Knife River (KNF) 10-Q 4 Nov 24 2024 Q3 Quarterly report Financial data

Cover page

Cover page - shares	9 Months Ended
	Sep. 30, 2024	Oct. 31, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Entity File Number	1-41642
Entity Registrant Name	Knife River Corporation
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	92-1008893
Entity Address, Address Line One	1150 West Century Avenue
Entity Address, Address Line Two	P.O. Box 5568
Entity Address, City or Town	Bismarck
Entity Address, State or Province	ND
Entity Address, Postal Zip Code	58506-5568
City Area Code	701
Local Phone Number	530-1400
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	KNF
Security Exchange Name	NYSE
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
Entity common stock, shares outstanding		56,612,705
Entity Central Index Key	0001955520
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Amendment Flag	false

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenue:
Revenue	$ 1,105,293	$ 1,090,372	$ 2,241,789	$ 2,183,462
Cost of revenue:
Cost of revenue	832,282	820,983	1,786,065	1,756,994
Gross profit	273,011	269,389	455,724	426,468
Selling, general and administrative expenses	63,874	59,168	183,569	167,276
Operating income	209,137	210,221	272,155	259,192
Interest expense	13,936	15,354	41,848	44,005
Other income	2,487	7	7,541	3,311
Income before income taxes	197,688	194,874	237,848	218,498
Income tax expense	49,584	48,219	59,443	56,327
Net income	$ 148,104	$ 146,655	$ 178,405	$ 162,171
Net income per share:
Basic (in dollars per share)	$ 2.62	$ 2.59	$ 3.15	$ 2.87
Diluted (in dollars per share)	$ 2.60	$ 2.58	$ 3.14	$ 2.86
Weighted average common shares outstanding:
Basic (in shares)	56,613	56,566	56,605	56,566
Diluted (in shares)	56,871	56,735	56,809	56,633
Construction materials
Revenue:
Revenue	$ 545,711	$ 553,057	$ 1,184,938	$ 1,177,726
Cost of revenue:
Cost of revenue	345,046	346,298	865,198	856,606
Contracting services
Revenue:
Revenue	559,582	537,315	1,056,851	1,005,736
Cost of revenue:
Cost of revenue	$ 487,236	$ 474,685	$ 920,867	$ 900,388

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 148,104	$ 146,655	$ 178,405	$ 162,171
Other comprehensive income:
Reclassification adjustment for loss on derivative instruments included in net income, net of tax of $0 and $0 for the three months ended and $0 and $28 for the nine months ended in 2024 and 2023, respectively	0	0	0	90
Postretirement liability adjustment:
Postretirement liability losses arising during the period, net of tax of $0 and $0 for the three months ended and $0 and $(6) for the nine months ended in 2024 and 2023, respectively	0	0	0	(17)
Amortization of postretirement liability losses included in net periodic benefit cost, net of tax of $25 and $16 for the three months ended and $75 and $47 for the nine months ended in 2024 and 2023, respectively	78	49	233	144
Postretirement liability adjustment	78	49	233	127
Other comprehensive income	78	49	233	217
Comprehensive income attributable to common stockholders	$ 148,182	$ 146,704	$ 178,638	$ 162,388

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Reclassification adjustment for loss on derivative instruments included in net income, tax	$ 0	$ 0	$ 0	$ 28
Postretirement liability losses arising during the period, net of tax	0	0	0	(6)
Amortization of postretirement liability losses included in net periodic benefit cost, tax	$ 25	$ 16	$ 75	$ 47

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Current assets:
Cash, cash equivalents and restricted cash	$ 267,442	$ 262,320	$ 116,159
Receivables, net	449,188	266,785	491,866
Costs and estimated earnings in excess of billings on uncompleted contracts	69,309	27,293	50,545
Inventories	347,300	319,623	314,711
Prepayments and other current assets	26,396	37,522	38,094
Total current assets	1,159,635	913,543	1,011,375
Noncurrent assets:
Property, plant and equipment	2,692,182	2,579,734	2,547,577
Less accumulated depreciation, depletion and amortization	1,346,022	1,264,687	1,248,042
Net property, plant and equipment	1,346,160	1,315,047	1,299,535
Goodwill	275,256	274,478	274,478
Other intangible assets, net	9,854	10,821	11,463
Operating lease right-of-use assets	47,430	44,706	44,309
Investments and other	45,782	41,218	39,722
Total noncurrent assets	1,724,482	1,686,270	1,669,507
Total assets	2,884,117	2,599,813	2,680,882
Current liabilities:
Long-term debt - current portion	8,791	7,082	7,082
Accounts payable	180,572	107,656	148,977
Billings in excess of costs and estimated earnings on uncompleted contracts	44,786	51,376	58,785
Taxes payable	15,991	9,300	53,281
Accrued compensation	42,071	48,098	37,922
Accrued interest	13,772	7,247	16,054
Current operating lease liabilities	13,544	12,948	13,702
Other accrued liabilities	106,576	103,564	89,164
Total current liabilities	426,103	347,271	424,967
Noncurrent liabilities:
Long-term debt	669,672	674,577	675,649
Deferred income taxes	187,915	174,542	173,989
Noncurrent operating lease liabilities	33,886	31,758	30,607
Other	117,611	105,653	132,652
Total liabilities	1,435,187	1,333,801	1,437,864
Commitments and contingencies
Commitments and contingencies
Stockholders' equity:
Common stock, 300,000,000 shares authorized, $0.01 par value, 57,043,841 shares issued and 56,612,705 shares outstanding at September 30, 2024; 56,997,350 shares issued and 56,566,214 shares outstanding at September 30, 2023; 57,009,542 shares issued and 56,578,406 shares outstanding at December 31, 2023	570	570	570
Other paid-in capital	618,799	614,513	613,024
Retained earnings	844,273	665,874	645,185
Treasury stock held at cost - 431,136 shares	(3,626)	(3,626)	(3,626)
Accumulated other comprehensive loss	(11,086)	(11,319)	(12,135)
Total stockholders' equity	1,448,930	1,266,012	1,243,018
Total liabilities and stockholders' equity	$ 2,884,117	$ 2,599,813	$ 2,680,882

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - $ / shares	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Statement of Financial Position [Abstract]
Common stock, authorized (in shares)	300,000,000	300,000,000	300,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common stock, issued (in shares)	57,043,841	57,009,542	56,997,350
Common stock, outstanding (in shares)	56,612,705	56,578,406	56,566,214
Treasury stock held at cost (in shares)	431,136	431,136	431,136

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Stock	Other Paid-in Capital	Retained Earnings	MDU Resources' Stock Held by Subsidiary	Treasury Stock	Accumula-ted Other Comprehen-sive Loss
Beginning balance (in shares) at Dec. 31, 2022		80,000
Beginning balance at Dec. 31, 2022	$ 1,028,589	$ 800	$ 549,106	$ 494,661	$ (3,626)	$ 0	$ (12,352)
Common stock held by subsidiary, beginning balance (in shares) at Dec. 31, 2022					(538,921)
Treasury stock, beginning balance (in shares) at Dec. 31, 2022						0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(41,320)			(41,320)
Other comprehensive income	93						93
Stock-based compensation expense	414		453	(39)
Net transfers to Centennial & Net transfers from Centennial and MDU Resources including Separation adjustments	(13,007)		(1,385)	(11,622)
Ending balance (in shares) at Mar. 31, 2023		80,000
Common stock held by subsidiary, ending balance (in shares) at Mar. 31, 2023					(538,921)
Treasury stock, ending balance (in shares) at Mar. 31, 2023						0
Ending balance at Mar. 31, 2023	974,769	$ 800	548,174	441,680	$ (3,626)	$ 0	(12,259)
Beginning balance (in shares) at Dec. 31, 2022		80,000
Beginning balance at Dec. 31, 2022	1,028,589	$ 800	549,106	494,661	$ (3,626)	$ 0	(12,352)
Common stock held by subsidiary, beginning balance (in shares) at Dec. 31, 2022					(538,921)
Treasury stock, beginning balance (in shares) at Dec. 31, 2022						0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	162,171
Other comprehensive income	$ 217
Ending balance (in shares) at Sep. 30, 2023	56,566,214	56,997,350
Common stock held by subsidiary, ending balance (in shares) at Sep. 30, 2023					0
Treasury stock, ending balance (in shares) at Sep. 30, 2023	(431,136)					(431,136)
Ending balance at Sep. 30, 2023	$ 1,243,018	$ 570	613,024	645,185	$ 0	$ (3,626)	(12,135)
Beginning balance (in shares) at Mar. 31, 2023		80,000
Beginning balance at Mar. 31, 2023	974,769	$ 800	548,174	441,680	$ (3,626)	$ 0	(12,259)
Common stock held by subsidiary, beginning balance (in shares) at Mar. 31, 2023					(538,921)
Treasury stock, beginning balance (in shares) at Mar. 31, 2023						0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	56,836			56,836
Other comprehensive income	75						75
Stock-based compensation expense	226		212	14
Transfer of MDU Resources' stock held by subsidiary (in share)					538,921
Transfer of MDU Resources' stock held by subsidiary	3,626				$ 3,626
Receipt of treasury stock at cost (in share)						(431,136)
Receipt of treasury stock at cost	(3,626)					$ (3,626)
Retirement of historical common stock in connection with the Separation (in share)		(80,000)
Retirement of historical common stock in connection with the Separation	0	$ (800)	800
Issuance of common stock in connection with the Separation (in shares)		56,997,350
Issuance of common stock in connection with the Separation	(26)	$ 570	(596)
Net transfers to Centennial & Net transfers from Centennial and MDU Resources including Separation adjustments	62,972		62,972
Ending balance (in shares) at Jun. 30, 2023		56,997,350
Common stock held by subsidiary, ending balance (in shares) at Jun. 30, 2023					0
Treasury stock, ending balance (in shares) at Jun. 30, 2023						(431,136)
Ending balance at Jun. 30, 2023	1,094,852	$ 570	611,562	498,530	$ 0	$ (3,626)	(12,184)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	146,655			146,655
Other comprehensive income	49						49
Stock-based compensation expense	$ 1,462		1,462
Ending balance (in shares) at Sep. 30, 2023	56,566,214	56,997,350
Common stock held by subsidiary, ending balance (in shares) at Sep. 30, 2023					0
Treasury stock, ending balance (in shares) at Sep. 30, 2023	(431,136)					(431,136)
Ending balance at Sep. 30, 2023	$ 1,243,018	$ 570	613,024	645,185	$ 0	$ (3,626)	(12,135)
Beginning balance (in shares) at Dec. 31, 2023	56,578,406	57,009,542
Beginning balance at Dec. 31, 2023	$ 1,266,012	$ 570	614,513	665,874	$ 0	$ (3,626)	(11,319)
Common stock held by subsidiary, beginning balance (in shares) at Dec. 31, 2023					0
Treasury stock, beginning balance (in shares) at Dec. 31, 2023	(431,136)					(431,136)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ (47,629)			(47,629)
Other comprehensive income	78						78
Stock-based compensation expense	1,811		1,811
Common stock issued for employee compensation, net of tax withholding (in shares)		31,298
Common stock issued for employee compensation, net of tax withholding	(1,645)		(1,645)
Ending balance (in shares) at Mar. 31, 2024		57,040,840
Common stock held by subsidiary, ending balance (in shares) at Mar. 31, 2024					0
Treasury stock, ending balance (in shares) at Mar. 31, 2024						(431,136)
Ending balance at Mar. 31, 2024	$ 1,218,627	$ 570	614,679	618,245	$ 0	$ (3,626)	(11,241)
Beginning balance (in shares) at Dec. 31, 2023	56,578,406	57,009,542
Beginning balance at Dec. 31, 2023	$ 1,266,012	$ 570	614,513	665,874	$ 0	$ (3,626)	(11,319)
Common stock held by subsidiary, beginning balance (in shares) at Dec. 31, 2023					0
Treasury stock, beginning balance (in shares) at Dec. 31, 2023	(431,136)					(431,136)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 178,405
Other comprehensive income	$ 233
Ending balance (in shares) at Sep. 30, 2024	56,612,705	57,043,841
Common stock held by subsidiary, ending balance (in shares) at Sep. 30, 2024					0
Treasury stock, ending balance (in shares) at Sep. 30, 2024	(431,136)					(431,136)
Ending balance at Sep. 30, 2024	$ 1,448,930	$ 570	618,799	844,273	$ 0	$ (3,626)	(11,086)
Beginning balance (in shares) at Mar. 31, 2024		57,040,840
Beginning balance at Mar. 31, 2024	1,218,627	$ 570	614,679	618,245	$ 0	$ (3,626)	(11,241)
Common stock held by subsidiary, beginning balance (in shares) at Mar. 31, 2024					0
Treasury stock, beginning balance (in shares) at Mar. 31, 2024						(431,136)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	77,929			77,929
Other comprehensive income	77						77
Stock-based compensation expense	2,101		2,106	(5)
Common stock issued for board of director fees (in share)		3,001
Common stock issued for board of director fees	(28)		(28)
Ending balance (in shares) at Jun. 30, 2024		57,043,841
Common stock held by subsidiary, ending balance (in shares) at Jun. 30, 2024					0
Treasury stock, ending balance (in shares) at Jun. 30, 2024						(431,136)
Ending balance at Jun. 30, 2024	1,298,706	$ 570	616,757	696,169	$ 0	$ (3,626)	(11,164)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	148,104			148,104
Other comprehensive income	78						78
Stock-based compensation expense	$ 2,042		2,042
Ending balance (in shares) at Sep. 30, 2024	56,612,705	57,043,841
Common stock held by subsidiary, ending balance (in shares) at Sep. 30, 2024					0
Treasury stock, ending balance (in shares) at Sep. 30, 2024	(431,136)					(431,136)
Ending balance at Sep. 30, 2024	$ 1,448,930	$ 570	$ 618,799	$ 844,273	$ 0	$ (3,626)	$ (11,086)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Operating activities:
Net income	$ 178,405	$ 162,171
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	101,519	92,511
Deferred income taxes	13,432	(1,884)
Provision for credit losses	603	1,386
Amortization of debt issuance costs	2,072	2,425
Employee stock-based compensation costs	5,728	2,127
Pension and postretirement benefit plan net periodic benefit cost	908	889
Unrealized gains on investments	(2,865)	(685)
Gains on sales of assets	(6,323)	(3,806)
Changes in current assets and liabilities, net of acquisitions:
Receivables	(224,758)	(302,536)
Due from related-party	0	16,050
Inventories	(27,262)	8,566
Other current assets	11,125	(20,127)
Accounts payable	77,152	91,663
Due to related-party	0	(7,310)
Other current liabilities	17,268	78,006
Pension and postretirement benefit plan contributions	(2,502)	(1,611)
Other noncurrent changes	5,388	35,092
Net cash provided by operating activities	149,890	152,927
Investing activities:
Capital expenditures	(127,161)	(86,450)
Acquisitions, net of cash acquired	(15,008)	0
Net proceeds from sale or disposition of property and other	7,605	5,227
Investments	(3,263)	(1,764)
Net cash used in investing activities	(137,827)	(82,987)
Financing activities:
Issuance of long-term related-party notes, net	0	205,275
Issuance of long-term debt	0	700,000
Repayment of long-term debt	(5,268)	(1,891)
Debt issuance costs	0	(16,640)
Proceeds from issuance of common stock	0	(26)
Tax withholding on stock-based compensation	(1,673)	0
Net transfers to Centennial	0	(850,589)
Net cash (used in) provided by financing activities	(6,941)	36,129
Increase in cash, cash equivalents and restricted cash	5,122	106,069
Cash, cash equivalents and restricted cash -- beginning of year	262,320	10,090
Cash, cash equivalents and restricted cash -- end of period	$ 267,442	$ 116,159

