Knife River (KNF) 10-K 27 Feb 24 2023 FY Annual report Financial data

Cover

Cover - USD ($)	12 Months Ended
	Dec. 31, 2023	Feb. 22, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Current Fiscal Year End Date	--12-31
Document Period End Date	Dec. 31, 2023
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 Well-known Seasoned Issuer	No
Entity Voluntary Filers	Yes
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
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 2,460,630,309
Entity common stock, shares outstanding		56,578,406
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Relevant portions of the registrant's 2024 Proxy Statement, to be filed no later than 120 days from December 31, 2023, are incorporated by reference in Part III, Items 10, 11, 12, 13 and 14 of this Annual Report on Form 10-K.
Entity Central Index Key	0001955520
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2023
Auditor [Abstract]
Auditor Name	Deloitte & Touche LLP
Auditor Location	Minneapolis, Minnesota
Auditor Firm ID	34

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue:
Revenue:	$ 2,830,350	$ 2,534,729	$ 2,228,930
Cost of revenue:
Cost of revenue:	2,291,415	2,173,835	1,881,981
Gross profit	538,935	360,894	346,949
Selling, general and administrative expenses	242,538	166,599	155,872
Operating income	296,397	194,295	191,077
Interest expense	58,096	30,121	19,218
Other (expense) income	7,007	(5,353)	1,355
Income before income taxes	245,308	158,821	173,214
Income taxes	62,436	42,601	43,459
Net income	$ 182,872	$ 116,220	$ 129,755
Net income per share:
Earnings per share – basic (in dollars per share)	$ 3.23	$ 2.05	$ 2.29
Earnings per share – diluted (in dollars per share)	$ 3.23	$ 2.05	$ 2.29
Weighted average common shares outstanding:
Weighted average common shares outstanding – basic (in shares)	56,568,000	56,566,000	56,566,000
Weighted average common shares outstanding – diluted (in shares)	56,668,000	56,566,000	56,566,000
Construction materials
Revenue:
Revenue:	$ 1,523,040	$ 1,347,008	$ 1,211,459
Cost of revenue:
Cost of revenue:	1,133,042	1,086,193	965,028
Contracting services
Revenue:
Revenue:	1,307,310	1,187,721	1,017,471
Cost of revenue:
Cost of revenue:	$ 1,158,373	$ 1,087,642	$ 916,953

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 182,872	$ 116,220	$ 129,755
Other comprehensive income:
Reclassification adjustment for loss on derivative instruments included in net income, net of tax of $28, $107 and $107 in 2023, 2022 and 2021, respectively	90	328	332
Pension and postretirement liability adjustment:
Pension and postretirement liability gains arising during the period, net of tax of $252, $3,586 and $1,011 in 2023, 2022 and 2021, respectively	751	10,935	3,041
Amortization of pension and postretirement liability losses included in net periodic benefit cost, net of tax of $64, $292 and $363 in 2023, 2022 and 2021, respectively	192	875	1,090
Pension and postretirement liability adjustment	943	11,810	4,131
Other comprehensive income	1,033	12,138	4,463
Comprehensive income attributable to common stockholders	$ 183,905	$ 128,358	$ 134,218

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Reclassification adjustment for loss on derivative instruments included in net income (loss), tax	$ 28	$ 107	$ 107
Postretirement liability gains (losses) arising during the period, tax	252	3,586	1,011
Amortization of postretirement liability losses included in net periodic benefit cost, tax (expense) benefit	$ 64	$ 292	$ 363

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash, cash equivalents and restricted cash	$ 262,320	$ 10,090
Receivables, net	266,785	210,157
Costs and estimated earnings in excess of billings on uncompleted contracts	27,293	31,145
Due from related-party	0	16,050
Inventories	319,623	323,277
Prepayments and other current assets	37,522	17,848
Total current assets	913,543	608,567
Noncurrent assets:
Net property, plant and equipment	1,315,047	1,315,213
Goodwill	274,478	274,540
Other intangible assets, net	10,821	13,430
Operating lease right-of-use assets	44,706	45,873
Investments and other	41,218	36,696
Total noncurrent assets	1,686,270	1,685,752
Total assets	2,599,813	2,294,319
Current liabilities:
Long-term debt - current portion	7,082	211
Related-party notes payable - current portion	0	238,000
Accounts payable	107,656	87,370
Billings in excess of costs and estimated earnings on uncompleted contracts	51,376	39,843
Accrued compensation	48,098	29,192
Due to related-party	0	20,286
Current operating lease liabilities	12,948	13,210
Other accrued liabilities	120,111	88,778
Total current liabilities	347,271	516,890
Noncurrent liabilities:
Long-term debt	674,577	427
Related-party notes payable	0	446,449
Deferred income taxes	174,542	175,804
Noncurrent operating lease liabilities	31,758	32,663
Other	105,653	93,497
Total liabilities	1,333,801	1,265,730
Commitments and contingencies
Stockholders’ equity:
Common stock, 300,000,000 shares authorized, $0.01 par value, 57,009,542 shares issued and 56,578,406 shares outstanding at December 31, 2023; 80,000 shares authorized, issued and outstanding, $10 par value, at December 31, 2022	570	800
Other paid-in capital	614,513	549,106
Retained earnings	665,874	494,661
MDU Resources common stock held by subsidiary at cost - 538,921 shares	0	(3,626)
Treasury stock held at cost - 431,136 shares	(3,626)	0
Accumulated other comprehensive loss	(11,319)	(12,352)
Total stockholders’ equity	1,266,012	1,028,589
Total liabilities and stockholders’ equity	$ 2,599,813	$ 2,294,319

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 10
Common stock, shares authorized (in shares)	300,000,000	80,000
Common stock, shares issued (in shares)	57,009,542	80,000
Common stock, shares outstanding (in shares)	56,578,406	80,000
Common stock held by subsidiary (in shares)		538,921
Treasury stock held at cost (in shares)	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	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2020		80,000
MDU Resources' stock held by subsidiary, beginning balance (in shares) at Dec. 31, 2020					538,921
Treasury stock, beginning balance (in shares) at Dec. 31, 2020						0
Beginning balance at Dec. 31, 2020	$ 878,244	$ 800	$ 550,262	$ 359,761	$ (3,626)	$ 0	$ (28,953)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	129,755			129,755
Other comprehensive income	4,463						4,463
Net transfers to Centennial	(59,618)		(548)	(59,070)
Ending balance (in shares) at Dec. 31, 2021		80,000
MDU Resources' stock held by subsidiary, ending balance (in shares) at Dec. 31, 2021					538,921
Treasury stock, ending balance (in shares) at Dec. 31, 2021						0
Ending balance at Dec. 31, 2021	952,844	$ 800	549,714	430,446	$ (3,626)	$ 0	(24,490)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	116,220			116,220
Other comprehensive income	12,138						12,138
Net transfers to Centennial	$ (52,613)		(608)	(52,005)
Ending balance (in shares) at Dec. 31, 2022	80,000	80,000
MDU Resources' stock held by subsidiary, ending balance (in shares) at Dec. 31, 2022	538,921				538,921
Treasury stock, ending balance (in shares) at Dec. 31, 2022						0
Ending balance at Dec. 31, 2022	$ 1,028,589	$ 800	549,106	494,661	$ (3,626)	$ 0	(12,352)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	182,872			182,872
Other comprehensive income	1,033						1,033
Stock-based compensation	2,851		2,888	(37)
Issuance of common stock to directors for services (in shares)		12,192
Issuance of common stock to directors for services	702		702
Retirement of historical common stock in connection with the Separation (in shares)		(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	0	$ 570	(570)
Transfer of MDU Resources stock held by subsidiary (in shares)					538,921
Transfer of MDU Resources stock held by subsidiary	3,626				$ 3,626
Receipt of treasury stock at historical cost (in shares)						(431,136)
Receipt of treasury stock at historical cost	(3,626)					$ (3,626)
Net transfers from Centennial and MDU Resources including Separation adjustments	62,972		62,972
Net transfers to Centennial	$ (13,007)		(1,385)	(11,622)
Ending balance (in shares) at Dec. 31, 2023	57,009,542	57,009,542
MDU Resources' stock held by subsidiary, ending balance (in shares) at Dec. 31, 2023					0
Treasury stock, ending balance (in shares) at Dec. 31, 2023	431,136					(431,136)
Ending balance at Dec. 31, 2023	$ 1,266,012	$ 570	$ 614,513	$ 665,874	$ 0	$ (3,626)	$ (11,319)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities:
Net income	$ 182,872	$ 116,220	$ 129,755
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	123,805	117,798	100,974
Deferred income taxes	(1,606)	2,078	32,858
Provision for credit losses	2,001	538	48
Amortization of debt issuance costs	3,115	483	402
Employee stock-based compensation costs	2,888	1,272	1,852
Pension and postretirement benefit plan net periodic benefit cost	1,182	1,306	1,092
Unrealized (gains) losses on investments	(2,202)	2,525	(1,632)
Gains on sale of assets	(27)	(14,092)	(6,638)
Equity in (loss) earnings of unconsolidated affiliates	(286)	438	(373)
Changes in current assets and liabilities, net of acquisitions:
Receivables	(54,817)	(32,506)	15,357
Due from related-party	16,050	(8,004)	2,889
Inventories	3,654	(31,033)	(42,441)
Other current assets	(19,556)	44	(4,574)
Accounts payable	33,092	17,489	(13,899)
Due to related-party	(7,310)	3,578	(957)
Other current liabilities	48,977	21,417	(21,011)
Pension and postretirement benefit plan contributions	(1,756)	(426)	(392)
Other noncurrent changes	5,650	8,319	(12,070)
Net cash provided by operating activities	335,726	207,444	181,240
Investing activities:
Capital expenditures	(124,283)	(178,162)	(174,229)
Acquisitions, net of cash acquired	0	1,745	(235,218)
Net proceeds from sale or disposition of property and other	8,284	22,878	12,017
Investments	(1,890)	(2,339)	(837)
Net cash used in investing activities	(117,889)	(155,878)	(398,267)
Financing activities:
Issuance of current related-party notes	0	208,000	0
Issuance (repayment) of long-term related-party notes, net	205,275	(207,007)	281,983
Issuance of long-term debt	700,000	0	0
Repayment of long-term debt	(3,653)	(298)	(221)
Debt issuance costs	(16,640)	(807)	0
Net transfers to Centennial	(850,589)	(55,212)	(57,959)
Net cash provided by (used in) financing activities	34,393	(55,324)	223,803
Increase (decrease) in cash, cash equivalents and restricted cash	252,230	(3,758)	6,776
Cash, cash equivalents and restricted cash - beginning of year	10,090	13,848	7,072
Cash, cash equivalents and restricted cash - end of year	$ 262,320	$ 10,090	$ 13,848

