common stock	(17,694)	(16,552)
Shares withheld for tax purposes	(1,314)	(1,312)
Other	(97)	(1,660)
Cash used in financing activities	(4,185)	10,284
Cash, cash equivalents and restricted cash	78,764	144,904
Increase (decrease) in cash, cash equivalents and restricted cash	42,244	120,233
Supplemental disclosure of cash flow information:
Income taxes paid, net of refunds	8,670	6,565
Interest paid, net of capitalization	$ 14,104	$ 10,522

Organization and Principles of

Organization and Principles of Consolidation	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Principles of Consolidation	ORGANIZATION AND PRINCIPLES OF CONSOLIDATION The accompanying consolidated financial statements represent the respective, consolidated financial results of Northwest Natural Holding Company (NW Holdings) and Northwest Natural Gas Company (NW Natural) and all respective companies that each registrant directly or indirectly controls, either through majority ownership or otherwise. This is a combined report of NW Holdings and NW Natural, which includes separate consolidated financial statements for each registrant. NW Natural's regulated natural gas distribution activities are reported in the natural gas distribution (NGD) segment. The NGD segment is NW Natural's core operating business and serves residential, commercial, and industrial customers in Oregon and southwest Washington. The NGD segment is the only reportable segment for NW Holdings and NW Natural. All other activities, water, wastewater and water services businesses, and other investments are aggregated and reported as other at their respective registrant. NW Holdings and NW Natural consolidate all entities in which they have a controlling financial interest. Investments in corporate joint ventures and partnerships that NW Holdings does not directly or indirectly control, and for which it is not the primary beneficiary, include NNG Financial's investment in Kelso-Beaver Pipeline and NWN Water's investment in Avion Water Company, Inc., which are accounted for under the equity method. See Note 13 for activity related to investments. NW Holdings and its direct and indirect subsidiaries are collectively referred to herein as NW Holdings, and NW Natural and its direct and indirect subsidiaries are collectively referred to herein as NW Natural. The consolidated financial statements of NW Holdings and NW Natural are presented after elimination of all intercompany balances and transactions. Information presented in these interim consolidated financial statements is unaudited, but includes all material adjustments management considers necessary for a fair statement of the results for each period reported including normal recurring accruals. These consolidated financial statements should be read in conjunction with the audited consolidated financial statements and related notes included in NW Holdings' and NW Natural's combined 2023 Annual Report on Form 10-K (2023 Form 10-K). A significant part of NW Holdings' and NW Natural's business is of a seasonal nature; therefore, NW Holdings and NW Natural results of operations for interim periods are not necessarily indicative of full year results. Seasonality affects the comparability of the results of other operations across quarters but not across years. Notes to the consolidated financial statements reflect the activity for both NW Holdings and NW Natural for all periods presented, unless otherwise noted. Certain reclassifications have been made to conform prior period information to the current presentation. The reclassifications did not have a material effect on our consolidated financial statements.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Significant Accounting Policies	SIGNIFICANT ACCOUNTING POLICIES Significant accounting policies are described in Note 2 of the 2023 Form 10-K. There were no material changes to those accounting policies during the three months ended March 31, 2024 other than those set forth in this Note 2. The following are current updates to certain critical accounting policy estimates and new accounting standards. Industry Regulation NW Holdings' principal business is to operate as a holding company for NW Natural and its other subsidiaries. NW Natural's principal business is the distribution of natural gas, which is regulated by the OPUC and WUTC. NW Natural also has natural gas storage services, which are regulated by the FERC, and to a certain extent by the OPUC and WUTC. Additionally, certain of NW Holdings' subsidiaries own water businesses, which are regulated by the public utility commission in the state in which the water utility is located, which is currently Oregon, Washington, Idaho, Texas and Arizona. Wastewater businesses, to the extent they are regulated, are generally regulated by the public utility commissions in the state in which the wastewater utility is located, which is currently Texas and Arizona. Accounting records and practices of the regulated businesses conform to the requirements and uniform system of accounts prescribed by these regulatory authorities in accordance with U.S. GAAP. The businesses in which customer rates are regulated have approved cost-based rates which are intended to allow such businesses to earn a reasonable return on invested capital. In applying regulatory accounting principles, NW Holdings and NW Natural capitalize or defer certain costs and revenues as regulatory assets and liabilities pursuant to orders of the applicable state public utility commission, which provide for the recovery of revenues or expenses from, or refunds to, utility customers in future periods, including a return or a carrying charge in certain cases. Amounts deferred as regulatory assets and liabilities for NW Holdings and NW Natural were as follows: Regulatory Assets March 31, December 31, In thousands 2024 2023 2023 NW Natural: Current: Unrealized loss on derivatives (1) $ 52,677 $ 44,370 $ 98,661 Gas costs 8,279 51,296 9,301 Environmental costs (2) 9,864 6,947 9,950 Decoupling (3) 958 — 2,288 Pension balancing (4) 7,131 7,131 7,131 Income taxes 2,208 2,208 2,208 Washington Climate Commitment Act compliance 19,761 — 20,537 COVID-19 deferrals and expenses, net 4,798 787 9,685 Other (5) 21,965 13,807 18,509 Total current - NW Natural 127,641 126,546 178,270 Other (NW Holdings) 25 — — Total current - NW Holdings $ 127,666 $ 126,546 $ 178,270 Non-current: Unrealized loss on derivatives (1) $ 12,744 $ 15,382 $ 28,055 Pension balancing (4) 25,016 30,613 27,460 Income taxes 9,930 10,540 10,731 Pension and other postretirement benefit liabilities 112,791 101,413 114,010 Environmental costs (2) 112,464 99,541 118,619 Gas costs 1,319 6,546 1,917 Decoupling (3) — — 1,017 Washington Climate Commitment Act compliance 4,223 6,312 — COVID-19 deferrals and expenses, net 1,128 12,815 1,080 Other (5) 29,452 28,232 30,529 Total non-current - NW Natural 309,067 311,394 333,418 Other (NW Holdings) 106 25 25 Total non-current - NW Holdings $ 309,173 $ 311,419 $ 333,443 Regulatory Liabilities March 31, December 31, In thousands 2024 2023 2023 NW Natural: Current: Gas costs $ 13,753 $ 5,670 $ 6,375 Unrealized gain on derivatives (1) 5,420 8,890 11,184 Decoupling (3) 10,137 12,606 7,612 Income taxes 4,726 5,143 4,726 Asset optimization revenue sharing 13,192 19,040 31,583 Washington Climate Commitment Act compliance 25,655 — 17,199 Other (5) 4,580 6,145 6,233 Total current - NW Natural 77,463 57,494 84,912 Other (NW Holdings) 196 29 50 Total current - NW Holdings $ 77,659 $ 57,523 $ 84,962 Non-current: Gas costs $ 5,555 $ 2,024 $ 8,556 Unrealized gain on derivatives (1) 2,700 1,432 373 Decoupling (3) 3,673 3,931 2,118 Income taxes (6) 165,719 170,289 169,485 Accrued asset removal costs (7) 503,539 474,764 496,235 Asset optimization revenue sharing — — 2,325 Other (5) 18,567 15,908 15,855 Total non-current - NW Natural 699,753 668,348 694,947 Other (NW Holdings) 950 980 949 Total non-current - NW Holdings $ 700,703 $ 669,328 $ 695,896 (1) Unrealized gains or losses on derivatives are non-cash items and therefore do not earn a rate of return or a carrying charge. These amounts are recoverable through NGD rates as part of the annual Purchased Gas Adjustment (PGA) mechanism when realized at settlement. (2) Refer to the Environmental Cost Deferral and Recovery table in Note 16 for a description of environmental costs. (3) This deferral represents the margin adjustment resulting from differences between actual and expected volumes. (4) Balance represents deferred net periodic benefit costs as approved by the OPUC. (5) Balances consist of deferrals and amortizations under approved regulatory mechanisms and typically earn a rate of return or carrying charge. (6) Balance represents excess deferred income tax benefits subject to regulatory flow-through. See Note 11. (7) Estimated costs of removal on certain regulated properties are collected through rates. We believe all costs incurred and deferred at March 31, 2024 are prudent. All regulatory assets are reviewed annually for recoverability, or more often if circumstances warrant. If we should determine that all or a portion of these regulatory assets no longer meet the criteria for continued application of regulatory accounting, then NW Holdings and NW Natural would be required to write-off the net unrecoverable balances in the period such determination is made. Supplemental Cash Flow Information Cash and Cash Equivalents Cash and cash equivalents include cash on hand plus highly liquid investment accounts with original maturity dates of three months or less. These investments are readily convertible to cash with fair value approximating cost. As of March 31, 2024, the amount invested in money market funds was $48.8 million at NW Natural and NW Holdings. As of March 31, 2023, the amount invested in money market funds was $107.6 million at NW Natural and $112.6 million at NW Holdings. These investments are measured using net asset value per share. Restricted Cash Restricted cash is primarily comprised of funds from public purpose charges for programs that assist low-income customers with bill payments or energy efficiency. These balances are included in other current assets in the NW Holdings and NW Natural balance sheets. There were no transfers between restricted cash and cash and cash equivalents during the three months ended March 31, 2024 and 2023. The following table provides a reconciliation of the cash, cash equivalents and restricted cash balances at NW Holdings as of March 31, 2024 and 2023 and December 31, 2023: March 31, December 31, In thousands 2024 2023 2023 Cash and cash equivalents $ 72,375 $ 140,821 $ 32,920 Restricted cash included in other current assets 16,883 15,173 16,704 Cash, cash equivalents and restricted cash $ 89,258 $ 155,994 $ 49,624 The following table provides a reconciliation of the cash, cash equivalents and restricted cash balances at NW Natural as of March 31, 2024 and 2023 and December 31, 2023: March 31, December 31, In thousands 2024 2023 2023 Cash and cash equivalents $ 61,906 $ 129,731 $ 19,841 Restricted cash included in other current assets 16,858 15,173 16,679 Cash, cash equivalents and restricted cash $ 78,764 $ 144,904 $ 36,520 Accounts Receivable and Allowance for Uncollectible Accounts Accounts receivable consist primarily of amounts due for natural gas sales and transportation services to NGD customers, plus amounts due for gas storage services. NW Holdings and NW Natural establish allowances for uncollectible accounts (allowance) for trade receivables, including accrued unbilled revenue, based on the aging of receivables, collection experience of past due account balances including payment plans, and historical trends of write-offs as a percent of revenues. A specific allowance is established and recorded for large individual customer receivables when amounts are identified as unlikely to be partially or fully recovered. Inactive accounts are written-off against the allowance after they are 120 days past due or when deemed uncollectible. Differences between the estimated allowance and actual write-offs will occur based on a number of factors, including changes in economic conditions, customer creditworthiness, and natural gas prices. The allowance for uncollectible accounts is adjusted quarterly, as necessary, based on information currently available. Allowance for Trade Receivables The payment term of our NGD receivables is generally 15 days. For these short-term receivables, it is not expected that forecasted economic conditions would significantly affect the loss estimates under stable economic conditions. For extreme situations like a financial crisis, natural disaster, and the economic slowdown caused by the COVID-19 pandemic, we enhanced our review and analysis. For the residential and commercial uncollectible provision, we primarily followed our standard methodology, which includes assessing historical write-off trends and current information on delinquent accounts. Beginning October 1, 2022, new collection rules from the OPUC applied to residential and commercial customers. This included enhanced protections for low-income customers, a return to pre-pandemic time payment arrangements terms, revised disconnection rules during the heating season, and other items. As a result of these Oregon rule changes and our recent collection process experience, we augmented our provision review for accounts in the following categories: closed or inactive accounts aged less than 120 days, accounts on payment plans, and all other open accounts not on payment plans. For industrial accounts, we continue to assess the provision on an account-by-account basis with specific reserves taken as necessary. NW Natural will continue to closely monitor and evaluate our accounts receivable and the provision for uncollectible accounts. The following table presents the activity related to the NW Holdings provision for uncollectible accounts by pool: As of As of December 31, 2023 Three Months Ended March 31, 2024 March 31, 2024 In thousands Beginning Balance Provision recorded, net of adjustments Write-offs recognized, net of recoveries Ending Balance Allowance for uncollectible accounts: Residential $ 2,397 $ 935 $ (192) $ 3,140 Commercial 501 93 (63) 531 Industrial 65 (9) — 56 Accrued unbilled and other 265 (31) (15) 219 Total NW Natural 3,228 988 (270) 3,946 Other - NW Holdings 227 8 — 235 Total NW Holdings $ 3,455 $ 996 $ (270) $ 4,181 Allowance for Net Investments in Sales-Type Leases NW Natural currently holds two net investments in sales-type leases, with substantially all of the net investment balance related to the North Mist natural gas storage agreement with Portland General Electric (PGE) which is billed under an OPUC-approved rate schedule. See Note 7 for more information on the North Mist lease. Due to the nature of this service, PGE may recover the costs of the lease through general rate cases. Therefore, we expect the risk of loss due to the credit of this lessee to be remote. As such, no allowance for uncollectibility was recorded for our sales-type lease receivables. NW Natural will continue monitoring the credit health of the lessees and the overall economic environment, including the economic factors closely tied to the financial health of our current and future lessees. Greenhouse Gas Allowances NW Natural is subject to greenhouse gas (GHG) emission reduction requirements under the Washington Climate Commitment Act (CCA) regulations. Under Washington's CCA, emission reduction compliance mechanisms include: 1) allowances distributed at no cost by the state, 2) purchasing allowances at state-run auctions or secondary markets, 3) purchasing carbon offsets, and 4) supplying alternative gaseous fuels, such as renewable natural gas and hydrogen. NW Natural will account for all purchased Washington allowances as inventory at the lower of cost or market. Any compliance instruments or allowances that are acquired through government allocations at no cost will be accounted for as inventory at no cost. As of March 31, 2024, NW Natural had $39.5 million of emissions allowances for compliance in Washington recorded as inventory. The CCA allows for the sale of compliance instruments or allowances, and as a result, should NW Natural sell these it will recognize revenue when title to the instrument or allowance is transferred to a counterparty, and NW Natural will recognize expense at the time of recognition of the related sale. In 2023 and 2024, NW Natural consigned no-cost allowances to Washington auctions and received a total of $18.6 million in cash, which proceeds were recorded as a regulatory liability for the benefit of customers. We measure the compliance obligation, which is based on emissions, at the carrying value of inventory held plus the fair value of any additional emission allowances NW Natural would need to purchase to satisfy the obligations. Under the Washington program, NW Natural has recognized a $24.0 million liability as of March 31, 2024. A portion of the costs to comply with the Washington program are currently being recovered from utility customers through rates beginning January 1, 2024. NW Natural recognized $24.0 million of deferred costs as of March 31, 2024. New Accounting Standards NW Natural and NW Holdings consider the applicability and impact of all accounting standards updates (ASUs) issued by the Financial Accounting Standards Board (FASB). ASUs not listed below were assessed and determined to be either not applicable or are expected to have minimal impact on consolidated financial position or results of operations. Recently Issued Accounting Pronouncements JOINT VENTURE FORMATIONS. In August 2023, the FASB issued ASU 2023-05, which requires a joint venture to initially measure all contributions received upon its formation at fair value. The standard is effective for all joint venture entities with a formation date on or after January 1, 2025, with early adoption permitted. The adoption of this standard is not anticipated to have a material impact on our results of operations, liquidity or capital resources. SEGMENT REPORTING. In November 2023, the FASB issued ASU 2023-07, which requires additional disclosures about significant segment expenses. The disclosures are required beginning with our annual report for the year ending December 31, 2024. The adoption of this standard is not anticipated to have a material impact on our results of operations, liquidity or capital resources. IMPROVEMENTS TO INCOME TAX DISCLOSURES. In December 2023, the FASB issued ASU 2023-09, which requires additional disclosures about income taxes. The disclosures are required beginning with our annual report for the year ending December 31, 2025. The adoption of this standard is not anticipated to have a material impact on our results of operations, liquidity or capital resources. Recent Securities and Exchange Commission (SEC) Final Rules

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE Basic earnings or loss per share are computed using NW Holdings' net income or loss and the weighted average number of common shares outstanding for each period presented. Diluted earnings per share are computed in the same manner, except using the weighted average number of common shares outstanding plus the effects of the assumed exercise of stock options and the payment of estimated stock awards from other stock-based compensation plans that are outstanding at the end of each period presented. Anti-dilutive stock awards are excluded from the calculation of diluted earnings or loss per common share. NW Holdings' diluted earnings or loss per share are calculated as follows: Three Months Ended March 31, In thousands, except per share data 2024 2023 Net income $ 63,823 $ 71,671 Average common shares outstanding - basic 37,765 35,609 Additional shares for stock-based compensation plans (See Note 8) 31 99 Average common shares outstanding - diluted 37,796 35,708 Earnings per share of common stock: Basic $ 1.69 $ 2.01 Diluted 1.69 2.01 Additional information: Anti-dilutive shares 15 1