Background

Background	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Background	Background Knife River is a people-first construction materials and contracting services company. We provide construction materials and contracting services to build safe roads, bridges, airport runways and other critical infrastructure needs that connect people with where they want to go and with the supplies they need. Knife River is one of the leading providers of crushed stone and sand and gravel in the United States and operates across 14 states. We conduct our operations through five reportable segments: Pacific, Northwest, Mountain, Central and Energy Services. In the fourth quarter of 2023, we realigned our reportable segments to better support our operational strategies. As a result, a portion of the Pacific segment’s businesses are now reported under the Energy Services segment. In addition, the North Central and South operating regions have been aggregated into one reportable segment, Central. We also reallocated certain amounts to the operating segments that were previously reported within Corporate Services. All periods have been recast to conform with the revised presentation. See Note 14 for additional information. Separation from MDU Resources On May 31, 2023, MDU Resources completed the previously announced separation of Knife River through the distribution of approximately 90 percent of the outstanding shares of common stock, par value $.01 per share, of Knife River to the stockholders of record of MDU Resources as of the close of business on May 22, 2023. MDU Resources retained approximately 10 percent of the outstanding shares of Knife River common stock. The Distribution was structured as a pro rata distribution of one share of Knife River common stock for every four shares of MDU Resources common stock. In November 2023, MDU Resources disposed of all 5,656,621 retained shares of Knife River common stock in an underwritten public offering. As a result of the Distribution, Knife River is now an independent public company and its common stock is listed under the symbol “KNF” on the New York Stock Exchange. All share and earnings per share information has been retroactively adjusted for all periods presented to reflect the Distribution.

Basis of presentation

Basis of presentation	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	Basis of presentation The accompanying consolidated interim financial statements were prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Interim financial statements do not include all disclosures provided in annual financial statements and, accordingly, these financial statements should be read in conjunction with the Company's 2023 Annual Report on Form 10-K ("Annual Report"). The information is unaudited but includes adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. Prior to the Separation, Knife River operated as a wholly owned subsidiary of Centennial Energy Holdings, Inc., a direct wholly owned subsidiary of MDU Resources and the direct parent company of Knife River prior to the spinoff ("Centennial") and an indirect, wholly owned subsidiary of MDU Resources and not as a stand-alone company. The accompanying consolidated financial statements and footnotes for the periods prior to the Separation were prepared on a "carve-out" basis using a legal entity approach in conformity with GAAP and were derived from the consolidated financial statements of MDU Resources as if Knife River operated on a stand-alone basis during these periods. All revenues and costs, as well as assets and liabilities, directly associated with our business activities are included in the consolidated financial statements. In the periods prior to the Separation, the consolidated financial statements include expense allocations for certain functions provided by MDU Resources and Centennial, including, but not limited to, certain general corporate expenses related to senior management, legal, human resources, finance and accounting, treasury, information technology, communications, procurement, tax, insurance and other shared services. These general corporate expenses are included in the Consolidated Statements of Operations within selling, general and administrative expenses and other income. There were no amounts allocated to Knife River for the three months ended September 30, 2023, and $9.0 million was allocated for the nine months ended September 30, 2023 in selling, general and administrative expenses. There were no amounts allocated for the three months ended September 30, 2023 and $348,000 was allocated for the nine months ended September 30, 2023 in other income. These items were allocated on the basis of direct usage when identifiable, with the remainder principally allocated on the basis of percent of total capital invested or other allocation methodologies that were considered to be a reasonable reflection of the utilization of the services provided to the benefits received, including the following: number of employees paid and stated as cost per check; number of employees served; weighted factor of travel, managed units, national account spending, equipment and fleet acquisitions; purchase order dollars spent and purchase order line count; number of payments, vouchers or unclaimed property reports; labor hours; time tracked; and projected workload. The allocations may not, however, reflect the expenses we would have incurred as a stand-alone company for the periods presented. These costs also may not be indicative of the expenses that we will incur in the future or would have incurred if we had obtained these services from a third party. Management has also evaluated the impact of events occurring after September 30, 2024, up to the date of issuance of these consolidated interim financial statements on November 4, 2024, that would require recognition or disclosure in the Consolidated Financial Statements. See Note 17 - Subsequent Events for more details on these events. Principles of consolidation For all periods, the consolidated financial statements were prepared in accordance with GAAP and include the accounts of Knife River and its wholly owned subsidiaries. All intercompany accounts and transactions between the businesses comprising Knife River have been eliminated in the accompanying audited consolidated financial statements. Use of estimates The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, at the date of the consolidated financial statements, as well as the reported amounts of revenues and expenses during the reporting period. Estimates are used for items such as long-lived assets and goodwill; fair values of acquired assets and liabilities under the acquisition method of accounting; aggregate reserves; property depreciable lives; tax provisions; revenue recognized using the cost-to-cost measure of progress for contracts; expected credit losses; environmental and other loss contingencies; costs on contracting services contracts; actuarially determined benefit costs; asset retirement obligations; lease classification; present value of right-of-use assets and lease liabilities; and the valuation of stock-based compensation. These estimates are based on management’s best knowledge of current events, historical experience, actions that we may undertake in the future and on various other assumptions that are believed to be reasonable under the circumstances. As additional information becomes available, or actual amounts are determinable, the recorded estimates are revised. Consequently, operating results can be affected by revisions to prior accounting estimates. Cash, cash equivalents and restricted cash We consider all highly liquid investments with an original maturity of three months or less, when purchased, to be cash and cash equivalents. Restricted cash represents deposits held by our captive insurance company that is required by state insurance regulations to remain in the captive insurance company. Cash, cash equivalents and restricted cash on the Consolidated Balance Sheets is comprised of: September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Cash and cash equivalents $ 220,368 $ 84,006 $ 219,324 Restricted cash 47,074 32,153 42,996 Cash, cash equivalents and restricted cash $ 267,442 $ 116,159 $ 262,320 Seasonality of operations Some of our operations are seasonal and revenues from, and certain expenses for, such operations may fluctuate significantly among quarterly periods, with lower activity in the winter months and higher activity in the summer months. Accordingly, the interim results for particular segments, and for Knife River as a whole, may not be indicative of results for the full fiscal year or other future periods.

New Accounting Standards

New Accounting Standards	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
New accounting standards	New accounting standards The following table provides a brief description of the accounting pronouncements applicable to Knife River and the potential impact on its consolidated financial statements and/or disclosures: Standard Description Standard Effective Date Impact on financial statements/disclosures Recently issued Financial Accounting Standards Board (FASB) accounting standards updates ("ASU") not yet adopted ASU 2023-07 - Improvements to Reportable Segment Disclosures In November 2023, the FASB issued guidance on modifying the disclosure requirements to improve reportable segment disclosure requirements through enhanced disclosures about significant segment expenses. The guidance also expands the interim disclosure requirements. The guidance is to be applied on a retrospective basis to the financial statements and footnotes and early adoption is permitted. Fiscal periods beginning after December 15, 2023 and interim periods beginning after December 31, 2024 The Company is currently evaluating the impact the guidance will have on its disclosures for the year ended December 31, 2024 and interim periods for fiscal year 2025. ASU 2023-09 - Improvements to Income Tax Disclosures In December 2023, the FASB issued guidance on modifying the disclosure requirements to increase transparency about income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid information. The guidance is to be applied on a prospective basis to the financial statements and footnotes, however, retrospective adoption is also permitted. The guidance also permits early adoption. Fiscal periods beginning after December 15, 2024 The Company is electing to early adopt the guidance for the year ended December 31, 2024, on a retrospective basis. The Company has reviewed the impact to its disclosures and although not material, will have updates to the income tax footnote.

Receivables and allowance for e

Receivables and allowance for expected credit losses	9 Months Ended
	Sep. 30, 2024
Credit Loss [Abstract]
Receivables and allowance for expected credit loss	Receivables and allowance for expected credit losses Receivables consist primarily of trade and contract receivables for the sale of goods and services net of expected credit losses. A majority of our receivables are due in 30 days or less. The total balance of receivables past due 90 days or more was $12.6 million, $14.4 million and $16.7 million at September 30, 2024, September 30, 2023 and December 31, 2023, respectively. Receivables were as follows: September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Trade receivables $ 229,887 $ 236,373 $ 124,134 Contract receivables 187,622 223,874 112,037 Retention receivables 35,980 37,814 36,782 Receivables, gross 453,489 498,061 272,953 Less expected credit loss 4,301 6,195 6,168 Receivables, net $ 449,188 $ 491,866 $ 266,785 The Company's expected credit losses are determined through a review using historical credit loss experience; changes in asset specific characteristics; current conditions; and reasonable and supportable future forecasts, among other specific account data, and is performed at least quarterly. We develop and document our methodology to determine our allowance for expected credit losses. Risk characteristics used by management may include customer mix, knowledge of customers and general economic conditions of the various local economies, among others. Specific account balances are written off when management determines the amounts to be uncollectible. Management has reviewed the balance reserved through the allowance for expected credit losses and believes it is reasonable. Details of the Company's expected credit losses were as follows: Pacific Northwest Mountain Central Energy Services Total (In thousands) As of December 31, 2023 $ 2,053 $ 1,004 $ 2,293 $ 718 $ 100 $ 6,168 Current expected credit loss provision 177 (223) (47) 87 — (6) Less write-offs charged against the allowance (53) 133 2 3 — 85 At March 31, 2024 $ 2,283 $ 648 $ 2,244 $ 802 $ 100 $ 6,077 Current expected credit loss provision 25 79 27 151 1 283 Less write-offs charged against the allowance 513 11 1,122 212 1 1,859 At June 30, 2024 $ 1,795 $ 716 $ 1,149 $ 741 $ 100 $ 4,501 Current expected credit loss provision 126 (19) (5) 223 1 326 Less write-offs charged against the allowance 74 108 233 106 5 526 At September 30, 2024 $ 1,847 $ 589 $ 911 $ 858 $ 96 $ 4,301 Pacific Northwest Mountain Central Energy Services Total (In thousands) As of December 31, 2022 $ 1,945 $ 1,253 $ 1,278 $ 901 $ 100 $ 5,477 Current expected credit loss provision 45 313 164 (90) — 432 Less write-offs charged against the allowance 1 68 18 — — 87 At March 31, 2023 $ 1,989 $ 1,498 $ 1,424 $ 811 $ 100 $ 5,822 Current expected credit loss provision 8 74 631 (131) 1 583 Less write-offs charged against the allowance 17 512 3 2 1 535 At June 30, 2023 $ 1,980 $ 1,060 $ 2,052 $ 678 $ 100 $ 5,870 Current expected credit loss provision 46 242 (152) 235 — 371 Less write-offs charged against the allowance 26 4 13 3 — 46 At September 30, 2023 $ 2,000 $ 1,298 $ 1,887 $ 910 $ 100 $ 6,195

Inventories

Inventories	9 Months Ended
	Sep. 30, 2024
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories on the Consolidated Balance Sheets were as follows: September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Finished products $ 240,746 $ 213,702 $ 225,319 Raw materials 67,830 63,156 61,776 Supplies and parts 38,724 37,853 32,528 Total $ 347,300 $ 314,711 $ 319,623 Inventories are valued at the lower of cost or net realizable value using the average cost method. Inventories include production costs incurred as part of our aggregate mining activities. These inventoriable production costs include all mining and processing costs associated with the production of aggregates. Stripping costs incurred during the production phase, which represent costs of removing overburden and waste materials to access mineral deposits, are a component of inventoriable production costs.