Organization and Basis of Prese

Organization and Basis of Presentation	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation Knife River is a people-first construction materials and contracting services company. The Company provides construction materials and contracting services to build safe roads, bridges and 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. The Company conducts its operations through five reportable segments: Pacific, Northwest, Mountain, Central and Energy Services. In the fourth quarter of 2023, the Company completed a reorganization of its reporting structure which resulted in changes being made to the management of its business to best align with its strategies. As a result of the reorganization, 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. All periods have been recast to conform with the revised presentation. See Note 15 for additional information. Separation from MDU Resources On May 31, 2023, MDU Resources completed the previously announced separation of the Company 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. The Separation was completed pursuant to a separation and distribution agreement and other agreements with MDU Resources related to the Separation, including, but not limited to, a tax matters agreement, an employee matters agreement and a transition services agreement. For an interim period following the Separation, certain functions will continue to be provided by MDU Resources under a transition services agreement. For more information on the transition services agreement, see Note 19. The Company has incurred certain costs in its establishment as an independent, publicly traded company and expects to incur ongoing additional costs associated with operating as an independent, publicly traded company. All share and earnings per share information has been retroactively adjusted for all periods presented to reflect the Distribution. Basis of Presentation Prior to the Separation, Knife River operated as a wholly owned subsidiary of Centennial and an indirect, wholly owned subsidiary of MDU Resources and not as a stand-alone company. The accompanying audited 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 audited consolidated financial statements of MDU Resources as if the Company operated on a stand-alone basis during these periods. All revenues and costs as well as assets and liabilities directly associated with the business activity of the Company are included in the financial statements. In the periods prior to the Separation, the audited 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 (expense). The amounts allocated to Knife River were $10.7 million, $18.0 million and $15.6 million for the years ended December 31, 2023, 2022 and 2021, respectively. These expenses were allocated to the Company 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 expense the Company would have incurred as a stand-alone company for the periods presented. These costs also may not be indicative of the expenses that the Company will incur in the future or would have incurred if the Company had obtained these services from a third party. Prior to the Separation, Knife River participated in Centennial’s centralized cash management program, including its overall financing arrangements. Knife River also had related-party note agreements in place with Centennial for the financing of its capital needs, which are reflected as related-party notes payable on the Consolidated Balance Sheet at December 31, 2022. Interest expense in the Consolidated Statements of Operations, for the periods prior to the Separation, reflects the allocation of interest on borrowing and funding associated with the related-party note agreements. Upon the completion of the Separation, Knife River implemented its own financing agreements with lenders. For additional information on the Company’s current debt financing, see Note 8. Related-party transactions between the Company and MDU Resources or Centennial for general operating activities and intercompany debt have been included in the audited consolidated financial statements for periods prior to the Separation. Outstanding balances as of the periods presented were reflected on Consolidated Balance Sheets as “Due from related-party” or “Due to related-party” and “Related-party notes payable”. The cash settlement of these transactions are included in the Consolidated Statements of Cash Flows as operating or financing activities following the nature of the transactions. The aggregate net effect of related-party transactions not settled in cash as part of the Separation have been reflected in the Consolidated Balance Sheets and Statements of Stockholders’ Equity within “Other paid-in capital” and within the Consolidated Statements of Cash Flows following the nature of the transactions with a majority included in the financing section. See Note 19 for additional information on related-party transactions. Management has also evaluated the impact of events occurring after December 31, 2023, up to the date of issuance of these audited consolidated financial statements on February 27, 2024, that would require recognition or disclosure in the audited Consolidated Financial Statements. Principles of consolidation For all periods, the audited consolidated financial statements were prepared in accordance with GAAP and include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions between the businesses comprising the Company have been eliminated in the accompanying audited consolidated financial statements. Use of estimates The preparation of financial statements in conformity with GAAP requires the Company 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 audited 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 the Company 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.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies New accounting standards The following table provides a brief description of the accounting pronouncements applicable to the Company and the potential impact on its audited consolidated financial statements and/or disclosures: Standard Description Standard Effective Date Impact on financial statements/disclosures Recently issued ASU’s 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 currently evaluating the impact the guidance will have on its disclosures for the year ended December 31, 2025. Cash, cash equivalents and restricted cash Revenue recognition Revenue is recognized when a performance obligation is satisfied by transferring control over a product or service to a customer. 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. The Company is considered an agent for certain taxes collected from customers. As such, the Company presents revenues net of these taxes at the time of sale to be remitted to governmental authorities, including sales and use taxes. The Company generates revenue from contracting services and construction materials sales. The Company focuses on the vertical integration of its contracting services with its construction materials to support the aggregate-based product lines. The Company provides contracting services to a customer when a contract has been signed by both the customer and a representative of the Company obligating a service to be provided in exchange for the consideration identified in the contract. The nature of the services provided generally include integrating a set of services and related construction materials into a single project to create a distinct bundle of goods and services, which the Company has determined are single performance obligations. The Company determines the transaction price to include the fixed consideration required pursuant to the original contract price together with any additional consideration, to which the Company expects to be entitled to, associated with executed change orders plus the estimate of variable consideration to which the Company expects to be entitled, subject to the constraint discussed below. The nature of the Company’s contracts gives rise to several types of variable consideration. Examples of variable consideration include: liquidated damages; performance bonuses or incentives and penalties; claims; unpriced change orders; and index pricing. The variable amounts usually arise upon achievement of certain performance metrics or change in project scope. The Company estimates the amount of revenue to be recognized on variable consideration using one of the two prescribed estimation methods, the expected value method or the most likely amount method, depending on which method best predicts the most likely amount of consideration the Company expects to be entitled to or expects to incur. Assumptions as to the occurrence of future events and the likelihood and amount of variable consideration are made during the contract performance period. Estimates of variable consideration and determination of whether to include estimated amounts in the transaction price are based largely on the assessment of anticipated performance and all information (historical, current and forecasted) that is reasonably available to management. The Company only includes variable consideration in the estimated transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur or when the uncertainty associated with the variable consideration is resolved. Changes in circumstances could impact management’s estimates made in determining the value of variable consideration recorded. When determining if the variable consideration is constrained, the Company considers if factors exist that could increase the likelihood or the magnitude of a potential reversal of revenue. The Company updates its estimate of the transaction price each reporting period and the effect of variable consideration on the transaction price is recognized as an adjustment to revenue on a cumulative catch-up basis. Contracting services revenue is recognized over time using an input method based on the cost-to-cost measure of progress on a project. This is the preferred method of measuring revenue because the costs incurred have been determined to represent the best indication of the overall progress toward the transfer of such goods or services promised to a customer. Under the cost-to-cost measure of progress, the costs incurred are compared with total estimated costs of a performance obligation. Revenues are recorded proportionately to the costs incurred. The percentage of completion is determined on a performance obligation basis. The Company also sells construction materials to third parties and internal customers. The contract for material sales is the use of a sales order or an invoice, which includes the pricing and payment terms. All material contracts contain a single performance obligation for the delivery of a single distinct product or a distinct separately identifiable bundle of products and services. Revenue is recognized at a point in time when the performance obligation has been satisfied with the delivery of the products or services. The warranties associated with the sales are those consistent with a standard warranty that the product meets certain specifications for quality or those required by law. For most contracts, amounts billed to customers are due within 30 days of receipt. There are no material obligations for returns, refunds or other similar obligations. Receivables and allowance for expected credit losses Receivables consist primarily of trade and contract receivables from the sale of goods and services net of expected credit losses. A majority of the Company’s receivables are due in 30 days or less. The total balance of receivables past due 90 days or more was $16.7 million and $11.2 million at December 31, 2023 and 2022, respectively. Receivables, net consisted of the following at December 31: 2023 2022 (In thousands) Trade receivables $ 124,134 $ 104,347 Contract receivables 112,037 82,428 Retention receivables 36,782 28,859 Receivables, gross 272,953 215,634 Less expected credit loss 6,168 5,477 Receivables, net $ 266,785 $ 210,157 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. The Company develops and documents its methodology to determine its allowance for expected credit losses. Risk characteristics used by the Company 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) At December 31, 2021 $ 1,952 $ 512 $ 1,610 $ 1,232 $ 100 $ 5,406 Current expected credit loss provision 21 946 (206) (229) 6 538 Less write-offs charged against the allowance 28 205 126 102 6 467 At December 31, 2022 $ 1,945 $ 1,253 $ 1,278 $ 901 $ 100 $ 5,477 Current expected credit loss provision 161 842 1,109 (112) 1 2,001 Less write-offs charged against the allowance 53 1,091 94 71 1 1,310 At December 31, 2023 $ 2,053 $ 1,004 $ 2,293 $ 718 $ 100 $ 6,168 Inventories Inventories at December 31 consisted of: 2023 2022 (In thousands) Finished products $ 225,319 $ 211,496 Raw materials 61,776 78,571 Supplies and parts 32,528 33,210 Total $ 319,623 $ 323,277 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 the Company’s 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. Property, plant and equipment Additions to property, plant and equipment are recorded at cost. Gains or losses resulting from the retirement or disposal of assets are recognized as a component of operating income. Generally, property, plant and equipment are depreciated on a straight-line basis over the average useful lives of the assets with the exception of large marine equipment, which is computed using units-of-production. Aggregate mining development costs are capitalized and classified as land improvements and depreciated over the lower of the estimated life of the reserves or the life of the associated improvement. The Company begins capitalizing development costs at a point when reserves are determined to be proven or probable and economically mineable. Capitalization of these costs ceases when production commences. The cost of acquiring reserves in connection with a business combination are valued at fair value. Aggregate reserves, from both owned and leased mining sites, are a component within property, plant and equipment and are depleted using the units-of-production method. The Company uses proven and probable aggregate reserves as the denominator in its units-of production calculation. Exploration costs are expensed as incurred in cost of revenue and production costs are either expensed or capitalized to inventory. Impairment of long-lived assets, excluding goodwill The Company reviews the carrying values of its long-lived assets, including mining and related assets, whenever events or changes in circumstances indicate that such carrying values may not be recoverable. The Company tests long-lived assets for impairment at a level significantly lower than that of goodwill impairment testing. Long-lived assets or groups of assets that are evaluated for impairment at the lowest level of largely independent identifiable cash flows at an individual operation or group of operations collectively serving a local market. The determination of whether an impairment has occurred is based on an estimate of undiscounted future cash flows attributable to the assets, compared to the carrying value of the assets. If impairment has occurred, the amount of the impairment recognized is determined by estimating the fair value of the assets and recording a loss if the carrying value is greater than the fair value. During the year ended December 31, 2023, the Company performed impairment testing on assets where triggering events were identified due to recent operating results or changes in plans with the asset groups. The undiscounted cash flows on an asset group with a net asset book value of $65 million indicated it was recoverable and not impaired. However, the Company recognized long-lived asset impairments of $5.8 million (before tax) in selling, general and administrative expenses assets are included as part of the Pacific and Northwest reportable segments. No impairment losses were recorded in 2022 or 2021. Goodwill Goodwill represents the excess of the purchase price over the fair value of identifiable net tangible and intangible assets acquired in a business combination. Goodwill is required to be tested for impairment annually, which the Company completes in the fourth quarter, or more frequently if events or changes in circumstances indicate that goodwill may be impaired. The Company has determined that the reporting units for its goodwill impairment test are its operating segments as they constitute a business for which discrete financial information is available and for which management regularly reviews the operating results. For more information on the Company’s operating segments, see Note 15. Goodwill impairment, if any, is measured by comparing the fair value of each reporting unit to its carrying value. If the fair value of a reporting unit exceeds its carrying value, the goodwill of the reporting unit is not impaired. If the carrying value of a reporting unit exceeds its fair value, the Company must record an impairment loss for the amount that the carrying value of the reporting unit, including goodwill, exceeds the fair value of the reporting unit. For the years ended December 31, 2023, 2022 and 2021, there were no impairment losses recorded. The Company performed its annual goodwill impairment test in the fourth quarter of 2023 and determined the fair value of each of Knife River’s reporting units substantially exceeded the carrying value at October 31, 2023. The Company uses a weighted average combination of both an income approach and a market approach to estimate the fair value of its reporting units for its goodwill impairment analysis. Determining the fair value of a reporting unit requires judgment and the use of significant estimates, which include assumptions about Knife River’s future revenue, profitability and cash flows, amount and timing of estimated capital expenditures, inflation rates, weighted average cost of capital, operational plans, and current and future economic conditions, among others. Knife River believes that the estimates and assumptions used in its impairment assessments are reasonable and based on available market information. Investments The Company’s investments include the cash surrender value of life insurance policies and insurance contracts. The Company measures its investment in the insurance contracts at fair value with any unrealized gains and losses recorded on the Consolidated Statements of Operations. Government Assistance The Company accounts for government assistance received for capital projects by reducing the cost of the project by the amount of assistance received. The Company records government assistance received as taxable income and writes-up the tax basis of the asset to include the amount of the assistance received. Government assistance received by the Company for the years ended December 31, 2023, 2022 and 2021, was not material. Joint Ventures The Company accounts for unconsolidated joint ventures using either the equity method or proportionate consolidation. As of December 31, 2023, the Company held an interest of 25 percent in a joint venture formed primarily for the purpose of pooling resources on construction contracts. Proportionate consolidation is used for joint ventures that include unincorporated legal entities and activities of the joint venture which are construction-related. For those joint ventures accounted for under proportionate consolidation, only the Company’s pro rata share of assets, liabilities, revenues and expenses are included in the Company’s Consolidated Balance Sheets and Consolidated Statements of Operations. For those joint ventures accounted for using proportionate consolidation, the Company recorded in its Consolidated Statements of Operations $4.9 million, $9.1 million, and $10.1 million of revenue for the years ended December 31, 2023, 2022 and 2021, respectively. The Company also reported an operating loss of $1.9 million for the year ended December 31, 2023, and operating income of $823,000 and $1.3 million for the years ended December 31, 2022 and 2021, respectively. As of December 31, 2023, 2022 and 2021, the Company had interest in assets from these joint ventures of $45,000, $912,000 and $643,000, respectively. For joint ventures accounted for under the equity method, the Company’s investment balances for the joint ventures are included in Investments in the Consolidated Balance Sheets and the Company’s pro rata share of net income is included in Other income in the Consolidated Statements of Operations. The Company’s investments in equity method joint ventures were a net asset of $68,000 and $13,000 for December 31, 2023 and 2022, respectively. In 2023, 2022 and 2021, the Company recognized income (loss) from equity method joint ventures of $55,000, $(426,000) and $14,000, respectively. Leases The recognition of leases requires the Company to make estimates and assumptions that affect the lease classification and the assets and liabilities recorded. The accuracy of lease assets and liabilities reported on the audited Consolidated Financial Statements depends on, among other things, management’s estimates of interest rates used to discount the lease assets and liabilities to their present value, as well as the lease terms based on the unique facts and circumstances of each lease. Lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term. The Company recognizes leases with an original lease term of 12 months or less in income on a straight-line basis over the term of the lease and does not recognize a corresponding right-of-use asset or lease liability. The Company determines the lease term based on the non-cancelable and cancelable periods in each contract. The non-cancelable period consists of the term of the contract that is legally enforceable and cannot be canceled by either party without incurring a significant penalty. The cancelable period is determined by various factors that are based on who has the right to cancel a contract. If only the lessor has the right to cancel the contract, the Company will assume the contract will continue. If the lessee is the only party that has the right to cancel the contract, the Company looks to asset, entity and market-based factors. If both the lessor and the lessee have the right to cancel the contract, the Company assumes the contract will not continue. The discount rate used to calculate the present value of the lease liabilities is based upon the implied rate within each contract. If the rate is unknown or cannot be determined, the Company uses an incremental borrowing rate, which is determined by the length of the contract, asset class and the Company’s borrowing rates, as of the commencement date of the contract. Insurance Knife River’s wholly-owned captive insurance company, Spring Creek Insurance Company, which is subject to applicable insurance rules and regulations, insures the Company’s exposure related to workers’ compensation, general liability and automobile liability on a primary basis. Knife River also purchases excess coverage from unrelated insurance carriers and obtains third-party coverage for other forms of insurance including, but not limited to, excess liability, contractor’s pollution liability, marine liability, directors and officers liability and employment practices liability. Spring Creek Insurance Company establishes a reserve for estimated ultimate losses on reported claims and those incurred but no yet reported utilizing actuarial projections. The reserves are classified within Other accrued liabilities or Noncurrent liabilities - other on the Consolidated Balance Sheets based on projections of when the estimated loss will be paid. The estimates that are utilized to record potential losses on claims are inherently subjective, and actual claims could differ from amounts recorded, which could result in increased or decreased expense in future periods. Additionally, Knife River maintains a self-insurance reserve for health insurance programs offered to eligible employees, included within Other accrued liabilities on the Consolidated Balance Sheets. The reserve includes an estimate for losses on reported claims as well as for amounts incurred but not yet reported, based on historical trends. Asset retirement obligations The Company records the fair value of a liability for an asset retirement obligation in the period in which it is incurred. When the liability is initially recorded, the Company capitalizes a cost by increasing the carrying amount of the related long-lived asset. Over time, the liability is accreted to its present value each period and the capitalized cost is depreciated over the useful life of the related asset. Upon settlement of the liability, the Company either settles the obligation for the recorded amount or incurs a gain or loss. Earnings per share The calculation for basic and diluted earnings per share for any period presented prior to the Separation have been retrospectively adjusted to the number of shares outstanding on May 31, 2023, the Separation and Distribution date. For periods prior to the Separation, it is assumed that there are no dilutive equity instruments as there were no Knife River stock-based awards outstanding at the time. Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the applicable period. Diluted earnings 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 restricted stock units. Weighted average common shares outstanding is comprised of issued shares of 57,009,542 less shares held in treasury of 431,136, as described in Note 11. Basic and diluted earnings per share are calculated as follows, based on a reconciliation of the weighted-average common shares outstanding on a basic and diluted basis: 2023 2022 2021 (In thousands, except per share amounts) Net income $ 182,872 $ 116,220 $ 129,755 Weighted average common shares outstanding - basic 56,568 56,566 56,566 Effect of dilutive restricted stock units 100 — — Weighted average common shares outstanding - diluted 56,668 56,566 56,566 Shares excluded from the calculation of diluted earnings per share — — — Net income per share - basic $ 3.23 $ 2.05 $ 2.29 Net income per share - diluted $ 3.23 $ 2.05 $ 2.29 Stock-based compensation Prior to the Separation, key employees of the Company participated in various stock-based compensation plans authorized and managed by MDU Resources. All awards granted under the plans were based on MDU Resources’ common shares, however, Knife River recognized the expense for its participants in its financial statements. At the time of the Separation, each outstanding MDU Resources’ time-vested restricted stock unit and performance share awards held by a Knife River employee was converted into Knife River time-vested restricted stock units. The converted awards will continue to vest over the original vesting period, which is generally three years from the grant date. All performance share awards that were converted at the time of the Separation were first adjusted using a combined performance factor based on MDU Resources’ actual performance as of December 31, 2022. The number of restricted stock units was determined by taking the closing per share price of MDU Resources on May 31, 2023, and dividing by the closing per share price of Knife River on June 1, 2023. The ratio used to convert the MDU Resources’ share-based awards was designed to preserve the aggregate intrinsic value of the award immediately after the Separation when compared to the aggregate intrinsic value of the award immediately prior to the Separation. The existing unvested stock-based awards issued through MDU Resources’ stock-based compensation plans were modified in connection with the Separation to maintain an equivalent value immediately before and after Separation. Incremental fair value for unvested awards will be recorded over the remaining vesting periods. In July 2023, the Company issued restricted stock units to certain key employees under the Knife River Long-Term Incentive Plan. The Company records the compensation expense for restricted stock units using a straight-line amortization method over the requisite service period. The cost for such awards is measured at the grant date fair value. The Company recognizes forfeitures as they occur and trues up expense on a cumulative catch-up basis at the time of any forfeitures. Income taxes Knife River and its subsidiaries file consolidated federal income tax returns and combined and separate state income tax returns. Pursuant to the tax sharing agreement that exists between Knife River and its subsidiaries, federal income taxes paid by Knife River, as parent of the consolidated group, are allocated to the individual subsidiaries based on separate company computations of tax. However, all income tax expense is reported within the Corporate Services segment. Knife River makes a similar allocation for state income taxes paid in connection with combined state filings. The Company provides deferred federal and state income taxes on all temporary differences between the book and tax basis of the Company’s assets and liabilities by using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date.