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2024
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION We primarily operate in one reportable business segment, which is NW Natural's local gas distribution business and is referred to as the NGD segment. NW Natural and NW Holdings also have investments and business activities not specifically related to the NGD segment, which are aggregated and reported as other and described below for each entity. Natural Gas Distribution NW Natural's local gas distribution segment is a regulated utility principally engaged in the purchase, sale, and delivery of natural gas and related services to customers in Oregon and southwest Washington. In addition to NW Natural's local gas distribution business, the NGD segment also includes the portion of the Mist underground storage facility used to serve NGD customers, the North Mist gas storage expansion in Oregon, NWN Gas Reserves, which is a wholly-owned subsidiary of Energy Corp, and NW Natural RNG Holding Company, LLC, a holding company established to invest in the development and procurement of regulated renewable natural gas for NW Natural. NW Natural NW Natural's activities in Other include Interstate Storage Services and third-party asset management services, appliance retail center operations, and corporate operating and non-operating revenues and expenses that cannot be allocated to NGD operations. Earnings from Interstate Storage Services assets are primarily related to firm storage capacity revenues. Earnings from third-party asset management services also include revenue, net of amounts shared with NGD customers, from management of NGD assets at Mist and upstream pipeline capacity when not needed to serve NGD customers. Under the Oregon sharing mechanism, NW Natural retains 80% of the pre-tax income from these services when the costs of the capacity were not included in NGD rates, or 10% of the pre-tax income when the costs have been included in these rates. The remaining 20% and 90%, respectively, are recorded to a deferred regulatory account for crediting back to NGD customers. NW Holdings NW Holdings' activities in Other include all remaining activities not associated with NW Natural, specifically: NW Natural Water Company, LLC (NW Natural Water or NWN Water), which consolidates the water and wastewater utility operations and water services businesses; NW N atural Water's equity investment in Avion Water Company, Inc. ; NWN Gas Storage, a wholly-owned subsidiary of NWN Energ y; other pipeline assets in NNG Financial; and NW Natural Renewables Holdings, LLC (NW Natural Renewables) and its non-regulated renewable natural gas activities . Other a lso includes corporate revenues and expenses that cannot be allocated to other operations, including certain business development activities . Segment Information Summary Inter-segment transactions were immaterial for the periods presented. The following table presents summary financial information concerning the reportable segment and other. Three Months Ended March 31, In thousands NGD Other NW Natural Other NW Holdings 2024 Operating revenues $ 417,864 $ 4,911 $ 422,775 $ 10,695 $ 433,470 Depreciation 30,830 277 31,107 1,991 33,098 Income (loss) from operations 107,973 2,658 110,631 (804) 109,827 Net income (loss) 65,715 1,843 67,558 (3,735) 63,823 Capital expenditures 71,494 543 72,037 10,180 82,217 Total assets at March 31, 2024 4,445,206 49,436 4,494,642 354,424 4,849,066 2023 Operating revenues $ 447,770 $ 6,743 $ 454,513 $ 7,910 $ 462,423 Depreciation 29,858 286 30,144 1,321 31,465 Income (loss) from operations 109,159 4,969 114,128 (620) 113,508 Net income (loss) 71,951 3,589 75,540 (3,869) 71,671 Capital expenditures 63,642 (44) 63,598 7,667 71,265 Total assets at March 31, 2023 4,246,245 54,390 4,300,635 291,461 4,592,096 Total assets at December 31, 2023 4,458,117 53,260 4,511,377 355,715 4,867,092 Natural Gas Distribution Margin NGD margin is the primary financial measure used by the Chief Operating Decision Maker (CODM) , consisting of NGD operating revenues, reduced by the associated cost of gas, environmental remediation expense, and revenue taxes. The cost of gas purchased for NGD customers is generally a pass-through cost in the amount of revenues billed to regulated NGD customers. Environmental remediation expense represents collections received from customers through environmental recovery mechanisms in Oregon and Washington as well as adjustments for the Oregon environmental earnings test when applicable. This is offset by environmental remediation expense presented in operating expenses. Revenue taxes are collected from NGD customers and remitted to taxing authorities. The collections from customers are offset by the expense recognition of the obligation to the taxing authority. By subtracting cost of gas, environmental remediation expense, and revenue taxes from NGD operating revenues, NGD margin provides a key metric used by the CODM in assessing the performance of the NGD segment. The following table presents additional segment information concerning NGD margin: Three Months Ended March 31, In thousands 2024 2023 NGD margin calculation: NGD distribution revenues $ 412,987 $ 443,061 Other regulated services 4,877 4,709 Total NGD operating revenues 417,864 447,770 Less: NGD cost of gas 175,773 205,805 Environmental remediation 5,746 5,375 Revenue taxes 18,195 18,975 NGD margin $ 218,150 $ 217,615

Equity

Equity	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Stockholders' Equity Note Disclosure	COMMON STOCK In August 2021, NW Holdings initiated an at-the-market (ATM) equity program by entering into an equity distribution agreement under which NW Holdings may issue and sell from time to time shares of common stock, no par value, having an aggregate gross sales price of up to $200 million. NW Holdings is under no obligation to offer and sell common stock under the ATM equity program, which expires in August 2024. Any shares of common stock offered under the ATM equity program are registered on NW Holdings’ universal shelf registration statement filed with the SEC. During the three months ended March 31, 2024, NW Holdings issued and sold 333,000 shares of common stock pursuant to the ATM equity program resulting in cash proceeds of $12.2 million, net of fees and commissions paid to agents of $0.2 million. As of March 31, 2024, NW Holdings had $31.0 million of equity available for issuance under the program. The ATM equity program was initiated to raise funds for general corporate purposes, including equity contributions to NW Holdings’ subsidiaries, NW Natural and NW Natural Water. Contributions to NW Natural and NW Natural Water will be used for general corporate purposes.

Revenue

Revenue	3 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer	REVENUE The following tables present disaggregated revenue: Three Months Ended March 31, In thousands NGD Other NW Natural Other NW Holdings 2024 Natural gas sales $ 410,839 $ — $ 410,839 $ — $ 410,839 Gas storage revenue, net — 3,005 3,005 — 3,005 Asset management revenue, net — 602 602 — 602 Appliance retail center revenue — 1,304 1,304 — 1,304 Other revenue 774 — 774 10,695 11,469 Revenue from contracts with customers 411,613 4,911 416,524 10,695 427,219 Alternative revenue 2,125 — 2,125 — 2,125 Leasing revenue 4,126 — 4,126 — 4,126 Total operating revenues $ 417,864 $ 4,911 $ 422,775 $ 10,695 $ 433,470 2023 Natural gas sales $ 451,394 $ — $ 451,394 $ — $ 451,394 Gas storage revenue, net — 2,799 2,799 — 2,799 Asset management revenue, net — 2,754 2,754 — 2,754 Appliance retail center revenue — 1,190 1,190 — 1,190 Other revenue 730 — 730 7,910 8,640 Revenue from contracts with customers 452,124 6,743 458,867 7,910 466,777 Alternative revenue (8,352) — (8,352) — (8,352) Leasing revenue 3,998 — 3,998 — 3,998 Total operating revenues $ 447,770 $ 6,743 $ 454,513 $ 7,910 $ 462,423 NW Natural's revenue represents substantially all of NW Holdings' revenue and is recognized for both registrants when the obligation to customers is satisfied and in the amount expected to be received in exchange for transferring goods or providing services. Revenue from contracts with customers contains one performance obligation that is generally satisfied over time, using the output method based on time elapsed, due to the continuous nature of the service provided. The transaction price is determined by a set price agreed upon in the contract or dependent on regulatory tariffs. Customer accounts are settled on a monthly basis or paid at time of sale and based on historical experience. It is probable that we will collect substantially all of the consideration to which we are entitled. We evaluated the probability of collection in accordance with the current expected credit losses standard. NW Holdings and NW Natural do not have any material contract assets, as net accounts receivable and accrued unbilled revenue balances are unconditional and only involve the passage of time until such balances are billed and collected. NW Holdings and NW Natural do not have any material contract liabilities. Revenue taxes are included in operating revenues with an equal and offsetting expense recognized in operating expenses in the consolidated statements of comprehensive income. Revenue-based taxes are primarily franchise taxes, which are collected from NGD customers and remitted to taxing authorities. Natural Gas Distribution Natural Gas Sales NW Natural's primary source of revenue is providing natural gas to customers in the NGD service territory, which includes residential, commercial, industrial and transportation customers. NGD revenue is generally recognized over time upon delivery of the gas commodity or service to the customer, and the amount of consideration received and recognized as revenue is dependent on the Oregon and Washington tariffs. Customer accounts are to be paid in full each month, and there is no right of return or warranty for services provided. Revenues include firm and interruptible sales and transportation services, franchise taxes recovered from the customer, late payment fees, service fees, and accruals for gas delivered but not yet billed (accrued unbilled revenue). The accrued unbilled revenue balance is based on estimates of deliveries during the period from the last meter reading and management judgment is required for a number of factors used in this calculation, including customer use and weather factors. We applied the significant financing practical expedient and have not adjusted the consideration NW Natural expects to receive from NGD customers for the effects of a significant financing component as all payment arrangements are settled annually. Due to the election of the right to invoice practical expedient, we do not disclose the value of unsatisfied performance obligations. Alternative Revenue Weather normalization (WARM) and decoupling mechanisms are considered to be alternative revenue programs. Alternative revenue programs are considered to be contracts between NW Natural and its regulator and are excluded from revenue from contracts with customers. Leasing Revenue Leasing revenue primarily consists of revenues from NW Natural's North Mist Storage contract with PGE in support of PGE's gas-fired electric power generation facilities under an initial 30-year contract with options to extend, totaling up to an additional 50 years upon mutual agreement of the parties. The facility is accounted for as a sales-type lease with regulatory accounting deferral treatment. The investment is included in rate base under an established cost-of-service tariff schedule, with revenues recognized according to the tariff schedule and as such, profit upon commencement was deferred and will be amortized over the lease term. Leasing revenue also contains rental revenue from small leases of property owned by NW Natural to third parties. The majority of these transactions are accounted for as operating leases and the revenue is recognized over the term of the lease agreement. Lease revenue is excluded from revenue from contracts with customers. See Note 7 for additional information. NW Natural Other Gas Storage Revenue NW Natural's other revenue includes gas storage activity, which includes Interstate Storage Services used to store natural gas for customers. Gas storage revenue is generally recognized over time as the gas storage service is provided to the customer and the amount of consideration received and recognized as revenue is dependent on set rates defined per the storage agreements. Noncash consideration in the form of dekatherms of natural gas is received as consideration for providing gas injection services to gas storage customers. This noncash consideration is measured at fair value using the average spot rate. Customer accounts are generally paid in full each month, and there is no right of return or warranty for services provided. Revenues include firm and interruptible storage services, net of the profit sharing amount refunded to NGD customers. Asset Management Revenue Revenues include the optimization of storage assets and pipeline capacity by a third-party and are provided net of the profit sharing amount refunded to NGD customers. Certain asset management revenues received are recognized over time using a straight-line approach over the term of each contract, and the amount of consideration received and recognized as revenue is dependent on a variable pricing model. Variable revenues earned above guaranteed amounts are estimated and recognized at the end of each period using the most likely amount approach. Additionally, other asset management revenues may be based on a fixed rate. Generally, asset management accounts are settled on a monthly basis. As of March 31, 2024, u nrecognized revenue for the fixed component of the transaction price related to gas storage and asset management revenue was approximately $77.2 million. Of this amount, approximately $15.9 million will be recognized during the remainder of 2024, $20.5 million in 2025, $16.1 million in 2026, $7.8 million in 2027, $3.9 million in 2028 and $13.0 million thereafter. The amounts presented here are calculated using current contracted rates. Appliance Retail Center Revenue NW Natural owns and operates an appliance store that is open to the public, where customers can purchase natural gas home appliances. Revenue from the sale of appliances is recognized at the point in time in which the appliance is transferred to the third party responsible for delivery and installation services and when the customer has legal title to the appliance. It is required that the sale be paid for in full prior to transfer of legal title. The amount of consideration received and recognized as revenue varies with changes in marketing incentives and discounts offered to customers. NW Holdings Other Water and Wastewater Services NW Holdings' primary source of other revenue is providing water and wastewater services to customers. Water and wastewater service revenue is generally recognized over time upon delivery of the water commodity or service to the customer, and the amount of consideration received and recognized as revenue is dependent on the tariffs established in the states we operate. Customer accounts are to be paid in full each month, bi-monthly, or quarterly, and there is no right of return or warranty for services provided. We applied the significant financing practical expedient and have not adjusted the consideration we expect to receive from water distribution and wastewater collection customers for the effects of a significant financing component as all payment arrangements are settled annually. Due to the election of the right to invoice practical expedient, we do not disclose the value of unsatisfied performance obligations.

Leases

Leases	3 Months Ended
	Mar. 31, 2024
Leases [Abstract]
Lessee, Operating Leases	LEASES Lease Revenue Leasing revenue primarily consists of NW Natural's North Mist natural gas storage agreement with PGE, which is billed under an OPUC-approved rate schedule and includes an initial 30-year term beginning May 2019 with options to extend, totaling up to an additional 50 years upon mutual agreement of the parties. Under U.S. GAAP, this agreement is classified as a sales-type lease and qualifies for regulatory accounting deferral treatment. The investment in the storage facility is included in rate base under a separately established cost-of-service tariff, with revenues recognized according to the tariff schedule. As such, the selling profit that was calculated upon commencement as part of the sale-type lease recognition was deferred and will be amortized over the lease term. Billing rates under the cost-of-service tariff will be updated annually to reflect current information including depreciable asset levels, forecasted operating expenses, and the results of regulatory proceedings, as applicable, and revenue received under this agreement is recognized as operating revenue on the consolidated statements of comprehensive income. There are no variable payments or residual value guarantees. The lease does not contain an option to purchase the underlying assets. NW Natural also maintains a sales-type lease for specialized compressor facilities to provide high pressure compressed natural gas (CNG) services. Lease payments are outlined in an OPUC-approved rate schedule over a 10-year term. There are no variable payments or residual value guarantees. The selling profit computed upon lease commencement was not significant. Our lessor portfolio also contains small leases of property owned by NW Natural and NW Holdings to third parties. These transactions are accounted for as operating leases and the revenue is recognized over the term of the lease agreement. The components of lease revenue at NW Natural were as follows: Three Months Ended March 31, In thousands 2024 2023 Lease revenue Operating leases $ 22 $ 19 Sales-type leases 4,104 3,979 Total lease revenue $ 4,126 $ 3,998 Additionally, lease revenue of $0.1 million and $0.2 million was recognized for the three months ended March 31, 2024 and 2023, respectively, related to operating leases associated with non-utility property rentals. Lease revenue related to these leases was presented in other income (expense), net on the consolidated statements of comprehensive income as it is non-operating income. Total future minimum lease payments to be received under non-cancelable leases at March 31, 2024 are as follows: In thousands Operating Sales-Type Total NW Natural: Remainder of 2024 $ 452 $ 11,900 $ 12,352 2025 599 15,306 15,905 2026 36 14,901 14,937 2027 22 14,521 14,543 2028 — 13,983 13,983 Thereafter — 208,218 208,218 Total minimum lease payments $ 1,109 278,829 $ 279,938 Less: imputed interest 151,120 Total leases receivable $ 127,709 Other (NW Holdings): Remainder of 2024 $ 39 $ — $ 39 2025 53 — 53 2026 56 — 56 2027 57 — 57 2028 58 — 58 Thereafter 800 — 800 Total minimum lease payments $ 1,063 $ — $ 1,063 NW Holdings: Remainder of 2024 $ 491 $ 11,900 $ 12,391 2025 652 15,306 15,958 2026 92 14,901 14,993 2027 79 14,521 14,600 2028 58 13,983 14,041 Thereafter 800 208,218 209,018 Total minimum lease payments $ 2,172 278,829 $ 281,001 Less: imputed interest 151,120 Total leases receivable $ 127,709 The total leases receivable above is reported under the NGD segment and the short- and long-term portions are included within other current assets and assets under sales-type leases on the consolidated balance sheets, respectively. The total amount of unguaranteed residual assets was $5.6 million, $5.2 million and $5.5 million at March 31, 2024 and 2023 and December 31, 2023, respectively, and is included in assets under sales-type leases on the consolidated balance sheets. Additionally, under regulatory accounting, the revenues and expenses associated with these agreements are presented on the consolidated statements of comprehensive income such that their presentation aligns with similar regulated activities at NW Natural. Lease Expense Operating Leases We have operating leases for land, buildings and equipment. Our primary lease is for NW Natural's headquarters and operations center. Our leases have remaining lease terms of 8 months to 16 years. Many of our lease agreements include options to extend the lease, which we do not include in our minimum lease terms unless they are reasonably certain to be exercised. Short-term leases with a term of 12 months or less are not recorded on the balance sheet. As most of our leases do not provide an implicit rate and are entered into by NW Natural, we use an estimated discount rate representing the rate we would have incurred to finance the funds necessary to purchase the leased asset and is based on information available at the lease commencement date in determining the present value of lease payments. The components of lease expense, a portion of which is capitalized, were as follows: Three Months Ended March 31, In thousands 2024 2023 NW Natural: Operating lease expense $ 1,862 $ 1,775 Short-term lease expense 81 80 Other (NW Holdings): Operating lease expense $ 45 $ 40 NW Holdings: Operating lease expense $ 1,907 $ 1,815 Short-term lease expense 81 80 Supplemental balance sheet information related to operating leases as of March 31, 2024 and 2023 and December 31, 2023 is as follows: In thousands March 31, December 31, 2024 2023 2023 NW Natural: Operating lease right of use asset $ 70,019 $ 72,077 $ 70,728 Operating lease liabilities - current liabilities $ 1,863 $ 1,538 $ 2,128 Operating lease liabilities - non-current liabilities 76,624 77,840 76,757 Total operating lease liabilities $ 78,487 $ 79,378 $ 78,885 Other (NW Holdings): Operating lease right of use asset $ 528 $ 622 $ 580 Operating lease liabilities - current liabilities $ 190 $ 162 $ 205 Operating lease liabilities - non-current liabilities 427 462 410 Total operating lease liabilities $ 617 $ 624 $ 615 NW Holdings: Operating lease right of use asset $ 70,547 $ 72,699 $ 71,308 Operating lease liabilities - current liabilities $ 2,053 $ 1,700 $ 2,333 Operating lease liabilities - non-current liabilities 77,051 78,302 77,167 Total operating lease liabilities $ 79,104 $ 80,002 $ 79,500 The weighted-average remaining lease terms and weighted-average discount rates for the operating leases at NW Natural were as follows: In thousands March 31, December 31, 2024 2023 2023 Weighted-average remaining lease term (years) 16.0 17.0 16.2 Weighted-average discount rate 7.3 % 7.3 % 7.3 % Headquarters and Operations Center Lease NW Natural commenced a 20-year operating lease agreement in March 2020 for a new headquarters and operations center in Portland, Oregon. There is an option to extend the term of the lease for two additional periods of seven years. There is a material timing difference between the minimum lease payments and expense recognition as calculated under operating lease accounting rules. OPUC issued an order allowing us to align our expense recognition with cash payments for ratemaking purposes. We recorded the difference between the minimum lease payments and the aggregate of the imputed interest on the finance lease obligation and amortization of the right-of-use asset as a deferred regulatory asset on our balance sheet. The balance of the regulatory asset was $8.3 million, $7.2 million and $8.0 million as of March 31, 2024 and 2023 and December 31, 2023, respectively. Maturities of operating lease liabilities at March 31, 2024 were as follows: In thousands NW Natural Other NW Holdings Remainder of 2024 $ 5,673 $ 138 $ 5,811 2025 7,362 176 7,538 2026 7,361 153 7,514 2027 7,538 107 7,645 2028 7,719 6 7,725 Thereafter 101,272 6 101,278 Total lease payments 136,925 586 137,511 Less: imputed interest 58,438 (31) 58,407 Total lease obligations 78,487 617 79,104 Less: current obligations 1,863 190 2,053 Long-term lease obligations $ 76,624 $ 427 $ 77,051 Supplemental cash flow information related to leases was as follows: Three Months Ended March 31, In thousands 2024 2023 NW Natural: Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,811 $ 1,767 Finance cash flows from finance leases 97 173 Right of use assets obtained in exchange for lease obligations Finance leases 97 173 Other (NW Holdings): Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 44 $ 39 Right of use assets obtained in exchange for lease obligations Finance leases — 90 NW Holdings: Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,855 $ 1,806 Finance cash flows from finance leases 97 173 Right of use assets obtained in exchange for lease obligations Finance leases 97 263 Finance Leases NW Natural also leases building storage spaces for use as a gas meter room in order to provide natural gas to multifamily or mixed use developments. These contracts are accounted for as finance leases and typically involve a one-time upfront payment with no remaining liability. The right of use assets for finance leases were $2.7 million, $2.4 million and $2.6 million at March 31, 2024 and 2023 and at December 31, 2023, respectively. As of March 31, 2024, there were no finance lease liabilities at NW Natural.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION Stock-based compensation plans are designed to promote stock ownership in NW Holdings by employees, including officers. These compensation plans include a Long Term Incentive Plan (LTIP) and an Employee Stock Purchase Plan (ESPP). For additional information on stock-based compensation plans, see Note 8 in the 2023 Form 10-K and the updates provided below. Long Term Incentive Plan Performance Shares LTIP performance shares incorporate a combination of market, performance, and service-based factors. During the three months ended March 31, 2024, the final performance factor under the 2022 LTIP was approved and 46,156 performance-based shares were granted under the 2022 LTIP for accounting purposes. As such, NW Natural and other subsidiaries began recognizing compensation expense. In February 2023 and 2024, LTIP shares were awarded to participants; however, the agreements allow for one of the performance factors to remain variable until the first quarter of the third year of the award period. As the performance factor will not be approved until the first quarters of 2025 and 2026, respectively, there is not a mutual understanding of the awards' key terms and conditions between NW Holdings and the participants as of March 31, 2024, and therefore, no expense was recognized for the 2023 and 2024 awards. NW Holdings will calculate the grant date fair value and NW Natural will recognize expense over the remaining service period for each award once the final performance factor has been approved. For the 2023 and 2024 LTIP awards, share payouts range from a threshold of 0% to a maximum of 200% based on achievement of pre-established goals. The performance criteria for the 2023 and 2024 performance shares consists of a three-year Return on Invested Capital (ROIC) threshold that must be satisfied and a cumulative EPS factor, which can be modified by a total shareholder return factor (TSR modifier) relative to the performance of peer group companies over the performance period of three years for each respective award. If the targets were achieved for the 2023 and 2024 awards, NW Holdings would grant for accounting purposes 50,542 and 73,150 shares in the first quarters of 2025 and 2026, respectively. As of March 31, 2024, there was $0.3 million of unrecognized compensation cost associated with the 2022 LTIP grant, which is expected to be recognized through 2024. Restricted Stock Units During the three months ended March 31, 2024, 57,704 RSUs were granted under the LTIP with a weighted-average grant date fair value of $38.87 per share. Generally, the RSUs awarded are forfeitable and include a performance-based threshold as well as a vesting period of four years from the grant date. The majority of our RSU grants obligate NW Holdings, upon vesting, to issue the RSU holder one share of common stock. The grant may also include a cash payment equal to the total amount of dividends paid per share between the grant date and vesting date of that portion of the RSU depending on the structure of the award agreement. The fair value of an RSU is equal to the closing market price of NW Holdings' common stock on the grant date. As of March 31, 2024, there was $4.2 million of unrecognized compensation cost from grants of RSUs, which is expected to be recognized over a period extending through 2028.