Net income per share

Net income per share	9 Months Ended
	Sep. 30, 2024
Earnings Per Share [Abstract]
Net income per share	Net income per share Basic net income per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the applicable period. Diluted net income per share is computed by dividing net income by the total of the weighted average number of shares of common stock outstanding during the applicable period, plus the effect of non-vested performance shares and restricted stock units. Weighted average common shares outstanding is comprised of issued shares of 57,043,841 less shares held in treasury of 431,136. Basic and diluted net income per share are calculated as follows, based on a reconciliation of the weighted-average common shares outstanding on a basic and diluted basis: Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 (In thousands, except per share amounts) Net income $ 148,104 $ 146,655 $ 178,405 $ 162,171 Weighted average common shares outstanding - basic 56,613 56,566 56,605 56,566 Effect of dilutive performance shares and restricted stock units 258 169 204 67 Weighted average common shares outstanding - diluted 56,871 56,735 56,809 56,633 Shares excluded from the calculation of diluted loss per share — — — — Net income per share - basic $ 2.62 $ 2.59 $ 3.15 $ 2.87 Net income per share - diluted $ 2.60 $ 2.58 $ 3.14 $ 2.86

Accumulated other comprehensive

Accumulated other comprehensive loss	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Accumulated other comprehensive loss	Accumulated other comprehensive loss The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Unrealized Postretirement Total (In thousands) As of December 31, 2023 $ — $ (11,319) $ (11,319) Amounts reclassified from accumulated other comprehensive loss — 78 78 Net current-period other comprehensive income — 78 78 At March 31, 2024 $ — $ (11,241) $ (11,241) Amounts reclassified from accumulated other comprehensive loss — 77 77 Net current-period other comprehensive income — 77 77 At June 30, 2024 $ — $ (11,164) $ (11,164) Amounts reclassified from accumulated other comprehensive loss — 78 78 Net current-period other comprehensive income — 78 78 At September 30, 2024 $ — $ (11,086) $ (11,086) Net Unrealized Postretirement Total (In thousands) As of December 31, 2022 $ (90) $ (12,262) $ (12,352) Amounts reclassified from accumulated other comprehensive loss 46 47 93 Net current-period other comprehensive income 46 47 93 At March 31, 2023 $ (44) $ (12,215) $ (12,259) Other comprehensive loss before reclassification — (17) (17) Amounts reclassified from accumulated other comprehensive loss 44 48 92 Net current-period other comprehensive income 44 31 75 At June 30, 2023 $ — $ (12,184) $ (12,184) Amounts reclassified from accumulated other comprehensive loss — 49 49 Net current-period other comprehensive income — 49 49 At September 30, 2023 $ — $ (12,135) $ (12,135) The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Operations. The reclassifications were as follows: Three Months Ended Nine Months Ended Location on Consolidated Statements of Operations September 30, September 30, 2024 2023 2024 2023 (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ — $ — $ — $ (118) Interest expense — — — 28 Income taxes — — — (90) Amortization of postretirement liability losses included in net periodic benefit cost (103) (65) (308) (191) Other income 25 16 75 47 Income taxes (78) (49) (233) (144) Total reclassifications $ (78) $ (49) $ (233) $ (234)

Revenue from contracts with cus

Revenue from contracts with customers	9 Months Ended
	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenue from contracts with customers	Revenue from contracts with customers Revenue is recognized when a performance obligation is satisfied by transferring control over a product or service to a customer. Revenue includes revenue from the sales of construction materials and contracting services. Revenue is measured based on consideration specified in a contract with a customer and excludes any sales incentives and amounts collected on behalf of third parties. Knife River is considered an agent for certain taxes collected from customers. As such, we present revenues net of these taxes at the time of sale to be remitted to governmental authorities, including sales and use taxes. Revenue for construction materials is recognized at a point in time when delivery of the products has taken place. Contracting revenue is recognized over time using an input method based on the cost-to-cost measure of progress on a project. Disaggregation In the following tables, revenue is disaggregated by category for each segment and includes sales of materials to both third parties and internal customers. Due to consolidation requirements, the internal sales revenues must be eliminated against the construction materials product used in downstream materials and contracting services to arrive at the external operating revenues. We believe this level of disaggregation best depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. For more information on the Company’s reportable segments, see Note 14. Three Months Ended September 30, 2024 Pacific Northwest Mountain Central Energy Services Corporate Services and Eliminations Total (In thousands) Aggregates $ 36,642 $ 54,038 $ 40,115 $ 62,685 $ — $ — $ 193,480 Ready-mix concrete 40,428 46,999 40,559 85,474 — — 213,460 Asphalt 11,859 47,170 60,022 95,998 — — 215,049 Liquid asphalt — — — — 110,917 — 110,917 Other 48,028 5,416 9 12,242 20,877 3,132 89,704 Contracting services public-sector 48,435 89,271 142,864 198,843 — — 479,413 Contracting services private-sector 9,316 17,545 42,830 10,478 — — 80,169 Internal sales (29,722) (42,614) (65,281) (110,905) (25,308) (3,069) (276,899) Revenues from contracts with customers $ 164,986 $ 217,825 $ 261,118 $ 354,815 $ 106,486 $ 63 $ 1,105,293 Three Months Ended September 30, 2023 Pacific Northwest Mountain Central Energy Services Corporate Services and Eliminations Total (In thousands) Aggregates $ 33,624 $ 57,398 $ 39,519 $ 63,044 $ — $ — $ 193,585 Ready-mix concrete 39,861 46,785 44,053 85,340 — — 216,039 Asphalt 14,050 43,462 59,673 105,592 — — 222,777 Liquid asphalt — — — — 122,596 — 122,596 Other 49,533 4,497 11 10,214 21,797 5,464 91,516 Contracting services public-sector 32,632 68,316 135,700 205,262 — — 441,910 Contracting services private-sector 17,745 25,144 43,944 8,572 — — 95,405 Internal sales (30,116) (36,683) (68,178) (123,099) (28,972) (6,408) (293,456) Revenues from contracts with customers $ 157,329 $ 208,919 $ 254,722 $ 354,925 $ 115,421 $ (944) $ 1,090,372 Nine Months Ended September 30, 2024 Pacific Northwest Mountain Central Energy Services Corporate Services and Eliminations Total (In thousands) Aggregates $ 87,450 $ 146,497 $ 80,708 $ 121,499 $ — $ — $ 436,154 Ready-mix concrete 108,316 124,435 89,361 170,722 — — 492,834 Asphalt 22,828 87,937 93,712 146,324 — — 350,801 Liquid asphalt — — — — 187,256 — 187,256 Other 115,714 14,563 22 25,015 38,325 12,786 206,425 Contracting services public-sector 74,623 196,614 258,746 322,696 — — 852,679 Contracting services private-sector 31,612 58,173 98,185 16,202 — — 204,172 Internal sales (65,342) (91,017) (106,021) (172,079) (41,735) (12,338) (488,532) Revenues from contracts with customers $ 375,201 $ 537,202 $ 514,713 $ 630,379 $ 183,846 $ 448 $ 2,241,789 Nine Months Ended September 30, 2023 Pacific Northwest Mountain Central Energy Services Corporate Services and Eliminations Total (In thousands) Aggregates $ 79,768 $ 147,937 $ 78,051 $ 117,766 $ — $ — $ 423,522 Ready-mix concrete 106,531 125,273 92,929 172,973 — — 497,706 Asphalt 21,640 84,908 89,955 164,830 — — 361,333 Liquid asphalt — — — — 203,802 — 203,802 Other 112,755 11,513 21 22,709 37,838 7,231 192,067 Contracting services public-sector 53,450 138,621 244,320 342,146 — — 778,537 Contracting services private-sector 37,220 80,258 94,706 15,015 — — 227,199 Internal sales (63,313) (84,937) (108,888) (191,860) (44,900) (6,806) (500,704) Revenues from contracts with customers $ 348,051 $ 503,573 $ 491,094 $ 643,579 $ 196,740 $ 425 $ 2,183,462

Uncompleted contracts

Uncompleted contracts	9 Months Ended
	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Uncompleted contracts	Uncompleted contracts The timing of revenue recognition may differ from the timing of invoicing to customers. The timing of invoicing to customers does not necessarily correlate with the timing of revenues being recognized under the cost-to-cost method of accounting. Contracts from contracting services are billed as work progresses in accordance with agreed upon contractual terms. Generally, billing to the customer occurs contemporaneous to revenue recognition. A variance in timing of the billings may result in a contract asset or a contract liability. A contract asset occurs when revenues are recognized under the cost-to-cost measure of progress, which exceeds amounts billed on uncompleted contracts. Such amounts will be billed as standard contract terms allow, usually based on various measures of performance or achievement. A contract liability occurs when there are billings in excess of revenues recognized under the cost-to-cost measure of progress on uncompleted contracts. Contract liabilities decrease as revenue is recognized from the satisfaction of the related performance obligation. The changes in contract assets and liabilities were as follows: September 30, 2024 December 31, 2023 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 69,309 $ 27,293 $ 42,016 Costs and estimated earnings in excess of billings on uncompleted contracts Contract liabilities (44,786) (51,376) 6,590 Billings in excess of costs and estimated earnings on uncompleted contracts Net contract assets (liabilities) $ 24,523 $ (24,083) $ 48,606 September 30, 2023 December 31, 2022 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 50,545 $ 31,145 $ 19,400 Costs and estimated earnings in excess of billings on uncompleted contracts Contract liabilities (58,785) (39,843) (18,942) Billings in excess of costs and estimated earnings on uncompleted contracts Net contract liabilities $ (8,240) $ (8,698) $ 458 The Company recognized $3.9 million and $48.8 million in revenue for the three and nine months ended September 30, 2024, respectively, which was previously included in contract liabilities at December 31, 2023. The Company recognized $3.4 million and $35.1 million in revenue for the three and nine months ended September 30, 2023, respectively, which was previously included in contract liabilities at December 31, 2022. The Company recognized a net increase in revenues of $15.9 million and $28.6 million for the three and nine months ended September 30, 2024, respectively, from performance obligations satisfied in prior periods. The Company recognized a net increase in revenues of $12.1 million and $10.6 million for the three and nine months ended September 30, 2023, respectively, from performance obligations satisfied in prior periods. Remaining performance obligations The remaining performance obligations, also referred to as backlog, include unrecognized revenues that we reasonably expect to be realized. These unrecognized revenues can include: projects that have a written award, a letter of intent, a notice to proceed, an agreed upon work order to perform work on mutually accepted terms and conditions, and change orders or claims to the extent management believes additional contract revenues will be earned and are deemed probable of collection. The majority of our contracts for contracting services have an original duration of less than one year. At September 30, 2024, the Company's remaining performance obligations were $755.1 million. We expect to recognize the following revenue amounts in future periods related to these remaining performance obligations: $688.8 million within the next 12 months or less; $55.1 million within the next 13 to 24 months; and $11.2 million in 25 months or more.

Goodwill and other intangible a

Goodwill and other intangible assets	9 Months Ended
	Sep. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and other intangible assets	Goodwill and other intangible assets The changes in the carrying amount of goodwill were as follows: Balance at January 1, 2024 Goodwill Acquired During the Year Measurement Period Adjustments Reallocation of Goodwill Balance at September 30, 2024 (In thousands) Pacific $ 32,621 $ 43 $ — $ — $ 32,664 Northwest 90,978 — — — 90,978 Mountain 26,816 — — — 26,816 North Central 75,879 735 — — 76,614 South 38,708 — — — 38,708 Energy Services 9,476 — — — 9,476 Total $ 274,478 $ 778 $ — $ — $ 275,256 Balance at January 1, 2023 Goodwill Acquired During the Year Measurement Period Adjustments Reallocation of Goodwill Balance at September 30, 2023 (In thousands) Pacific $ 38,339 $ — $ (62) $ — $ 38,277 Northwest 90,978 — — — 90,978 Mountain 26,816 — — — 26,816 North Central 75,879 — — — 75,879 South 38,708 — — — 38,708 Energy Services 3,820 — — — 3,820 Total $ 274,540 $ — $ (62) $ — $ 274,478 Balance at January 1, 2023 Goodwill Acquired During the Year Measurement Period Adjustments Reallocation of Goodwill Balance at December 31, 2023 (In thousands) Pacific $ 38,339 $ — $ (62) $ (5,656) $ 32,621 Northwest 90,978 — — — 90,978 Mountain 26,816 — — — 26,816 North Central 75,879 — — — 75,879 South 38,708 — — — 38,708 Energy Services 3,820 — — 5,656 9,476 Total $ 274,540 $ — $ (62) $ — $ 274,478 Other amortizable intangible assets were as follows: September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Customer relationships $ 19,059 $ 18,540 $ 18,540 Less accumulated amortization 10,419 8,668 9,102 8,640 9,872 9,438 Noncompete agreements 3,926 4,039 4,039 Less accumulated amortization 3,452 3,358 3,473 474 681 566 Other 1,796 2,479 2,479 Less accumulated amortization 1,056 1,569 1,662 740 910 817 Total $ 9,854 $ 11,463 $ 10,821 Amortization expense for amortizable intangible assets for the three and nine months ended September 30, 2024, was $522,000 and $1.6 million, respectively. Amortization expense for amortizable intangible assets for the three and nine months ended September 30, 2023, was $647,000 and $2.0 million, respectively. Estimated amortization expense for identifiable intangible assets as of September 30, 2024, was: Remainder of 2024 2025 2026 2027 2028 Thereafter (In thousands) Amortization expense $ 677 $ 1,991 $ 1,811 $ 1,789 $ 1,744 $ 1,842

Fair value measurements

Fair value measurements	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Fair value measurements	Fair value measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. The fair value guidance establishes a hierarchy for grouping assets and liabilities, based on the significance of inputs. The estimated fair values of the Company's assets and liabilities measured on a recurring basis are determined using the market approach. Financial instruments measured at fair value on a recurring basis We measure our investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income. We anticipate using these investments, which consist of insurance contracts, to satisfy our obligations under our unfunded, nonqualified defined benefit and defined contribution plans for our executive officers and certain key management employees, and invests in these fixed-income and equity securities for the purpose of earning investment returns and capital appreciation. These investments, which totaled $28.5 million, $23.5 million and $24.9 million at September 30, 2024 and 2023, and December 31, 2023, respectively, are classified as investments on the Consolidated Balance Sheets. The net unrealized gains on these investments were $1.3 million and $2.9 million for the three and nine months ended September 30, 2024, respectively. The net unrealized loss on these investments was $597,000 for the three months ended September 30, 2023 and the net unrealized gain on these investments was $685,000 for the nine months ended September 30, 2023. The change in fair value, which is considered part of the cost of the plan, is classified in other income on the Consolidated Statements of Operations. The Company's assets measured at fair value on a recurring basis were as follows: Fair Value Measurements at September 30, 2024, Using Quoted Prices in Significant Significant Balance at September 30, 2024 (In thousands) Assets: Money market funds $ — $ 4,034 $ — $ 4,034 Insurance contracts* — 28,498 — 28,498 Total assets measured at fair value $ — $ 32,532 $ — $ 32,532 * The insurance contracts invest approximately 36 percent in fixed-income investments, 23 percent in common stock of large-cap companies, 15 percent in cash equivalents, 10 percent in common stock of mid-cap companies, 9 percent target date investments, 5 percent in common stock of small-cap companies, 1 percent in international investments and 1 percent in real estate investments. Fair Value Measurements at September 30, 2023, Using Quoted Prices in Significant Significant Balance at June 30, 2023 (In thousands) Assets: Money market funds $ — $ 3,199 $ — $ 3,199 Insurance contracts* — 23,483 — 23,483 Total assets measured at fair value $ — $ 26,682 $ — $ 26,682 * The insurance contracts invest approximately 41 percent in fixed-income investments, 19 percent in cash equivalents, 18 percent in common stock of large-cap companies, 8 percent in common stock of mid-cap companies, 8 percent target date investments, 5 percent in common stock of small-cap companies and 1 percent international investments. Fair Value Measurements at December 31, 2023, Using Quoted Prices in Significant Significant Balance at December 31, 2023 (In thousands) Assets: Money market funds $ — $ 3,241 $ — $ 3,241 Insurance contracts* — 24,896 — 24,896 Total assets measured at fair value $ — $ 28,137 $ — $ 28,137 * The insurance contracts invest approximately 40 percent in fixed-income investments, 19 percent in common stock of large-cap companies, 18 percent in cash equivalents, 8 percent in target date investments, 8 percent in common stock of mid-cap companies, 6 percent in common stock of small-cap companies and 1 percent in international investments. The Company’s Level 2 money market funds are valued at the net asset value of shares held at the end of the period, based on published market quotations on active markets, or using other known sources including pricing from outside sources. The estimated fair value of the Company’s Level 2 insurance contracts is based on contractual cash surrender values that are determined primarily by investments in managed separate accounts of the insurer. These amounts approximate fair value. The managed separate accounts are valued based on other observable inputs or corroborated market data. Though we believe the methods used to estimate fair value are consistent with those used by other market participants, the use of other methods or assumptions could result in a different estimate of fair value. Nonfinancial instruments measured at fair value on a nonrecurring basis We apply the provisions of the fair value measurement standard to our nonrecurring, non-financial measurements, including long-lived asset impairments. These assets are not measured at fair value on an ongoing basis but are subject to fair value adjustments only in certain circumstances. We review the carrying value of our long-lived assets, excluding goodwill, whenever events or changes in circumstances indicate that such carrying amounts may not be recoverable. The assets and liabilities of the acquisitions that occurred during the third quarter of 2024 were calculated using a market or cost approach. The fair value of some of the assets was determined based on Level 3 inputs including estimated future cash flows, discount rates, growth rates and sales projections, all of which require significant management judgment. The Company's long-term debt is not measured at fair value on the Consolidated Balance Sheets and the fair value is being provided for disclosure purposes only. The fair value was categorized as Level 2 in the fair value hierarchy and was based on discounted cash flows using current market interest rates. The estimated fair value of the Company's Level 2 long-term debt was as follows: September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Carrying amount $ 691,717 $ 698,747 $ 696,985 Fair value $ 719,351 $ 700,687 $ 725,086 The carrying amounts of our remaining financial instruments included in current assets and current liabilities approximate their fair values.