Disaggregation of Revenue

Disaggregation of Revenue	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	Disaggregation of Revenue In the following table, revenue is disaggregated by category for each reportable segment. The Company believes 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 15. Presented in the following tables are the 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 the contracting services to arrive at the external operating revenues. Due to the restructuring of segments the 2022 and 2021 information has been recast. Year ended December 31, 2023 Pacific Northwest Mountain Central Energy Services Corporate Services Total (In thousands) Aggregates $ 104,726 $ 189,946 $ 100,505 $ 152,691 $ — $ — $ 547,868 Ready-mix concrete 142,291 163,382 120,534 227,735 — — 653,942 Asphalt 32,178 103,327 112,897 204,018 — — 452,420 Liquid asphalt — — — — 253,196 — 253,196 Other 142,742 15,751 16 28,745 49,363 12,414 249,031 Contracting services publicsector 71,362 197,372 308,711 426,318 — — 1,003,763 Contracting services privatesector 54,978 103,011 124,282 21,276 — — 303,547 Internal sales (86,115) (109,108) (133,328) (235,875) (57,373) (11,618) (633,417) Revenues from contracts with customers $ 462,162 $ 663,681 $ 633,617 $ 824,908 $ 245,186 $ 796 $ 2,830,350 Year ended December 31, 2022 Pacific Northwest Mountain Central Energy Services Corporate Services Total (In thousands) Aggregates $ 92,266 $ 171,633 $ 83,343 $ 149,419 $ — $ — $ 496,661 Ready-mix concrete 127,569 157,951 106,654 217,335 — — 609,509 Asphalt 35,735 97,299 93,263 201,171 — — 427,468 Liquid asphalt — — — — 207,474 — 207,474 Other 114,079 14,844 36 24,956 45,245 618 199,778 Contracting services publicsector 81,989 173,981 249,573 412,487 — — 918,030 Contracting services privatesector 47,497 88,713 119,136 14,345 — — 269,691 Internal sales (81,105) (105,647) (110,095) (242,563) (54,006) (466) (593,882) Revenues from contracts with customers $ 418,030 $ 598,774 $ 541,910 $ 777,150 $ 198,713 $ 152 $ 2,534,729 Year ended December 31, 2021 Pacific Northwest Mountain Central Energy Services Corporate Services Total (In thousands) Aggregates $ 89,913 $ 135,182 $ 72,567 $ 146,348 $ — $ — $ 444,010 Ready-mix concrete 123,905 152,079 100,412 207,993 — — 584,389 Asphalt 26,348 78,937 69,310 165,251 — — 339,846 Liquid asphalt — — — — 166,052 — 166,052 Other 104,804 12,786 91 22,807 37,714 4 178,206 Contracting services publicsector 83,013 118,970 211,603 363,172 — — 776,758 Contracting services privatesector 44,603 68,171 112,058 15,881 — — 240,713 Internal sales (75,837) (91,184) (86,498) (200,681) (46,844) — (501,044) Revenues from contracts with customers $ 396,749 $ 474,941 $ 479,543 $ 720,771 $ 156,922 $ 4 $ 2,228,930

Uncompleted Contracts

Uncompleted Contracts	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Uncompleted Contracts	Uncompleted Contracts Costs, estimated earnings, and billings on uncompleted contracts at December 31 are summarized as follows: 2023 2022 (In thousands) Costs incurred on uncompleted contracts $ 1,395,603 $ 1,217,480 Estimated earnings 208,926 153,317 1,604,529 1,370,797 Less billings to date (1,628,612) (1,379,495) Net contract liability $ (24,083) $ (8,698) 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. Such amounts are included in the accompanying Consolidated Balance Sheets at December 31 under the following captions: 2023 2022 Change Location on Consolidated Balance Sheet (In thousands) Contract assets $ 27,293 $ 31,145 $ (3,852) Costs and estimated earnings in excess of billings on uncompleted contracts Contract liabilities (51,376) (39,843) (11,533) Billings in excess of costs and estimated earnings on uncompleted contracts Net contract liabilities $ (24,083) $ (8,698) $ (15,385) 2022 2021 Change Location on Consolidated Balance Sheet (In thousands) Contract assets $ 31,145 $ 22,005 $ 9,140 Costs and estimated earnings in excess of billings on uncompleted contracts Contract liabilities (39,843) (32,348) (7,495) Billings in excess of costs and estimated earnings on uncompleted contracts Net contract liabilities $ (8,698) $ (10,343) $ 1,645 The Company recognized $37.5 million and $30.2 million in revenue for the years ended December 31, 2023 and 2022, respectively, which was previously included in contract liabilities at December 31, 2022 and 2021, respectively. The Company recognized a net increase in revenues of approximately $12.3 million and $11.0 million for the years ended December 31, 2023 and 2022, respectively, from performance obligations satisfied in prior periods. Remaining performance obligations The remaining performance obligations, also referred to as backlog, include unrecognized revenues that the Company reasonably expects 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 the Company’s contracts for contracting services have an original duration of less than one year. At December 31, 2023, the Company’s remaining performance obligations were $662.2 million. The Company expects to recognize the following revenue amounts in future periods related to these remaining performance obligations: $610.8 million within the next 12 months; $37.1 million within the next 13 to 24 months; and $14.3 million thereafter.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment at December 31 was as follows: 2023 2022 Weighted Average Depreciable Life in Years (In thousands) Land $ 154,475 $ 150,809 — Aggregate reserves 589,034 592,097 * Buildings and improvements 216,473 165,833 22.32 Machinery, vehicles and equipment 1,590,908 1,492,506 11.68 Construction in progress 28,844 88,163 — Less: accumulated depreciation and depletion 1,264,687 1,174,195 Net property, plant and equipment $ 1,315,047 $ 1,315,213 __________________ * Depleted on the units-of-production method based on proven and probable aggregate reserves. Total depreciation and depletion expense was $119.2 million, $113.6 million and $93.9 million for the years ended December 31, 2023, 2022 and 2021, respectively.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets In the fourth quarter of 2023, in connection with the reorganization of the Company’s reporting structure, a portion of the Pacific reporting unit’s businesses were reorganized into the Energy Services reporting unit. As a result of the reorganization, the Company reallocated $5.7 million of the goodwill balance associated with the Pacific reporting unit to the Energy Services reporting unit based on the relative fair values of the Pacific reporting unit components. The estimated fair values were determined using the income approach. The Company reassessed the goodwill in connection with the reorganization and determined there was no impairment. The changes in the carrying amount of goodwill were as follows: Balance at January 1, 2023 Goodwill Acquired Measurement Period 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 Balance at January 1, 2022 Goodwill Acquired During the Year Measurement Period Adjustments Reallocation of Goodwill Balance at December 31, 2022 (In thousands) Pacific $ 38,101 $ 238 $ — $ — $ 38,339 Northwest 93,102 — (2,124) — 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 $ 276,426 $ 238 $ (2,124) $ — $ 274,540 Other amortizable intangible assets at December 31, were as follows: Average Useful Life In Years 2023 2022 (In thousands) Customer relationships 2-7 $ 18,540 $ 18,540 Less accumulated amortization 9,102 7,367 9,438 11,173 Noncompete agreements 1-3 4,039 4,039 Less accumulated amortization 3,473 2,985 566 1,054 Other 15-20 2,479 5,279 Less accumulated amortization 1,662 4,076 817 1,203 Total $ 10,821 $ 13,430 Amortization expense for amortizable intangible assets for the years ended December 31, 2023, 2022 and 2021, was $2.6 million, $2.8 million and $2.6 million, respectively. Estimated amortization expense for identifiable intangible assets as of December 31, 2023, was: 2024 2025 2026 2027 2028 Thereafter (In thousands) Amortization expense $2,228 $1,919 $1,739 $1,716 $1,672 $1,547

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2023
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 The Company measures its investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income. The Company anticipates using these investments, which consist of insurance contracts, to satisfy its obligations under its unfunded, nonqualified defined benefit and defined contribution plans for the Company’s 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 $24.9 million and $20.1 million as of December 31, 2023 and 2022, respectively, are classified as investments on the Consolidated Balance Sheets. The net unrealized gains on these investments for the years ended December 31, 2023 and 2021, were $1.9 million and $1.4 million, respectively. The net unrealized losses on these investments for the year ended December 31, 2022, were $2.8 million. 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. As part of the Separation, the Company retired certain insurance contracts used to satisfy its obligations under its unfunded, nonqualified defined contribution plan for the Company's executive officers and certain key management employees. The proceeds of the retired contracts totaled $5.3 million, which were used to purchase life insurance policies and re-invested in fixed-income and equity securities in the fourth quarter of 2023. The Company’s assets measured at fair value on a recurring basis were as follows: Fair Value Measurements at December 31, 2023, Using Quoted Prices in Significant Other 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. Fair Value Measurements at December 31, 2022, Using Quoted Prices in Significant Other Significant Balance at December 31, 2022 (In thousands) Assets: Money market funds $ — $ 2,448 $ — $ 2,448 Insurance contracts* — 20,083 — 20,083 Total assets measured at fair value $ — $ 22,531 $ — $ 22,531 __________________ * The insurance contracts invest approximately 63 percent in fixed-income investments, 15 percent in common stock of large-cap companies, 8 percent in common stock of mid-cap companies, 6 percent in common stock of small-cap companies, 6 percent in target date investments and 2 percent in cash equivalents. 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 are 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 the Company believes 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 The Company applies the provisions of the fair value measurement standard to its 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. The Company reviews the carrying value of its long-lived assets, excluding goodwill, whenever events or changes in circumstances indicate that such carrying amounts may not be recoverable. 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: December 31, 2023 (In thousands) Carrying amount $ 696,985 Fair value $ 725,086