Debt

Debt	3 Months Ended
	Mar. 31, 2024
Debt Disclosure [Abstract]
Debt	DEBT Short-Term Debt At March 31, 2024, March 31, 2023 and December 31, 2023, short-term debt consisted of the following: March 31, 2024 March 31, 2023 December 31, 2023 In millions Balance Outstanding Weighted Average Interest Rate (1) Balance Outstanding Weighted Average Interest Rate (1) Balance Outstanding Weighted Average Interest Rate (1) NW Natural: Commercial paper $ 31.7 5.5 % $ — — % $ 16.8 5.5 % Other (NW Holdings): Credit agreement 63.0 6.3 % 72.5 5.9 % 73.0 6.4 % NW Holdings $ 94.7 $ 72.5 $ 89.8 (1) Weighted average interest rate on outstanding short-term debt Long-Term Debt At March 31, 2024, March 31, 2023 and December 31, 2023, NW Holdings' long-term debt consisted of the following: March 31, 2024 March 31, 2023 December 31, 2023 In millions Balance Outstanding Weighted Average Interest Rate (1) Balance Outstanding Weighted Average Interest Rate (1) Balance Outstanding Weighted Average Interest Rate (2) NW Natural first mortgage bonds $ 1,374.7 4.6 % $ 1,334.7 4.6 % $ 1,374.7 4.7 % NW Holdings unsecured senior bonds 150.0 5.8 % — — % — — % NW Holdings credit agreement — — % 100.0 5.4 % 100.0 5.5 % NWN Water credit agreement — — % 50.0 5.3 % 50.0 5.8 % NWN Water term loan 55.0 4.7 % 55.0 4.9 % 55.0 4.7 % Other long-term debt 6.5 6.0 6.6 Long-term debt, gross 1,586.2 1,545.7 1,586.3 Less: unamortized debt issuance costs 10.6 10.4 10.0 Less: current maturities 0.9 240.7 150.9 Total long-term debt $ 1,574.7 $ 1,294.6 $ 1,425.4 (1) Weighted average interest rate for the three months ended March 31, 2024 and March 31, 2023 (2) Weighted average interest rate for the year ended December 31, 2023 NW Natural's first mortgage bonds (FMBs) have maturity dates ranging from 2025 through 2053 and interest rates ranging from 2.82% to 7.85%. NW Holdings' unsecured senior bonds have maturity dates ranging from 2028 through 2029 and interest rates ranging from 5.78% to 5.84%. NWN Water's term loan is due in 2026. In March 2024, NW Holdings retired a $100.0 million credit agreement and NWN Water retired a $50.0 million credit agreement. No debt is scheduled to mature in the next twelve months as of March 31, 2024 at NW Natural. Issuance of Long-Term Debt In December 2023, NW Holdings entered into a Note Purchase Agreement between NW Holdings and the institutional investors named as purchasers therein. The Note Purchase Agreement provided for the issuance of (i) $100.0 million aggregate principal amount of NW Holdings’ 5.78% Senior Notes, Series A, due March 7, 2028 (5.78% Notes) and (ii) $50.0 million aggregate principal amount of NW Holdings’ 5.84% Senior Notes, Series B, due March 7, 2029 (5.84% Notes) in reliance on an exemption from registration under Section 4(a)(2) of the Securities Act of 1933, as amended. The 5.78% Notes and the 5.84% Notes were issued on March 7, 2024, pursuant to the Note Purchase Agreement. The proceeds from the Note Purchase Agreement were used to settle an existing term loan at NW Holdings for $100.0 million and make an equity contribution to NWN Water, which was used to settle an existing term loan for $50 million. Interest Rate Swap Agreements NW Holdings and NWN Water entered into interest rate swap agreements with major financial institutions that effectively converted variable-rate debt to a fixed rate. Interest payments made between the effective date and expiration date are hedged by the swap agreements. The notional amount, effective date, expiration date and benchmark rate of the swap agreements are shown in the table below: In millions Notional Amount Effective Date Expiration Date Fixed Rate NW Holdings $ 100.0 1/17/2023 3/15/2024 4.7 % NWN Water $ 55.0 1/19/2023 6/10/2026 3.8 % Fair Value of Long-Term Debt NW Holdings' and NW Natural's outstanding debt does not trade in active markets. The fair value of debt is estimated using the value of outstanding debt at natural gas distribution companies with similar credit ratings, terms, and remaining maturities to NW Holdings' and NW Natural's debt that actively trade in public markets. These valuations are based on Level 2 inputs as defined in the fair value hierarchy. See Note 2 in the 2023 Form 10-K for a description of the fair value hierarchy. The following table provides an estimate of the fair value of long-term debt, including current maturities of long-term debt, using market prices in effect on the valuation date: March 31, December 31, In thousands 2024 2023 2023 NW Natural: Gross long-term debt $ 1,374,700 $ 1,334,700 $ 1,374,700 Unamortized debt issuance costs (9,801) (10,278) (9,968) Carrying amount 1,364,899 1,324,422 1,364,732 Estimated fair value (1) 1,214,625 1,186,110 1,236,559 NW Holdings: Gross long-term debt $ 1,586,189 $ 1,545,730 $ 1,586,344 Unamortized debt issuance costs (10,585) (10,428) (10,044) Carrying amount 1,575,604 1,535,302 1,576,300 Estimated fair value (1) 1,425,765 1,395,321 1,447,941 (1) Estimated fair value does not include unamortized debt issuance costs.

Pension and Other Postretiremen

Pension and Other Postretirement Benefit Costs	3 Months Ended
	Mar. 31, 2024
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Pension and Other Postretirement Benefit Costs	PENSION AND OTHER POSTRETIREMENT BENEFIT COSTS NW Natural maintains a qualified non-contributory defined benefit pension plan (Pension Plan), non-qualified supplemental pension plans for eligible executive officers and other key employees, and other postretirement employee benefit plans. NW Natural also has a qualified defined contribution plan (Retirement K Savings Plan) for all eligible employees. The Pension Plan and Retirement K Savings Plan have plan assets, which are held in qualified trusts to fund retirement benefits. The service cost component of net periodic benefit cost for NW Natural pension and other postretirement benefit plans is recognized in operations and maintenance expense in the consolidated statements of comprehensive income. The other non-service cost components are recognized in other income (expense), net in the consolidated statements of comprehensive income. The following table provides the components of net periodic benefit cost (credit) for the pension and other postretirement benefit plans: Three Months Ended March 31, Pension Benefits Other In thousands 2024 2023 2024 2023 Service cost $ 980 $ 1,049 $ 25 $ 28 Interest cost 5,160 5,218 248 248 Expected return on plan assets (5,935) (6,661) — — Amortization of net actuarial loss 1,495 139 — — Net periodic benefit cost (credit) 1,700 (255) 273 276 Amount allocated to construction (425) (474) (8) (11) Net periodic benefit cost (credit) charged to expense 1,275 (729) 265 265 Amortization of regulatory balancing account 2,801 2,801 — — Net amount charged to expense $ 4,076 $ 2,072 $ 265 $ 265 Net periodic benefit costs are reduced by amounts capitalized to NGD plant. In addition, net periodic benefit costs were recorded to a regulatory balancing account as approved by the OPUC and amortized accordingly. The following table presents amounts recognized in accumulated other comprehensive loss (AOCL) and the changes in AOCL related to non-qualified employee benefit plans: Three Months Ended March 31, In thousands 2024 2023 Beginning balance $ (7,237) $ (6,414) Amounts reclassified to AOCL (183) — Amounts reclassified from AOCL: Amortization of actuarial losses 173 139 Total reclassifications before tax (10) 139 Tax benefit (112) (37) Total reclassifications for the period (122) 102 Ending balance $ (7,359) $ (6,312) Employer Contributions to Company-Sponsored Defined Benefit Pension Plans NW Natural made no cash contributions to its qualified defined benefit pension plans during the three months ended March 31, 2024 or 2023. During 2024, NW Natural expects to make cash contributions of approximately $20.6 million to the Pension Plan. Defined Contribution Plan NW Natural's Retirement K Savings Plan is a qualified defined contribution plan under Internal Revenue Code Sections 401(a) and 401(k). NW Natural contributions totaled $3.5 million and $3.4 million for the three months ended March 31, 2024 and 2023, respectively. See Note 10 in the 2023 Form 10-K for more information concerning these retirement and other postretirement benefit plans.

Income Tax

Income Tax	3 Months Ended
	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Income Tax	INCOME TAX An estimate of annual income tax expense is made each interim period using estimates for annual pre-tax income, regulatory flow-through adjustments, tax credits, and other items. The estimated annual effective tax rate is applied to year-to-date, pre-tax income to determine income tax expense for the interim period consistent with the annual estimate. Discrete events are recorded in the interim period in which they occur or become known. The effective income tax rate varied from the federal statutory rate due to the following: Three Months Ended March 31, NW Holdings NW Natural In thousands 2024 2023 2024 2023 Income tax at statutory rate (federal) $ 18,514 $ 20,332 $ 19,579 $ 21,412 State income tax 7,577 8,149 7,849 8,406 Increase (decrease): Differences required to be flowed-through by regulatory commissions (1,579) (2,909) (1,580) (2,909) Other, net (173) (425) (175) (487) Total provision for income taxes $ 24,339 $ 25,147 $ 25,673 $ 26,422 Effective income tax rate 27.6 % 26.0 % 27.5 % 25.9 % The NW Holdings and NW Natural effective income tax rates for the three months ended March 31, 2024 compared to the same period in 2023 changed primarily as a result of lower regulatory flow-through. The income tax benefit resulting from applying a lower U.S. corporate income tax rate to gas reserves investments, that originally occurred in 2017 as a result of the TCJA, was completely amortized to the benefit of customers in 2023. See Note 11 in the 2023 Form 10-K for more detail on income taxes and effective tax rates.

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment Disclosure [Text Block]	PROPERTY, PLANT, AND EQUIPMENT The following table sets forth the major classifications of property, plant, and equipment and accumulated depreciation: March 31, December 31, In thousands 2024 2023 2023 NW Natural: NGD plant in service $ 4,268,191 $ 4,026,183 $ 4,206,455 NGD construction work in progress 137,958 97,128 105,166 Less: Accumulated depreciation 1,177,007 1,131,256 1,159,367 NGD plant, net 3,229,142 2,992,055 3,152,254 Other plant in service 71,175 70,364 71,175 Other construction work in progress 11,607 6,624 10,963 Less: Accumulated depreciation 22,859 21,804 22,595 Other plant, net 59,923 55,184 59,543 Total property, plant, and equipment, net $ 3,289,065 $ 3,047,239 $ 3,211,797 Other (NW Holdings): Other plant in service $ 156,020 $ 97,286 $ 147,040 Other construction work in progress 15,153 22,891 15,810 Less: Accumulated depreciation 18,714 11,438 16,593 Other plant, net 152,459 108,739 146,257 NW Holdings: Total property, plant, and equipment, net $ 3,441,524 $ 3,155,978 $ 3,358,054 NW Natural: Capital expenditures in accrued liabilities $ 31,233 $ 17,255 $ 24,168 NW Holdings: Capital expenditures in accrued liabilities $ 32,494 $ 17,730 $ 27,879 NW Natural Other plant balances include non-utility gas storage assets at the Mist facility and other long-lived assets not related to NGD. NW Holdings Other plant balances include long-lived assets associated with water and wastewater operations and non-regulated activities not held by NW Natural or its subsidiaries.

Investments

Investments	3 Months Ended
	Mar. 31, 2024
Investments [Abstract]
Investments [Text Block]	INVESTMENTS Investments include gas reserves, financial investments in life insurance policies, and equity method investments. The following table summarizes other investments: NW Holdings NW Natural March 31, December 31, March 31, December 31, In thousands 2024 2023 2023 2024 2023 2023 Investments in life insurance policies $ 45,937 $ 47,666 $ 45,713 $ 45,937 $ 47,666 $ 45,713 Investments in gas reserves, non-current 20,406 22,229 20,893 20,406 22,229 20,893 Investment in unconsolidated affiliates 17,738 23,716 36,345 — 8,207 19,539 Total other investments $ 84,081 $ 93,611 $ 102,951 $ 66,343 $ 78,102 $ 86,145 Investment in Life Insurance Policies Other investments include financial investments in life insurance policies, which are accounted for at cash surrender value, net of policy loans. See Note 13 in the 2023 Form 10-K. NW Natural Gas Reserves NW Natural has invested $188 million through the gas reserves program in the Jonah Field located in Wyoming as of March 31, 2024. Gas reserves are stated at cost, net of regulatory amortization, with the associated deferred tax benefits of $3.8 million, $4.4 million, and $4.0 million, which are recorded as liabilities in the March 31, 2024, March 31, 2023, and December 31, 2023 consolidated balance sheets, respectively. NW Natural's investment is included in NW Holdings' and NW Natural's consolidated balance sheets under other current assets and other investments (non-current portion) with the maximum loss exposure limited to the investment balance. The amount of gas reserves included in other current assets was $2.2 million, $3.3 million, and $2.3 million as of March 31, 2024, March 31, 2023, and December 31, 2023, respectively. See Note 13 in the 2023 Form 10-K. Investments in Unconsolidated Affiliates In December 2021, NWN Water purchased a 37.3% ownership stake in Avion Water Company, Inc. (Avion Water), an investor-owned water utility for $14.5 million. NWN Water subsequently increased its ownership stake in Avion Water as follows: In millions Amount Ownership % July 2022 $ 1.0 40.3 % June 2023 $ 1.0 43.1 % January 2024 $ 1.0 45.6 % Avion Water operates in Bend, Oregon and the surrounding communities, serving approximately 15,000 customer connections and employing 35 people. The carrying value of the equity method investment is $9.8 million higher than the underlying equity in the net assets of the investee at March 31, 2024 due to equity method goodwill. NW Natural Water's share in the earnings (loss) of Avion Water is included in other income (expense), net. In 2020, NW Natural began a partnership with BioCarbN to invest in renewable natural gas (RNG) development facilities that are designed to access biogas derived from water treatment at Tyson Foods’ processing plants, subject to approval by all parties. In January 2022, commissioning of the first facility, Lexington Renewable Energy LLC (Lexington), was completed. In April 2023, commissioning of the second facility, Dakota City Renewable Energy LLC (Dakota City), was completed. NW Natural recorded the investment as an equity method investment. As of December 31, 2023, NW Natural had an investment balance in Lexington and Dakota City totaling $19.5 million . In January 2024, NW Natural replaced BioCarbN as manager of the Lexington and Dakota City companies. As a result, NW Natural determined that these investments no longer qualified as an equity method investment and were fully consolidated for the three months ended March 31, 2024 .