Debt

Debt	9 Months Ended
	Sep. 30, 2024
Debt Disclosure [Abstract]
Debt	Debt Certain debt instruments of the Company contain restrictive covenants and cross-default provisions. In order to borrow under the debt agreements, we must be in compliance with the applicable covenants and certain other conditions, all of which the Company, as applicable, was in compliance with at September 30, 2024. In the event we do not comply with the applicable covenants and other conditions, alternative sources of funding may need to be pursued. Long-term Debt Outstanding Long-term debt outstanding was as follows: Weighted Average Interest Rate at September 30, 2024 September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Term loan agreement due on May 31, 2028 6.45 % $ 266,406 $ 273,281 $ 271,562 Senior notes due on May 1, 2031 7.75 % 425,000 425,000 425,000 Other notes due on January 1, 2061 — % 311 466 423 Less unamortized debt issuance costs 13,254 16,016 15,326 Total long-term debt 678,463 682,731 681,659 Less current maturities 8,791 7,082 7,082 Net long-term debt $ 669,672 $ 675,649 $ 674,577 Schedule of Debt Maturities Long-term debt maturities, which excludes unamortized debt issuance costs, at September 30, 2024, were as follows: Remainder of 2024 2025 2026 2027 2028 Thereafter (In thousands) Long-term debt maturities $ 1,916 $ 10,425 $ 13,750 $ 17,188 $ 223,438 $ 425,000

Cash flow information

Cash flow information	9 Months Ended
	Sep. 30, 2024
Supplemental Cash Flow Information [Abstract]
Cash flow information	Cash flow information Cash expenditures for interest and income taxes were as follows: Nine Months Ended September 30, 2024 2023 (In thousands) Interest paid, net $ 35,321 $ 32,028 Income taxes paid, net $ 33,362 $ 22,183 Noncash investing and financing transactions were as follows: Nine Months Ended September 30, 2024 2023 (In thousands) Right-of-use assets obtained in exchange for new operating lease liabilities $ 15,130 $ 9,717 Property, plant and equipment additions in accounts payable $ 1,770 $ 2,832 Equity contribution from Centennial related to the Separation $ — $ 64,724 Equity contribution to MDU Resources for asset/liability transfers related to the Separation $ — $ (1,548) MDU Resources' stock issued prior to spin in connection with a business combination $ — $ 383

Business segment data

Business segment data	9 Months Ended
	Sep. 30, 2024
Segment Reporting [Abstract]
Business segment data	Business segment data We focus on the vertical integration of our products and services by offering customers a single source for construction materials and related contracting services. We operate in 14 states across the United States through our operating segments: Pacific, Northwest, Mountain, North Central, South and Energy Services. These operating segments are used to determine the Company’s reportable segments, Pacific, Northwest, Mountain, Central and Energy Services, which are based on our method of internal reporting and management of our business. Four of the reportable segments are aligned by key geographic areas due to the production of construction materials and related contracting services and one is based on product line. Each segment is led by a segment manager who reports to the Company’s chief operating officer, who is also the Company's chief operating decision maker, along with the chief executive officer. The chief operating decision maker evaluates the performance of the segments and allocates resources to them based on earnings before interest, taxes, depreciation, depletion and amortization ("EBITDA"). In the fourth quarter of 2023, we realigned our reportable segments to better support our operational strategies. The liquid asphalt and related services portion of the Pacific segment's businesses are now reported under the Energy Services segment. In addition, the North Central and South operating regions have been aggregated into one reportable segment, Central. We also reallocated certain amounts to the operating segments that were previously reported within Corporate Services. All periods have been recast to conform with the revised presentation. Each geographic segment offers a vertically integrated suite of products and services, including aggregates, ready-mix concrete, asphalt and contracting services, while the Energy Services segment produces and supplies liquid asphalt, primarily for use in asphalt road construction, and is a supplier to some of the other segments. Each geographic segment mines, processes and sells construction aggregates (crushed stone and sand and gravel); produces and sells asphalt; and produces and sells ready-mix concrete as well as vertically integrating its contracting services to support the aggregate-based product lines. Contracting services include heavy-civil construction, asphalt and concrete paving, and site development and grading. Although not common to all locations, the geographic segments also sell cement, merchandise and other building materials and related services . Corporate Services represents the unallocated costs of certain corporate functions, such as accounting, legal, treasury, information technology, human resources and other corporate expenses that support the operating segments. We account for intersegment sales and transfers as if the sales or transfers were to third parties. The accounting policies applicable to each segment are consistent with those used in the audited consolidated financial statements. The information below follows the same accounting policies as described in the audited financial statements and notes included in the Company's 2023 Annual Report. Information on the Company's segments was as follows: Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 (In thousands) External operating revenues: Pacific $ 164,986 $ 157,329 $ 375,201 $ 348,051 Northwest 217,825 208,919 537,202 503,573 Mountain 261,118 254,722 514,713 491,094 Central 354,815 354,925 630,379 643,579 Energy Services 106,486 115,421 183,846 196,740 Total reportable segment external operating revenues $ 1,105,230 $ 1,091,316 $ 2,241,341 $ 2,183,037 Intersegment operating revenues: Pacific $ 29,722 $ 30,116 $ 65,342 $ 63,313 Northwest 42,614 36,683 91,017 84,937 Mountain 65,281 68,178 106,021 108,888 Central 110,905 123,099 172,079 191,860 Energy Services 25,308 28,972 41,735 44,900 Total reportable segment intersegment operating revenues $ 273,830 $ 287,048 $ 476,194 $ 493,898 EBITDA: Pacific $ 29,497 $ 28,557 $ 46,543 $ 46,161 Northwest 55,914 48,467 126,831 101,335 Mountain 59,446 59,434 96,500 86,004 Central 79,830 74,779 97,295 86,279 Energy Services 33,708 45,714 50,593 64,519 Total reportable segment EBITDA $ 258,395 $ 256,951 $ 417,762 $ 384,298 A reconciliation of consolidated operating revenues to reportable segment operating revenues is as follows: Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 (In thousands) Consolidated operating revenues $ 1,105,293 $ 1,090,372 $ 2,241,789 $ 2,183,462 Plus: Intersegment operating revenues 276,899 293,456 488,532 500,704 Less: Corporate Services revenue 3,132 5,464 12,786 7,231 Total reportable segment operating revenues $ 1,379,060 $ 1,378,364 $ 2,717,535 $ 2,676,935 A reconciliation of consolidated net income before income taxes to reportable segment EBITDA is as follows: Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 (In thousands) Total consolidated net income before income taxes $ 197,688 $ 194,874 $ 237,848 $ 218,498 Plus: Depreciation, depletion and amortization 34,796 31,752 101,519 92,511 Interest expense, net* 12,113 14,774 36,069 41,399 Less: Corporate Services EBITDA (13,798) (15,551) (42,326) (31,890) Total EBITDA for reportable segments $ 258,395 $ 256,951 $ 417,762 $ 384,298 * Interest, net is interest expense net of interest income.

Commitments and contingencies

Commitments and contingencies	9 Months Ended
	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies The Company is party to claims and lawsuits arising out of its business and that of its consolidated subsidiaries, which may include, but are not limited to, matters involving property damage, personal injury, and environmental, contractual and statutory obligations. We accrue a liability for those contingencies when the incurrence of a loss is probable and the amount can be reasonably estimated. If a range of amounts can be reasonably estimated and no amount within the range is a better estimate than any other amount, then the minimum of the range is accrued. We do not accrue liabilities when the likelihood that the liability has been incurred is probable but the amount cannot be reasonably estimated or when the liability is believed to be only reasonably possible or remote. For contingencies where an unfavorable outcome is probable or reasonably possible and which are material, we disclose the nature of the contingency and, in some circumstances, an estimate of the possible loss. Accruals are based on the best information available, but in certain situations management is unable to estimate an amount or range of a reasonably possible loss including, but not limited to when: (1) the damages are unsubstantiated or indeterminate, (2) the proceedings are in the early stages, (3) numerous parties are involved, or (4) the matter involves novel or unsettled legal theories. At September 30, 2024 and 2023, and December 31, 2023, we accrued contingent liabilities as a result of litigation, which have not been discounted, of $3.2 million, $645,000 and $873,000, respectively. Most of these claims and lawsuits are covered by insurance, thus the Company's exposure is typically limited to its deductible amount. Management will continue to monitor each matter and adjust accruals as might be warranted based on new information and further developments. Management believes that the outcomes with respect to probable and reasonably possible losses in excess of the amounts accrued, net of insurance recoveries, while uncertain, either cannot be estimated or will not have a material effect upon the Company's financial position, results of operations or cash flows. Unless otherwise required by GAAP, legal costs are expensed as they are incurred. Environmental matters The Company is a party to claims for the cleanup of a superfund site in Portland, Oregon. There were no material changes to the environmental matters that were previously reported in the audited financial statements and notes included in the Company's 2023 Annual Report. Guarantees Knife River and certain of its subsidiaries have outstanding obligations to third parties where the Company has guaranteed their performance. These guarantees are related to contracts for contracting services and certain other guarantees. At September 30, 2024, the fixed maximum amounts guaranteed under these agreements aggregated to $11.5 million, all of which have no scheduled maturity date. Certain of the guarantees also have no fixed maximum amounts specified. There were no amounts outstanding under the previously mentioned guarantees at September 30, 2024. Knife River and certain of its subsidiaries have outstanding letters of credit to third parties related to insurance policies and other agreements. At September 30, 2024, the fixed maximum amounts guaranteed under these letters of credit aggregated $20.6 million. At September 30, 2024, the amounts of scheduled expiration of the maximum amounts guaranteed under these letters of credit aggregate to $0 in 2024, $20.5 million in 2025, $0 in 2026 and $104,000 in 2027. There were no amounts outstanding under the previously mentioned letters of credit at September 30, 2024. In the normal course of business, we have surety bonds related to contracts for contracting services, reclamation obligations and insurance policies of its subsidiaries. In the event a subsidiary of Knife River does not fulfill a bonded obligation, the Company would be responsible to the surety bond company for completion of the bonded contract or obligation. A large portion of the surety bonds are expected to expire within the next 12 months; however, we will likely continue to enter into surety bonds for our subsidiaries in the future. At September 30, 2024, approximately $686.8 million of surety bonds were outstanding, which were not reflected on the Consolidated Balance Sheet.

Related party transactions

Related party transactions	9 Months Ended
	Sep. 30, 2024
Related Party Transactions [Abstract]
Related party transactions	Related-party transactions Transition services agreements As part of the Separation, MDU Resources provided transition services to Knife River and Knife River is providing transition services to MDU Resources in accordance with the Transition Services Agreement entered into on May 30, 2023. The Company paid $40,000 and $1.3 million for the three months ended and $1.3 million and $1.9 million for the nine months ended September 30, 2024 and 2023, respectively, related to these activities, which were reflected in selling, general and administrative expenses on the Consolidated Statements of Operations. The Company received $14,000 and $407,000 for the three months ended and $152,000 and $684,000 for the nine months ended September 30, 2024 and 2023, respectively, related to these activities, which were reflected in other income on the Consolidated Statements of Operations. The majority of the transition services were completed over a period of one year after the Separation. The Company expects minimal continued services by Knife River to MDU Resources through May 2025. For additional information on the presentation of related-party transactions, see Note 2.