Debt

Debt	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Debt	Debt Certain debt instruments of the Company contain restrictive and financial covenants and cross-default provisions. In order to borrow under the debt instruments, the Company must be in compliance with the applicable covenants and certain other conditions, all of which management believes the Company, as applicable, was in compliance with at December 31, 2023. In the event the Company does not comply with the applicable covenants and other conditions, it would be in default on its agreements and 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 December 31, 2023 December 31, 2023 (In thousands) Term loan agreement due on May 31, 2028 7.24 % $ 271,562 Senior notes due on May 1, 2031 7.75 % 425,000 Other notes due on January 1, 2061 — % 423 Less unamortized debt issuance costs 15,326 Total long-term debt 681,659 Less current maturities 7,082 Net long-term debt $ 674,577 Senior Notes On April 25, 2023, the Company issued $425.0 million of 7.75 percent senior notes due May 1, 2031, pursuant to an indenture. Term Loan and Revolving Credit Facility On May 31, 2023, the Company entered into a five-year secured credit agreement, which provides for a $275.0 million term loan and a $350.0 million revolving credit facility. As of December 31, 2023, the Company had no borrowings outstanding under the revolving credit facility and had a borrowing capacity of $329.0 million under the revolving credit facility, which is net of $21.0 million of outstanding letters of credit. The secured credit agreement bears interest equal to, at the Company’s option, either (i) a base rate determined by reference to the highest of (a) the prime rate, (b) the federal funds rate plus 0.50 percent, and (c) SOFR plus 1.10 percent, plus an applicable margin of 0.75 percent to 1.50 percent, based upon the Company’s leverage ratio, for base rate loans or (ii) a SOFR rate determined by the interest period relevant to such borrowing plus an applicable margin of 1.75 percent to 2.50 percent, based upon the Company’s leverage ratio. The Company will incur a quarterly commitment fee on the undrawn portion of the revolving credit facility of 0.25 percent to 0.50 percent, based on the Company’s leverage ratio. The term loan has a mandatory annual amortization of 2.50 percent for years one and two, 5.00 percent for years three and four, and 7.50 percent in the fifth year. The agreement contains customary covenants and provisions, including a covenant of Knife River not to permit, at any time, the ratio of total debt to trailing twelve month Adjusted EBITDA, as defined by the agreement, to be greater than 4.75 to 1.00. The agreement also contains an interest coverage ratio covenant stating that Knife River’s trailing twelve month Adjusted EBITDA, as defined by the agreement, to interest expense is to be no less than 2.25 to 1.00. The covenants also include restrictions on the sale of certain assets, loans and investments. Schedule of Debt Maturities Long-term debt maturities, which excludes unamortized debt issuance costs, for the five years and thereafter following December 31, 2023, were as follows: 2024 2025 2026 2027 2028 Thereafter (In thousands) Long-term debt maturities $ 7,082 $ 10,520 $ 13,759 $ 17,187 $ 223,437 $ 425,000

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Leases	Leases Most of the leases the Company enters into are for equipment, buildings and vehicles as part of their ongoing operations. The Company determines if an arrangement contains a lease at inception of a contract and accounts for all leases in accordance with ASC 842 - Leases . Lessee accounting The leases the Company has entered into as part of its ongoing operations are considered operating leases and are recognized on the Consolidated Balance Sheets as operating lease right-of-use assets, current operating lease liabilities and noncurrent operating lease liabilities. The corresponding lease costs are included in cost of revenue and selling, general and administrative expenses on the Consolidated Statements of Operations. Generally, the leases for vehicles and equipment have a term of five years or less and buildings have a longer term of up to 35 years or more. To date, the Company does not have any residual value guarantee amounts probable of being owed to a lessor, financing leases or material agreements with related parties. The following tables provide information on the Company’s operating leases at and for the years ended December 31: 2023 2022 2021 (In thousands) Lease costs: Operating lease cost $ 18,199 $ 17,941 $ 21,914 Variable lease cost 383 98 84 Short-term lease cost 53,987 55,871 53,016 Total lease costs $ 72,569 $ 73,910 $ 75,014 2023 2022 (Dollars in thousands) Weighted average remaining lease term 1.62 years 2.03 years Weighted average discount rate 5.13 % 4.05 % Cash paid for amounts included in the measurement of lease liabilities $ 18,199 $ 17,941 The reconciliation of future undiscounted cash flows to operating lease liabilities presented on the Consolidated Balance Sheet at December 31, 2023, was as follows (in thousands): 2024 $ 14,128 2025 10,286 2026 7,207 2027 5,115 2028 3,174 Thereafter 13,329 Total 53,239 Less discount 8,533 Total operating lease liabilities $ 44,706

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2023
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations The Company has asset retirement obligations, which are liabilities associated with its legally required obligations to reclaim owned and leased aggregate properties, asphalt plant sites, ready-mix plant sites and other properties. For the years ended December 31, 2023 and 2022, the current portion of the Company’s liability, which is included in other accrued liabilities, was $6.9 million and $4.4 million, respectively, and the noncurrent amount, which is included in other liabilities, was $34.9 million and $33.0 million, respectively. Total accretion and depreciation expenses for the years ended December 31, 2023, 2022 and 2021, were $2.6 million, $2.1 million and $2.1 million, respectively, and are included in cost of revenue on the Consolidated Statements of Operations. A reconciliation of the Company’s liability for the years ended December 31 was as follows: 2023 2022 (In thousands) Balance at beginning of year $ 37,361 $ 33,406 Liabilities incurred 5,190 4,657 Liabilities settled (2,726) (2,117) Accretion expense 1,957 1,415 Balance at end of year $ 41,782 $ 37,361

Equity

Equity	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Equity	Equity On May 31, 2023, the Company issued 56,997,350 shares of common stock with a par value of $0.01 in connection with the Separation. The Company historically held 538,921 shares of MDU Resources common stock through one of its subsidiaries. The historical shares are presented as MDU Resources’ stock held by subsidiary on the Consolidated Statements of Equity. In connection with the Separation, Knife River entered into an agreement with MDU Resources to transfer the stock of MDU Resources held by its subsidiary to MDU Resources in exchange for 431,136 shares of Knife River common stock. The number of shares transferred to Knife River was based on the value of the stock at the time of the Separation. The historical MDU Resources common stock held by the subsidiary at cost of $3.6 million at December 31, 2023, on the Consolidated Balance Sheets reflects the value of the MDU Resources common stock at the time it was granted to Knife River’s subsidiary. The 431,136 shares of Knife River common stock are presented as Treasury stock held at cost in the Consolidated Balance Sheet and reduce the number of common stock shares outstanding.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation Prior to the Separation, key employees of the Company participated in various stock-based compensation plans authorized and managed by MDU Resources. All awards granted under the plans were based on MDU Resources’ common shares, however, Knife River recognized the expense for its participants in its financial statements. At the time of Separation, all outstanding stock-based compensation shares of MDU Resources were converted into Knife River restricted stock units. Restricted stock units are valued based on the closing stock price on the grant date. The conversion of the stock and the fair value of the awards was determined using the policies described in Note 2. As a result of the modification, Knife River incurred $194,000 of incremental compensation expense related to the conversion of only the restricted stock units, which is being recognized over the remaining service periods of the applicable awards. There was no incremental compensation expense incurred related to the performance share awards. The Company has a stock-based compensation plan under which it is currently authorized to grant 2.5 million restricted stock units and other stock awards. As of December 31, 2023, there were 2.4 million shares available to grant under this plan. The Company either purchases shares on the open market or issues new shares of common stock to satisfy the vesting of stock-based awards. Total stock-based compensation expense (after tax) was $2.7 million, $1.2 million and $1.4 million in 2023, 2022 and 2021, respectively. The Company uses the straight-line amortization method to recognize compensation expense related to restricted stock units, which only has a service condition. As of December 31, 2023, total remaining unrecognized compensation expense related to the restricted stock units was approximately $5.0 million (before income taxes), which will be amortized over a weighted average period of 1.8 years. Stock Awards Non-employee directors receive shares of common stock in addition to and in lieu of cash payments for directors’ fees. There were 12,192 shares with a fair value of $702,000 issued to non-employee directors during the year ended December 31, 2023. Restricted stock units In February 2023, 2022 and 2021, key employees of the Company were granted restricted stock units under MDU Resources’ long-term performance-based incentive plan authorized by MDU Resources’ compensation committee. The compensation committee has the authority to select the recipients of awards, determine the type and size of awards, and establish certain terms and conditions of award grants. The shares vest over three years, contingent on continued employment. Compensation expense is recognized over the vesting period. As previously discussed, the outstanding restricted stock awards granted to Knife River employees were converted to restricted stock units of Knife River in connection with the Separation. At the time of the Separation, the outstanding performance share awards were also converted to restricted stock units of Knife River as shown in the table later in this Note. In July 2023, key employees of the Company were granted restricted stock units under Knife River’s long-term performance-based incentive plan authorized by the Company’s compensation committee. The compensation committee has the authority to select the recipients of awards, determine the type and size of awards, and establish certain terms and conditions of award grants. The shares vest over three years, contingent on continued employment. Compensation expense is recognized over the vesting period. As of December 31, 2023, the outstanding restricted stock units were as follows: Grant Date Service Period Number of Shares Weighted Average Grant-Date Fair Value May 2023 2022-2024 66,887 $ 36.60 May 2023 2023-2025 82,680 $ 36.60 July 2023 2023-2025 71,650 $ 43.00 Historical performance share awards In February 2022 and 2021, key employees of the Company were granted performance share awards under MDU Resources’ long-term performance-based incentive plan authorized by MDU Resources’ compensation committee. The compensation committee has the authority to select the recipients of awards, determine the type and size of awards, and establish certain terms and conditions of award grants. Share awards are generally earned over a three-year vesting period and tied to specific financial metrics. Upon vesting, participants may receive dividends that accumulate during the vesting period. Share awards were generally earned over a three-year vesting period and tied to financial metrics. However, as previously discussed, the outstanding performance share awards of Knife River employees were converted to restricted stock units of Knife River in connection with the Separation. Under the market condition for these performance share awards, participants may earn from zero to 200 percent of the apportioned target grant of shares based on MDU Resources’ total stockholder return relative to that of the selected peer group. Compensation expense was based on the grant-date fair value as determined by Monte Carlo simulation. The blended volatility term structure ranges are comprised of 50 percent historical volatility and 50 percent implied volatility. Risk-free interest rates were based on U.S. Treasury security rates in effect as of the grant date. Assumptions used for grants applicable to the market condition for certain performance shares issued in 2022 and 2021 were: 2022 2021 Weighted average grant date fair value $36.25 $37.96 Blended volatility range 24.07 % - 31.41 % 35.37 % - 46.35 % Risk-free interest rate range 0.71 % - 1.68 % 0.02 % - 0.20 % Weighted average discounted dividends per share $2.93 $3.16 Under the performance conditions for these performance share awards, participants may earn from zero to 200 percent of the apportioned target grant of shares. The performance conditions were based on MDU Resources’ compound annual growth rate in earnings from continuing operations. The weighted average grant-date fair value per share for the performance shares applicable to these performance conditions issued in 2022 and 2021 was $27.73 and $27.35, respectively. The fair value of the performance shares that vested during the years ended December 31, 2022 and 2021, was $962,000 and $1.7 million, respectively. For the year ended December 31, 2023, the following summarizes the activity of the performance share awards to the converted Knife River restricted stock units. Performance Share Awards Restricted Stock Units Number of Shares Weighted Average Grant-Date Fair Value Number of Shares Weighted Average Grant-Date Fair Value Nonvested at the beginning of period 69,601 $ 32.32 23,197 $ 27.54 Granted pre-Separation by MDU Resources — 81,507 $ 31.16 Adjustments for performance (13,261) $ 32.51 — Forfeited pre-Separation (4,510) $ 32.29 (4,941) $ 30.06 Nonvested pre-Separation 51,830 $ 32.27 99,763 $ 30.37 Conversion to Knife River restricted stock units (51,830) 125,050 Granted post Separation — 71,650 Vested shares — (53,958) Forfeited post Separation — (21,288) Nonvested at end of period — 221,217

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The Company’s accumulated other comprehensive loss is comprised of losses on derivative instruments qualifying as hedges and postretirement liability adjustments. The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Unrealized Loss on Derivative Instruments Qualifying as Hedges Post-retirement Liability Adjustment Total Accumulated Other Comprehensive Loss (In thousands) At December 31, 2021 $ (418) $ (24,072) $ (24,490) Other comprehensive income before reclassifications — 10,935 10,935 Amounts reclassified from accumulated other comprehensive loss 328 875 1,203 Net current-period other comprehensive income 328 11,810 12,138 At December 31, 2022 (90) (12,262) (12,352) Other comprehensive income before reclassifications — 751 751 Amounts reclassified from accumulated other comprehensive loss 90 192 282 Net current-period other comprehensive income 90 943 1,033 At December 31, 2023 $ — $ (11,319) $ (11,319) The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parentheses indicate a decrease to net income on the Consolidated Statements of Operations. The reclassifications for the years ended December 31 were as follows: 2023 2022 2021 Location on Consolidated Statements of Income (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ (118) $ (435) $ (439) Interest expense 28 107 107 Income taxes (90) (328) (332) Amortization of postretirement liability losses included in net periodic benefit cost (256) (1,167) (1,453) Other income (expense) 64 292 363 Income taxes (192) (875) (1,090) Total reclassifications $ (282) $ (1,203) $ (1,422)

Cash Flow Information

Cash Flow Information	12 Months Ended
	Dec. 31, 2023
Supplemental Cash Flow Information [Abstract]
Cash Flow Information	Cash Flow Information Cash expenditures for interest and income taxes for the years ended December 31 were as follows: 2023 2022 2021 (In thousands) Interest paid, net $ 54,925 $ 28,148 $ 19,121 Income taxes paid, net $ 76,689 $ 21,186 $ 34,784 Noncash investing and financing transactions at December 31 were as follows: 2023 2022 2021 (In thousands) Property, plant and equipment additions in accounts payable $ 12,672 $ 13,965 $ 15,840 Right-of-use assets obtained in exchange for new operating lease liabilities $ 14,967 $ 11,763 $ 11,497 Equity contribution from Centennial related to the Separation $ 64,724 $ — $ — Equity contribution to MDU Resources for asset/liability transfers related to the Separation $ (1,537) $ — $ — MDU Resources’ stock issued in connection with a business combination $ 383 $ 7,304 $ — Debt assumed in connection with a business combination $ — $ — $ 10 Accrual for holdback payment related to a business combination $ — $ 70 $ —