Business Combinations Business

Business Combinations Business Combinations	3 Months Ended
	Mar. 31, 2024
Business Combinations [Abstract]
Business Combination Disclosure	BUSINESS COMBINATIONS 2024 Business Combinations NWN Water did not acquire any businesses qualifying as business combinations during the three months ended March 31, 2024. 2023 Business Combinations During the year ended December 31, 2023 , NWN Water and its subsidiaries acquired the assets of five businesses qualifying as business combinations. The aggregate fair value of the preliminary consideration transferred for these acquisitions was $22.8 million, most of which was preliminarily allocated to property, plant and equipment and goodwill. These transactions align with NW Holdings' water and wastewater sector strategy as it continues to expand its service territories and included: • Pedersen Family, LLC in Washington • King Water Corporation in Washington • Rose Valley Water Company in Arizona • Hiland Water in Oregon • Truxton and Cerbat in Arizona As each of these acquisitions met the criteria of a business combination, a preliminary allocation of the consideration to the acquired net assets based on their estimated fair value as of the acquisition date was performed. The allocation for each of these business combinations is considered preliminary as of March 31, 2024, except for Pedersen Family, LLC. In accordance with U.S. GAAP, the fair value determination involves management judgment in determining the significant estimates and assumptions used and was made using existing regulatory conditions for net assets. These allocations are considered preliminary as of March 31, 2024, as facts and circumstances that existed as of the acquisition date may be discovered as we continue to integrate the acquired businesses. As a result, subsequent adjustments to the preliminary valuation of tangible assets, contract assets and liabilities, tax positions, and goodwill may be required. Subsequent adjustments are not expected to be significant, and any such adjustments are expected to be completed within the one-year measurement period for all acquisitions described above. Intangible Assets In connection with the acquisition of King Water Corporation, NWN Water recorded long-term customer relationship intangible assets totaling $2.6 million, which will be amortized over 24 years. There was $0.1 million of amortization expense recognized for the three months ended March 31, 2024. Projected amortization expense at NW Holdings for customer relationship intangible assets for each of the next five years is $0.1 million in each year. The amortization will change in future periods if other intangible assets are acquired, impairments are recognized or the preliminary valuations as part of our purchase price allocation is refined. Goodwill NW Holdings allocates goodwill to reporting units based on the expected benefit from the business combination. We perform an annual impairment assessment of goodwill at the reporting unit level, or more frequently if events and circumstances indicate that goodwill might be impaired. An impairment loss is recognized if the carrying value of a reporting unit’s goodwill exceeds its fair value. As a result of all acquisitions completed, total goodwill was $163.0 million, $149.8 million, and $163.3 million as of March 31, 2024, March 31, 2023, and December 31, 2023, respectively. All of our goodwill is related to water and wastewater acquisitions and is included in the other category for segment reporting purposes. The annual impairment assessment of goodwill occurs in the fourth quarter of each year. There have been no impairments recognized to date.

Derivative Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	DERIVATIVE INSTRUMENTS NW Natural NW Natural enters into financial derivative contracts to hedge a portion of the NGD segment's natural gas sales requirements. These contracts include swaps, options, and option combinations. These derivative financial instruments are primarily used to manage commodity price variability. A small portion of NW Natural's derivative hedging strategy involves hedging gas volumes and foreign currency forward contracts. The foreign currency forward contracts are used to hedge the fluctuation in foreign currency exchange rates for pipeline demand charges paid in Canadian dollars. In the normal course of business, NW Natural also enters into indexed-price physical forward natural gas commodity purchase contracts and options to meet the requirements of NGD customers. These contracts qualify for regulatory deferral accounting treatment. Notional Amounts The following table presents the absolute notional amounts related to open positions on NW Natural derivative instruments: March 31, December 31, In thousands 2024 2023 2023 Natural gas (in therms): Financial 690,905 681,850 948,425 Physical 374,350 295,382 571,610 Foreign exchange $ 10,457 $ 10,444 $ 11,926 Purchased Gas Adjustment (PGA) Rates and hedging approaches vary between states due to different rate structures and hedging mechanisms. Under the PGA mechanism in Oregon, derivatives entered into by NW Natural for the procurement or hedging of natural gas for future gas years generally receive regulatory deferral accounting treatment. In general, commodity hedging for the current gas year is completed prior to the start of the gas year, and hedge prices are fully recovered and reflected in the weighted-average cost of gas in the PGA filing. Hedge contracts entered into after the start of the PGA period for the current PGA year are subject to the PGA incentive sharing mechanism in Oregon. Under the PGA mechanism in Washington, NW Natural incorporates a risk-responsive hedging strategy, and receives full regulatory deferral accounting treatment for all of its hedges in Washington. NW Natural entered the 2023-24 gas year with forecasted sales volume hedged at approximately 82% in total, including 66% in financial hedges and 16% in physical gas supplies. The total hedged for Oregon was approximately 85%, including 69% in financial hedges and 16% in physical gas supplies. The total hedged for Washington was approximately 55%, including 42% in financial hedges and 13% in physical gas supplies. Unrealized and Realized Gain/Loss The following table reflects the income statement presentation for the unrealized gains and losses from NW Natural's derivative instruments: Three Months Ended March 31, 2024 2023 In thousands Natural gas commodity Foreign Exchange Natural gas commodity Foreign Exchange Benefit (expense) to cost of gas $ 37,964 $ (179) $ (61,321) $ 13 Operating revenues (expense) — — — — Amounts deferred to regulatory accounts on balance sheet (37,964) 179 61,321 (13) Total gain (loss) in pre-tax earnings $ — $ — $ — $ — Unrealized Gain/Loss Outstanding derivative instruments related to regulated NGD operations are deferred in accordance with regulatory accounting standards. The cost of foreign currency forward and natural gas derivative contracts are recognized immediately in the cost of gas; however, costs above or below the amount embedded in the current year PGA are subject to a regulatory deferral tariff and therefore, are recorded as a regulatory asset or liability. Realized Gain/Loss NW Natural realized net losses of $50.5 million and net gains of $172.4 million for the three months ended March 31, 2024 and 2023, respectively, from the settlement of natural gas financial derivative contracts. Realized gains and losses offset the higher or lower cost of gas purchased, resulting in no incremental amounts to collect or refund to customers. Credit Risk Management of Financial Derivatives Instruments No collateral was posted with or by NW Natural counterparties as of March 31, 2024 or 2023. NW Natural attempts to minimize the potential exposure to collateral calls by diversifying counterparties and using credit limits to manage liquidity risk. Counterparties generally allow a certain credit limit threshold before requiring NW Natural to post collateral against unrealized loss positions. Given NW Natural's credit ratings, counterparty credit limits and portfolio diversification, it was not subject to collateral calls in 2024 or 2023. The collateral call exposure is set forth under credit support agreements, which generally contain credit limits. NW Natural could also be subject to collateral call exposure where it has agreed to provide adequate assurance, which is not specific as to the amount of credit limit allowed but could potentially require additional collateral posting by NW Natural in the event of a material adverse change in NW Natural's ability to perform. NW Natural's financial derivative instruments are subject to master netting arrangements; however, they are presented on a gross basis in the consolidated balance sheets. NW Natural and its counterparties have the ability to set-off obligations to each other under specified circumstances. Such circumstances may include a defaulting party, a credit change due to a merger affecting either party, or any other termination event. If netted by its counterparties, NW Natural's physical and financial derivative position would result in an asset o f $4.1 million and a liability of $61.4 million as of March 31, 2024, an asset of $1.6 million and a liability of $51.5 million as of March 31, 2023, and an asset of $9.0 million and a liability of $124.2 million as of December 31, 2023. NW Natural is exposed to derivative credit and liquidity risk primarily through securing fixed-price natural gas commodity swaps and interest rate swaps with financial counterparties. NW Natural utilizes master netting arrangements with International Swaps and Derivatives Association (ISDA) contracts to minimize these risks including ISDA Credit Support Agreements with counterparties based on their credit ratings. Additionally, NW Natural uses counterparty, industry, sector and country diversification to minimize credit risk. In certain cases, NW Natural may require counterparties to post collateral, guarantees, or letters of credit to maintain its minimum credit requirement standards or for liquidity management purposes. See Note 15 in the 2023 Form 10-K for additional information. Fair Value In accordance with fair value accounting, NW Natural includes non-performance risk in calculating fair value adjustments. This includes a credit risk adjustment based on the credit spreads of NW Natural counterparties when in an unrealized gain position, or on NW Natural's own credit spread when it is in an unrealized loss position. The inputs in our valuation models include natural gas futures, volatility, credit default swap spreads and interest rates. Additionally, the assessment of non-performance risk is generally derived from the credit default swap market and from bond market credit spreads. The impact of the credit risk adjustment for all financial derivatives outstanding to the fair value calculation was $0.3 million, which decreased the liability at March 31, 2024. The net fair value was a liability of $57.3 million, a liability of $49.9 million, and a liability of $115.2 million as of March 31, 2024 and 2023, and December 31, 2023, respectively. No Level 3 inputs were used in our derivative valuations during the three months ended March 31, 2024, and 2023. See Note 2 in the 2023 Form 10-K. NW Holdings and NWN Water Interest Rate Swap Agreements NW Holdings and NWN Water entered into interest rate swap agreements with major financial institutions that effectively converted variable-rate debt to a fixed rate. Interest payments made between the effective date and expiration date are hedged by the swap agreements. The notional amount, effective date, expiration date and benchmark rate of the swap agreements are shown in the table below: In millions Notional Amount Effective Date Expiration Date Fixed Rate NW Holdings $ 100.0 1/17/2023 3/15/2024 4.7 % NWN Water $ 55.0 1/19/2023 6/10/2026 3.8 % Unrealized gains and losses related to these interest rate swap agreements are recorded in AOCI on the consolidated balance sheet and totaled $0.5 million and $0.2 million, net of tax, as of March 31, 2024 and December 31, 2023, respectively. The interest rate swap at NW Holdings expired March 15, 2024. Realized gains or losses occur as a result of monthly swap settlements. A gain of $0.4 million was reclassified from AOCI to net income during the three months ended March 31, 2024. The estimated amount of gains recorded in AOCI as of March 31, 2024 that are expected to be reclassified to net income within the next twelve months is $0.5 million.

Environmental Matters

Environmental Matters	3 Months Ended
	Mar. 31, 2024
Environmental Remediation Obligations [Abstract]
Environmental Matters	ENVIRONMENTAL MATTERS NW Natural owns, or previously owned, properties that may require environmental remediation or action. The range of loss for environmental liabilities is estimated based on current remediation technology, enacted laws and regulations, industry experience gained at similar sites, and an assessment of the probable level of involvement and financial condition of other potentially responsible parties (PRPs). When amounts are prudently expended related to site remediation of those sites described herein, NW Natural has recovery mechanisms in place to collect 96.7% of remediation costs allocable to Oregon customers and 3.3% of costs allocable to Washington customers. These sites are subject to the remediation process prescribed by the Environmental Protection Agency (EPA) and the Oregon Department of Environmental Quality (ODEQ). The process begins with a remedial investigation (RI) to determine the nature and extent of contamination and then a risk assessment (RA) to establish whether the contamination at the site poses unacceptable risks to humans and the environment. Next, a feasibility study (FS) or an engineering evaluation/cost analysis (EE/CA) evaluates various remedial alternatives. It is at this point in the process when NW Natural is able to estimate a range of remediation costs and record a reasonable potential remediation liability, or make an adjustment to the existing liability. From this study, the regulatory agency selects a remedy and issues a Record of Decision (ROD). After a ROD is issued, NW Natural would seek to negotiate a consent decree or consent judgment for designing and implementing the remedy. NW Natural would have the ability to further refine estimates of remediation liabilities based upon an approved remedial design. Remediation may include treatment of contaminated media such as sediment, soil and groundwater, removal and disposal of media, institutional controls such as legal restrictions on future property use, or natural recovery. Following construction of the remedy, the EPA and ODEQ also have requirements for ongoing maintenance, monitoring and other post-remediation care that may continue for many years. Where appropriate and reasonably known, NW Natural will provide for these costs in the remediation liabilities described below. Due to the numerous uncertainties surrounding the course of environmental remediation and the preliminary nature of several site investigations, in some cases, NW Natural may not be able to reasonably estimate the high end of the range of possible loss. In those cases, the nature of the possible loss has been disclosed, as has the fact that the high end of the range cannot be reasonably estimated where a range of potential loss is available. Unless there is an estimate within the range of possible losses that is more likely than other cost estimates within that range, NW Natural records the liability at the low end of this range. It is likely changes in these estimates and ranges will occur throughout the remediation process for each of these sites due to the continued evaluation and clarification concerning responsibility, the complexity of environmental laws and regulations and the determination by regulators of remediation alternatives. In addition to remediation costs, NW Natural could also be subject to Natural Resource Damages (NRD) claims. NW Natural will assess the likelihood and probability of each claim and recognize a liability if deemed appropriate. Refer to "Other Portland Harbor" below. Environmental Sites The following table summarizes information regarding liabilities related to environmental sites, which are recorded in other current liabilities and other noncurrent liabilities in NW Natural's balance sheet: Current Liabilities Non-Current Liabilities March 31, December 31, March 31, December 31, In thousands 2024 2023 2023 2024 2023 2023 Portland Harbor site: Gasco/Siltronic Sediments $ 9,989 $ 8,588 $ 12,428 $ 41,365 $ 42,766 $ 42,550 Other Portland Harbor 2,978 2,868 3,035 10,707 10,707 11,270 Gasco/Siltronic Upland site 13,875 13,275 16,304 33,307 34,519 34,235 Front Street site 546 456 687 513 939 939 Oregon Steel Mills — — — 179 179 179 Total $ 27,388 $ 25,187 $ 32,454 $ 86,071 $ 89,110 $ 89,173 Portland Harbor Site The Portland Harbor is an EPA listed Superfund site that is approximately 10 miles long on the Willamette River and is adjacent to NW Natural's Gasco uplands site. NW Natural is one of over one hundred PRPs, each jointly and severally liable, at the Superfund site. In January 2017, the EPA issued its Record of Decision, which selects the remedy for the clean-up of the Portland Harbor site (Portland Harbor ROD). The Portland Harbor ROD estimates the present value total cost at approximately $1.05 billion with an accuracy between -30% and +50% of actual costs. NW Natural's potential liability is a portion of the costs of the remedy for the entire Portland Harbor Superfund site. The cost of that remedy is expected to be allocated among more than one hundred PRPs. NW Natural is participating in a non-binding allocation process with other PRPs in an effort to resolve its potential liability. The Portland Harbor ROD does not provide any additional clarification around allocation of costs among PRPs; accordingly, NW Natural has not modified any of the recorded liabilities at this time as a result of the issuance of the Portland Harbor ROD. NW Natural manages its liability related to the Superfund site as two distinct projects: the Gasco Sediments Site and Other Portland Harbor projects. GASCO SEDIMENTS. In 2009, NW Natural and Siltronic Corporation entered into a separate Administrative Order on Consent with the EPA to evaluate and design specific remedies for sediments adjacent to the Gasco uplands and Siltronic uplands sites. NW Natural submitted a draft EE/CA to the EPA in May 2012 and the EE/CA estimated the cost of potential remedial alternatives for this site. In March 2020, NW Natural and the EPA amended the Administrative Order on Consent to include additional remedial design activities downstream of the Gasco sediments site and in the navigation channel. Siltronic Corporation is not a party to the amended order. NW Natural is completing pre-design studies and has submitted a draft Basis of Design Report. These preliminary design steps do not include a cost estimate for cleanup. No remedial design is more likely than the EE/CA alternatives at this time, and NW Natural expects further design discussion and iteration with the EPA. The estimated costs for the various sediment remedy alternatives in the draft EE/CA, for the additional studies and design work needed before the cleanup can occur, and for regulatory oversight throughout the cleanup range from $51.4 million to $350 million. NW Natural has recorded a liability of $51.4 million for the Gasco sediment clean-up, which reflects the low end of the range. At this time, we believe sediments at the Gasco sediments site represent the largest portion of NW Natural's liability related to the Portland Harbor site discussed above. In September 2023, the EPA approved the In Situ Stabilization and Solidification (ISS) Work Plan for the ISS field pilot study, which was successfully completed during the fall of 2023. Information obtained from the pilot study will be used to support remedial design of the Gasco sediments project. OTHER PORTLAND HARBOR. While we believe liabilities associated with the Gasco sediments site represent NW Natural's largest exposure, there are other potential exposures associated with the Portland Harbor ROD, including NRD costs and harborwide remedial design and cleanup costs (including downstream petroleum contamination), for which allocations among the PRPs have not yet been determined. NW Natural and other parties have signed a cooperative agreement with the Portland Harbor Natural Resource Trustee council to participate in a phased NRD assessment to estimate liabilities to support an early restoration-based settlement of NRD claims. One member of this Trustee council, the Yakama Nation, withdrew from the council in 2009, and in 2017, filed suit against NW Natural and 29 other parties seeking remedial costs and NRD assessment costs associated with the Portland Harbor site, set forth in the complaint. The complaint seeks recovery of alleged costs totaling $0.3 million in connection with the selection of a remedial action for the Portland Harbor site as well as declaratory judgment for unspecified future remedial action costs and for costs to assess the injury, loss or destruction of natural resources resulting from the release of hazardous substances at and from the Portland Harbor site. The Yakama Nation has filed two amended complaints addressing certain pleading defects and dismissing the State of Oregon. On the motion of NW Natural and certain other defendants, the federal court has stayed the case pending the outcome of the non-binding allocation proceeding discussed above. NW Natural has recorded a liability for NRD claims which is at the low end of the range of the potential liability; the high end of the range cannot be reasonably estimated at this time. The NRD liability is not included in the aforementioned range of costs provided in the Portland Harbor ROD. Gasco Uplands Site A predecessor of NW Natural, Portland Gas and Coke Company, owned a former gas manufacturing plant that was closed in 1958 (Gasco site) and is adjacent to the Portland Harbor site described above. The Gasco site has been under investigation by NW Natural for environmental contamination under the ODEQ Voluntary Cleanup Program (VCP). It is not included in the range of remedial costs for the Portland Harbor site noted above. The Gasco site is managed in two parts, the uplands portion and the groundwater source control action. NW Natural submitted a revised Remedial Investigation Report for the uplands to ODEQ in May 2007. In March 2015, ODEQ approved the Risk Assessment (RA) for this site, enabling commencement of work on the FS in 2016. A draft FS is currently anticipated to be submitted in 2025. NW Natural has recognized a liability for the remediation of the uplands portion of the site which is at the low end of the range of potential liability; the high end of the range cannot be reasonably estimated at this time. In October 2016, ODEQ and NW Natural agreed to amend their VCP agreement for the Gasco uplands to incorporate a portion of the Siltronic property formerly owned by Portland Gas & Coke between 1939 and 1960 into the Gasco RA and FS. Previously, NW Natural was conducting an investigation of manufactured gas plant constituents on the entire Siltronic uplands for ODEQ. Siltronic will be working with ODEQ directly on environmental impacts to the remainder of its property. In September 2013, NW Natural completed construction of a groundwater source control system, including a water treatment station, at the Gasco site. NW Natural has estimated the cost associated with the ongoing operation of the system and has recognized a liability which is at the low end of the range of potential cost. NW Natural cannot estimate the high end of the range at this time due to the uncertainty associated with the duration of running the water treatment station, which is highly dependent on the remedy determined for both the upland portion as well as the final remedy for the Gasco sediments site. Other Sites In addition to those sites above, NW Natural has environmental exposures at three other sites: Central Service Center, Front Street and Oregon Steel Mills. NW Natural may have exposure at other sites that have not been identified at this time. Due to the uncertainty of the design of remediation, regulation, timing of the remediation and in the case of the Oregon Steel Mills site, pending litigation, liabilities for each of these sites have been recognized at their respective low end of the range of potential liability; the high end of the range could not be reasonably estimated at this time. FRONT STREET SITE. The Front Street site was the former location of a gas manufacturing plant NW Natural operated (the former Portland Gas Manufacturing site, or PGM). At ODEQ’s request, NW Natural conducted a sediment and source control investigation and provided findings to ODEQ. In December 2015, an FS on the former Portland Gas Manufacturing site was completed. In July 2017, ODEQ issued the PGM ROD. The ROD specifies the selected remedy, which requires a combination of dredging, capping, treatment, and natural recovery. In addition, the selected remedy also requires institutional controls and long-term inspection and maintenance. Construction of the remedy began in July 2020 and was completed in October 2020. The second year of post-construction monitoring was completed in 2022 and demonstrated that the cap was intact and performing as designed. NW Natural has recognized an additional liability of $1.1 million associated with long-term monitoring and post-construction work. OREGON STEEL MILLS SITE. Refer to " Legal Proceedings" below. Environmental Cost Deferral and Recovery NW Natural has authorizations in Oregon and Washington to defer costs related to remediation of properties that are owned or were previously owned by NW Natural. In Oregon, a Site Remediation and Recovery Mechanism (SRRM) is currently in place to recover prudently incurred costs allocable to Oregon customers, subject to an earnings test. On October 21, 2019, the WUTC authorized an Environmental Cost Recovery Mechanism (ECRM) for recovery of prudently incurred costs allocable to Washington customers beginning November 1, 2019 . See Note 17 in the 2023 Form 10-K for a description of SRRM and ECRM collection processes. The following table presents information regarding the total regulatory asset deferred: March 31, December 31, In thousands 2024 2023 2023 Deferred costs and interest (1) $ 60,291 $ 47,651 $ 57,758 Accrued site liabilities (2) 113,426 114,253 121,575 Insurance proceeds and interest (51,389) (55,416) (50,764) Total regulatory asset deferral (1) 122,328 106,488 128,569 Current regulatory assets (3) 9,864 6,947 9,950 Long-term regulatory assets (3) 112,464 99,541 118,619 (1) Includes pre-review and post-review deferred costs, amounts currently in amortization, and interest, net of amounts collected from customers. (2) Excludes 3.3% of the Front Street site liability as the OPUC only allows recovery of 96.7% of costs for those sites allocable to Oregon, including those that historically served only Oregon customers. Amounts excluded from regulatory assets were $34 thousand at March 31, 2024, $45 thousand at March 31, 2023, and $53 thousand at December 31, 2023. (3) Environmental costs relate to specific sites approved for regulatory deferral by the OPUC and WUTC. In Oregon, NW Natural earns a carrying charge on cash amounts paid, whereas amounts accrued but not yet paid do not earn a carrying charge until expended. It also accrues a carrying charge on insurance proceeds for amounts owed to customers. In Washington, neither the cash paid for insurance proceeds received accrue a carrying charge. Current environmental costs represent remediation costs management expects to collect from customers in the next 12 months. Amounts included in this estimate are still subject to a prudence and earnings test review by the OPUC and do not include the $5.0 million tariff rider. The amounts allocable to Oregon are recoverable through NGD rates, subject to an earnings test. Environmental Earnings Test To the extent NW Natural earns at or below its authorized Return on Equity (ROE) as defined by the SRRM, remediation expenses and interest in excess of the $5.0 million tariff rider and $5.0 million insurance proceeds are recoverable through the SRRM. To the extent NW Natural earns more than its authorized ROE in a year, it is required to cover environmental expenses and interest on expenses greater than the $10.0 million with those earnings that exceed its authorized ROE. Legal Proceedings NW Holdings is not currently party to any direct claims or litigation, though in the future it may be subject to claims and litigation arising in the ordinary course of business. NW Natural is subject to claims and litigation arising in the ordinary course of business including the matters discussed above. Although the final outcome of any of these legal proceedings cannot be predicted with certainty, including the matter relating to the Oregon Steel Mills site referenced below, NW Natural and NW Holdings do not expect that the ultimate disposition of any of these matters will have a material effect on their financial condition, results of operations or cash flows. See also Part II, Item 1, “Legal Proceedings". Oregon Steel Mills Site See Note 17 in the 2023 Form 10-K. For additional information regarding other commitments and contingencies, see Note 16 in the 2023 Form 10-K.