Subsequent event

Subsequent event	9 Months Ended
	Sep. 30, 2024
Subsequent Events [Abstract]
Subsequent event	Subsequent event On November 2, 2024, the Company acquired the business of Albina Asphalt, a liquid asphalt provider with operations in Washington, Oregon and California, and will be included in the Company's Energy Services segment. To date, the initial accounting for the acquisition is incomplete. Due to the limited time since the date of the acquisition, it is impracticable for the Company to make business combination disclosures related to the acquisition. The Company is still gathering the necessary information to provide such disclosures in future filings.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net income (loss)	$ 148,104	$ 77,929	$ (47,629)	$ 146,655	$ 56,836	$ (41,320)	$ 178,405	$ 162,171

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Basis of presentation (Policies

Basis of presentation (Policies)	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	The accompanying consolidated interim financial statements were prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Interim financial statements do not include all disclosures provided in annual financial statements and, accordingly, these financial statements should be read in conjunction with the Company's 2023 Annual Report on Form 10-K ("Annual Report"). The information is unaudited but includes adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. Prior to the Separation, Knife River operated as a wholly owned subsidiary of Centennial Energy Holdings, Inc., a direct wholly owned subsidiary of MDU Resources and the direct parent company of Knife River prior to the spinoff ("Centennial") and an indirect, wholly owned subsidiary of MDU Resources and not as a stand-alone company. The accompanying consolidated financial statements and footnotes for the periods prior to the Separation were prepared on a "carve-out" basis using a legal entity approach in conformity with GAAP and were derived from the consolidated financial statements of MDU Resources as if Knife River operated on a stand-alone basis during these periods. All revenues and costs, as well as assets and liabilities, directly associated with our business activities are included in the consolidated financial statements. In the periods prior to the Separation, the consolidated financial statements include expense allocations for certain functions provided by MDU Resources and Centennial, including, but not limited to, certain general corporate expenses related to senior management, legal, human resources, finance and accounting, treasury, information technology, communications, procurement, tax, insurance and other shared services. These general corporate expenses are included in the Consolidated Statements of Operations within selling, general and administrative expenses and other income. There were no amounts allocated to Knife River for the three months ended September 30, 2023, and $9.0 million was allocated for the nine months ended September 30, 2023 in selling, general and administrative expenses. There were no amounts allocated for the three months ended September 30, 2023 and $348,000 was allocated for the nine months ended September 30, 2023 in other income. These items were allocated on the basis of direct usage when identifiable, with the remainder principally allocated on the basis of percent of total capital invested or other allocation methodologies that were considered to be a reasonable reflection of the utilization of the services provided to the benefits received, including the following: number of employees paid and stated as cost per check; number of employees served; weighted factor of travel, managed units, national account spending, equipment and fleet acquisitions; purchase order dollars spent and purchase order line count; number of payments, vouchers or unclaimed property reports; labor hours; time tracked; and projected workload. The allocations may not, however, reflect the expenses we would have incurred as a stand-alone company for the periods presented. These costs also may not be indicative of the expenses that we will incur in the future or would have incurred if we had obtained these services from a third party. Management has also evaluated the impact of events occurring after September 30, 2024, up to the date of issuance of these consolidated interim financial statements on November 4, 2024, that would require recognition or disclosure in the Consolidated Financial Statements. See Note 17 - Subsequent Events for more details on these events.
Principles of consolidation	Principles of consolidation
Use of estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, at the date of the consolidated financial statements, as well as the reported amounts of revenues and expenses during the reporting period. Estimates are used for items such as long-lived assets and goodwill; fair values of acquired assets and liabilities under the acquisition method of accounting; aggregate reserves; property depreciable lives; tax provisions; revenue recognized using the cost-to-cost measure of progress for contracts; expected credit losses; environmental and other loss contingencies; costs on contracting services contracts; actuarially determined benefit costs; asset retirement obligations; lease classification; present value of right-of-use assets and lease liabilities; and the valuation of stock-based compensation. These estimates are based on management’s best knowledge of current events, historical experience, actions that we may undertake in the future and on various other assumptions that are believed to be reasonable under the circumstances. As additional information becomes available, or actual amounts are determinable, the recorded estimates are revised. Consequently, operating results can be affected by revisions to prior accounting estimates.
Cash, cash equivalents and restricted cash	Cash, cash equivalents and restricted cash
Seasonality of operations	Seasonality of operations Some of our operations are seasonal and revenues from, and certain expenses for, such operations may fluctuate significantly among quarterly periods, with lower activity in the winter months and higher activity in the summer months. Accordingly, the interim results for particular segments, and for Knife River as a whole, may not be indicative of results for the full fiscal year or other future periods.
New accounting standards	The following table provides a brief description of the accounting pronouncements applicable to Knife River and the potential impact on its consolidated financial statements and/or disclosures: Standard Description Standard Effective Date Impact on financial statements/disclosures Recently issued Financial Accounting Standards Board (FASB) accounting standards updates ("ASU") not yet adopted ASU 2023-07 - Improvements to Reportable Segment Disclosures In November 2023, the FASB issued guidance on modifying the disclosure requirements to improve reportable segment disclosure requirements through enhanced disclosures about significant segment expenses. The guidance also expands the interim disclosure requirements. The guidance is to be applied on a retrospective basis to the financial statements and footnotes and early adoption is permitted. Fiscal periods beginning after December 15, 2023 and interim periods beginning after December 31, 2024 The Company is currently evaluating the impact the guidance will have on its disclosures for the year ended December 31, 2024 and interim periods for fiscal year 2025. ASU 2023-09 - Improvements to Income Tax Disclosures In December 2023, the FASB issued guidance on modifying the disclosure requirements to increase transparency about income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid information. The guidance is to be applied on a prospective basis to the financial statements and footnotes, however, retrospective adoption is also permitted. The guidance also permits early adoption. Fiscal periods beginning after December 15, 2024 The Company is electing to early adopt the guidance for the year ended December 31, 2024, on a retrospective basis. The Company has reviewed the impact to its disclosures and although not material, will have updates to the income tax footnote.
Schedule of Accounting Standards Update and Change in Accounting Principle	The following table provides a brief description of the accounting pronouncements applicable to Knife River and the potential impact on its consolidated financial statements and/or disclosures: Standard Description Standard Effective Date Impact on financial statements/disclosures Recently issued Financial Accounting Standards Board (FASB) accounting standards updates ("ASU") not yet adopted ASU 2023-07 - Improvements to Reportable Segment Disclosures In November 2023, the FASB issued guidance on modifying the disclosure requirements to improve reportable segment disclosure requirements through enhanced disclosures about significant segment expenses. The guidance also expands the interim disclosure requirements. The guidance is to be applied on a retrospective basis to the financial statements and footnotes and early adoption is permitted. Fiscal periods beginning after December 15, 2023 and interim periods beginning after December 31, 2024 The Company is currently evaluating the impact the guidance will have on its disclosures for the year ended December 31, 2024 and interim periods for fiscal year 2025. ASU 2023-09 - Improvements to Income Tax Disclosures In December 2023, the FASB issued guidance on modifying the disclosure requirements to increase transparency about income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid information. The guidance is to be applied on a prospective basis to the financial statements and footnotes, however, retrospective adoption is also permitted. The guidance also permits early adoption. Fiscal periods beginning after December 15, 2024 The Company is electing to early adopt the guidance for the year ended December 31, 2024, on a retrospective basis. The Company has reviewed the impact to its disclosures and although not material, will have updates to the income tax footnote.
Expected credit loss	Receivables consist primarily of trade and contract receivables for the sale of goods and services net of expected credit losses. A majority of our receivables are due in 30 days or less.The Company's expected credit losses are determined through a review using historical credit loss experience; changes in asset specific characteristics; current conditions; and reasonable and supportable future forecasts, among other specific account data, and is performed at least quarterly. We develop and document our methodology to determine our allowance for expected credit losses. Risk characteristics used by management may include customer mix, knowledge of customers and general economic conditions of the various local economies, among others. Specific account balances are written off when management determines the amounts to be uncollectible.
Inventories	Inventories are valued at the lower of cost or net realizable value using the average cost method. Inventories include production costs incurred as part of our aggregate mining activities. These inventoriable production costs include all mining and processing costs associated with the production of aggregates. Stripping costs incurred during the production phase, which represent costs of removing overburden and waste materials to access mineral deposits, are a component of inventoriable production costs.
Net income per share	Basic net income per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the applicable period. Diluted net income per share is computed by dividing net income by the total of the weighted average number of shares of common stock outstanding during the applicable period, plus the effect of non-vested performance shares and restricted stock units.
Disaggregation of revenue	Revenue is recognized when a performance obligation is satisfied by transferring control over a product or service to a customer. Revenue includes revenue from the sales of construction materials and contracting services. Revenue is measured based on consideration specified in a contract with a customer and excludes any sales incentives and amounts collected on behalf of third parties. Knife River is considered an agent for certain taxes collected from customers. As such, we present revenues net of these taxes at the time of sale to be remitted to governmental authorities, including sales and use taxes. Revenue for construction materials is recognized at a point in time when delivery of the products has taken place. Contracting revenue is recognized over time using an input method based on the cost-to-cost measure of progress on a project.
Fair value measurements	We measure our investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income.
Business segment data	Company’s reportable segments, Pacific, Northwest, Mountain, Central and Energy Services, which are based on our method of internal reporting and management of our business. Four of the reportable segments are aligned by key geographic areas due to the production of construction materials and related contracting services and one is based on product line. Each segment is led by a segment manager who reports to the Company’s chief operating officer, who is also the Company's chief operating decision maker, along with the chief executive officer. The chief operating decision maker evaluates the performance of the segments and allocates resources to them based on earnings before interest, taxes, depreciation, depletion and amortization ("EBITDA"). In the fourth quarter of 2023, we realigned our reportable segments to better support our operational strategies. The liquid asphalt and related services portion of the Pacific segment's businesses are now reported under the Energy Services segment. In addition, the North Central and South operating regions have been aggregated into one reportable segment, Central. We also reallocated certain amounts to the operating segments that were previously reported within Corporate Services. All periods have been recast to conform with the revised presentation.
Commitments and contingencies	The Company is party to claims and lawsuits arising out of its business and that of its consolidated subsidiaries, which may include, but are not limited to, matters involving property damage, personal injury, and environmental, contractual and statutory obligations. We accrue a liability for those contingencies when the incurrence of a loss is probable and the amount can be reasonably estimated. If a range of amounts can be reasonably estimated and no amount within the range is a better estimate than any other amount, then the minimum of the range is accrued. We do not accrue liabilities when the likelihood that the liability has been incurred is probable but the amount cannot be reasonably estimated or when the liability is believed to be only reasonably possible or remote. For contingencies where an unfavorable outcome is probable or reasonably possible and which are material, we disclose the nature of the contingency and, in some circumstances, an estimate of the possible loss. Accruals are based on the best information available, but in certain situations management is unable to estimate an amount or range of a reasonably possible loss including, but not limited to when: (1) the damages are unsubstantiated or indeterminate, (2) the proceedings are in the early stages, (3) numerous parties are involved, or (4) the matter involves novel or unsettled legal theories.

Basis of presentation (Tables)

Basis of presentation (Tables)	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Cash and Cash Equivalents	Restricted cash represents deposits held by our captive insurance company that is required by state insurance regulations to remain in the captive insurance company. Cash, cash equivalents and restricted cash on the Consolidated Balance Sheets is comprised of: September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Cash and cash equivalents $ 220,368 $ 84,006 $ 219,324 Restricted cash 47,074 32,153 42,996 Cash, cash equivalents and restricted cash $ 267,442 $ 116,159 $ 262,320
Schedule of Restrictions on Cash and Cash Equivalents	Restricted cash represents deposits held by our captive insurance company that is required by state insurance regulations to remain in the captive insurance company. Cash, cash equivalents and restricted cash on the Consolidated Balance Sheets is comprised of: September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Cash and cash equivalents $ 220,368 $ 84,006 $ 219,324 Restricted cash 47,074 32,153 42,996 Cash, cash equivalents and restricted cash $ 267,442 $ 116,159 $ 262,320

New Accounting Standards (Table

New Accounting Standards (Tables)	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Schedule of Accounting Standards Update and Change in Accounting Principle	The following table provides a brief description of the accounting pronouncements applicable to Knife River and the potential impact on its consolidated financial statements and/or disclosures: Standard Description Standard Effective Date Impact on financial statements/disclosures Recently issued Financial Accounting Standards Board (FASB) accounting standards updates ("ASU") not yet adopted ASU 2023-07 - Improvements to Reportable Segment Disclosures In November 2023, the FASB issued guidance on modifying the disclosure requirements to improve reportable segment disclosure requirements through enhanced disclosures about significant segment expenses. The guidance also expands the interim disclosure requirements. The guidance is to be applied on a retrospective basis to the financial statements and footnotes and early adoption is permitted. Fiscal periods beginning after December 15, 2023 and interim periods beginning after December 31, 2024 The Company is currently evaluating the impact the guidance will have on its disclosures for the year ended December 31, 2024 and interim periods for fiscal year 2025. ASU 2023-09 - Improvements to Income Tax Disclosures In December 2023, the FASB issued guidance on modifying the disclosure requirements to increase transparency about income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid information. The guidance is to be applied on a prospective basis to the financial statements and footnotes, however, retrospective adoption is also permitted. The guidance also permits early adoption. Fiscal periods beginning after December 15, 2024 The Company is electing to early adopt the guidance for the year ended December 31, 2024, on a retrospective basis. The Company has reviewed the impact to its disclosures and although not material, will have updates to the income tax footnote.