Business Segment Data

Business Segment Data	12 Months Ended
	Dec. 31, 2023
Segment Reporting [Abstract]
Business Segment Data	Business Segment Data The Company focuses on the vertical integration of its products and services by offering customers a single-source for construction materials and related contracting services. The Company operates in 14 states across the United States. Its operating segments include: Pacific, Northwest, Mountain, North Central, South and Energy Services. The operating segments are used to determine the Company’s reportable segments and are based on the Company’s method of internal reporting and management of the business. There are five reportable segments, four of which are aligned by key geographic areas due to the production of construction materials and related contracting services and one of which is based on product line. The Energy Services segment, which has locations throughout the Company’s geographic footprint, produces and supplies liquid asphalt and related services. Each segment is led by a segment manager that reports to the Company’s chief operating officer who is also the Company’s chief operating decision maker. The Company’s 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. In the fourth quarter of 2023, the Company completed a reorganization of its reporting structure, which has resulted in changes being made to the management of its business to best align with its strategies. Based on how the chief operating decision maker manages the Company, the reportable segments are: Pacific, Northwest, Mountain, Central and Energy Services. The Company also has the Corporate Services segment. As a result of the reorganization, 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. 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 including 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. The Company accounts 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 Note 2. Information on the Company’s segments as of December 31, and for the years then ended was as follows: 2023 2022 2021 (In thousands) External operating revenues: Pacific $ 462,162 $ 418,030 $ 396,749 Northwest 663,681 598,774 474,941 Mountain 633,617 541,910 479,543 Central 824,908 777,150 720,771 Energy Services 245,186 198,713 156,922 Corporate Services 796 152 4 Total external operating revenues $ 2,830,350 $ 2,534,729 $ 2,228,930 2023 2022 2021 (In thousands) Intersegment operating revenues: Pacific $ 86,115 $ 81,105 $ 75,837 Northwest 109,108 105,647 91,184 Mountain 133,328 110,095 86,498 Central 235,875 242,563 200,681 Energy Services 57,373 54,006 46,844 Corporate Services 11,618 466 — Total intersegment operating revenues $ 633,417 $ 593,882 $ 501,044 EBITDA: Pacific $ 56,206 $ 44,044 $ 57,915 Northwest 121,098 103,885 80,624 Mountain 103,142 72,604 65,017 Central 116,653 86,572 81,459 Energy Services 78,124 28,310 31,564 Corporate Services (53,219) (28,675) (23,173) Total segment EBITDA $ 422,004 $ 306,740 $ 293,406 Capital expenditures: Pacific $ 21,512 $ 31,462 $ 25,154 Northwest 31,653 60,697 278,946 Mountain 25,506 35,098 47,648 Central 39,302 46,574 51,144 Energy Services 4,099 5,651 4,577 Corporate Services 918 2,365 10,055 Total capital expenditures* $ 122,990 $ 181,847 $ 417,524 Assets: Pacific $ 432,820 $ 408,805 $ 384,573 Northwest 781,640 772,159 714,098 Mountain 315,661 293,121 278,608 Central 663,134 607,200 603,008 Energy Services 128,383 138,323 131,244 Corporate Services 278,175 74,711 70,293 Total assets $ 2,599,813 $ 2,294,319 $ 2,181,824 2023 2022 2021 (In thousands) Property, plant and equipment: Pacific $ 528,008 $ 517,794 $ 490,499 Northwest 839,060 813,513 759,482 Mountain 419,537 400,907 369,732 Central 646,929 615,893 594,330 Energy Services 102,844 98,698 93,272 Corporate Services 43,356 42,603 40,383 Less accumulated depreciation and depletion 1,264,687 1,174,195 1,097,388 Net property, plant and equipment $ 1,315,047 $ 1,315,213 $ 1,250,310 __________________ * Capital expenditures for 2023, 2022 and 2021 include noncash transactions for capital expenditure-related accounts payable, the issuance of equity securities in connection with an acquisition and accrual of a holdback payment in connection with an acquisition totaling $(910,000), $(5.4) million and $(8.1) million, respectively. A reconciliation of reportable segment operating revenues to consolidated operating revenues is as follows: 2023 2022 2021 (In thousands) Total reportable segment operating revenues $ 3,451,353 $ 3,127,993 $ 2,729,970 Corporate Services revenue 12,414 618 4 Less: Elimination of intersegment operating revenues 633,417 593,882 501,044 Total consolidated operating revenues $ 2,830,350 $ 2,534,729 $ 2,228,930 A reconciliation of reportable segment assets to consolidated assets is as follows: 2023 2022 2021 (In thousands) Total assets for reportable segments $ 2,321,637 $ 2,219,608 $ 2,111,531 Other assets 4,049,800 3,439,435 3,239,393 Less: Elimination of intercompany receivables and investment in subsidiaries 3,771,624 3,364,724 3,169,100 Total consolidated assets $ 2,599,813 $ 2,294,319 $ 2,181,824 A reconciliation of reportable segment EBITDA to consolidated income before income taxes is as follows: 2023 2022 2021 (In thousands) Total EBITDA for reportable segments $ 475,223 $ 335,415 $ 316,579 Corporate Services EBITDA (53,219) (28,675) (23,173) Less: Depreciation, depletion and amortization 123,805 117,798 100,974 Interest expense, net* 52,891 30,121 19,218 Total consolidated income before income taxes $ 245,308 $ 158,821 $ 173,214 __________________ * Interest expense, net is interest expense net of interest income