Significant Accounting Polici_2

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Industry Regulation	Industry Regulation NW Holdings' principal business is to operate as a holding company for NW Natural and its other subsidiaries. NW Natural's principal business is the distribution of natural gas, which is regulated by the OPUC and WUTC. NW Natural also has natural gas storage services, which are regulated by the FERC, and to a certain extent by the OPUC and WUTC. Additionally, certain of NW Holdings' subsidiaries own water businesses, which are regulated by the public utility commission in the state in which the water utility is located, which is currently Oregon, Washington, Idaho, Texas and Arizona. Wastewater businesses, to the extent they are regulated, are generally regulated by the public utility commissions in the state in which the wastewater utility is located, which is currently Texas and Arizona. Accounting records and practices of the regulated businesses conform to the requirements and uniform system of accounts prescribed by these regulatory authorities in accordance with U.S. GAAP. The businesses in which customer rates are regulated have approved cost-based rates which are intended to allow such businesses to earn a reasonable return on invested capital. In applying regulatory accounting principles, NW Holdings and NW Natural capitalize or defer certain costs and revenues as regulatory assets and liabilities pursuant to orders of the applicable state public utility commission, which provide for the recovery of revenues or expenses from, or refunds to, utility customers in future periods, including a return or a carrying charge in certain cases.
New Accounting Standards	New Accounting Standards NW Natural and NW Holdings consider the applicability and impact of all accounting standards updates (ASUs) issued by the Financial Accounting Standards Board (FASB). ASUs not listed below were assessed and determined to be either not applicable or are expected to have minimal impact on consolidated financial position or results of operations. Recently Issued Accounting Pronouncements JOINT VENTURE FORMATIONS. In August 2023, the FASB issued ASU 2023-05, which requires a joint venture to initially measure all contributions received upon its formation at fair value. The standard is effective for all joint venture entities with a formation date on or after January 1, 2025, with early adoption permitted. The adoption of this standard is not anticipated to have a material impact on our results of operations, liquidity or capital resources. SEGMENT REPORTING. In November 2023, the FASB issued ASU 2023-07, which requires additional disclosures about significant segment expenses. The disclosures are required beginning with our annual report for the year ending December 31, 2024. The adoption of this standard is not anticipated to have a material impact on our results of operations, liquidity or capital resources. IMPROVEMENTS TO INCOME TAX DISCLOSURES. In December 2023, the FASB issued ASU 2023-09, which requires additional disclosures about income taxes. The disclosures are required beginning with our annual report for the year ending December 31, 2025. The adoption of this standard is not anticipated to have a material impact on our results of operations, liquidity or capital resources. Recent Securities and Exchange Commission (SEC) Final Rules

Significant Accounting Polici_3

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Schedule of Regulatory Assets	Amounts deferred as regulatory assets and liabilities for NW Holdings and NW Natural were as follows: Regulatory Assets March 31, December 31, In thousands 2024 2023 2023 NW Natural: Current: Unrealized loss on derivatives (1) $ 52,677 $ 44,370 $ 98,661 Gas costs 8,279 51,296 9,301 Environmental costs (2) 9,864 6,947 9,950 Decoupling (3) 958 — 2,288 Pension balancing (4) 7,131 7,131 7,131 Income taxes 2,208 2,208 2,208 Washington Climate Commitment Act compliance 19,761 — 20,537 COVID-19 deferrals and expenses, net 4,798 787 9,685 Other (5) 21,965 13,807 18,509 Total current - NW Natural 127,641 126,546 178,270 Other (NW Holdings) 25 — — Total current - NW Holdings $ 127,666 $ 126,546 $ 178,270 Non-current: Unrealized loss on derivatives (1) $ 12,744 $ 15,382 $ 28,055 Pension balancing (4) 25,016 30,613 27,460 Income taxes 9,930 10,540 10,731 Pension and other postretirement benefit liabilities 112,791 101,413 114,010 Environmental costs (2) 112,464 99,541 118,619 Gas costs 1,319 6,546 1,917 Decoupling (3) — — 1,017 Washington Climate Commitment Act compliance 4,223 6,312 — COVID-19 deferrals and expenses, net 1,128 12,815 1,080 Other (5) 29,452 28,232 30,529 Total non-current - NW Natural 309,067 311,394 333,418 Other (NW Holdings) 106 25 25 Total non-current - NW Holdings $ 309,173 $ 311,419 $ 333,443
Schedule of Regulatory Liabilities	Regulatory Liabilities March 31, December 31, In thousands 2024 2023 2023 NW Natural: Current: Gas costs $ 13,753 $ 5,670 $ 6,375 Unrealized gain on derivatives (1) 5,420 8,890 11,184 Decoupling (3) 10,137 12,606 7,612 Income taxes 4,726 5,143 4,726 Asset optimization revenue sharing 13,192 19,040 31,583 Washington Climate Commitment Act compliance 25,655 — 17,199 Other (5) 4,580 6,145 6,233 Total current - NW Natural 77,463 57,494 84,912 Other (NW Holdings) 196 29 50 Total current - NW Holdings $ 77,659 $ 57,523 $ 84,962 Non-current: Gas costs $ 5,555 $ 2,024 $ 8,556 Unrealized gain on derivatives (1) 2,700 1,432 373 Decoupling (3) 3,673 3,931 2,118 Income taxes (6) 165,719 170,289 169,485 Accrued asset removal costs (7) 503,539 474,764 496,235 Asset optimization revenue sharing — — 2,325 Other (5) 18,567 15,908 15,855 Total non-current - NW Natural 699,753 668,348 694,947 Other (NW Holdings) 950 980 949 Total non-current - NW Holdings $ 700,703 $ 669,328 $ 695,896 (1) Unrealized gains or losses on derivatives are non-cash items and therefore do not earn a rate of return or a carrying charge. These amounts are recoverable through NGD rates as part of the annual Purchased Gas Adjustment (PGA) mechanism when realized at settlement. (2) Refer to the Environmental Cost Deferral and Recovery table in Note 16 for a description of environmental costs. (3) This deferral represents the margin adjustment resulting from differences between actual and expected volumes. (4) Balance represents deferred net periodic benefit costs as approved by the OPUC. (5) Balances consist of deferrals and amortizations under approved regulatory mechanisms and typically earn a rate of return or carrying charge. (6) Balance represents excess deferred income tax benefits subject to regulatory flow-through. See Note 11. (7)
Schedule of Cash Flow, Supplemental Disclosures	The following table provides a reconciliation of the cash, cash equivalents and restricted cash balances at NW Holdings as of March 31, 2024 and 2023 and December 31, 2023: March 31, December 31, In thousands 2024 2023 2023 Cash and cash equivalents $ 72,375 $ 140,821 $ 32,920 Restricted cash included in other current assets 16,883 15,173 16,704 Cash, cash equivalents and restricted cash $ 89,258 $ 155,994 $ 49,624 The following table provides a reconciliation of the cash, cash equivalents and restricted cash balances at NW Natural as of March 31, 2024 and 2023 and December 31, 2023: March 31, December 31, In thousands 2024 2023 2023 Cash and cash equivalents $ 61,906 $ 129,731 $ 19,841 Restricted cash included in other current assets 16,858 15,173 16,679 Cash, cash equivalents and restricted cash $ 78,764 $ 144,904 $ 36,520
Accounts Receivable, Allowance for Credit Loss [Table Text Block]	The following table presents the activity related to the NW Holdings provision for uncollectible accounts by pool: As of As of December 31, 2023 Three Months Ended March 31, 2024 March 31, 2024 In thousands Beginning Balance Provision recorded, net of adjustments Write-offs recognized, net of recoveries Ending Balance Allowance for uncollectible accounts: Residential $ 2,397 $ 935 $ (192) $ 3,140 Commercial 501 93 (63) 531 Industrial 65 (9) — 56 Accrued unbilled and other 265 (31) (15) 219 Total NW Natural 3,228 988 (270) 3,946 Other - NW Holdings 227 8 — 235 Total NW Holdings $ 3,455 $ 996 $ (270) $ 4,181

Earnings Per Share_2

Earnings Per Share	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
EPS Calculation	NW Holdings' diluted earnings or loss per share are calculated as follows: Three Months Ended March 31, In thousands, except per share data 2024 2023 Net income $ 63,823 $ 71,671 Average common shares outstanding - basic 37,765 35,609 Additional shares for stock-based compensation plans (See Note 8) 31 99 Average common shares outstanding - diluted 37,796 35,708 Earnings per share of common stock: Basic $ 1.69 $ 2.01 Diluted 1.69 2.01 Additional information: Anti-dilutive shares 15 1

Segment Information_2

Segment Information	3 Months Ended
	Mar. 31, 2024
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The following table presents summary financial information concerning the reportable segment and other. Three Months Ended March 31, In thousands NGD Other NW Natural Other NW Holdings 2024 Operating revenues $ 417,864 $ 4,911 $ 422,775 $ 10,695 $ 433,470 Depreciation 30,830 277 31,107 1,991 33,098 Income (loss) from operations 107,973 2,658 110,631 (804) 109,827 Net income (loss) 65,715 1,843 67,558 (3,735) 63,823 Capital expenditures 71,494 543 72,037 10,180 82,217 Total assets at March 31, 2024 4,445,206 49,436 4,494,642 354,424 4,849,066 2023 Operating revenues $ 447,770 $ 6,743 $ 454,513 $ 7,910 $ 462,423 Depreciation 29,858 286 30,144 1,321 31,465 Income (loss) from operations 109,159 4,969 114,128 (620) 113,508 Net income (loss) 71,951 3,589 75,540 (3,869) 71,671 Capital expenditures 63,642 (44) 63,598 7,667 71,265 Total assets at March 31, 2023 4,246,245 54,390 4,300,635 291,461 4,592,096 Total assets at December 31, 2023 4,458,117 53,260 4,511,377 355,715 4,867,092
NGD Margin	The following table presents additional segment information concerning NGD margin: Three Months Ended March 31, In thousands 2024 2023 NGD margin calculation: NGD distribution revenues $ 412,987 $ 443,061 Other regulated services 4,877 4,709 Total NGD operating revenues 417,864 447,770 Less: NGD cost of gas 175,773 205,805 Environmental remediation 5,746 5,375 Revenue taxes 18,195 18,975 NGD margin $ 218,150 $ 217,615

Revenue_2

Revenue	3 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following tables present disaggregated revenue: Three Months Ended March 31, In thousands NGD Other NW Natural Other NW Holdings 2024 Natural gas sales $ 410,839 $ — $ 410,839 $ — $ 410,839 Gas storage revenue, net — 3,005 3,005 — 3,005 Asset management revenue, net — 602 602 — 602 Appliance retail center revenue — 1,304 1,304 — 1,304 Other revenue 774 — 774 10,695 11,469 Revenue from contracts with customers 411,613 4,911 416,524 10,695 427,219 Alternative revenue 2,125 — 2,125 — 2,125 Leasing revenue 4,126 — 4,126 — 4,126 Total operating revenues $ 417,864 $ 4,911 $ 422,775 $ 10,695 $ 433,470 2023 Natural gas sales $ 451,394 $ — $ 451,394 $ — $ 451,394 Gas storage revenue, net — 2,799 2,799 — 2,799 Asset management revenue, net — 2,754 2,754 — 2,754 Appliance retail center revenue — 1,190 1,190 — 1,190 Other revenue 730 — 730 7,910 8,640 Revenue from contracts with customers 452,124 6,743 458,867 7,910 466,777 Alternative revenue (8,352) — (8,352) — (8,352) Leasing revenue 3,998 — 3,998 — 3,998 Total operating revenues $ 447,770 $ 6,743 $ 454,513 $ 7,910 $ 462,423