Receivables and allowance for_2

Receivables and allowance for expected credit losses (Tables)	9 Months Ended
	Sep. 30, 2024
Credit Loss [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable	Receivables were as follows: September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Trade receivables $ 229,887 $ 236,373 $ 124,134 Contract receivables 187,622 223,874 112,037 Retention receivables 35,980 37,814 36,782 Receivables, gross 453,489 498,061 272,953 Less expected credit loss 4,301 6,195 6,168 Receivables, net $ 449,188 $ 491,866 $ 266,785
Schedule of Accounts Receivable, Allowance for Credit Loss	Details of the Company's expected credit losses were as follows: Pacific Northwest Mountain Central Energy Services Total (In thousands) As of December 31, 2023 $ 2,053 $ 1,004 $ 2,293 $ 718 $ 100 $ 6,168 Current expected credit loss provision 177 (223) (47) 87 — (6) Less write-offs charged against the allowance (53) 133 2 3 — 85 At March 31, 2024 $ 2,283 $ 648 $ 2,244 $ 802 $ 100 $ 6,077 Current expected credit loss provision 25 79 27 151 1 283 Less write-offs charged against the allowance 513 11 1,122 212 1 1,859 At June 30, 2024 $ 1,795 $ 716 $ 1,149 $ 741 $ 100 $ 4,501 Current expected credit loss provision 126 (19) (5) 223 1 326 Less write-offs charged against the allowance 74 108 233 106 5 526 At September 30, 2024 $ 1,847 $ 589 $ 911 $ 858 $ 96 $ 4,301 Pacific Northwest Mountain Central Energy Services Total (In thousands) As of December 31, 2022 $ 1,945 $ 1,253 $ 1,278 $ 901 $ 100 $ 5,477 Current expected credit loss provision 45 313 164 (90) — 432 Less write-offs charged against the allowance 1 68 18 — — 87 At March 31, 2023 $ 1,989 $ 1,498 $ 1,424 $ 811 $ 100 $ 5,822 Current expected credit loss provision 8 74 631 (131) 1 583 Less write-offs charged against the allowance 17 512 3 2 1 535 At June 30, 2023 $ 1,980 $ 1,060 $ 2,052 $ 678 $ 100 $ 5,870 Current expected credit loss provision 46 242 (152) 235 — 371 Less write-offs charged against the allowance 26 4 13 3 — 46 At September 30, 2023 $ 2,000 $ 1,298 $ 1,887 $ 910 $ 100 $ 6,195

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2024
Inventory Disclosure [Abstract]
Schedule of Inventory	Inventories on the Consolidated Balance Sheets were as follows: September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Finished products $ 240,746 $ 213,702 $ 225,319 Raw materials 67,830 63,156 61,776 Supplies and parts 38,724 37,853 32,528 Total $ 347,300 $ 314,711 $ 319,623

Net income per share (Tables)

Net income per share (Tables)	9 Months Ended
	Sep. 30, 2024
Earnings Per Share [Abstract]
Schedule of Reconciliation of the Weighted-Average Common Shares Outstanding on a Basic and Diluted Basis	Basic and diluted net income per share are calculated as follows, based on a reconciliation of the weighted-average common shares outstanding on a basic and diluted basis: Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 (In thousands, except per share amounts) Net income $ 148,104 $ 146,655 $ 178,405 $ 162,171 Weighted average common shares outstanding - basic 56,613 56,566 56,605 56,566 Effect of dilutive performance shares and restricted stock units 258 169 204 67 Weighted average common shares outstanding - diluted 56,871 56,735 56,809 56,633 Shares excluded from the calculation of diluted loss per share — — — — Net income per share - basic $ 2.62 $ 2.59 $ 3.15 $ 2.87 Net income per share - diluted $ 2.60 $ 2.58 $ 3.14 $ 2.86

Accumulated other comprehensi_2

Accumulated other comprehensive loss (Tables)	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Schedule of After-Tax Changes in the Components of Accumulated Other Comprehensive Loss	The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Unrealized Postretirement Total (In thousands) As of December 31, 2023 $ — $ (11,319) $ (11,319) Amounts reclassified from accumulated other comprehensive loss — 78 78 Net current-period other comprehensive income — 78 78 At March 31, 2024 $ — $ (11,241) $ (11,241) Amounts reclassified from accumulated other comprehensive loss — 77 77 Net current-period other comprehensive income — 77 77 At June 30, 2024 $ — $ (11,164) $ (11,164) Amounts reclassified from accumulated other comprehensive loss — 78 78 Net current-period other comprehensive income — 78 78 At September 30, 2024 $ — $ (11,086) $ (11,086) Net Unrealized Postretirement Total (In thousands) As of December 31, 2022 $ (90) $ (12,262) $ (12,352) Amounts reclassified from accumulated other comprehensive loss 46 47 93 Net current-period other comprehensive income 46 47 93 At March 31, 2023 $ (44) $ (12,215) $ (12,259) Other comprehensive loss before reclassification — (17) (17) Amounts reclassified from accumulated other comprehensive loss 44 48 92 Net current-period other comprehensive income 44 31 75 At June 30, 2023 $ — $ (12,184) $ (12,184) Amounts reclassified from accumulated other comprehensive loss — 49 49 Net current-period other comprehensive income — 49 49 At September 30, 2023 $ — $ (12,135) $ (12,135)
Schedule of Reclassification out of Accumulated Other Comprehensive Loss	The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Operations. The reclassifications were as follows: Three Months Ended Nine Months Ended Location on Consolidated Statements of Operations September 30, September 30, 2024 2023 2024 2023 (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ — $ — $ — $ (118) Interest expense — — — 28 Income taxes — — — (90) Amortization of postretirement liability losses included in net periodic benefit cost (103) (65) (308) (191) Other income 25 16 75 47 Income taxes (78) (49) (233) (144) Total reclassifications $ (78) $ (49) $ (233) $ (234)

Revenue from contracts with c_2

Revenue from contracts with customers (Tables)	9 Months Ended
	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	Three Months Ended September 30, 2024 Pacific Northwest Mountain Central Energy Services Corporate Services and Eliminations Total (In thousands) Aggregates $ 36,642 $ 54,038 $ 40,115 $ 62,685 $ — $ — $ 193,480 Ready-mix concrete 40,428 46,999 40,559 85,474 — — 213,460 Asphalt 11,859 47,170 60,022 95,998 — — 215,049 Liquid asphalt — — — — 110,917 — 110,917 Other 48,028 5,416 9 12,242 20,877 3,132 89,704 Contracting services public-sector 48,435 89,271 142,864 198,843 — — 479,413 Contracting services private-sector 9,316 17,545 42,830 10,478 — — 80,169 Internal sales (29,722) (42,614) (65,281) (110,905) (25,308) (3,069) (276,899) Revenues from contracts with customers $ 164,986 $ 217,825 $ 261,118 $ 354,815 $ 106,486 $ 63 $ 1,105,293 Three Months Ended September 30, 2023 Pacific Northwest Mountain Central Energy Services Corporate Services and Eliminations Total (In thousands) Aggregates $ 33,624 $ 57,398 $ 39,519 $ 63,044 $ — $ — $ 193,585 Ready-mix concrete 39,861 46,785 44,053 85,340 — — 216,039 Asphalt 14,050 43,462 59,673 105,592 — — 222,777 Liquid asphalt — — — — 122,596 — 122,596 Other 49,533 4,497 11 10,214 21,797 5,464 91,516 Contracting services public-sector 32,632 68,316 135,700 205,262 — — 441,910 Contracting services private-sector 17,745 25,144 43,944 8,572 — — 95,405 Internal sales (30,116) (36,683) (68,178) (123,099) (28,972) (6,408) (293,456) Revenues from contracts with customers $ 157,329 $ 208,919 $ 254,722 $ 354,925 $ 115,421 $ (944) $ 1,090,372 Nine Months Ended September 30, 2024 Pacific Northwest Mountain Central Energy Services Corporate Services and Eliminations Total (In thousands) Aggregates $ 87,450 $ 146,497 $ 80,708 $ 121,499 $ — $ — $ 436,154 Ready-mix concrete 108,316 124,435 89,361 170,722 — — 492,834 Asphalt 22,828 87,937 93,712 146,324 — — 350,801 Liquid asphalt — — — — 187,256 — 187,256 Other 115,714 14,563 22 25,015 38,325 12,786 206,425 Contracting services public-sector 74,623 196,614 258,746 322,696 — — 852,679 Contracting services private-sector 31,612 58,173 98,185 16,202 — — 204,172 Internal sales (65,342) (91,017) (106,021) (172,079) (41,735) (12,338) (488,532) Revenues from contracts with customers $ 375,201 $ 537,202 $ 514,713 $ 630,379 $ 183,846 $ 448 $ 2,241,789 Nine Months Ended September 30, 2023 Pacific Northwest Mountain Central Energy Services Corporate Services and Eliminations Total (In thousands) Aggregates $ 79,768 $ 147,937 $ 78,051 $ 117,766 $ — $ — $ 423,522 Ready-mix concrete 106,531 125,273 92,929 172,973 — — 497,706 Asphalt 21,640 84,908 89,955 164,830 — — 361,333 Liquid asphalt — — — — 203,802 — 203,802 Other 112,755 11,513 21 22,709 37,838 7,231 192,067 Contracting services public-sector 53,450 138,621 244,320 342,146 — — 778,537 Contracting services private-sector 37,220 80,258 94,706 15,015 — — 227,199 Internal sales (63,313) (84,937) (108,888) (191,860) (44,900) (6,806) (500,704) Revenues from contracts with customers $ 348,051 $ 503,573 $ 491,094 $ 643,579 $ 196,740 $ 425 $ 2,183,462

Uncompleted contracts (Tables)

Uncompleted contracts (Tables)	9 Months Ended
	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Schedule of Changes in Contract Assets and Liabilities	The changes in contract assets and liabilities were as follows: September 30, 2024 December 31, 2023 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 69,309 $ 27,293 $ 42,016 Costs and estimated earnings in excess of billings on uncompleted contracts Contract liabilities (44,786) (51,376) 6,590 Billings in excess of costs and estimated earnings on uncompleted contracts Net contract assets (liabilities) $ 24,523 $ (24,083) $ 48,606 September 30, 2023 December 31, 2022 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 50,545 $ 31,145 $ 19,400 Costs and estimated earnings in excess of billings on uncompleted contracts Contract liabilities (58,785) (39,843) (18,942) Billings in excess of costs and estimated earnings on uncompleted contracts Net contract liabilities $ (8,240) $ (8,698) $ 458

Goodwill and other intangible_2

Goodwill and other intangible assets (Tables)	9 Months Ended
	Sep. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The changes in the carrying amount of goodwill were as follows: Balance at January 1, 2024 Goodwill Acquired During the Year Measurement Period Adjustments Reallocation of Goodwill Balance at September 30, 2024 (In thousands) Pacific $ 32,621 $ 43 $ — $ — $ 32,664 Northwest 90,978 — — — 90,978 Mountain 26,816 — — — 26,816 North Central 75,879 735 — — 76,614 South 38,708 — — — 38,708 Energy Services 9,476 — — — 9,476 Total $ 274,478 $ 778 $ — $ — $ 275,256 Balance at January 1, 2023 Goodwill Acquired During the Year Measurement Period Adjustments Reallocation of Goodwill Balance at September 30, 2023 (In thousands) Pacific $ 38,339 $ — $ (62) $ — $ 38,277 Northwest 90,978 — — — 90,978 Mountain 26,816 — — — 26,816 North Central 75,879 — — — 75,879 South 38,708 — — — 38,708 Energy Services 3,820 — — — 3,820 Total $ 274,540 $ — $ (62) $ — $ 274,478 Balance at January 1, 2023 Goodwill Acquired During the Year Measurement Period Adjustments Reallocation of Goodwill Balance at December 31, 2023 (In thousands) Pacific $ 38,339 $ — $ (62) $ (5,656) $ 32,621 Northwest 90,978 — — — 90,978 Mountain 26,816 — — — 26,816 North Central 75,879 — — — 75,879 South 38,708 — — — 38,708 Energy Services 3,820 — — 5,656 9,476 Total $ 274,540 $ — $ (62) $ — $ 274,478
Schedule of Other Amortizable Intangible Assets	Other amortizable intangible assets were as follows: September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Customer relationships $ 19,059 $ 18,540 $ 18,540 Less accumulated amortization 10,419 8,668 9,102 8,640 9,872 9,438 Noncompete agreements 3,926 4,039 4,039 Less accumulated amortization 3,452 3,358 3,473 474 681 566 Other 1,796 2,479 2,479 Less accumulated amortization 1,056 1,569 1,662 740 910 817 Total $ 9,854 $ 11,463 $ 10,821
Schedule of Future Amortization Expense	Estimated amortization expense for identifiable intangible assets as of September 30, 2024, was: Remainder of 2024 2025 2026 2027 2028 Thereafter (In thousands) Amortization expense $ 677 $ 1,991 $ 1,811 $ 1,789 $ 1,744 $ 1,842

Fair value measurements (Tables

Fair value measurements (Tables)	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Schedule of Assets Measured at Fair Value on a Recurring Basis	The Company's assets measured at fair value on a recurring basis were as follows: Fair Value Measurements at September 30, 2024, Using Quoted Prices in Significant Significant Balance at September 30, 2024 (In thousands) Assets: Money market funds $ — $ 4,034 $ — $ 4,034 Insurance contracts* — 28,498 — 28,498 Total assets measured at fair value $ — $ 32,532 $ — $ 32,532 * The insurance contracts invest approximately 36 percent in fixed-income investments, 23 percent in common stock of large-cap companies, 15 percent in cash equivalents, 10 percent in common stock of mid-cap companies, 9 percent target date investments, 5 percent in common stock of small-cap companies, 1 percent in international investments and 1 percent in real estate investments. Fair Value Measurements at September 30, 2023, Using Quoted Prices in Significant Significant Balance at June 30, 2023 (In thousands) Assets: Money market funds $ — $ 3,199 $ — $ 3,199 Insurance contracts* — 23,483 — 23,483 Total assets measured at fair value $ — $ 26,682 $ — $ 26,682 * The insurance contracts invest approximately 41 percent in fixed-income investments, 19 percent in cash equivalents, 18 percent in common stock of large-cap companies, 8 percent in common stock of mid-cap companies, 8 percent target date investments, 5 percent in common stock of small-cap companies and 1 percent international investments. Fair Value Measurements at December 31, 2023, Using Quoted Prices in Significant Significant Balance at December 31, 2023 (In thousands) Assets: Money market funds $ — $ 3,241 $ — $ 3,241 Insurance contracts* — 24,896 — 24,896 Total assets measured at fair value $ — $ 28,137 $ — $ 28,137 * The insurance contracts invest approximately 40 percent in fixed-income investments, 19 percent in common stock of large-cap companies, 18 percent in cash equivalents, 8 percent in target date investments, 8 percent in common stock of mid-cap companies, 6 percent in common stock of small-cap companies and 1 percent in international investments.
Schedule of Fair Value of Long-Term Debt	The estimated fair value of the Company's Level 2 long-term debt was as follows: September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Carrying amount $ 691,717 $ 698,747 $ 696,985 Fair value $ 719,351 $ 700,687 $ 725,086

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2024
Debt Disclosure [Abstract]
Schedule of Long-Term Debt Outstanding	Long-term debt outstanding was as follows: Weighted Average Interest Rate at September 30, 2024 September 30, 2024 September 30, 2023 December 31, 2023 (In thousands) Term loan agreement due on May 31, 2028 6.45 % $ 266,406 $ 273,281 $ 271,562 Senior notes due on May 1, 2031 7.75 % 425,000 425,000 425,000 Other notes due on January 1, 2061 — % 311 466 423 Less unamortized debt issuance costs 13,254 16,016 15,326 Total long-term debt 678,463 682,731 681,659 Less current maturities 8,791 7,082 7,082 Net long-term debt $ 669,672 $ 675,649 $ 674,577
Schedule of Debt Maturities	Long-term debt maturities, which excludes unamortized debt issuance costs, at September 30, 2024, were as follows: Remainder of 2024 2025 2026 2027 2028 Thereafter (In thousands) Long-term debt maturities $ 1,916 $ 10,425 $ 13,750 $ 17,188 $ 223,438 $ 425,000

Cash flow information (Tables)