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense on the Consolidated Statements of Operations for the years ended December 31 was as follows: 2023 2022 2021 (In thousands) Current: Federal $ 45,746 $ 27,293 $ 4,270 State 18,296 13,230 6,331 64,042 40,523 10,601 Deferred: Income taxes: Federal 263 1,715 26,793 State (1,869) 363 6,065 (1,606) 2,078 32,858 Total income tax expense $ 62,436 $ 42,601 $ 43,459 Components of deferred tax assets and deferred tax liabilities at December 31 were as follows: 2023 2022 (In thousands) Deferred tax assets: Deferred compensation/compensation related $ 22,358 $ 15,329 Operating lease liabilities 11,468 11,804 Asset retirement obligations 10,862 9,687 Net operating loss/credit carryforward 10,811 12,039 Accrued pension costs 10,556 11,070 Capitalized inventory overheads 7,388 7,260 Other 9,458 8,412 Total deferred tax assets $ 82,901 $ 75,601 2023 2022 (In thousands) Deferred tax liabilities: Basis differences on property, plant and equipment $ 206,507 $ 203,099 Intangible assets 12,220 10,975 Operating lease right-of-use-assets 11,468 11,804 Other 16,437 13,488 Total deferred tax liabilities 246,632 239,366 Valuation allowance 10,811 12,039 Net deferred income tax liability $ (174,542) $ (175,804) As of December 31, 2023 and 2022, the Company had various state income tax net operating loss carryforwards of $133.6 million and $160.1 million, respectively, and federal and state income tax credit carryforwards, excluding alternative minimum tax credit carryforwards, of $591,000 for both years. The state income tax credit carryforwards are due to expire in 2024. Changes in tax regulations or assumptions regarding current and future taxable income could require additional valuation allowances in the future. The following table reconciles the change in the net deferred income tax liability from December 31, 2022, to December 31, 2023, to deferred income tax expense: 2023 2022 (In thousands) Change in net deferred income tax liability from the preceding table $ (1,262) $ 7,278 Deferred income taxes established due to an acquisition — (1,215) Deferred taxes associated with other comprehensive loss (344) (3,985) Deferred income tax expense for the period $ (1,606) $ 2,078 Total income tax expense differs from the amount computed by applying the statutory federal income tax rate to income before taxes. The reasons for this difference were as follows: Years ended December 31, 2023 2022 2021 Amount % Amount % Amount % (Dollars in thousands) Computed tax at federal statutory rate $ 51,515 21.0 $ 33,353 21.0 $ 36,375 21.0 Increases (reductions) resulting from: State income taxes, net of federal income tax 12,756 5.2 9,702 6.1 9,429 5.4 Depletion allowance (2,756) (1.1) (2,123) (1.3) (1,893) (1.1) Other 921 0.4 1,669 1.0 (452) (0.2) Total income tax expense $ 62,436 25.5 $ 42,601 26.8 $ 43,459 25.1 The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction, and various state and local jurisdictions. The Company is no longer subject to U.S. federal or non-U.S. income tax examinations by tax authorities for years ending prior to 2020. With few exceptions, as of December 31, 2023, the Company is no longer subject to state and local income tax examinations by tax authorities for years ending prior to 2020. For the years ended December 31, 2023, 2022 and 2021, total reserves for uncertain tax positions were not material. The Company recognizes interest and penalties accrued relative to unrecognized tax benefits in income tax expense.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans Pension and other postretirement benefit plans The Company participates in self-sponsored qualified defined benefit pension plans which are accounted for as single-employer plans and are reflected in the Company’s audited consolidated financial statements. The Company uses a measurement date of December 31 for all its pension and postretirement benefit plans. Prior to 2010, defined benefit pension plan benefits and accruals for the nonunion plan were frozen and on June 30, 2015, the remaining union plan was frozen. These employees were eligible to receive additional defined contribution plan benefits. Prior to the Separation, the Company participated in a multiple-employer postretirement benefit plan sponsored by MDU Resources. In connection with the Separation, the Company assumed all the obligations and liabilities of Knife River’s employees in that plan, along with all MDU Resources employees that transferred to Knife River as a result of the Separation. Subsequent to the Separation, the postretirement benefit plans in which the Company participates are single employer plans. Employees hired after December 31, 2010 are not eligible for retiree medical benefits. Effective January 1, 2011, eligibility to receive retiree medical benefits was modified such that eligible employees who attained age 55 with 10 years of continuous, full‐time service by December 31, 2010, will have an option to select one of two retiree medical insurance benefits. All other eligible employees must meet the new eligibility criteria of age 60 and 10 years of continuous, full‐time service at the time they retire. These employees will be eligible for a company funded retiree reimbursement account. Employees hired after December 31, 2014 are not eligible for retiree medical benefits. In 2012, the Company modified health care coverage for certain retirees. Effective January 1, 2013, post-65 coverage was replaced by a fixed-dollar subsidy for retirees and spouses to be used to purchase individual insurance through a healthcare exchange. Changes in benefit obligation and plan assets and amounts recognized in the Consolidated Balance Sheets at December 31, were as follows: Pension Benefits Other Postretirement Benefits 2023 2022 2023 2022 (In thousands) Change in benefit obligation: Benefit obligation at beginning of year $ 33,758 $ 44,363 $ 14,616 $ 19,480 Service cost — — 361 522 Interest cost 1,633 1,127 721 514 Plan participants’ contributions — — — 3 Actuarial (gain) loss 477 (9,174) (346) (5,319) Benefits paid (2,488) (2,558) (593) (584) Benefit obligation at end of year 33,380 33,758 14,759 14,616 Change in net plan assets: Fair value of plan assets at beginning of year 28,431 39,345 (314) 314 Actual return on plan assets 3,074 (8,356) 321 (473) Employer contribution 1,170 — 586 426 Plan participants’ contributions — — — 3 Benefits paid (2,488) (2,558) (593) (584) Fair value of net plan assets at end of year 30,187 28,431 — (314) Funded status - under $ (3,193) $ (5,327) $ (14,759) $ (14,930) Amounts recognized in the Consolidated Balance Sheets at December 31: Other accrued liabilities $ — $ — $ 699 $ 1,044 Noncurrent liabilities - other 3,193 5,327 14,060 13,886 Benefit obligation liabilities $ 3,193 $ 5,327 $ 14,759 $ 14,930 Amounts recognized in accumulated other comprehensive loss consist of: Actuarial (gain) loss $ 17,780 $ 19,087 $ (2,560) $ (2,057) Prior service credit — — (30) (109) Total $ 17,780 $ 19,087 $ (2,590) $ (2,166) Employer contributions and benefits paid in the preceding table include only those amounts contributed directly to, or paid directly from, plan assets. In 2023, the actuarial loss recognized in the pension benefit obligation was largely the combination of losses resulting from decreased discount rates, offset in part by higher asset gains. The actuarial gain recognized in the other postretirement benefit obligation was largely the combinations of gains due to a decrease in expected claims, offset in part by losses resulting from decreased discount rates. In 2022, the actuarial gain recognized in the benefit obligation was primarily the result of an increase in the discount rate. For more information on the discount rates, see the table below. Unrecognized pension actuarial gains and losses in excess of 10 percent of the greater of the projected benefit obligation or the market-related value of assets are amortized over the average life expectancy of plan participants for frozen plans. The market-related value of assets is determined using a five years average of assets. The pension plans all have accumulated benefit obligations in excess of plan assets. The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for these plans at December 31, were as follows: 2023 2022 (In thousands) Projected benefit obligation $ 33,380 $ 33,758 Accumulated benefit obligation $ 33,380 $ 33,758 Fair value of plan assets $ 30,187 $ 28,431 The components of net periodic benefit cost (credit), other than the service cost component, are included in other income (expense) on the Consolidated Statements of Operations. Prior service credit is amortized on a straight- line basis over the average remaining service period of active participants. These components related to the Company’s pension and other postretirement benefit plans for the years ended December 31, were as follows: Pension Benefits Other Postretirement Benefits 2023 2022 2021 2023 2022 2021 (In thousands) Components of net periodic benefit cost (credit): Service cost $ — $ — $ — $ 361 $ 522 $ 567 Interest cost 1,633 1,127 1,053 721 514 492 Expected return on assets (1,800) (1,973) (2,028) 11 (12) (19) Amortization of prior service credit — — — (79) (79) (79) Amortization of actuarial gain (loss) 510 856 971 (175) 351 135 Net periodic benefit cost (credit) 343 10 (4) 839 1,296 1,096 Other changes in plan assets and benefit obligations recognized in accumulated other comprehensive loss: Net (gain) loss (797) 1,155 (162) (678) (4,833) (2,763) Amortization of actuarial gain (loss) (510) (856) (1,108) 175 (351) (135) Amortization of prior service credit — — — 79 79 90 Total recognized in accumulated other comprehensive loss (1,307) 299 (1,270) (424) (5,105) (2,808) Total recognized in net periodic benefit cost (credit) and accumulated other comprehensive loss $ (964) $ 309 $ (1,274) $ 415 $ (3,809) $ (1,712) Weighted average assumptions used to determine benefit obligations at December 31, were as follows: Pension Benefits Other Postretirement Benefits 2023 2022 2023 2022 Discount rate 4.83 % 5.06 % 4.84 % 5.07 % Expected return on plan assets 6.50 % 6.50 % — % 6.00 % Rate of compensation increase N/A N/A 4.00 % 3.00 % Weighted average assumptions used to determine net periodic benefit cost (credit) for the years ended December 31, were as follows: Pension Benefits Other Postretirement Benefits 2023 2022 2023 2022 Discount rate 5.06 % 2.62 % 5.06 % 2.69 % Expected return on plan assets 6.50 % 6.00 % 6.00 % 5.50 % Rate of compensation increase N/A N/A 3.00 % 3.00 % The expected rate of return on pension plan assets is based on a targeted asset allocation range determined by the funded ratio of the plan. As of December 31, 2023, the expected rate of return on pension plan assets is based on the targeted asset allocation range of 40 percent to 50 percent equity securities and 50 percent to 60 percent fixed-income securities and the expected rate of return from these asset categories. Health care rate assumptions for the Company’s other postretirement benefit plans as of December 31, were as follows: 2023 2022 Health care trend rate assumed for next year 7.5 % 7.5 % Health care cost trend rate – ultimate 4.5 % 4.5 % Year in which ultimate trend rate achieved 2034 2033 The Company’s other postretirement benefit plans include health care and life insurance benefits for certain retirees. The plans underlying these benefits may require contributions by the retiree depending on such retiree’s age and years of service at retirement or the date of retirement. The Company contributes a flat dollar amount to the monthly premiums, which is updated annually on January 1. The Company expects to contribute $912,000 and $700,000 to its defined benefit pension and postretirement benefit plans in 2024, respectively. The following benefit payments, which reflect future service, as appropriate, at December 31, 2023, are as follows: Years Pension Benefits Other Postretirement Benefits (In thousands) 2024 $ 2,890 $ 695 2025 2,780 867 2026 2,740 1,053 2027 2,680 1,136 2028 2,620 1,235 2029-2033 12,200 6,507 Outside investment managers manage the Company’s pension and postretirement assets. The Company’s investment policy with respect to pension and other postretirement assets is to make investments solely in the interest of the participants and beneficiaries of the plans and for the exclusive purpose of providing benefits accrued and defraying the reasonable expenses of administration. The Company strives to maintain investment diversification to assist in minimizing the risk of large losses. The Company’s policy guidelines allow for investment of funds in cash equivalents, fixed-income securities and equity securities. The guidelines prohibit investment in commodities and futures contracts, equity private placement, employer securities, leveraged or derivative securities, options, direct real estate investments, precious metals, venture capital and limited partnerships. The guidelines also prohibit short selling and margin transactions. The Company’s practice is to periodically review and rebalance asset categories based on its targeted asset allocation percentage policy. 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 ASC establishes a hierarchy for grouping assets and liabilities, based on the significance of inputs. The estimated fair values of the Company’s pension plans’ assets are determined using the market approach. The carrying value of the pension plans’ Level 2 cash equivalents approximates fair value and is determined using observable inputs in active markets or the net asset value of shares held at year end, which is determined using other observable inputs, including pricing from outside sources. The estimated fair value of the pension plans’ Level 1 and Level 2 equity securities are based on the closing price reported on the active market on which the individual securities are traded or other known sources including pricing from outside sources. The estimated fair value of the pension plans’ Level 1 and Level 2 collective and mutual funds are based on the net asset value of shares held at year end, based on either published market quotations on active markets or other known sources, including pricing from outside sources. The estimated fair value of the pension plans’ Level 2 corporate and municipal bonds is determined using other observable inputs, including benchmark yields, reported trades, broker/dealer quotes, bids, offers, future cash flows and other reference data. The estimated fair value of the pension plans’ Level 1 U.S. Government securities are valued based on quoted prices on an active market. The estimated fair value of the pension plans’ Level 2 U.S. Government securities are valued mainly using other observable inputs, including benchmark yields, reported trades, broker/dealer quotes, bids, offers, to be announced prices, future cash flows and other reference data. The estimated fair value of the pension plans’ Level 2 pooled separate accounts are determined using observable inputs in active markets or the net asset value of shares held at year end, or other observable inputs. Some of these securities are valued using pricing from outside sources. All investments measured at net asset value in the tables that follow are invested in commingled funds, separate accounts or common collective trusts which do not have publicly quoted prices. The fair value of the commingled funds, separate accounts and common collective trusts are determined based on the net asset value of the underlying investments. The fair value of the underlying investments held by the commingled funds, separate accounts and common collective trusts is generally based on quoted prices in active markets. Though the Company believes 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. The fair value of the Company’s pension plans’ assets by class were as follows: Fair Value Measurements at December 31, 2023, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at December 31, 2023 (In thousands) Assets: Cash equivalents $ — $ 1,021 $ — $ 1,021 Collective and mutual funds (a) 25,981 2,565 — 28,546 Investments measured at net asset value (b) — — — 620 Total assets measured at fair value $ 25,981 $ 3,586 $ — $ 30,187 __________________ (a) Collective and mutual funds invest approximately 33 percent in corporate bonds, 23 percent in U.S. Government securities, 15 percent in common stock of large-cap U.S. companies, 13 percent in other investments, 8 percent in common stock of international companies and 8 percent in cash and cash equivalents. (b) In accordance with ASC 820 - Fair Value, Measurements certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the Consolidated Balance Sheets. Fair Value Measurements at December 31, 2022, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at December 31, 2022 (In thousands) Assets: Cash equivalents $ — $ 859 $ — $ 859 Equity securities: U.S. companies 777 — — 777 International companies — 49 — 49 Collective and mutual funds (a) 12,729 3,508 — 16,237 Corporate bonds — 8,554 — 8,554 Municipal bonds — 621 — 621 U.S. Government securities 320 92 — 412 Pooled separate accounts (b) — 337 — 337 Investments measured at net asset value (c) — — — 585 Total assets measured at fair value $ 13,826 $ 14,020 $ — $ 28,431 __________________ (a) Collective and mutual funds invest approximately 29 percent in corporate bonds, 24 percent in common stock of large-cap U.S. companies, 16 percent in common stock of international companies, 7 percent in cash and cash equivalents, 7 percent in U.S. Government securities and 17 percent in other investments. (b) Pooled separate accounts are invested 100 percent in cash and cash equivalents. (c) In accordance with ASC 820 - Fair Value, Measurements certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the Consolidated Balance Sheets. The estimated fair values of the Company’s other postretirement benefit plans’ assets are determined using the market approach. The estimated fair value of the other postretirement benefit plans’ Level 2 cash equivalents is valued at the net asset value of shares held at year end, based on published market quotations on active markets, or using other known sources including pricing from outside sources. The estimated fair value of the other postretirement benefit plans’ Level 1 and Level 2 equity securities is based on the closing price reported on the active market on which the individual securities are traded or other known sources, including pricing from outside sources. The estimated fair value of the other postretirement benefit plans’ Level 2 insurance contract 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 the Company believes 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. Due to the Separation, there are no assets in the postretirement benefit plans as of May 31, 2023. The fair value of the Company’s other postretirement benefit plans’ assets (excluding cash) by asset class were as follows: Fair Value Measurements at December 31, 2022, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at December 31, 2022 (In thousands) Assets: Cash equivalents $ — $ (17) $ — $ (17) Equity securities: U.S. companies (11) — — (11) Insurance contract* — (286) — (286) Total assets measured at fair value $ (11) $ (303) $ — $ (314) __________________ * The insurance contract invests approximately 69 percent in corporate bonds, 14 percent in common stock of large-cap U.S. companies, 13 percent in U.S. government securities, and 4 percent in common stock of small-cap U.S. companies. Nonqualified benefit plans Prior to the Separation, the Company participated in unfunded, nonqualified defined benefit plans sponsored by MDU Resources. In connection with the Separation, the Company assumed all the obligations and liabilities of Knife River’s employees in those plans, along with all MDU Resources employees that transferred to Knife River as a result of the Separation. Subsequent to the Separation, the unfunded, nonqualified defined benefit plans in which the Company participates are single employer plans for executive officers and certain key management employees. The plans generally provide for defined benefit payments at age 65 following the employee’s retirement or, upon death, to their beneficiaries for a 15-year period. In February 2016, MDU Resources froze the unfunded, nonqualified defined benefit plans to new participants and eliminated benefit increases. Vesting for participants not fully vested was retained. The projected benefit obligation and accumulated benefit obligation for the Company’s participants in these plans at December 31, were as follows: 2023 2022 (In thousands) Projected benefit obligation $ 15,873 $ 16,047 Accumulated benefit obligation $ 15,873 $ 16,047 The components of net periodic benefit cost are included in other income (expense) 2023 2022 2021 (In thousands) Components of net periodic benefit cost: Interest cost $ 765 $ 460 $ 407 Recognized net actuarial loss — 39 223 Net periodic benefit cost $ 765 $ 499 $ 630 Weighted average assumptions used at December 31, were as follows: 2023 2022 Benefit obligation discount rate 4.74 % 4.97 % Benefit obligation rate of compensation increase N/A N/A Net periodic benefit cost discount rate 4.93 % 2.38 % Net periodic benefit cost rate of compensation increase N/A N/A The amount of future benefit payments for the unfunded, nonqualified defined benefit plans at December 31, 2023 are expected to aggregate as follows: 2024 2025 2026 2027 2028 2029-2033 (In thousands) Nonqualified benefits $ 1,620 $ 1,720 $ 1,700 $ 1,650 $ 1,690 $ 5,600 Prior to the Separation, the Company participated in nonqualified defined contribution plans for certain key management employees sponsored by MDU Resources. In connection with the Separation, the Company assumed all the obligations and liabilities of Knife River’s employees in those plans, along with all MDU Resources’ employees that transferred to Knife River as a result of the Separation. In 2020, the MDU Resources’ plan was frozen to new participants and no new Company contributions were made to the plan after December 31, 2020. Vesting for participants not fully vested was retained. MDU Resources adopted a new nonqualified defined contribution plan in 2020, effective January 1, 2021, to replace the plan originally established in 2012 with similar provisions. Expenses incurred by Knife River under these plans for 2023, 2022 and 2021 were $1.5 million, $1.2 million and $900,000, respectively. The amount of investments that the Company anticipates using to satisfy obligations under these plans at December 31, was as follows: 2023 2022 (In thousands) Investments Insurance contract* $ 24,896 $ 20,083 Life insurance** 7,175 7,234 Other 3,241 2,448 Total investments $ 35,312 $ 29,765 __________________ * For more information on the insurance contract, see Note 7. ** Investments of life insurance are carried on plan participants (payable upon the employee’s death). Defined contribution plans Knife River sponsors a defined contribution plan in which the Company participates. The costs incurred by the Company under this plan for eligible employees were $31.1 million, $27.6 million and $26.6 million in 2023, 2022 and 2021, respectively. Multiemployer plans The Company contributes to a number of MEPPs under the terms of collective-bargaining agreements that cover its union-represented employees. The risks of participating in these multiemployer plans are different from single-employer plans in the following aspects: • Assets contributed to the MEPP by one employer may be used to provide benefits to employees of other participating employers. • If a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers. • If the Company chooses to stop participating in some of its MEPPs, the Company may be required to pay those plans an amount based on the underfunded status of the plan, referred to as a withdrawal liability. The Company’s participation in these plans is outlined in the following table. Unless otherwise noted, the most recent Pension Protection Act zone status available in 2023, 2022 and 2021 is for the plan’s year-end at December 31, 2022, December 31, 2021 and December 31, 2020, respectively. The zone status is based on information that the Company received from the plan and is certified by the plan’s actuary. Among other factors, plans in the “red zone,” or critical status, are generally less than 65 percent funded, plans in the “yellow zone,” or endangered status, are between 65 percent and 80 percent funded, and plans in the “green zone,” or healthy status, are at least 80 percent funded. Pension Fund EIN/Pension Plan Number Pension Protection Act Zone Status FIP/RP Status Pending/ Implemented Contributions Surcharge Imposed Expiration Date of Collective Bargaining Agreement 2023 2022 2023 2022 2021 (In thousands) Alaska Laborers Employer Retirement Fund 916028298-001 Red as of 6/30/22 Red as of 6/30/21 Implemented $ 887 $ 805 $ 737 No 12/31/2023 * Minnesota Teamsters Construction Division Pension Fund 416187751-001 Green Green No 418 644 713 No 4/30/2024 Pension Trust Fund for Operating Engineers 946090764-001 Yellow Yellow Implemented 2,476 2,484 2,495 No 3/31/2026- 6/30/2026 Western Conference of Teamsters Pension Plan 916145047-001 Green Green No 3,307 3,127 3,006 No 07/01/2023- 6/30/2026 * Other funds 5,653 5,938 5,519 Total contributions $ 12,741 $ 12,998 $ 12,470 __________________ * Plan includes contributions required by collective bargaining agreements which have expired but contain provisions automatically renewing their terms in the absence of a subsequent negotiated agreement. The Company was listed in the plans’ Forms 5500 as providing more than 5 percent of the total contributions for the following plans and plan years: Pension Fund Year Contributions to Plan Exceeded More Than 5 Percent of Total Contributions (as of December 31, of the Plan’s Year-End) DB Pension Plan of AGC-IUOE Local 701 Pension Trust Fund 2022 and 2021 Minnesota Teamsters Construction Division Pension Fund 2022 and 2021 Southwest Marine Pension Trust 2022 and 2021 The Company also contributes to a number of multiemployer other postretirement plans under the terms of collective-bargaining agreements that cover its union-represented employees. These plans provide benefits such as health insurance, disability insurance and life insurance to retired union employees. Many of the multiemployer other postretirement plans are combined with active multiemployer health and welfare plans. The Company’s total contributions to its multiemployer other postretirement plans, which also includes contributions to active multiemployer health and welfare plans, were $1.8 million, $1.8 million and $3.2 million for the years ended December 31, 2023, 2022 and 2021, respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
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. The Company accrues 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. The Company does 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, the Company discloses 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 December 31, 2023 and 2022, the Company accrued liabilities which have not been discounted, of $873,000 and $1.0 million, respectively. At December 31, 2023 and 2022, the Company also recorded corresponding insurance receivables of $42,000 and $325,000, respectively, related to the accrued liabilities. The accruals are for contingencies, including litigation and environmental matters. Most of these claims and lawsuits are covered by insurance, thus the Company’s exposure is typically limited to its deductible amount. The Company 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 Portland Harbor Site . In December 2000, Knife River - Northwest was named by the EPA as a PRP in connection with the cleanup of the riverbed site adjacent to a commercial property site acquired by Knife River - Northwest from Georgia-Pacific West, Inc. along the Willamette River. The riverbed site is part of the Portland, Oregon, Harbor Superfund Site where the EPA wants responsible parties to share in the costs of cleanup. The EPA entered into a consent order with certain other PRPs referred to as the Lower Willamette Group for a remedial investigation and feasibility study. The Lower Willamette Group has indicated that it incurred over $115 million in investigation related costs before it concluded its work and disbanded. Knife River - Northwest has joined with approximately 100 other PRPs, including the former Lower Willamette Group members, in a voluntary process to establish an allocation of costs for the site. Costs to be allocated would include costs incurred by the Lower Willamette Group as well as costs incurred by other participants to implement and fund remediation of the site. In January 2017, the EPA issued a Record of Decision adopting a selected remedy which is expected to take 13 years to complete with a then estimated present value of approximately $1 billion. Corrective action will not be taken until remedial design/remedial action plans are approved by the EPA. In 2020, the EPA encouraged certain PRPs to enter into consent agreements to perform remedial design covering the entire site and proposed dividing the site into multiple subareas for remedial design. Certain PRPs executed consent agreements for remedial design work and certain others were issued unilateral administrative orders to perform design work. Knife River - Northwest is not subject to either a voluntary agreement or unilateral order to perform remedial design work. In February 2021, the EPA announced that 100 percent of the site’s area requiring active cleanup are in the remedial design process. The remedial design work is ongoing and site-wide remediation activities are not expected to commence for a number of years. Knife River - Northwest was also notified that the Portland Harbor Natural Resource Trustee Council intends to perform an injury assessment to natural resources resulting from the release of hazardous substances at the site. It is not possible to estimate the costs of natural resource damages until an assessment is completed and allocations are undertaken. At this time, Knife River - Northwest does not believe it is a responsible party and has notified Georgia-Pacific West, Inc., that it intends to seek indemnity for liabilities incurred in relation to the above matters pursuant to the terms of their sale agreement. The Company believes it is not probable that it will incur any material environmental remediation costs or damages in relation to the above referenced matter. Purchase commitments The Company has entered into various commitments, largely purchased cement, liquid asphalt, minimum royalties and fuel. The commitment terms vary in length, up to 25 years. The commitments under these contracts as of December 31, 2023, were: 2024 2025 2026 2027 2028 Thereafter (In thousands) Purchase commitments $ 59,211 $ 27,758 $ 27,342 $ 2,028 $ 1,542 $ 8,212 These commitments were not reflected in the Company’s audited consolidated financial statements. Amounts purchased under various commitments for the years ended December 31, 2023, 2022 and 2021 were $128.7 million, $167.6 million and $137.4 million, respectively. Guarantees Certain subsidiaries of the Company have outstanding guarantees to third parties where the Company has guaranteed their performance. These guarantees are related to contracts for contracting services and certain other guarantees. At December 31, 2023, the fixed maximum amounts guaranteed under these agreements aggregated $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 December 31, 2023. The Company has outstanding letters of credit to third parties related to insurance policies, reclamation obligations and other agreements. At December 31, 2023, the fixed maximum amounts guaranteed under these letters of credit aggregated to $21.0 million. The amounts of scheduled expiration of the maximum amounts guaranteed under these letters of credit aggregate to $20.7 million in 2024 and $300,000 in 2025. There were no amounts outstanding under the previously mentioned letters of credit at December 31, 2023. In the normal course of business, the Company has surety bonds related to contracts for contracting services and reclamation obligations of its subsidiaries. In the event a subsidiary of the Company 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 is expected to expire within the next 12 months; however, the Company will likely continue to enter into surety bonds for its subsidiaries in the future. At December 31, 2023, approximately $597.5 million of surety bonds were outstanding, which were not reflected on the Consolidated Balance Sheet.