Leases_2

Leases	3 Months Ended
	Mar. 31, 2024
Leases [Abstract]
Lease Revenue	The components of lease revenue at NW Natural were as follows: Three Months Ended March 31, In thousands 2024 2023 Lease revenue Operating leases $ 22 $ 19 Sales-type leases 4,104 3,979 Total lease revenue $ 4,126 $ 3,998
Lessor, Operating Lease, Payments to be Received, Maturity	Total future minimum lease payments to be received under non-cancelable leases at March 31, 2024 are as follows: In thousands Operating Sales-Type Total NW Natural: Remainder of 2024 $ 452 $ 11,900 $ 12,352 2025 599 15,306 15,905 2026 36 14,901 14,937 2027 22 14,521 14,543 2028 — 13,983 13,983 Thereafter — 208,218 208,218 Total minimum lease payments $ 1,109 278,829 $ 279,938 Less: imputed interest 151,120 Total leases receivable $ 127,709 Other (NW Holdings): Remainder of 2024 $ 39 $ — $ 39 2025 53 — 53 2026 56 — 56 2027 57 — 57 2028 58 — 58 Thereafter 800 — 800 Total minimum lease payments $ 1,063 $ — $ 1,063 NW Holdings: Remainder of 2024 $ 491 $ 11,900 $ 12,391 2025 652 15,306 15,958 2026 92 14,901 14,993 2027 79 14,521 14,600 2028 58 13,983 14,041 Thereafter 800 208,218 209,018 Total minimum lease payments $ 2,172 278,829 $ 281,001 Less: imputed interest 151,120 Total leases receivable $ 127,709
Lease Expense	The components of lease expense, a portion of which is capitalized, were as follows: Three Months Ended March 31, In thousands 2024 2023 NW Natural: Operating lease expense $ 1,862 $ 1,775 Short-term lease expense 81 80 Other (NW Holdings): Operating lease expense $ 45 $ 40 NW Holdings: Operating lease expense $ 1,907 $ 1,815 Short-term lease expense 81 80
Operating Lease, Lease Asset and Liabilities	Supplemental balance sheet information related to operating leases as of March 31, 2024 and 2023 and December 31, 2023 is as follows: In thousands March 31, December 31, 2024 2023 2023 NW Natural: Operating lease right of use asset $ 70,019 $ 72,077 $ 70,728 Operating lease liabilities - current liabilities $ 1,863 $ 1,538 $ 2,128 Operating lease liabilities - non-current liabilities 76,624 77,840 76,757 Total operating lease liabilities $ 78,487 $ 79,378 $ 78,885 Other (NW Holdings): Operating lease right of use asset $ 528 $ 622 $ 580 Operating lease liabilities - current liabilities $ 190 $ 162 $ 205 Operating lease liabilities - non-current liabilities 427 462 410 Total operating lease liabilities $ 617 $ 624 $ 615 NW Holdings: Operating lease right of use asset $ 70,547 $ 72,699 $ 71,308 Operating lease liabilities - current liabilities $ 2,053 $ 1,700 $ 2,333 Operating lease liabilities - non-current liabilities 77,051 78,302 77,167 Total operating lease liabilities $ 79,104 $ 80,002 $ 79,500
Operating Lease, Weighted Average Remaining Term and Discount Rates [Table Text Block]	The weighted-average remaining lease terms and weighted-average discount rates for the operating leases at NW Natural were as follows: In thousands March 31, December 31, 2024 2023 2023 Weighted-average remaining lease term (years) 16.0 17.0 16.2 Weighted-average discount rate 7.3 % 7.3 % 7.3 %
Lessee, Operating Lease, Liability, Maturity	Maturities of operating lease liabilities at March 31, 2024 were as follows: In thousands NW Natural Other NW Holdings Remainder of 2024 $ 5,673 $ 138 $ 5,811 2025 7,362 176 7,538 2026 7,361 153 7,514 2027 7,538 107 7,645 2028 7,719 6 7,725 Thereafter 101,272 6 101,278 Total lease payments 136,925 586 137,511 Less: imputed interest 58,438 (31) 58,407 Total lease obligations 78,487 617 79,104 Less: current obligations 1,863 190 2,053 Long-term lease obligations $ 76,624 $ 427 $ 77,051
Lessee, Leases, Supplemental Cash Flow Information	Supplemental cash flow information related to leases was as follows: Three Months Ended March 31, In thousands 2024 2023 NW Natural: Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,811 $ 1,767 Finance cash flows from finance leases 97 173 Right of use assets obtained in exchange for lease obligations Finance leases 97 173 Other (NW Holdings): Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 44 $ 39 Right of use assets obtained in exchange for lease obligations Finance leases — 90 NW Holdings: Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,855 $ 1,806 Finance cash flows from finance leases 97 173 Right of use assets obtained in exchange for lease obligations Finance leases 97 263

Debt_2

Debt	3 Months Ended
	Mar. 31, 2024
Debt Disclosure [Abstract]
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments	The following table provides an estimate of the fair value of long-term debt, including current maturities of long-term debt, using market prices in effect on the valuation date: March 31, December 31, In thousands 2024 2023 2023 NW Natural: Gross long-term debt $ 1,374,700 $ 1,334,700 $ 1,374,700 Unamortized debt issuance costs (9,801) (10,278) (9,968) Carrying amount 1,364,899 1,324,422 1,364,732 Estimated fair value (1) 1,214,625 1,186,110 1,236,559 NW Holdings: Gross long-term debt $ 1,586,189 $ 1,545,730 $ 1,586,344 Unamortized debt issuance costs (10,585) (10,428) (10,044) Carrying amount 1,575,604 1,535,302 1,576,300 Estimated fair value (1) 1,425,765 1,395,321 1,447,941 (1) Estimated fair value does not include unamortized debt issuance costs.

Pension and Other Postretirem_2

Pension and Other Postretirement Benefit Costs	3 Months Ended
	Mar. 31, 2024
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Schedule of Net Benefit Costs	The following table provides the components of net periodic benefit cost (credit) for the pension and other postretirement benefit plans: Three Months Ended March 31, Pension Benefits Other In thousands 2024 2023 2024 2023 Service cost $ 980 $ 1,049 $ 25 $ 28 Interest cost 5,160 5,218 248 248 Expected return on plan assets (5,935) (6,661) — — Amortization of net actuarial loss 1,495 139 — — Net periodic benefit cost (credit) 1,700 (255) 273 276 Amount allocated to construction (425) (474) (8) (11) Net periodic benefit cost (credit) charged to expense 1,275 (729) 265 265 Amortization of regulatory balancing account 2,801 2,801 — — Net amount charged to expense $ 4,076 $ 2,072 $ 265 $ 265
Schedule of Amounts Recognized in Other Comprehensive Income (Loss)	The following table presents amounts recognized in accumulated other comprehensive loss (AOCL) and the changes in AOCL related to non-qualified employee benefit plans: Three Months Ended March 31, In thousands 2024 2023 Beginning balance $ (7,237) $ (6,414) Amounts reclassified to AOCL (183) — Amounts reclassified from AOCL: Amortization of actuarial losses 173 139 Total reclassifications before tax (10) 139 Tax benefit (112) (37) Total reclassifications for the period (122) 102 Ending balance $ (7,359) $ (6,312)

Income Tax_2

Income Tax	3 Months Ended
	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The effective income tax rate varied from the federal statutory rate due to the following: Three Months Ended March 31, NW Holdings NW Natural In thousands 2024 2023 2024 2023 Income tax at statutory rate (federal) $ 18,514 $ 20,332 $ 19,579 $ 21,412 State income tax 7,577 8,149 7,849 8,406 Increase (decrease): Differences required to be flowed-through by regulatory commissions (1,579) (2,909) (1,580) (2,909) Other, net (173) (425) (175) (487) Total provision for income taxes $ 24,339 $ 25,147 $ 25,673 $ 26,422 Effective income tax rate 27.6 % 26.0 % 27.5 % 25.9 %

Property, Plant and Equipment_2

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Public Utility Property, Plant, and Equipment [Table Text Block]	The following table sets forth the major classifications of property, plant, and equipment and accumulated depreciation: March 31, December 31, In thousands 2024 2023 2023 NW Natural: NGD plant in service $ 4,268,191 $ 4,026,183 $ 4,206,455 NGD construction work in progress 137,958 97,128 105,166 Less: Accumulated depreciation 1,177,007 1,131,256 1,159,367 NGD plant, net 3,229,142 2,992,055 3,152,254 Other plant in service 71,175 70,364 71,175 Other construction work in progress 11,607 6,624 10,963 Less: Accumulated depreciation 22,859 21,804 22,595 Other plant, net 59,923 55,184 59,543 Total property, plant, and equipment, net $ 3,289,065 $ 3,047,239 $ 3,211,797 Other (NW Holdings): Other plant in service $ 156,020 $ 97,286 $ 147,040 Other construction work in progress 15,153 22,891 15,810 Less: Accumulated depreciation 18,714 11,438 16,593 Other plant, net 152,459 108,739 146,257 NW Holdings: Total property, plant, and equipment, net $ 3,441,524 $ 3,155,978 $ 3,358,054 NW Natural: Capital expenditures in accrued liabilities $ 31,233 $ 17,255 $ 24,168 NW Holdings: Capital expenditures in accrued liabilities $ 32,494 $ 17,730 $ 27,879 NW Natural Other plant balances include non-utility gas storage assets at the Mist facility and other long-lived assets not related to NGD. NW Holdings Other plant balances include long-lived assets associated with water and wastewater operations and non-regulated activities not held by NW Natural or its subsidiaries.

Investments_2

Investments	3 Months Ended
	Mar. 31, 2024
Investments [Abstract]
Investment [Table Text Block]	Investments include gas reserves, financial investments in life insurance policies, and equity method investments. The following table summarizes other investments: NW Holdings NW Natural March 31, December 31, March 31, December 31, In thousands 2024 2023 2023 2024 2023 2023 Investments in life insurance policies $ 45,937 $ 47,666 $ 45,713 $ 45,937 $ 47,666 $ 45,713 Investments in gas reserves, non-current 20,406 22,229 20,893 20,406 22,229 20,893 Investment in unconsolidated affiliates 17,738 23,716 36,345 — 8,207 19,539 Total other investments $ 84,081 $ 93,611 $ 102,951 $ 66,343 $ 78,102 $ 86,145

Derivative Instruments_2

Derivative Instruments	3 Months Ended
	Mar. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions	The following table presents the absolute notional amounts related to open positions on NW Natural derivative instruments: March 31, December 31, In thousands 2024 2023 2023 Natural gas (in therms): Financial 690,905 681,850 948,425 Physical 374,350 295,382 571,610 Foreign exchange $ 10,457 $ 10,444 $ 11,926
Income Statement Presentation of Derivative Instruments	The following table reflects the income statement presentation for the unrealized gains and losses from NW Natural's derivative instruments: Three Months Ended March 31, 2024 2023 In thousands Natural gas commodity Foreign Exchange Natural gas commodity Foreign Exchange Benefit (expense) to cost of gas $ 37,964 $ (179) $ (61,321) $ 13 Operating revenues (expense) — — — — Amounts deferred to regulatory accounts on balance sheet (37,964) 179 61,321 (13) Total gain (loss) in pre-tax earnings $ — $ — $ — $ —

Environmental Matters_2

Environmental Matters	3 Months Ended
	Mar. 31, 2024
Environmental Remediation Obligations [Abstract]
Schedule of Environmental Loss Contingencies by Site	The following table summarizes information regarding liabilities related to environmental sites, which are recorded in other current liabilities and other noncurrent liabilities in NW Natural's balance sheet: Current Liabilities Non-Current Liabilities March 31, December 31, March 31, December 31, In thousands 2024 2023 2023 2024 2023 2023 Portland Harbor site: Gasco/Siltronic Sediments $ 9,989 $ 8,588 $ 12,428 $ 41,365 $ 42,766 $ 42,550 Other Portland Harbor 2,978 2,868 3,035 10,707 10,707 11,270 Gasco/Siltronic Upland site 13,875 13,275 16,304 33,307 34,519 34,235 Front Street site 546 456 687 513 939 939 Oregon Steel Mills — — — 179 179 179 Total $ 27,388 $ 25,187 $ 32,454 $ 86,071 $ 89,110 $ 89,173
Environmental Regulatory Table	The following table presents information regarding the total regulatory asset deferred: March 31, December 31, In thousands 2024 2023 2023 Deferred costs and interest (1) $ 60,291 $ 47,651 $ 57,758 Accrued site liabilities (2) 113,426 114,253 121,575 Insurance proceeds and interest (51,389) (55,416) (50,764) Total regulatory asset deferral (1) 122,328 106,488 128,569 Current regulatory assets (3) 9,864 6,947 9,950 Long-term regulatory assets (3) 112,464 99,541 118,619 (1) Includes pre-review and post-review deferred costs, amounts currently in amortization, and interest, net of amounts collected from customers. (2) Excludes 3.3% of the Front Street site liability as the OPUC only allows recovery of 96.7% of costs for those sites allocable to Oregon, including those that historically served only Oregon customers. Amounts excluded from regulatory assets were $34 thousand at March 31, 2024, $45 thousand at March 31, 2023, and $53 thousand at December 31, 2023. (3) Environmental costs relate to specific sites approved for regulatory deferral by the OPUC and WUTC. In Oregon, NW Natural earns a carrying charge on cash amounts paid, whereas amounts accrued but not yet paid do not earn a carrying charge until expended. It also accrues a carrying charge on insurance proceeds for amounts owed to customers. In Washington, neither the cash paid for insurance proceeds received accrue a carrying charge. Current environmental costs represent remediation costs management expects to collect from customers in the next 12 months. Amounts included in this estimate are still subject to a prudence and earnings test review by the OPUC and do not include the $5.0 million tariff rider. The amounts allocable to Oregon are recoverable through NGD rates, subject to an earnings test.

Significant Accounting Polici_4

Significant Accounting Policies - Regulatory Asset Disclosure - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 127,666	$ 178,270	$ 126,546
Regulatory Assets, Noncurrent	$ 309,173	333,443	311,419
Inactive Account, Period Outstanding Prior to Write-Off	120 days
General Payment Term of NGD Receivables	15 days
Age of Closed or Inactive Accounts	120 days
Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 25	0	0
Regulatory Assets, Noncurrent	106	25	25
Northwest Natural Gas Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	127,641	178,270	126,546
Regulatory Assets, Noncurrent	309,067	333,418	311,394
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	52,677	98,661	44,370
Regulatory Assets, Noncurrent	12,744	28,055	15,382
Northwest Natural Gas Company [Member] | Pension balancing [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	7,131	7,131	7,131
Regulatory Assets, Noncurrent	25,016	27,460	30,613
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,208	2,208	2,208
Regulatory Assets, Noncurrent	9,930	10,731	10,540
Northwest Natural Gas Company [Member] | Pension and other postretirement benefit liabilities [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	112,791	114,010	101,413
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	9,864	9,950	6,947
Regulatory Assets, Noncurrent	112,464	118,619	99,541
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	8,279	9,301	51,296
Regulatory Assets, Noncurrent	1,319	1,917	6,546
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	958	2,288	0
Regulatory Assets, Noncurrent	0	1,017	0
Northwest Natural Gas Company [Member] | Washington Climate Commitment Act compliance
Regulatory Assets [Line Items]
Regulatory Assets, Current	19,761	20,537	0
Regulatory Assets, Noncurrent	4,223	0	6,312
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Current	21,965	18,509	13,807
Regulatory Assets, Noncurrent	29,452	30,529	28,232
Northwest Natural Gas Company [Member] | COVID-19 Related Costs
Regulatory Assets [Line Items]
Regulatory Assets, Current	4,798	9,685	787
Regulatory Assets, Noncurrent	$ 1,128	$ 1,080	$ 12,815

Significant Accounting Polici_5

Significant Accounting Policies - Regulatory Liability Disclosure - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	$ 77,659	$ 84,962	$ 57,523
Regulatory Liability, Noncurrent	700,703	695,896	669,328
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	196	50	29
Regulatory Liability, Noncurrent	950	949	980
Northwest Natural Gas Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	77,463	84,912	57,494
Regulatory Liability, Noncurrent	699,753	694,947	668,348
Northwest Natural Gas Company [Member] | Gas costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	13,753	6,375	5,670
Regulatory Liability, Noncurrent	5,555	8,556	2,024
Northwest Natural Gas Company [Member] | Deferred Derivative Gain (Loss) [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	5,420	11,184	8,890
Regulatory Liability, Noncurrent	2,700	373	1,432
Northwest Natural Gas Company [Member] | Decoupling [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	10,137	7,612	12,606
Regulatory Liability, Noncurrent	3,673	2,118	3,931
Northwest Natural Gas Company [Member] | Income taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	4,726	4,726	5,143
Regulatory Liability, Noncurrent	165,719	169,485	170,289
Northwest Natural Gas Company [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	4,580	6,233	6,145
Regulatory Liability, Noncurrent	18,567	15,855	15,908
Northwest Natural Gas Company [Member] | Accrued asset removal costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	503,539	496,235	474,764
Northwest Natural Gas Company [Member] | Asset Optimization Revenue Sharing
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	13,192	31,583	19,040
Regulatory Liability, Noncurrent	0	2,325	0
Northwest Natural Gas Company [Member] | Washington Climate Commitment Act compliance
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	25,655	$ 17,199	$ 0
Regulatory Liability	$ 18,600

Supplemental Cash Flow

Supplemental Cash Flow - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 72,375	$ 32,920	$ 140,821
Restricted Cash	16,883	16,704	15,173
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	89,258	49,624	155,994	$ 40,964
Money Market Funds, at Carrying Value	48,800		112,600
Northwest Natural Gas Company [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	61,906	19,841	129,731
Restricted Cash	16,858	16,679	15,173
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	78,764	$ 36,520	144,904	$ 24,671
Money Market Funds, at Carrying Value	$ 48,800		$ 107,600

Significant Accounting Polici_6

Significant Accounting Policies - Credit Losses - ASU 2016-13 $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) numberOfLeases	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Number of Net Investments in Sales-Type Leases | numberOfLeases	2
Sales-type Lease, Net Investment in Lease, Allowance for Credit Loss	$ 0
Regulatory Assets, Noncurrent	309,173	$ 333,443	$ 311,419
Other Northwest Holdings [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	235	227
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	8
Accounts Receivable, Allowance for Credit Loss, Recovery	0
Northwest Holdings [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	4,181	3,455
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	996
Accounts Receivable, Allowance for Credit Loss, Recovery	(270)
Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	3,946	3,228
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	988
Accounts Receivable, Allowance for Credit Loss, Recovery	(270)
Regulatory Assets, Noncurrent	309,067	333,418	$ 311,394
Residential [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	3,140	2,397
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	935
Accounts Receivable, Allowance for Credit Loss, Recovery	(192)
Commercial [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	531	501
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	93
Accounts Receivable, Allowance for Credit Loss, Recovery	(63)
Industrial [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	56	65
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	(9)
Accounts Receivable, Allowance for Credit Loss, Recovery	0
Accrued unbilled and other [Member] | Northwest Natural Gas Company [Member]
Accounts Receivable, Noncurrent, Credit Quality Indicator [Line Items]
Accounts Receivable, Allowance for Credit Loss	219	$ 265
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	(31)
Accounts Receivable, Allowance for Credit Loss, Recovery	$ (15)

Greenhouse Gas Allowances

Greenhouse Gas Allowances $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
CCI Deferred Costs	$ 24,000
Washington Climate Commitment Act Allowances
Proceeds from Other Operating Activities	18,600
WASHINGTON
CCI Credits Liability	24,000
Inventory, Emissions Allowances	$ 39,500

Earnings Per Share_2_3

Earnings Per Share - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Earnings Per Share [Abstract]
Net income	$ 63,823	$ 71,671
Average common shares outstanding:
Average common shares outstanding - basic (in shares)	37,765	35,609
Additional shares for stock-based compensation plans	31	99
Average common shares outstanding - diluted (in shares)	37,796	35,708
Earnings (loss) per share of common stock
Basic (in dollars per share)	$ 1.69	$ 2.01
Diluted (in dollars per share)	$ 1.69	$ 2.01
Antidilutive shares	15	1

Segment Information - Narrative

Segment Information - Narrative	3 Months Ended
	Mar. 31, 2024
Operating Segments [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments	1
Oregon [Member] | Northwest Holdings and Northwest Natural [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Percent Of Pre Tax Income From Gas Storage Retained When The Costs Of The Capacity Are Not In Utility Rates	80%
Percent Of Pre Tax Income From Gas Storage Retained When The Costs Of The Capacity Are In Utility Rates	10%
Percent Of Pre Tax Income From Gas Storage Credited To Deferred Regulatory Account	20%
Percent Of Pre Tax Income From Gas Storage Credited To Deferred Regulatory Account When In Rates	90%