Cash flow information (Tables)	9 Months Ended
	Sep. 30, 2024
Supplemental Cash Flow Information [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Cash expenditures for interest and income taxes were as follows: Nine Months Ended September 30, 2024 2023 (In thousands) Interest paid, net $ 35,321 $ 32,028 Income taxes paid, net $ 33,362 $ 22,183 Noncash investing and financing transactions were as follows: Nine Months Ended September 30, 2024 2023 (In thousands) Right-of-use assets obtained in exchange for new operating lease liabilities $ 15,130 $ 9,717 Property, plant and equipment additions in accounts payable $ 1,770 $ 2,832 Equity contribution from Centennial related to the Separation $ — $ 64,724 Equity contribution to MDU Resources for asset/liability transfers related to the Separation $ — $ (1,548) MDU Resources' stock issued prior to spin in connection with a business combination $ — $ 383

Business segment data (Tables)

Business segment data (Tables)	9 Months Ended
	Sep. 30, 2024
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The information below follows the same accounting policies as described in the audited financial statements and notes included in the Company's 2023 Annual Report. Information on the Company's segments was as follows: Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 (In thousands) External operating revenues: Pacific $ 164,986 $ 157,329 $ 375,201 $ 348,051 Northwest 217,825 208,919 537,202 503,573 Mountain 261,118 254,722 514,713 491,094 Central 354,815 354,925 630,379 643,579 Energy Services 106,486 115,421 183,846 196,740 Total reportable segment external operating revenues $ 1,105,230 $ 1,091,316 $ 2,241,341 $ 2,183,037 Intersegment operating revenues: Pacific $ 29,722 $ 30,116 $ 65,342 $ 63,313 Northwest 42,614 36,683 91,017 84,937 Mountain 65,281 68,178 106,021 108,888 Central 110,905 123,099 172,079 191,860 Energy Services 25,308 28,972 41,735 44,900 Total reportable segment intersegment operating revenues $ 273,830 $ 287,048 $ 476,194 $ 493,898 EBITDA: Pacific $ 29,497 $ 28,557 $ 46,543 $ 46,161 Northwest 55,914 48,467 126,831 101,335 Mountain 59,446 59,434 96,500 86,004 Central 79,830 74,779 97,295 86,279 Energy Services 33,708 45,714 50,593 64,519 Total reportable segment EBITDA $ 258,395 $ 256,951 $ 417,762 $ 384,298
Schedule of Operating Revenues Reconciliation	A reconciliation of consolidated operating revenues to reportable segment operating revenues is as follows: Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 (In thousands) Consolidated operating revenues $ 1,105,293 $ 1,090,372 $ 2,241,789 $ 2,183,462 Plus: Intersegment operating revenues 276,899 293,456 488,532 500,704 Less: Corporate Services revenue 3,132 5,464 12,786 7,231 Total reportable segment operating revenues $ 1,379,060 $ 1,378,364 $ 2,717,535 $ 2,676,935
Schedule of EBITDA Reconciliation	A reconciliation of consolidated net income before income taxes to reportable segment EBITDA is as follows: Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 (In thousands) Total consolidated net income before income taxes $ 197,688 $ 194,874 $ 237,848 $ 218,498 Plus: Depreciation, depletion and amortization 34,796 31,752 101,519 92,511 Interest expense, net* 12,113 14,774 36,069 41,399 Less: Corporate Services EBITDA (13,798) (15,551) (42,326) (31,890) Total EBITDA for reportable segments $ 258,395 $ 256,951 $ 417,762 $ 384,298 * Interest, net is interest expense net of interest income.

Background (Details)

Background (Details)	1 Months Ended	9 Months Ended
	Nov. 30, 2023 shares	Sep. 30, 2024 reportableSegment state $ / shares	Dec. 31, 2023 $ / shares	Sep. 30, 2023 $ / shares	May 31, 2023 $ / shares
Organization [Line Items]
Number of states in which entity operates | state		14
Number of reportable segments | reportableSegment		5
Separation transaction, percent of outstanding shares distributed					90%
Common stock, par value (in dollars per share) | $ / shares		$ 0.01	$ 0.01	$ 0.01	$ 0.01
Separation transaction, outstanding shares distributed (in shares) | shares	5,656,621
Separation transaction, distribution ratio					0.25
Knife River
Organization [Line Items]
Subsidiary, ownership percentage, noncontrolling owner					10%

Basis of presentation - Narrati

Basis of presentation - Narrative (Details) - Related Party - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023
Selling, General and Administrative Expenses
Accounting Policies [Line Items]
Costs and expenses, related party	$ 0	$ 9,000
Other Nonoperating Income (Expense)
Accounting Policies [Line Items]
Costs and expenses, related party	$ 0	$ 348

Basis of presentation - Schedul

Basis of presentation - Schedule of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 220,368	$ 219,324	$ 84,006
Restricted cash	47,074	42,996	32,153
Cash, cash equivalents and restricted cash	$ 267,442	$ 262,320	$ 116,159	$ 10,090

Receivables and allowance for_3

Receivables and allowance for expected credit losses - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Credit Loss [Abstract]
Accounts receivable, noncurrent, 90 days or more past due, still accruing	$ 12.6	$ 16.7	$ 14.4

Receivables and allowance for_4

Receivables and allowance for expected credit losses - Schedule of Receivables (Details) - Trade Accounts Receivable - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	$ 229,887			$ 124,134	$ 236,373
Contract receivables	187,622			112,037	223,874
Retention receivables	35,980			36,782	37,814
Receivables, gross	453,489			272,953	498,061
Less expected credit loss	4,301	$ 4,501	$ 6,077	6,168	6,195	$ 5,870	$ 5,822	$ 5,477
Receivables, net	$ 449,188			$ 266,785	$ 491,866

Receivables and allowance for_5

Receivables and allowance for expected credit losses - Schedule of Details of Expected Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Current expected credit loss provision							$ 603	$ 1,386
Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 4,501	$ 6,077	$ 6,168	$ 5,870	$ 5,822	$ 5,477	6,168	5,477
Current expected credit loss provision	326	283	(6)	371	583	432
Less write-offs charged against the allowance	526	1,859	85	46	535	87
Ending balance	4,301	4,501	6,077	6,195	5,870	5,822	4,301	6,195
Pacific | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,795	2,283	2,053	1,980	1,989	1,945	2,053	1,945
Current expected credit loss provision	126	25	177	46	8	45
Less write-offs charged against the allowance	74	513	(53)	26	17	1
Ending balance	1,847	1,795	2,283	2,000	1,980	1,989	1,847	2,000
Northwest | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	716	648	1,004	1,060	1,498	1,253	1,004	1,253
Current expected credit loss provision	(19)	79	(223)	242	74	313
Less write-offs charged against the allowance	108	11	133	4	512	68
Ending balance	589	716	648	1,298	1,060	1,498	589	1,298
Mountain | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,149	2,244	2,293	2,052	1,424	1,278	2,293	1,278
Current expected credit loss provision	(5)	27	(47)	(152)	631	164
Less write-offs charged against the allowance	233	1,122	2	13	3	18
Ending balance	911	1,149	2,244	1,887	2,052	1,424	911	1,887
Central | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	741	802	718	678	811	901	718	901
Current expected credit loss provision	223	151	87	235	(131)	(90)
Less write-offs charged against the allowance	106	212	3	3	2	0
Ending balance	858	741	802	910	678	811	858	910
Energy Services | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	100	100	100	100	100	100	100	100
Current expected credit loss provision	1	1	0	0	1	0
Less write-offs charged against the allowance	5	1	0	0	1	0
Ending balance	$ 96	$ 100	$ 100	$ 100	$ 100	$ 100	$ 96	$ 100

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Inventory Disclosure [Abstract]
Finished products	$ 240,746	$ 225,319	$ 213,702
Raw materials	67,830	61,776	63,156
Supplies and parts	38,724	32,528	37,853
Total	$ 347,300	$ 319,623	$ 314,711

Net income per share- Narrative

Net income per share- Narrative (Details) - shares	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Earnings Per Share [Abstract]
Common stock, issued (in shares)	57,043,841	57,009,542	56,997,350
Treasury stock held at cost (in shares)	431,136	431,136	431,136

Net income per share- Schedule

Net income per share- Schedule of Reconciliation of the Weighted-Average Common Shares Outstanding on a Basic and Diluted Basis (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Earnings Per Share [Abstract]
Net income	$ 148,104	$ 77,929	$ (47,629)	$ 146,655	$ 56,836	$ (41,320)	$ 178,405	$ 162,171
Weighted average common shares outstanding - basic (in shares)	56,613			56,566			56,605	56,566
Effect of dilutive performance shares and restricted stock units (in shares)	258			169			204	67
Weighted average common shares outstanding - diluted (in shares)	56,871			56,735			56,809	56,633
Shares excluded from the calculation of diluted loss per share (in shares)	0			0			0	0
Net income per share - basic (in dollars per share)	$ 2.62			$ 2.59			$ 3.15	$ 2.87
Net income per share - diluted (in dollars per share)	$ 2.60			$ 2.58			$ 3.14	$ 2.86

Accumulated other comprehensi_3

Accumulated other comprehensive loss - Schedule of After-Tax Changes in the Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023
Accumulated other comprehensive loss [Roll Forward]
Beginning balance	$ 1,298,706	$ 1,218,627	$ 1,266,012	$ 1,094,852	$ 974,769	$ 1,028,589
Ending balance	1,448,930	1,298,706	1,218,627	1,243,018	1,094,852	974,769
Net Unrealized Loss on Derivative Instruments Qualifying as Hedges
Accumulated other comprehensive loss [Roll Forward]
Beginning balance	0	0	0	0	(44)	(90)
Other comprehensive loss before reclassification					0
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0	44	46
Net current-period other comprehensive income	0	0	0	0	44	46
Ending balance	0	0	0	0	0	(44)
Postretirement Liability Adjustment
Accumulated other comprehensive loss [Roll Forward]
Beginning balance	(11,164)	(11,241)	(11,319)	(12,184)	(12,215)	(12,262)
Other comprehensive loss before reclassification					(17)
Amounts reclassified from accumulated other comprehensive loss	78	77	78	49	48	47
Net current-period other comprehensive income	78	77	78	49	31	47
Ending balance	(11,086)	(11,164)	(11,241)	(12,135)	(12,184)	(12,215)
Total Accumulated Other Comprehensive Loss
Accumulated other comprehensive loss [Roll Forward]
Beginning balance	(11,164)	(11,241)	(11,319)	(12,184)	(12,259)	(12,352)
Other comprehensive loss before reclassification					(17)
Amounts reclassified from accumulated other comprehensive loss	78	77	78	49	92	93
Net current-period other comprehensive income	78	77	78	49	75	93
Ending balance	$ (11,086)	$ (11,164)	$ (11,241)	$ (12,135)	$ (12,184)	$ (12,259)

Accumulated other comprehensi_4

Accumulated other comprehensive loss - Schedule of Reclassification out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Interest expense	$ (13,936)			$ (15,354)			$ (41,848)	$ (44,005)
Income taxes	(49,584)			(48,219)			(59,443)	(56,327)
Other income	2,487			7			7,541	3,311
Net income (loss)	148,104	$ 77,929	$ (47,629)	146,655	$ 56,836	$ (41,320)	178,405	162,171
Reclassification out of accumulated other comprehensive loss
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Net income (loss)	(78)			(49)			(233)	(234)
Net Unrealized Loss on Derivative Instruments Qualifying as Hedges | Reclassification out of accumulated other comprehensive loss | Interest rate contract
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Interest expense	0			0			0	(118)
Income taxes	0			0			0	28
Net income (loss)	0			0			0	(90)
Amortization of postretirement liability losses included in net periodic benefit cost | Reclassification out of accumulated other comprehensive loss
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Income taxes	25			16			75	47
Other income	(103)			(65)			(308)	(191)
Net income (loss)	$ (78)			$ (49)			$ (233)	$ (144)

Revenue from contracts with c_3

Revenue from contracts with customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Revenues	$ 1,105,293	$ 1,090,372	$ 2,241,789	$ 2,183,462
Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	1,105,230	1,091,316	2,241,341	2,183,037
Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(276,899)	(293,456)	(488,532)	(500,704)
Aggregates
Disaggregation of Revenue [Line Items]
Revenues	193,480	193,585	436,154	423,522
Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	213,460	216,039	492,834	497,706
Asphalt
Disaggregation of Revenue [Line Items]
Revenues	215,049	222,777	350,801	361,333
Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues	110,917	122,596	187,256	203,802
Other
Disaggregation of Revenue [Line Items]
Revenues	89,704	91,516	206,425	192,067
Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	479,413	441,910	852,679	778,537
Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	80,169	95,405	204,172	227,199
Pacific | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	164,986	157,329	375,201	348,051
Pacific | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(29,722)	(30,116)	(65,342)	(63,313)
Pacific | Aggregates
Disaggregation of Revenue [Line Items]
Revenues	36,642	33,624	87,450	79,768
Pacific | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	40,428	39,861	108,316	106,531
Pacific | Asphalt
Disaggregation of Revenue [Line Items]
Revenues	11,859	14,050	22,828	21,640
Pacific | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Pacific | Other
Disaggregation of Revenue [Line Items]
Revenues	48,028	49,533	115,714	112,755
Pacific | Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	48,435	32,632	74,623	53,450
Pacific | Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	9,316	17,745	31,612	37,220
Northwest | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	217,825	208,919	537,202	503,573
Northwest | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(42,614)	(36,683)	(91,017)	(84,937)
Northwest | Aggregates
Disaggregation of Revenue [Line Items]
Revenues	54,038	57,398	146,497	147,937
Northwest | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	46,999	46,785	124,435	125,273
Northwest | Asphalt
Disaggregation of Revenue [Line Items]
Revenues	47,170	43,462	87,937	84,908
Northwest | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Northwest | Other
Disaggregation of Revenue [Line Items]
Revenues	5,416	4,497	14,563	11,513
Northwest | Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	89,271	68,316	196,614	138,621
Northwest | Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	17,545	25,144	58,173	80,258
Mountain | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	261,118	254,722	514,713	491,094
Mountain | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(65,281)	(68,178)	(106,021)	(108,888)
Mountain | Aggregates
Disaggregation of Revenue [Line Items]
Revenues	40,115	39,519	80,708	78,051
Mountain | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	40,559	44,053	89,361	92,929
Mountain | Asphalt
Disaggregation of Revenue [Line Items]
Revenues	60,022	59,673	93,712	89,955
Mountain | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Mountain | Other
Disaggregation of Revenue [Line Items]
Revenues	9	11	22	21
Mountain | Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	142,864	135,700	258,746	244,320
Mountain | Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	42,830	43,944	98,185	94,706
Central | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	354,815	354,925	630,379	643,579
Central | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(110,905)	(123,099)	(172,079)	(191,860)
Central | Aggregates
Disaggregation of Revenue [Line Items]
Revenues	62,685	63,044	121,499	117,766
Central | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	85,474	85,340	170,722	172,973
Central | Asphalt
Disaggregation of Revenue [Line Items]
Revenues	95,998	105,592	146,324	164,830
Central | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Central | Other
Disaggregation of Revenue [Line Items]
Revenues	12,242	10,214	25,015	22,709
Central | Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	198,843	205,262	322,696	342,146
Central | Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	10,478	8,572	16,202	15,015
Energy Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	106,486	115,421	183,846	196,740
Energy Services | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(25,308)	(28,972)	(41,735)	(44,900)
Energy Services | Aggregates
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Energy Services | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Energy Services | Asphalt
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Energy Services | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues	110,917	122,596	187,256	203,802
Energy Services | Other
Disaggregation of Revenue [Line Items]
Revenues	20,877	21,797	38,325	37,838
Energy Services | Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Energy Services | Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Corporate Services and Eliminations | Corporate, Non-Segment & Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenues	63	(944)	448	425
Corporate Services and Eliminations | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(3,069)	(6,408)	(12,338)	(6,806)
Corporate Services and Eliminations | Aggregates
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Corporate Services and Eliminations | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Corporate Services and Eliminations | Asphalt
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Corporate Services and Eliminations | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Corporate Services and Eliminations | Other
Disaggregation of Revenue [Line Items]
Revenues	3,132	5,464	12,786	7,231
Corporate Services and Eliminations | Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Corporate Services and Eliminations | Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	$ 0	$ 0	$ 0	$ 0