Related-Party Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2023
Related Party Transactions [Abstract]
Related-party Transactions	Related-Party Transactions Allocation of corporate expenses Prior to the Separation, Centennial and MDU Resources provided expense allocations for corporate services provided to the Company, including costs related to senior management, legal, human resources, finance and accounting, treasury, information technology, and other shared services. Some of these services will continue to be provided by MDU Resources on a temporary basis under a transition services agreement. For the years ended December 31, 2023, 2022 and 2021, the Company was allocated $10.7 million, $18.0 million and $15.6 million, respectively, for these corporate services. These expenses have been allocated to the Company on the basis of direct usage when identifiable, with the remainder allocated on the basis of percent of total capital invested, the percent of total average commercial paper borrowings at Centennial or other allocation methodologies that are 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. Management believes these cost allocations are a reasonable reflection of the utilization of services provided to, or the benefit derived by, the Company during the periods presented. The allocations may not, however, be indicative of the actual expenses that would have been incurred had the Company operated as a stand-alone public company for these periods. Actual costs that would have been incurred if the Company had been a stand-alone public company would depend on a number of factors, including the chosen organizational structure, whether functions were outsourced or performed by Company employees, and strategic decisions made in areas such as selling and marketing, information technology and infrastructure. See Note 2 for further information. Cash management and financing Centennial had a central cash management and financing program in which the Company participated until the Separation. Through the use of these programs, Centennial was able to more effectively direct and manage the daily cash requirements and financing needs for each wholly owned subsidiary through the consolidation of all cash activity at the Centennial level. As cash was received and disbursed by Centennial, it was accounted for by the Company through related-party receivables and payables. Until the Separation, the Company had related-party note agreements in place with Centennial for the financing of its capital needs. Post Separation, the Company has relied on its own credit. Interest expense in the Consolidated Statements of Operations reflects the allocation of interest on borrowing and funding related to these note agreements. The Company’s cash that was not included in the central cash management program is classified as cash and cash equivalents on the Consolidated Balance Sheets. See Note 2 for further information. Related-party notes payable The related-party notes payable to Centennial at May 30, 2023, was $889.7 million. As part of the Separation, Centennial made an equity contribution to the Company to release the Company of its obligation related to the outstanding notes payable. Also as part of the Separation, the Company issued $425.0 million of 7.75 percent senior notes due May 1, 2031, a credit agreement consisting of a $275.0 million term loan and a $350.0 million revolving credit facility, of which $190.0 million was drawn down at the time of the Separation. On May 31, 2023, the Company paid a dividend of $825.0 million from these proceeds to Centennial, which Centennial used to repay a portion of the Company’s outstanding indebtedness. These transactions resulted in the Company receiving a net equity contribution of $64.7 million and is included in “Net transfers from Centennial and MDU Resources including separation adjustments” in the Consolidated Statement of Equity. Refer to Note 8 for additional information on the debt facilities entered into in connection with the Separation. These borrowings have been included in both current and noncurrent liabilities in related-party notes payable in the Consolidated Balance Sheets. Intercompany short-term and long-term borrowing arrangements at December 31, 2022 was as follows: Weighted average Interest rate at December 31, 2022 2022 (In thousands) Centennial term loan agreements with maturities ranging from March 17, 2023 to December 18, 2023 5.44 % $ 208,000 Centennial senior notes with maturities ranging from June 27, 2023 to April 4, 2034 4.34 % 410,000 Borrowing arrangements under Centennial commercial paper program, supported by Centennial’s credit agreements 5.27 % 66,449 Total long-term related-party notes payable 684,449 Less: current maturities 238,000 Net long-term related-party notes payable $ 446,449 Transition services agreements As part of the Separation, MDU Resources is providing transition services to the Company and the Company is providing transition services to MDU Resources in accordance with the Transition Services Agreement entered into on May 30, 2023. For the year December 31, 2023, the Company paid $3.0 million related to these activities, which was reflected in selling, general and administrative expenses on the Consolidated Statements of Operations. For the year ended December 31, 2023, the Company received $824,000 related to these activities, which was reflected in other income (expense) on the Consolidated Statements of Operations. The majority of the transition services are expected to be completed over a period of one year, but no longer than two years after the Separation.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net income	$ 182,872	$ 116,220	$ 129,755

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Dec. 31, 2023
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