Segment Information - Schedule

Segment Information - Schedule of Summarized Financial Information by Segment - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Operating revenues	$ 433,470	$ 462,423
Depreciation	33,098	31,465
Income from operations	109,827	113,508
Total assets	4,849,066	4,592,096	$ 4,867,092
Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	417,864	447,770
Depreciation	30,830	29,858
Income from operations	107,973	109,159
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	65,715	71,951
Segment, Expenditure, Addition to Long-Lived Assets	71,494	63,642
Total assets	4,445,206	4,246,245	4,458,117
Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,911	6,743
Depreciation	277	286
Income from operations	2,658	4,969
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	1,843	3,589
Segment, Expenditure, Addition to Long-Lived Assets	543	(44)
Total assets	49,436	54,390	53,260
Northwest Natural Gas Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	422,775	454,513
Depreciation	31,107	30,144
Income from operations	110,631	114,128
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	67,558	75,540
Segment, Expenditure, Addition to Long-Lived Assets	72,037	63,598
Total assets	4,494,642	4,300,635	4,511,377
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	10,695	7,910
Depreciation	1,991	1,321
Income from operations	(804)	(620)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(3,735)	(3,869)
Segment, Expenditure, Addition to Long-Lived Assets	10,180	7,667
Total assets	354,424	291,461	355,715
Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	422,775	454,513
Depreciation	31,107	30,144
Income from operations	110,631	114,128
Total assets	4,494,642	4,300,635	4,511,377
Northwest Natural Gas Company [Member] | Natural Gas Distribution [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	417,864	447,770
Northwest Natural Gas Company [Member] | Other Northwest Natural [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,911	6,743
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	422,775	454,513
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating revenues	433,470	462,423
Depreciation	33,098	31,465
Income from operations	109,827	113,508
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	63,823	71,671
Segment, Expenditure, Addition to Long-Lived Assets	82,217	71,265
Total assets	$ 4,849,066	$ 4,592,096	$ 4,867,092

Segment Information - Additiona

Segment Information - Additional Segment Information - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Segment Reporting Information [Line Items]
Operating revenues	$ 433,470	$ 462,423
Cost of gas	175,717	205,749
Environmental remediation	5,746	5,375
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Natural Gas Distribution revenues	412,987	443,061
Other regulated services	4,877	4,709
Operating revenues	417,864	447,770
Cost of gas	175,773	205,805
Environmental remediation	5,746	5,375
Revenue taxes	18,195	18,975
NGD margin	$ 218,150	$ 217,615

Equity - Narrative

Equity - Narrative - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2021
Class of Stock [Line Items]
Par Value (in dollars per share)	$ 0	$ 0	$ 0
Shares issued (in shares)	38,027,266	35,929,228	37,631,212
Proceeds from common stock issued, net	$ 12,218	$ 16,669
Avion Water | Other Northwest Holdings [Member]
Class of Stock [Line Items]
Investment balance in Avion				$ 14,500
ATM Equity Program
Class of Stock [Line Items]
Par Value (in dollars per share)	$ 0
Sale of Stock, Consideration Received on Transaction	$ 12,200
Sale of Stock, Commissions and Fees Paid	$ 200
Stock Issued During Period, Shares, New Issues	333,000
nwn:AttheMarketEquityProgramEquityAvailableforIssuance	$ 31,000
Maximum [Member] | Scenario, Plan | ATM Equity Program
Class of Stock [Line Items]
Cumulative Proceeds Received on All Transactions	$ 200,000

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 427,219	$ 466,777
Revenues	433,470	462,423
Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	410,839	451,394
Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,005	2,799
Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	602	2,754
Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,304	1,190
Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	11,469	8,640
Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,125	(8,352)
Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	4,126	3,998
Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenues	422,775	454,513
Operating leases	22	19
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	416,524	458,867
Revenues	422,775	454,513
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	410,839	451,394
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,005	2,799
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	602	2,754
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,304	1,190
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	774	730
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,125	(8,352)
Northwest Natural Gas Company [Member] | Northwest Natural Gas Company [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	4,126	3,998
Operating Segments [Member] | Natural Gas Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenues	417,864	447,770
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	411,613	452,124
Revenues	417,864	447,770
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	410,839	451,394
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	774	730
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,125	(8,352)
Operating Segments [Member] | Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	4,126	3,998
Operating Segments [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenues	422,775	454,513
Corporate, Non-Segment [Member] | Other Northwest Natural [Member]
Disaggregation of Revenue [Line Items]
Revenues	4,911	6,743
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,911	6,743
Revenues	4,911	6,743
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,005	2,799
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	602	2,754
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,304	1,190
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	0	0
Corporate, Non-Segment [Member] | Other Northwest Natural [Member] | Northwest Natural Gas Company [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	10,695	7,910
Revenues	10,695	7,910
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Natural Gas Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Gas Storage Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Asset Management Revenue, Net of Regulatory Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Appliance Center Revenue [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Other revenue [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	10,695	7,910
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Alternative revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	0	0
Corporate, Non-Segment [Member] | Other Northwest Holdings [Member] | Leasing revenue [Member]
Disaggregation of Revenue [Line Items]
Operating leases	$ 0	$ 0

Revenue - Revenue, Remaining Pe

Revenue - Revenue, Remaining Performance Obligation $ in Thousands	Mar. 31, 2024 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Lessor, Sales-type Lease, Term of Contract	30 years
Lessor, Sales-type Lease, Renewal Term	50 years
Revenue, Remaining Performance Obligation, Amount	$ 77,200
Natural Gas Distribution [Member] | Northwest Natural Gas Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract with Customer, Refund Liability	0
Other Northwest Natural [Member] | Northwest Natural Gas Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract with Customer, Refund Liability	0
Other Northwest Holdings [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract with Customer, Refund Liability	$ 0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	9 months
Revenue, Remaining Performance Obligation, Amount	$ 15,900
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	1 year
Revenue, Remaining Performance Obligation, Amount	$ 20,500
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	1 year
Revenue, Remaining Performance Obligation, Amount	$ 16,100
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	1 year
Revenue, Remaining Performance Obligation, Amount	$ 7,800
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2028-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	1 year
Revenue, Remaining Performance Obligation, Amount	$ 3,900
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2029-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Year	0 years
Revenue, Remaining Performance Obligation, Amount	$ 13,000

Leases - Lease Revenue

Leases - Lease Revenue - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Lessor, Lease, Description [Line Items]
Lessor, Sales-type Lease, Renewal Term	50 years
Lessor, Sales-type Lease, Term of Contract	30 years
Residual Value of Leased Asset	$ 5,600	$ 5,200	$ 5,500
Lease Revenue [Abstract]
Total lease revenue	100	200
Operating Leases Payment to be Received [Abstract]
Operating Lease, Payments to be Received, Remainder of Fiscal Year	491
Lessor, Operating Lease, Payment to be Received, Year One	652
Operating Lease, Payments to be Received, Two Years	92
Operating Lease, Payments to be Received, Three Years	79
Operating Lease, Payments to be Received, Four Years	58
Operating Lease, Payments to be Received, Thereafter	800
Total minimum lease payments	2,172
Total Lease Payments to be Received [Abstract]
Lease Payments to be Received, Remainder of Fiscal Year	12,391
Lease Payments to be Received, Two Years	15,958
Lease Payments to be Received, Three Years	14,993
Lease Payments to be Received, Four Years	14,600
Lease Payments to be Received, Five Years	14,041
Lease Payments to be Received, Thereafter	209,018
Total minimum lease payments	281,001
Northwest Natural Gas Company [Member]
Lease Revenue [Abstract]
Operating leases	22	19
Sales-type leases	4,104	3,979
Total lease revenue	4,126	$ 3,998
Operating Leases Payment to be Received [Abstract]
Operating Lease, Payments to be Received, Remainder of Fiscal Year	452
Lessor, Operating Lease, Payment to be Received, Year One	599
Operating Lease, Payments to be Received, Two Years	36
Operating Lease, Payments to be Received, Three Years	22
Operating Lease, Payments to be Received, Four Years	0
Operating Lease, Payments to be Received, Thereafter	0
Total minimum lease payments	1,109
Total Lease Payments to be Received [Abstract]
Lease Payments to be Received, Remainder of Fiscal Year	12,352
Lease Payments to be Received, Two Years	15,905
Lease Payments to be Received, Three Years	14,937
Lease Payments to be Received, Four Years	14,543
Lease Payments to be Received, Five Years	13,983
Lease Payments to be Received, Thereafter	208,218
Total minimum lease payments	279,938
Other Northwest Holdings [Member]
Operating Leases Payment to be Received [Abstract]
Operating Lease, Payments to be Received, Remainder of Fiscal Year	39
Lessor, Operating Lease, Payment to be Received, Year One	53
Operating Lease, Payments to be Received, Two Years	56
Operating Lease, Payments to be Received, Three Years	57
Operating Lease, Payments to be Received, Four Years	58
Operating Lease, Payments to be Received, Thereafter	800
Total minimum lease payments	1,063
Total Lease Payments to be Received [Abstract]
Lease Payments to be Received, Remainder of Fiscal Year	39
Lease Payments to be Received, Two Years	53
Lease Payments to be Received, Three Years	56
Lease Payments to be Received, Four Years	57
Lease Payments to be Received, Five Years	58
Lease Payments to be Received, Thereafter	800
Total minimum lease payments	$ 1,063
Compressed Natural Gas Lease [Member]
Lessor, Lease, Description [Line Items]
Lessor, Sales-type Lease, Term of Contract	10 years
Residual Value of Leased Asset	$ 0
Variable Lease, Payment	0
North Mist Lease [Member]
Lessor, Lease, Description [Line Items]
Residual Value of Leased Asset	0
Variable Lease, Payment	0
Sales-type Lease [Member]
Sales-type Leases Payments to be Received [Abstract]
Sales-type Lease, Payments to be Received, Remainder of Fiscal Year	11,900
Sales-Type and Direct Financing Leases, Lease Receivable, to be Received, Year One	15,306
Sales-type Lease, Payments to be Received, Two Years	14,901
Sales-type Lease, Payments to be Received, Three Years	14,521
Sales-type Lease, Payments to be Received, Four Years	13,983
Sales-type Lease, Payments to be Received, Thereafter	208,218
Total minimum lease payments	278,829
Less: imputed interest	151,120
Total leases receivable	127,709
Sales-type Lease [Member] | Northwest Natural Gas Company [Member]
Sales-type Leases Payments to be Received [Abstract]
Sales-type Lease, Payments to be Received, Remainder of Fiscal Year	11,900
Sales-Type and Direct Financing Leases, Lease Receivable, to be Received, Year One	15,306
Sales-type Lease, Payments to be Received, Two Years	14,901
Sales-type Lease, Payments to be Received, Three Years	14,521
Sales-type Lease, Payments to be Received, Four Years	13,983
Sales-type Lease, Payments to be Received, Thereafter	208,218
Total minimum lease payments	278,829
Less: imputed interest	151,120
Total leases receivable	127,709
Sales-type Lease [Member] | Other Northwest Holdings [Member]
Sales-type Leases Payments to be Received [Abstract]
Sales-type Lease, Payments to be Received, Remainder of Fiscal Year	0
Sales-Type and Direct Financing Leases, Lease Receivable, to be Received, Year One	0
Sales-type Lease, Payments to be Received, Two Years	0
Sales-type Lease, Payments to be Received, Three Years	0
Sales-type Lease, Payments to be Received, Four Years	0
Sales-type Lease, Payments to be Received, Thereafter	0
Total minimum lease payments	$ 0

Leases - Lease Expense

Leases - Lease Expense - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Lease Expense [Abstract]
Operating Lease, Expense	$ 1,907	$ 1,815
Short-term Lease, Cost	$ 81	80
Lessee, Operating Lease, Maximum Term of Short-term Leases not recorded on the Balance Sheet	12 months
Minimum [Member]
Operating Lease Terms [Abstract]
Lessee, Operating Lease, Term of Contract	8 months
Maximum [Member]
Operating Lease Terms [Abstract]
Lessee, Operating Lease, Term of Contract	16 years
Northwest Natural Gas Company [Member]
Lease Expense [Abstract]
Operating Lease, Expense	$ 1,862	1,775
Short-term Lease, Cost	81	80
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Lease Expense [Abstract]
Operating Lease, Expense	$ 45	$ 40

Leases - Lease Asset and Liabil

Leases - Lease Asset and Liabilities - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	$ 70,547	$ 72,699	$ 71,308
Operating lease liabilities current liabilities	2,053	1,700	2,333
Operating lease liabilities noncurrent liabilities	77,051	78,302	77,167
Total operating lease liabilities	$ 79,104	$ 80,002	$ 79,500
Operating Lease, Weighted Average Remaining Lease Term	16 years	17 years	16 years 2 months 12 days
Operating Lease, Weighted Average Discount Rate, Percent	7.30%	7.30%	7.30%
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	$ 137,511
Regulatory Assets, Noncurrent	309,173	$ 311,419	$ 333,443
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	5,811
Lessee, Operating Lease, Liability, to be Paid, Year One	7,538
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,514
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,645
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,725
Lessee, Operating Lease, Liability, Payments, Due after Year Five	101,278
Lessee, Operating Lease, Liability, Payments, Due	137,511
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	58,407
Total operating lease liabilities	79,104	80,002	79,500
Operating lease liabilities current liabilities	2,053	1,700	2,333
Operating lease liabilities noncurrent liabilities	77,051	78,302	77,167
Finance Lease, Liability, Payments, Due Next Twelve Months	0		0
Leases Cash Flow [Abstract]
Operating Lease, Payments	1,855	1,806
Finance Lease, Principal Payments	97	173
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	97	263
Finance Leases [Abstract]
Finance Lease, Liability	0
Finance Lease, Right-of-Use Asset	2,700	2,400	2,600
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	528	622	580
Operating lease liabilities current liabilities	190	162	205
Operating lease liabilities noncurrent liabilities	427	462	410
Total operating lease liabilities	617	624	615
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	586
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	138
Lessee, Operating Lease, Liability, to be Paid, Year One	176
Lessee, Operating Lease, Liability, Payments, Due Year Two	153
Lessee, Operating Lease, Liability, Payments, Due Year Three	107
Lessee, Operating Lease, Liability, Payments, Due Year Four	6
Lessee, Operating Lease, Liability, Payments, Due after Year Five	6
Lessee, Operating Lease, Liability, Payments, Due	586
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(31)
Total operating lease liabilities	617	624	615
Operating lease liabilities current liabilities	190	162	205
Operating lease liabilities noncurrent liabilities	427	462	410
Leases Cash Flow [Abstract]
Operating Lease, Payments	44	39
Northwest Natural Gas Company [Member]
Operating Lease Asset and Liabilities [Abstract]
Operating lease right of use asset	70,019	72,077	70,728
Operating lease liabilities current liabilities	1,863	1,538	2,128
Operating lease liabilities noncurrent liabilities	76,624	77,840	76,757
Total operating lease liabilities	78,487	79,378	78,885
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Liability, Payments, Due	136,925
Regulatory Assets, Noncurrent	309,067	311,394	333,418
Maturity of Operating Lease Liabilities [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	5,673
Lessee, Operating Lease, Liability, to be Paid, Year One	7,362
Lessee, Operating Lease, Liability, Payments, Due Year Two	7,361
Lessee, Operating Lease, Liability, Payments, Due Year Three	7,538
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,719
Lessee, Operating Lease, Liability, Payments, Due after Year Five	101,272
Lessee, Operating Lease, Liability, Payments, Due	136,925
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	58,438
Total operating lease liabilities	78,487	79,378	78,885
Operating lease liabilities current liabilities	1,863	1,538	2,128
Operating lease liabilities noncurrent liabilities	76,624	77,840	76,757
Leases Cash Flow [Abstract]
Operating Lease, Payments	1,811	1,767
Finance Lease, Principal Payments	97	173
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	97	173
Other Northwest Holdings [Member] | Corporate, Non-Segment [Member]
Leases Cash Flow [Abstract]
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 0	90
New Headquarters Lease [Member]
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Term of Contract	20 years
Regulatory Assets, Noncurrent	$ 8,300	$ 7,200	$ 8,000
New Headquarters Lease Renewal Term 2 of 2 [Member] | New Headquarters Lease [Member]
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Renewal Term	7 years
New Headquarters Lease Renewal Term 1 of 2 [Member] | New Headquarters Lease [Member]
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Renewal Term	7 years
Maximum [Member]
Commencement of Significant Lease [Abstract]
Lessee, Operating Lease, Term of Contract	16 years

Stock-Based Compensation_2

Stock-Based Compensation - Long Term Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2024
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted (in shares)			46,156
Award vesting period			3 years
Unrecognized compensation costs			$ 300
Performance Shares | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion ratio, percent of target			0%
Performance Shares | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion ratio, percent of target			200%
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Number of RSUs granted in period (in shares)			57,704
Weighted-average grant date fair value (in dollars per share)			$ 38.87
Unrecognized compensation costs			$ 4,200
2023 and 2024 Awards | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense			$ 0
Forecast [Member] | 2023 and 2024 Awards | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Award Target Share	73,150	50,542

Debt Short-term Debt

Debt Short-term Debt - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Short-term Debt [Line Items]
Short-term debt	$ 94,700	$ 89,780	$ 72,500
Northwest Natural Gas Company [Member]
Short-term Debt [Line Items]
Short-term debt	31,700	16,780	0
Line of Credit [Member]
Short-term Debt [Line Items]
Short-term debt	$ 63,000	$ 73,000	$ 72,500
Debt, Weighted Average Interest Rate	6.30%	6.40%	5.90%
Commercial Paper [Member] | Northwest Natural Gas Company [Member]
Short-term Debt [Line Items]
Short-term debt	$ 31,700	$ 16,800	$ 0
Debt, Weighted Average Interest Rate	5.50%	5.50%	0%