Uncompleted contracts - Schedul

Uncompleted contracts - Schedule of Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Contract assets	$ 69,309	$ 50,545	$ 27,293	$ 31,145
Change in contract assets	42,016	19,400
Contract liabilities	(44,786)	(58,785)	(51,376)	(39,843)
Change in contract liabilities	6,590	(18,942)
Net contract assets (liabilities)	24,523	(8,240)	$ (24,083)	$ (8,698)
Change in net contract assets (liabilities)	$ 48,606	$ 458

Uncompleted contracts - Narrati

Uncompleted contracts - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Amounts included in contract liability at the beginning of the period	$ 3.9	$ 3.4	$ 48.8	$ 35.1
Contract with customer, performance obligation satisfied in previous period	15.9	$ 12.1	28.6	$ 10.6
Remaining performance obligations	755.1		755.1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01 | Revenue, Description Of Timing, 12 Months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 688.8		$ 688.8
Remaining performance obligations, expected timing	12 months		12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01 | Revenue, Description Of Timing, 13 To 24 Months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 55.1		$ 55.1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01 | Revenue, Description Of Timing, 25 Months Or More
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 11.2		$ 11.2
Remaining performance obligations, expected timing	25 months		25 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01 | Minimum | Revenue, Description Of Timing, 13 To 24 Months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, expected timing	13 months		13 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01 | Maximum | Revenue, Description Of Timing, 13 To 24 Months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, expected timing	24 months		24 months

Goodwill and other intangible_3

Goodwill and other intangible assets - Schedule of Goodwill (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 274,478	$ 274,540	$ 274,540
Goodwill Acquired During the Year	778	0	0
Measurement Period Adjustments	0	(62)	(62)
Reallocation of Goodwill	0	0	0
Goodwill, ending balance	275,256	274,478	274,478
Pacific
Goodwill [Roll Forward]
Goodwill, beginning balance	32,621	38,339	38,339
Goodwill Acquired During the Year	43	0	0
Measurement Period Adjustments	0	(62)	(62)
Reallocation of Goodwill	0	0	(5,656)
Goodwill, ending balance	32,664	38,277	32,621
Northwest
Goodwill [Roll Forward]
Goodwill, beginning balance	90,978	90,978	90,978
Goodwill Acquired During the Year	0	0	0
Measurement Period Adjustments	0	0	0
Reallocation of Goodwill	0	0	0
Goodwill, ending balance	90,978	90,978	90,978
Mountain
Goodwill [Roll Forward]
Goodwill, beginning balance	26,816	26,816	26,816
Goodwill Acquired During the Year	0	0	0
Measurement Period Adjustments	0	0	0
Reallocation of Goodwill	0	0	0
Goodwill, ending balance	26,816	26,816	26,816
North Central
Goodwill [Roll Forward]
Goodwill, beginning balance	75,879	75,879	75,879
Goodwill Acquired During the Year	735	0	0
Measurement Period Adjustments	0	0	0
Reallocation of Goodwill	0	0	0
Goodwill, ending balance	76,614	75,879	75,879
South
Goodwill [Roll Forward]
Goodwill, beginning balance	38,708	38,708	38,708
Goodwill Acquired During the Year	0	0	0
Measurement Period Adjustments	0	0	0
Reallocation of Goodwill	0	0	0
Goodwill, ending balance	38,708	38,708	38,708
Energy Services
Goodwill [Roll Forward]
Goodwill, beginning balance	9,476	3,820	3,820
Goodwill Acquired During the Year	0	0	0
Measurement Period Adjustments	0	0	0
Reallocation of Goodwill	0	0	5,656
Goodwill, ending balance	$ 9,476	$ 3,820	$ 9,476

Goodwill and other intangible_4

Goodwill and other intangible assets - Schedule of Other Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Finite-Lived Intangible Assets [Line Items]
Total	$ 9,854	$ 10,821	$ 11,463
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	19,059	18,540	18,540
Less accumulated amortization	10,419	9,102	8,668
Total	8,640	9,438	9,872
Noncompete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	3,926	4,039	4,039
Less accumulated amortization	3,452	3,473	3,358
Total	474	566	681
Other
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	1,796	2,479	2,479
Less accumulated amortization	1,056	1,662	1,569
Total	$ 740	$ 817	$ 910

Goodwill and other intangible_5

Goodwill and other intangible assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 522	$ 647	$ 1,600	$ 2,000

Goodwill and other intangible_6

Goodwill and other intangible assets - Schedule of Future Amortization Expense (Details) $ in Thousands	Sep. 30, 2024 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2024	$ 677
2025	1,991
2026	1,811
2027	1,789
2028	1,744
Thereafter	$ 1,842

Fair value measurements - Narra

Fair value measurements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Investments used to satisfy nonqualified benefit plans obligations	$ 28,500	$ 23,500	$ 28,500	$ 23,500	$ 24,900
Net unrealized gain (loss) on investments used to satisfy obligations under nonqualified benefit plans	$ 1,300	$ (597)	$ 2,900	$ 685

Fair value measurements - Sched

Fair value measurements - Schedule of Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Concentration risks, percentage [Abstract]
Percentage in fixed-income and other investments	36%	40%	41%
Percentage investment in common stock of large-cap companies	23%	19%	18%
Percentage investment in cash and cash equivalents	15%	18%	19%
Percentage investment in common stock of mid-cap companies	10%	8%	8%
Percentage investment in target date investments	9%	8%	8%
Percentage investment in common stock of small-cap companies	5%	6%	5%
Percentage investment in international investments	1%	1%	1%
Percentage investment in real estate investments	1%
Fair value, measurements, recurring
Fair value measurements [Line Items]
Money market funds	$ 4,034	$ 3,241	$ 3,199
Insurance contracts	28,498	24,896	23,483
Total assets measured at fair value	32,532	28,137	26,682
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Money market funds	0	0	0
Insurance contracts	0	0	0
Total assets measured at fair value	0	0	0
Significant Other Observable Inputs (Level 2) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Money market funds	4,034	3,241	3,199
Insurance contracts	28,498	24,896	23,483
Total assets measured at fair value	32,532	28,137	26,682
Significant Unobservable Inputs (Level 3) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Money market funds	0	0	0
Insurance contracts	0	0	0
Total assets measured at fair value	$ 0	$ 0	$ 0

Fair value measurements - Sch_2

Fair value measurements - Schedule of Fair Value of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Carrying amount
Fair value, balance sheet grouping [Line Items]
Long-term debt, fair value	$ 691,717	$ 696,985	$ 698,747
Fair value
Fair value, balance sheet grouping [Line Items]
Long-term debt, fair value	$ 719,351	$ 725,086	$ 700,687

Debt - Schedule of Long-Term De

Debt - Schedule of Long-Term Debt Outstanding (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Long-term debt outstanding [Line Items]
Less unamortized debt issuance costs	$ 13,254	$ 15,326	$ 16,016
Total long-term debt	678,463	681,659	682,731
Less current maturities	8,791	7,082	7,082
Net long-term debt	$ 669,672	674,577	675,649
Term loan agreement due on May 31, 2028
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate at September 30, 2024	6.45%
Long-term debt, gross	$ 266,406	271,562	273,281
Senior notes due on May 1, 2031
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate at September 30, 2024	7.75%
Long-term debt, gross	$ 425,000	425,000	425,000
Other notes due on January 1, 2061
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate at September 30, 2024	0%
Long-term debt, gross	$ 311	$ 423	$ 466

Debt - Schedule of Debt Maturit

Debt - Schedule of Debt Maturities (Details) $ in Thousands	Sep. 30, 2024 USD ($)
Debt Disclosure [Abstract]
Remainder of 2024	$ 1,916
2025	10,425
2026	13,750
2027	17,188
2028	223,438
Thereafter	$ 425,000

Cash flow information (Details)

Cash flow information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Supplemental Cash Flow Information [Abstract]
Interest paid, net	$ 35,321	$ 32,028
Income taxes paid, net	33,362	22,183
Right-of-use assets obtained in exchange for new operating lease liabilities	15,130	9,717
Property, plant and equipment additions in accounts payable	1,770	2,832
Equity contribution from Centennial related to the Separation	0	64,724
Equity contribution to MDU Resources for asset/liability transfers related to the Separation	0	(1,548)
MDU Resources' stock issued prior to spin in connection with a business combination	$ 0	$ 383

Business segment data - Narrati

Business segment data - Narrative (Details)	Sep. 30, 2024 state segment
Segment Reporting [Abstract]
Number of states in which entity operates | state	14
Number of reportable segments aligned with geographic areas | segment	4

Business segment data - Schedul

Business segment data - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Revenues	$ 1,105,293	$ 1,090,372	$ 2,241,789	$ 2,183,462
Operating Segments
Segment Reporting Information [Line Items]
Revenues	1,105,230	1,091,316	2,241,341	2,183,037
EBITDA:	258,395	256,951	417,762	384,298
Operating Segments | Pacific
Segment Reporting Information [Line Items]
Revenues	164,986	157,329	375,201	348,051
EBITDA:	29,497	28,557	46,543	46,161
Operating Segments | Northwest
Segment Reporting Information [Line Items]
Revenues	217,825	208,919	537,202	503,573
EBITDA:	55,914	48,467	126,831	101,335
Operating Segments | Mountain
Segment Reporting Information [Line Items]
Revenues	261,118	254,722	514,713	491,094
EBITDA:	59,446	59,434	96,500	86,004
Operating Segments | Central
Segment Reporting Information [Line Items]
Revenues	354,815	354,925	630,379	643,579
EBITDA:	79,830	74,779	97,295	86,279
Operating Segments | Energy Services
Segment Reporting Information [Line Items]
Revenues	106,486	115,421	183,846	196,740
EBITDA:	33,708	45,714	50,593	64,519
Intersegment eliminations
Segment Reporting Information [Line Items]
Revenues	(276,899)	(293,456)	(488,532)	(500,704)
Intersegment eliminations | Pacific
Segment Reporting Information [Line Items]
Revenues	(29,722)	(30,116)	(65,342)	(63,313)
Intersegment eliminations | Northwest
Segment Reporting Information [Line Items]
Revenues	(42,614)	(36,683)	(91,017)	(84,937)
Intersegment eliminations | Mountain
Segment Reporting Information [Line Items]
Revenues	(65,281)	(68,178)	(106,021)	(108,888)
Intersegment eliminations | Central
Segment Reporting Information [Line Items]
Revenues	(110,905)	(123,099)	(172,079)	(191,860)
Intersegment eliminations | Energy Services
Segment Reporting Information [Line Items]
Revenues	(25,308)	(28,972)	(41,735)	(44,900)
Intersegment eliminations | Total reportable segment intersegment operating revenues
Segment Reporting Information [Line Items]
Revenues	$ (273,830)	$ (287,048)	$ (476,194)	$ (493,898)

Business segment data - Sched_2

Business segment data - Schedule of Operating Revenues Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 1,105,293	$ 1,090,372	$ 2,241,789	$ 2,183,462
Intersegment operating revenues
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	(276,899)	(293,456)	(488,532)	(500,704)
Corporate, Non-Segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	3,132	5,464	12,786	7,231
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,105,230	1,091,316	2,241,341	2,183,037
Operating Segments | Total reportable segment operating revenues
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 1,379,060	$ 1,378,364	$ 2,717,535	$ 2,676,935

Business segment data - Sched_3

Business segment data - Schedule of EBITDA Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Total consolidated net income before income taxes	$ 197,688	$ 194,874	$ 237,848	$ 218,498
Depreciation, depletion and amortization	34,796	31,752	101,519	92,511
Interest expense, net	12,113	14,774	36,069	41,399
Corporate, Non-Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
EBITDA	(13,798)	(15,551)	(42,326)	(31,890)
Operating Segments
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
EBITDA	$ 258,395	$ 256,951	$ 417,762	$ 384,298

Commitments and contingencies (

Commitments and contingencies (Details) - USD ($)	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Loss Contingencies [Line Items]
Potential liabilities related to litigation and environmental matters	$ 3,200,000	$ 873,000	$ 645,000
Guarantor obligations, maximum exposure, undiscounted	11,500,000
Amount outstanding under guarantees that is reflected on balance sheet	0
Letters of credit set to expire current year	0
Letters of credit set to expire in next fiscal year	20,500,000
Letters of credit set to expire, year two	0
Letters of credit set to expire, year three	104,000
Outstanding letters of credit	$ 0
Surety bond expiration period	12 months
Amount of surety bonds outstanding	$ 686,800,000
Letter of Credit
Loss Contingencies [Line Items]
Line of credit facility, maximum borrowing capacity	$ 20,600,000

Related party transactions (Det

Related party transactions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Related Party Transaction [Line Items]
Selling, general and administrative expenses	$ 63,874	$ 59,168	$ 183,569	$ 167,276
Other income	2,487	7	7,541	3,311
Related Party
Related Party Transaction [Line Items]
Selling, general and administrative expenses	40	1,300	1,300	1,900
Other income	$ 14	$ 407	$ 152	$ 684
Transition services, period			1 year