Long-Term Debt

Long-Term Debt - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Mar. 15, 2024
Debt Instrument [Line Items]
Long-term Debt	$ 1,575,604	$ 1,535,302	$ 1,576,300
Other Long-Term Debt	6,500	6,000	6,600
Unamortized debt issuance costs	10,585	10,428	10,044
Long-term Debt, Gross	1,586,189	1,545,730	1,586,344
Long-term debt, Current Maturities, Gross	900	240,700	150,900
Long-term debt	1,574,735	1,294,590	1,425,435
Current maturities of long-term debt	869	240,712	150,865
Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Long-term Debt	1,364,899	1,324,422	1,364,732
Unamortized debt issuance costs	$ 9,801	$ 10,278	$ 9,968
Weighted average interest rate	4.60%	4.60%	4.70%
Long-term Debt, Gross	$ 1,374,700	$ 1,334,700	$ 1,374,700
Long-term debt	1,364,899	1,234,460	1,364,732
Current maturities of long-term debt	$ 0	89,962	0
Northwest Natural Gas Company [Member] | Minimum [Member]
Debt Instrument [Line Items]
Stated interest rate	2.82%
Northwest Natural Gas Company [Member] | Maximum [Member]
Debt Instrument [Line Items]
Stated interest rate	7.85%
Northwest Holdings and Northwest Natural [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ 10,600	$ 10,400	$ 10,000
18 Month Credit Agreement Due March 15, 2024
Debt Instrument [Line Items]
Weighted average interest rate	0%	5.40%	5.50%
Proceeds from Issuance of Debt	$ 0	$ 100,000	$ 100,000
Long-term Debt, Gross				$ 100,000
Derivative, Fixed Interest Rate	4.70%
18 Month Credit Agreement Due March 15, 2024 | Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Repayments of Debt	$ 100,000
18 Month Credit Agreement Due March 15, 2024 | NWN Water
Debt Instrument [Line Items]
Weighted average interest rate	0%	5.30%	5.80%
Proceeds from Issuance of Debt	$ 0	$ 50,000	$ 50,000
Repayments of Debt	$ 50,000
NWN Water Term Loan Due 2026
Debt Instrument [Line Items]
Derivative, Fixed Interest Rate	3.80%
NWN Water Term Loan Due 2026 | Corporate, Non-Segment [Member] | Other Northwest Holdings [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 55,000
NWN Water Term Loan Due 2026 | NWN Water
Debt Instrument [Line Items]
Long-term Debt	$ 55,000	$ 55,000	$ 55,000
Weighted average interest rate	4.70%	4.90%	4.70%
Note 5780 Series due 2028
Debt Instrument [Line Items]
Stated interest rate	5.78%
Proceeds from Issuance of Debt	$ 100,000
Note 5840 Series due 2029
Debt Instrument [Line Items]
Stated interest rate	5.84%
Proceeds from Issuance of Debt	$ 50,000
NW Holdings Unsecured Senior Bonds
Debt Instrument [Line Items]
Weighted average interest rate	5.80%	0%	0%
Proceeds from Issuance of Debt	$ 150,000	$ 0	$ 0

Debt Fair Value of Long Term De

Debt Fair Value of Long Term Debt - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Debt Instrument [Line Items]
Gross long-term debt	$ 1,586,189	$ 1,586,344	$ 1,545,730
Unamortized debt issuance costs	(10,585)	(10,044)	(10,428)
Long-term Debt	1,575,604	1,576,300	1,535,302
Estimated fair value	1,425,765	1,447,941	1,395,321
Northwest Natural Gas Company [Member]
Debt Instrument [Line Items]
Gross long-term debt	1,374,700	1,374,700	1,334,700
Unamortized debt issuance costs	(9,801)	(9,968)	(10,278)
Long-term Debt	1,364,899	1,364,732	1,324,422
Estimated fair value	$ 1,214,625	$ 1,236,559	$ 1,186,110

Pension and Other Postretirem_3

Pension and Other Postretirement Benefit Costs - Net Periodic Benefit Cost - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 980	$ 1,049
Interest cost	5,160	5,218
Expected return on plan assets	(5,935)	(6,661)
Defined Benefit Plan, Amortization of Gain (Loss)	1,495	139
Net periodic benefit cost	1,700	(255)
Amount allocated to construction	(425)	(474)
Defined Benefit Plan Net Periodic Benefit Cost Charged To Expense	1,275	(729)
Amortization of Regulatory Balancing Account	2,801	2,801
Net amount charged to expense	4,076	2,072
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	25	28
Interest cost	248	248
Expected return on plan assets	0	0
Defined Benefit Plan, Amortization of Gain (Loss)	0	0
Net periodic benefit cost	273	276
Amount allocated to construction	(8)	(11)
Defined Benefit Plan Net Periodic Benefit Cost Charged To Expense	265	265
Amortization of Regulatory Balancing Account	0	0
Net amount charged to expense	$ 265	$ 265

Pension and Other Postretirem_4

Pension and Other Postretirement Benefit Costs - Amounts Recognized in Accumulated Other Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Beginning balance	$ (7,049)
Ending balance	(6,825)	$ (6,594)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive loss	(6,825)	(6,594)
Northwest Natural Gas Company [Member]
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Beginning balance	(7,237)
Ending balance	(7,359)	(6,312)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive loss	(7,359)	(6,312)
Non-Qualified Pension Plans, Defined Benefit | Northwest Natural Gas Company [Member]
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Beginning balance	(7,237)	(6,414)
Amortization of actuarial losses	173	139
Total reclassifications before tax	(10)	139
Tax benefit	(112)	(37)
Total reclassifications for the period	(122)	102
Ending balance	(7,359)	(6,312)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment to AOCI, before Tax	183	0
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive loss	(7,359)	(6,312)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment to AOCI, before Tax	183	0
Amortization of actuarial losses	173	139
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	(10)	139
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax, Attributable to Parent	112	37
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	$ (122)	$ 102

Pension and Other Postretirem_5

Pension and Other Postretirement Benefit Costs - Narrative - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Defined benefit pension plan cash contributions	$ 0
Estimated future employer contributions in next fiscal year	20,600
Employer contributions	3,500	$ 3,400
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive loss	(6,825)	(6,594)	$ (7,049)
Northwest Natural Gas Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive loss	(7,359)	(6,312)	(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	(7,359)	(6,312)	$ (7,237)	$ (6,414)
Amortization of actuarial losses	173	139
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	(10)	139
Tax benefit	(112)	(37)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	$ (122)	$ 102

Income Tax_2_3

Income Tax - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes at statutory rates (federal and state)	$ 18,514	$ 20,332
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	7,577	8,149
Differences required to be flowed-through by regulatory commissions	(1,579)	(2,909)
Other, net	(173)	(425)
Total provision for income taxes on continuing operations	$ 24,339	$ 25,147
Effective tax rate for continuing operations	27.60%	26%
Northwest Natural Gas Company [Member]
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes at statutory rates (federal and state)	$ 19,579	$ 21,412
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	7,849	8,406
Differences required to be flowed-through by regulatory commissions	(1,580)	(2,909)
Other, net	(175)	(487)
Total provision for income taxes on continuing operations	$ 25,673	$ 26,422
Effective tax rate for continuing operations	27.50%	25.90%

Property, Plant and Equipment_3

Property, Plant and Equipment - USD ($)	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	$ 4,660,104,000	$ 4,556,609,000	$ 4,320,476,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,218,580,000	1,198,555,000	1,164,498,000
Total property, plant, and equipment, net	3,441,524,000	3,358,054,000	3,155,978,000
Natural Gas Distribution [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	4,268,191,000	4,206,455,000	4,026,183,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	137,958,000	105,166,000	97,128,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,177,007,000	1,159,367,000	1,131,256,000
Total property, plant, and equipment, net	3,229,142,000	3,152,254,000	2,992,055,000
Other Northwest Natural [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	71,175,000	71,175,000	70,364,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	11,607,000	10,963,000	6,624,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	22,859,000	22,595,000	21,804,000
Total property, plant, and equipment, net	59,923,000	59,543,000	55,184,000
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment, net	3,289,065,000	3,211,797,000	3,047,239,000
Property, Plant, Equipment non-cash	31,233,000	24,168,000	17,255,000
Other Northwest Holdings [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	156,020,000	147,040,000	97,286,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	15,153,000	15,810,000	22,891,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	18,714,000	16,593,000	11,438,000
Total property, plant, and equipment, net	152,459,000	146,257,000	108,739,000
Northwest Holdings [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, Equipment non-cash	32,494,000	27,879,000	17,730,000
Northwest Natural Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment	4,488,931,000	4,393,759,000	4,200,299,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,199,866,000	1,181,962,000	1,153,060,000
Total property, plant, and equipment, net	$ 3,289,065,000	$ 3,211,797,000	$ 3,047,239,000

Investments_2_3

Investments $ in Thousands	Mar. 31, 2024 USD ($) numberOfConnections employee	Jan. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Jul. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Schedule of Equity Method Investments [Line Items]
Life Insurance, Corporate or Bank Owned, Amount	$ 45,937		$ 45,713		$ 47,666
Gas reserves, noncurrent	20,406		20,893		22,229
Equity Method Investment, Aggregate Cost	17,738		36,345		23,716
Other investments	84,081		102,951		93,611
Total cumulative gas reserves investment	188,000
Deferred Taxes Related To Gas Reserves	3,800		4,000		4,400
Gas reserves, current	2,200		2,300		3,300
Northwest Natural Gas Company [Member]
Schedule of Equity Method Investments [Line Items]
Life Insurance, Corporate or Bank Owned, Amount	45,937		45,713		47,666
Gas reserves, noncurrent	20,406		20,893		22,229
Equity Method Investment, Aggregate Cost	0		19,539		8,207
Other investments	$ 66,343		$ 86,145		$ 78,102
Other Northwest Holdings [Member] | Avion Water
Schedule of Equity Method Investments [Line Items]
Ownership percentage of Avion		45.60%		43.10%		40.30%	37.30%
Investment balance in Avion							$ 14,500
Equity Method Investment, Number of Customer Connections | numberOfConnections	15,000
Equity Method Investment, Number of Employees | employee	35
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 9,800
Equity Method Investment, Additional Underlying Equity in Net Assets		$ 1,000		$ 1,000		$ 1,000

Business Combinations Busines_2

Business Combinations Business Combinations	3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 31, 2024 USD ($)	Jun. 30, 2023 USD ($) numberOfConnections	Dec. 31, 2029 USD ($)	Dec. 31, 2028 USD ($)	Dec. 31, 2027 USD ($)	Dec. 31, 2026 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2021	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)
Business Acquisition [Line Items]
Number of Businesses Acquired | numberOfConnections		5
Goodwill	$ 162,966,000								$ 163,344,000	$ 149,836,000
Goodwill, Impairment Loss	0
Business Combination, Consideration Transferred		$ 22,800,000
Business Combination, Consideration Transferred		$ 22,800,000
Customer Relationships
Business Acquisition [Line Items]
Finite-Lived Intangible Assets Acquired	$ 2,600,000
Acquired Finite-Lived Intangible Assets, Weighted Average Useful Life	24 years
Amortization of Intangible Assets	$ 100,000
Customer Relationships | Forecast [Member]
Business Acquisition [Line Items]
Amortization of Intangible Assets			$ 100,000	$ 100,000	$ 100,000	$ 100,000	$ 100,000
Other insignificant acquisitions [Member]
Business Acquisition [Line Items]
Number of Businesses Acquired								0

Derivative Instruments Notional

Derivative Instruments Notional Amounts - Northwest Natural Gas Company [Member] therm in Thousands, $ in Thousands	Mar. 31, 2024 USD ($) therm	Dec. 31, 2023 USD ($) therm	Mar. 31, 2023 USD ($) therm
Gas Year 2023 - 2024
Derivative [Line Items]
TargetHedgeAchieved	82%
Gas Year 2023 - 2024 | Oregon [Member]
Derivative [Line Items]
TargetHedgeAchieved	85%
Gas Year 2023 - 2024 | WASHINGTON
Derivative [Line Items]
TargetHedgeAchieved	55%
Financial [Member] | Gas Year 2023 - 2024
Derivative [Line Items]
TargetHedgeAchieved	66%
Financial [Member] | Gas Year 2023 - 2024 | Oregon [Member]
Derivative [Line Items]
TargetHedgeAchieved	69%
Financial [Member] | Gas Year 2023 - 2024 | WASHINGTON
Derivative [Line Items]
TargetHedgeAchieved	42%
Physical [Member] | Gas Year 2023 - 2024
Derivative [Line Items]
TargetHedgeAchieved	16%
Physical [Member] | Gas Year 2023 - 2024 | Oregon [Member]
Derivative [Line Items]
TargetHedgeAchieved	16%
Physical [Member] | Gas Year 2023 - 2024 | WASHINGTON
Derivative [Line Items]
TargetHedgeAchieved	13%
Natural Gas Therms [Member] | Financial [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	690,905	948,425	681,850
Natural Gas Therms [Member] | Physical [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	374,350	571,610	295,382
Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount | $	$ 10,457	$ 11,926	$ 10,444

Unrealized and Realized Gain_Lo

Unrealized and Realized Gain/Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Derivative [Line Items]
Derivative, Gain on Derivative	$ 172,400
Derivative, Gain (Loss) on Derivative, Net	346	$ (411)
Derivative, Loss on Derivative	50,500
Financial [Member]
Derivative [Line Items]
Incremental Cost or Benefit to Collect or Refund to Customers	0
Northwest Holdings and Northwest Natural [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	0
Northwest Holdings and Northwest Natural [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	0
Northwest Holdings and Northwest Natural [Member] | Benefit (expense) to cost of gas | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	37,964	61,321
Northwest Holdings and Northwest Natural [Member] | Benefit (expense) to cost of gas | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(179)	13
Northwest Holdings and Northwest Natural [Member] | Sales [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	0
Northwest Holdings and Northwest Natural [Member] | Sales [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	0
Deferred Derivative Gain (Loss) [Member] | Northwest Holdings and Northwest Natural [Member] | Natural gas commodity
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(37,964)	61,321
Deferred Derivative Gain (Loss) [Member] | Northwest Holdings and Northwest Natural [Member] | Foreign exchange
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ 179	$ (13)

Derivative Instruments Credit R

Derivative Instruments Credit Rating - USD ($)	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Collateral Posted with NW Natural Counterparties [Member]
Derivative [Line Items]
Additional Collateral, Aggregate Fair Value	$ 0		$ 0
Northwest Natural Gas Company [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	4,100,000	$ 9,000,000	1,600,000
Derivative liability	$ 61,400,000	$ 124,200,000	$ 51,500,000

Derivative Instruments Fair Val

Derivative Instruments Fair Value - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Mar. 31, 2025	Dec. 31, 2023	Mar. 31, 2023
Derivative [Line Items]
Derivative, Fair Value, Net	$ (57,300)		$ (115,200)	$ (49,900)
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	500		$ 200
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	400
Derivative Credit Risk Valuation Adjustment, Derivative Liabilities	$ 300
Forecast [Member]
Derivative [Line Items]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		$ 500

Environmental Matters_2_3

Environmental Matters $ in Thousands	Mar. 31, 2024 USD ($)
Oregon [Member]
Site Contingency [Line Items]
Remediation Recovery Percentage	96.70%
WASHINGTON
Site Contingency [Line Items]
Remediation Recovery Percentage	3.30%
Inventory, Emissions Allowances	$ 39,500

Environmental Matters - Environ

Environmental Matters - Environmental Sites $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2017 USD ($)	Mar. 31, 2024 USD ($) property party	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)
Site Contingency [Line Items]
Current Liabilities		$ 27,388	$ 32,454	$ 25,187
Non-Current Liabilities		86,071	89,173	89,110
Gasco/Siltronic Sediments
Site Contingency [Line Items]
Current Liabilities		9,989	12,428	8,588
Non-Current Liabilities		41,365	42,550	42,766
Site Contingency, Environmental Remediation Costs Recognized		51,400
Gasco/Siltronic Sediments | Minimum [Member]
Site Contingency [Line Items]
Environmental Exit Costs, Anticipated Cost		51,400
Gasco/Siltronic Sediments | Maximum [Member]
Site Contingency [Line Items]
Environmental Exit Costs, Anticipated Cost		350,000
Portland Harbor Other [Member]
Site Contingency [Line Items]
Current Liabilities		2,978	3,035	2,868
Non-Current Liabilities		$ 10,707	11,270	10,707
Gasco Uplands [Member]
Site Contingency [Line Items]
Site contingency: number of management pieces		2
Gasco/Siltronic Upland [Member]
Site Contingency [Line Items]
Current Liabilities		$ 13,875	16,304	13,275
Non-Current Liabilities		33,307	34,235	34,519
Front Street [Member]
Site Contingency [Line Items]
Current Liabilities		546	687	456
Non-Current Liabilities		513	939	939
Additional studies and design costs		1,100
Oregon Steel Mills [Member]
Site Contingency [Line Items]
Current Liabilities		0	0	0
Non-Current Liabilities		$ 179	$ 179	$ 179
Portland Harbor [Member]
Site Contingency [Line Items]
Number of potentially responsible parties (more than) | party		100
EPA final feasibility study and proposed remediation plan, clean-up costs, portland harbor	$ 1,050,000
Number of remediation projects | property		2
Portland Harbor [Member] | Minimum [Member]
Site Contingency [Line Items]
Percentage of clean-up costs	(30.00%)
Portland Harbor [Member] | Maximum [Member]
Site Contingency [Line Items]
Percentage of clean-up costs	50%
Yakama Nation [Member] | Portland Harbor Other [Member]
Site Contingency [Line Items]
Trustee Council Members - Number of Claimants		1
Site Contingency, Number of Other Third-Party Defendants		29
NRD liability claim yakama nation		$ 300
Number of Amended Complaints Filed		2

Environmental Matters - Regulat

Environmental Matters - Regulatory Deferred Assets - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Site Contingency [Line Items]
Regulatory Assets, Current	$ 127,666	$ 178,270	$ 126,546
Regulatory Assets, Noncurrent	$ 309,173	$ 333,443	$ 311,419
Remediation Non-recovery Percentage	3.30%	3.30%	3.30%
Annual tariff rider collection	$ 5,000
Annual insurance proceeds to apply against remediation costs	5,000
Total annual remediation expense and interest	$ 10,000
Oregon [Member]
Site Contingency [Line Items]
Remediation Recovery Percentage	96.70%
Front Street [Member] | Environmental costs [Member]
Site Contingency [Line Items]
Accrued site liabilities	$ 34	$ 53	$ 45
Northwest Natural Gas Company [Member]
Site Contingency [Line Items]
Regulatory Assets, Current	127,641	178,270	126,546
Regulatory Assets, Noncurrent	309,067	333,418	311,394
Northwest Natural Gas Company [Member] | Environmental costs [Member]
Site Contingency [Line Items]
Deferred costs and interest	60,291	57,758	47,651
Accrued site liabilities	113,426	121,575	114,253
Insurance proceeds and interest	(51,389)	(50,764)	(55,416)
Regulatory Assets	122,328	128,569	106,488
Regulatory Assets, Current	9,864	9,950	6,947
Regulatory Assets, Noncurrent	$ 112,464	$ 118,619	$ 99,541

Subsequent Events

Subsequent Events $ in Thousands	6 Months Ended
	Jun. 30, 2023 USD ($)
Subsequent Event [Line Items]
Business Combination, Consideration Transferred	$ 22,800