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of presentation	Knife River operated as a wholly owned subsidiary of Centennial and an indirect, wholly owned subsidiary of MDU Resources and not as a stand-alone company. The accompanying audited 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 audited consolidated financial statements of MDU Resources as if the Company operated on a stand-alone basis during these periods.For all periods, the audited consolidated financial statements were prepared in accordance with GAAP and include the accounts of the Company and its wholly owned subsidiaries.
Use of estimates	The preparation of financial statements in conformity with GAAP requires the Company 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 audited 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 the Company 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.
New accounting standards	The following table provides a brief description of the accounting pronouncements applicable to the Company and the potential impact on its audited consolidated financial statements and/or disclosures: Standard Description Standard Effective Date Impact on financial statements/disclosures Recently issued ASU’s 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 currently evaluating the impact the guidance will have on its disclosures for the year ended December 31, 2025.
Cash, cash equivalents and restricted cash	The Company considers all highly liquid investments with an original maturity of three months or less, when purchased, to be cash and cash equivalents. At December 31, 2023, the $262.3 million of cash, cash equivalents and restricted cash on the Consolidated Statements of Cash Flows is comprised of $219.3 million of cash and cash equivalents and $43.0 million of restricted cash. At December 31, 2022, the Company had no restricted cash. Restricted cash represents deposits held by Knife River’s captive insurance company that is required by state insurance regulations to remain in the captive insurance company
Revenue recognition	Revenue is recognized when a performance obligation is satisfied by transferring control over a product or service to a customer. 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. The Company is considered an agent for certain taxes collected from customers. As such, the Company presents revenues net of these taxes at the time of sale to be remitted to governmental authorities, including sales and use taxes. The Company generates revenue from contracting services and construction materials sales. The Company focuses on the vertical integration of its contracting services with its construction materials to support the aggregate-based product lines. The Company provides contracting services to a customer when a contract has been signed by both the customer and a representative of the Company obligating a service to be provided in exchange for the consideration identified in the contract. The nature of the services provided generally include integrating a set of services and related construction materials into a single project to create a distinct bundle of goods and services, which the Company has determined are single performance obligations. The Company determines the transaction price to include the fixed consideration required pursuant to the original contract price together with any additional consideration, to which the Company expects to be entitled to, associated with executed change orders plus the estimate of variable consideration to which the Company expects to be entitled, subject to the constraint discussed below. The nature of the Company’s contracts gives rise to several types of variable consideration. Examples of variable consideration include: liquidated damages; performance bonuses or incentives and penalties; claims; unpriced change orders; and index pricing. The variable amounts usually arise upon achievement of certain performance metrics or change in project scope. The Company estimates the amount of revenue to be recognized on variable consideration using one of the two prescribed estimation methods, the expected value method or the most likely amount method, depending on which method best predicts the most likely amount of consideration the Company expects to be entitled to or expects to incur. Assumptions as to the occurrence of future events and the likelihood and amount of variable consideration are made during the contract performance period. Estimates of variable consideration and determination of whether to include estimated amounts in the transaction price are based largely on the assessment of anticipated performance and all information (historical, current and forecasted) that is reasonably available to management. The Company only includes variable consideration in the estimated transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur or when the uncertainty associated with the variable consideration is resolved. Changes in circumstances could impact management’s estimates made in determining the value of variable consideration recorded. When determining if the variable consideration is constrained, the Company considers if factors exist that could increase the likelihood or the magnitude of a potential reversal of revenue. The Company updates its estimate of the transaction price each reporting period and the effect of variable consideration on the transaction price is recognized as an adjustment to revenue on a cumulative catch-up basis. Contracting services revenue is recognized over time using an input method based on the cost-to-cost measure of progress on a project. This is the preferred method of measuring revenue because the costs incurred have been determined to represent the best indication of the overall progress toward the transfer of such goods or services promised to a customer. Under the cost-to-cost measure of progress, the costs incurred are compared with total estimated costs of a performance obligation. Revenues are recorded proportionately to the costs incurred. The percentage of completion is determined on a performance obligation basis. The Company also sells construction materials to third parties and internal customers. The contract for material sales is the use of a sales order or an invoice, which includes the pricing and payment terms. All material contracts contain a single performance obligation for the delivery of a single distinct product or a distinct separately identifiable bundle of products and services. Revenue is recognized at a point in time when the performance obligation has been satisfied with the delivery of the products or services. The warranties associated with the sales are those consistent with a standard warranty that the product meets certain specifications for quality or those required by law. For most contracts, amounts billed to customers are due within 30 days of receipt. There are no material obligations for returns, refunds or other similar obligations.
Receivables	Receivables consist primarily of trade and contract receivables from the sale of goods and services net of expected credit losses. A majority of the Company’s receivables are due in 30 days or less.
Expected credit losses	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. The Company develops and documents its methodology to determine its allowance for expected credit losses. Risk characteristics used by the Company 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 the Company’s 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.
Property, plant and equipment	Additions to property, plant and equipment are recorded at cost. Gains or losses resulting from the retirement or disposal of assets are recognized as a component of operating income. Generally, property, plant and equipment are depreciated on a straight-line basis over the average useful lives of the assets with the exception of large marine equipment, which is computed using units-of-production. Aggregate mining development costs are capitalized and classified as land improvements and depreciated over the lower of the estimated life of the reserves or the life of the associated improvement. The Company begins capitalizing development costs at a point when reserves are determined to be proven or probable and economically mineable. Capitalization of these costs ceases when production commences. The cost of acquiring reserves in connection with a business combination are valued at fair value. Aggregate reserves, from both owned and leased mining sites, are a component within property, plant and equipment and are depleted using the units-of-production method. The Company uses proven and probable aggregate reserves as the denominator in its units-of production calculation. Exploration costs are expensed as incurred in cost of revenue and production costs are either expensed or capitalized to inventory.
Impairment of long-lived assets, excluding goodwill	The Company reviews the carrying values of its long-lived assets, including mining and related assets, whenever events or changes in circumstances indicate that such carrying values may not be recoverable. The Company tests long-lived assets for impairment at a level significantly lower than that of goodwill impairment testing. Long-lived assets or groups of assets that are evaluated for impairment at the lowest level of largely independent identifiable cash flows at an individual operation or group of operations collectively serving a local market. The determination of whether an impairment has occurred is based on an estimate of undiscounted future cash flows attributable to the assets, compared to the carrying value of the assets. If impairment has occurred, the amount of the impairment recognized is determined by estimating the fair value of the assets and recording a loss if the carrying value is greater than the fair value.
Goodwill	Goodwill represents the excess of the purchase price over the fair value of identifiable net tangible and intangible assets acquired in a business combination. Goodwill is required to be tested for impairment annually, which the Company completes in the fourth quarter, or more frequently if events or changes in circumstances indicate that goodwill may be impaired. The Company has determined that the reporting units for its goodwill impairment test are its operating segments as they constitute a business for which discrete financial information is available and for which management regularly reviews the operating results. For more information on the Company’s operating segments, see Note 15. Goodwill impairment, if any, is measured by comparing the fair value of each reporting unit to its carrying value. If the fair value of a reporting unit exceeds its carrying value, the goodwill of the reporting unit is not impaired. If the carrying value of a reporting unit exceeds its fair value, the Company must record an impairment loss for the amount that the carrying value of the reporting unit, including goodwill, exceeds the fair value of the reporting unit. For the years ended December 31, 2023, 2022 and 2021, there were no impairment losses recorded. The Company performed its annual goodwill impairment test in the fourth quarter of 2023 and determined the fair value of each of Knife River’s reporting units substantially exceeded the carrying value at October 31, 2023.
Investments	The Company’s investments include the cash surrender value of life insurance policies and insurance contracts. The Company measures its investment in the insurance contracts at fair value with any unrealized gains and losses recorded on the Consolidated Statements of Operations.
Government assistance	The Company accounts for government assistance received for capital projects by reducing the cost of the project by the amount of assistance received. The Company records government assistance received as taxable income and writes-up the tax basis of the asset to include the amount of the assistance received.
Joint ventures accounted for using proportionate consolidation	Proportionate consolidation is used for joint ventures that include unincorporated legal entities and activities of the joint venture which are construction-related. For those joint ventures accounted for under proportionate consolidation, only the Company’s pro rata share of assets, liabilities, revenues and expenses are included in the Company’s Consolidated Balance Sheets and Consolidated Statements of Operations.
Joint ventures accounted for under the equity method	For joint ventures accounted for under the equity method, the Company’s investment balances for the joint ventures are included in Investments in the Consolidated Balance Sheets and the Company’s pro rata share of net income is included in Other income in the Consolidated Statements of Operations.
Leases	Lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term. The Company recognizes leases with an original lease term of 12 months or less in income on a straight-line basis over the term of the lease and does not recognize a corresponding right-of-use asset or lease liability. The Company determines the lease term based on the non-cancelable and cancelable periods in each contract. The non-cancelable period consists of the term of the contract that is legally enforceable and cannot be canceled by either party without incurring a significant penalty. The cancelable period is determined by various factors that are based on who has the right to cancel a contract. If only the lessor has the right to cancel the contract, the Company will assume the contract will continue. If the lessee is the only party that has the right to cancel the contract, the Company looks to asset, entity and market-based factors. If both the lessor and the lessee have the right to cancel the contract, the Company assumes the contract will not continue. The discount rate used to calculate the present value of the lease liabilities is based upon the implied rate within each contract. If the rate is unknown or cannot be determined, the Company uses an incremental borrowing rate, which is determined by the length of the contract, asset class and the Company’s borrowing rates, as of the commencement date of the contract.
Insurance	Spring Creek Insurance Company establishes a reserve for estimated ultimate losses on reported claims and those incurred but no yet reported utilizing actuarial projections. The reserves are classified within Other accrued liabilities or Noncurrent liabilities - other on the Consolidated Balance Sheets based on projections of when the estimated loss will be paid. The estimates that are utilized to record potential losses on claims are inherently subjective, and actual claims could differ from amounts recorded, which could result in increased or decreased expense in future periods.
Asset retirement obligations	The Company records the fair value of a liability for an asset retirement obligation in the period in which it is incurred. When the liability is initially recorded, the Company capitalizes a cost by increasing the carrying amount of the related long-lived asset. Over time, the liability is accreted to its present value each period and the capitalized cost is depreciated over the useful life of the related asset. Upon settlement of the liability, the Company either settles the obligation for the recorded amount or incurs a gain or loss.
Earnings per share	The calculation for basic and diluted earnings per share for any period presented prior to the Separation have been retrospectively adjusted to the number of shares outstanding on May 31, 2023, the Separation and Distribution date. For periods prior to the Separation, it is assumed that there are no dilutive equity instruments as there were no Knife River stock-based awards outstanding at the time. Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the applicable period. Diluted earnings 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 restricted stock units. Weighted average common shares outstanding is comprised of issued shares of 57,009,542 less shares held in treasury of 431,136, as described in Note 11. Basic and diluted earnings per share are calculated as follows, based on a reconciliation of the weighted-average common shares outstanding on a basic and diluted basis:
Stock-based compensation	Prior to the Separation, key employees of the Company participated in various stock-based compensation plans authorized and managed by MDU Resources. All awards granted under the plans were based on MDU Resources’ common shares, however, Knife River recognized the expense for its participants in its financial statements. At the time of the Separation, each outstanding MDU Resources’ time-vested restricted stock unit and performance share awards held by a Knife River employee was converted into Knife River time-vested restricted stock units. The converted awards will continue to vest over the original vesting period, which is generally three years from the grant date. All performance share awards that were converted at the time of the Separation were first adjusted using a combined performance factor based on MDU Resources’ actual performance as of December 31, 2022. The number of restricted stock units was determined by taking the closing per share price of MDU Resources on May 31, 2023, and dividing by the closing per share price of Knife River on June 1, 2023. The ratio used to convert the MDU Resources’ share-based awards was designed to preserve the aggregate intrinsic value of the award immediately after the Separation when compared to the aggregate intrinsic value of the award immediately prior to the Separation. The existing unvested stock-based awards issued through MDU Resources’ stock-based compensation plans were modified in connection with the Separation to maintain an equivalent value immediately before and after Separation. Incremental fair value for unvested awards will be recorded over the remaining vesting periods. In July 2023, the Company issued restricted stock units to certain key employees under the Knife River Long-Term Incentive Plan. The Company records the compensation expense for restricted stock units using a straight-line amortization method over the requisite service period. The cost for such awards is measured at the grant date fair value. The Company recognizes forfeitures as they occur and trues up expense on a cumulative catch-up basis at the time of any forfeitures.
Income taxes	Knife River and its subsidiaries file consolidated federal income tax returns and combined and separate state income tax returns. Pursuant to the tax sharing agreement that exists between Knife River and its subsidiaries, federal income taxes paid by Knife River, as parent of the consolidated group, are allocated to the individual subsidiaries based on separate company computations of tax. However, all income tax expense is reported within the Corporate Services segment. Knife River makes a similar allocation for state income taxes paid in connection with combined state filings. The Company provides deferred federal and state income taxes on all temporary differences between the book and tax basis of the Company’s assets and liabilities by using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date.
Pension and other postretirement benefit plans	The Company participates in self-sponsored qualified defined benefit pension plans which are accounted for as single-employer plans and are reflected in the Company’s audited consolidated financial statements. The Company uses a measurement date of December 31 for all its pension and postretirement benefit plans. Prior to 2010, defined benefit pension plan benefits and accruals for the nonunion plan were frozen and on June 30, 2015, the remaining union plan was frozen. These employees were eligible to receive additional defined contribution plan benefits. Prior to the Separation, the Company participated in a multiple-employer postretirement benefit plan sponsored by MDU Resources. In connection with the Separation, the Company assumed all the obligations and liabilities of Knife River’s employees in that plan, along with all MDU Resources employees that transferred to Knife River as a result of the Separation. Subsequent to the Separation, the postretirement benefit plans in which the Company participates are single employer plans. Employees hired after December 31, 2010 are not eligible for retiree medical benefits. Effective January 1, 2011, eligibility to receive retiree medical benefits was modified such that eligible employees who attained age 55 with 10 years of continuous, full‐time service by December 31, 2010, will have an option to select one of two retiree medical insurance benefits. All other eligible employees must meet the new eligibility criteria of age 60 and 10 years of continuous, full‐time service at the time they retire. These employees will be eligible for a company funded retiree reimbursement account. Employees hired after December 31, 2014 are not eligible for retiree medical benefits. In 2012, the Company modified health care coverage for certain retirees. Effective January 1, 2013, post-65 coverage was replaced by a fixed-dollar subsidy for retirees and spouses to be used to purchase individual insurance through a healthcare exchange. Outside investment managers manage the Company’s pension and postretirement assets. The Company’s investment policy with respect to pension and other postretirement assets is to make investments solely in the interest of the participants and beneficiaries of the plans and for the exclusive purpose of providing benefits accrued and defraying the reasonable expenses of administration. The Company strives to maintain investment diversification to assist in minimizing the risk of large losses. The Company’s policy guidelines allow for investment of funds in cash equivalents, fixed-income securities and equity securities. The guidelines prohibit investment in commodities and futures contracts, equity private placement, employer securities, leveraged or derivative securities, options, direct real estate investments, precious metals, venture capital and limited partnerships. The guidelines also prohibit short selling and margin transactions. The Company’s practice is to periodically review and rebalance asset categories based on its targeted asset allocation percentage policy. 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 ASC establishes a hierarchy for grouping assets and liabilities, based on the significance of inputs. The estimated fair values of the Company’s pension plans’ assets are determined using the market approach. The carrying value of the pension plans’ Level 2 cash equivalents approximates fair value and is determined using observable inputs in active markets or the net asset value of shares held at year end, which is determined using other observable inputs, including pricing from outside sources. The estimated fair value of the pension plans’ Level 1 and Level 2 equity securities are based on the closing price reported on the active market on which the individual securities are traded or other known sources including pricing from outside sources. The estimated fair value of the pension plans’ Level 1 and Level 2 collective and mutual funds are based on the net asset value of shares held at year end, based on either published market quotations on active markets or other known sources, including pricing from outside sources. The estimated fair value of the pension plans’ Level 2 corporate and municipal bonds is determined using other observable inputs, including benchmark yields, reported trades, broker/dealer quotes, bids, offers, future cash flows and other reference data. The estimated fair value of the pension plans’ Level 1 U.S. Government securities are valued based on quoted prices on an active market. The estimated fair value of the pension plans’ Level 2 U.S. Government securities are valued mainly using other observable inputs, including benchmark yields, reported trades, broker/dealer quotes, bids, offers, to be announced prices, future cash flows and other reference data. The estimated fair value of the pension plans’ Level 2 pooled separate accounts are determined using observable inputs in active markets or the net asset value of shares held at year end, or other observable inputs. Some of these securities are valued using pricing from outside sources. All investments measured at net asset value in the tables that follow are invested in commingled funds, separate accounts or common collective trusts which do not have publicly quoted prices. The fair value of the commingled funds, separate accounts and common collective trusts are determined based on the net asset value of the underlying investments. The fair value of the underlying investments held by the commingled funds, separate accounts and common collective trusts is generally based on quoted prices in active markets.
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. The Company accrues 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. The Company does 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, the Company discloses 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.
Business segment data	Each segment is led by a segment manager that reports to the Company’s chief operating officer who is also the Company’s chief operating decision maker. The Company’s 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. In the fourth quarter of 2023, the Company completed a reorganization of its reporting structure, which has resulted in changes being made to the management of its business to best align with its strategies. Based on how the chief operating decision maker manages the Company, the reportable segments are: Pacific, Northwest, Mountain, Central and Energy Services. The Company also has the Corporate Services segment. As a result of the reorganization, 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. All periods have been recast to conform with the revised presentation.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Accounting Standards Update and Change in Accounting Principle	The following table provides a brief description of the accounting pronouncements applicable to the Company and the potential impact on its audited consolidated financial statements and/or disclosures: Standard Description Standard Effective Date Impact on financial statements/disclosures Recently issued ASU’s 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 currently evaluating the impact the guidance will have on its disclosures for the year ended December 31, 2025.
Schedule of Accounts, Notes, Loans and Financing Receivable	Receivables, net consisted of the following at December 31: 2023 2022 (In thousands) Trade receivables $ 124,134 $ 104,347 Contract receivables 112,037 82,428 Retention receivables 36,782 28,859 Receivables, gross 272,953 215,634 Less expected credit loss 6,168 5,477 Receivables, net $ 266,785 $ 210,157
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) At December 31, 2021 $ 1,952 $ 512 $ 1,610 $ 1,232 $ 100 $ 5,406 Current expected credit loss provision 21 946 (206) (229) 6 538 Less write-offs charged against the allowance 28 205 126 102 6 467 At December 31, 2022 $ 1,945 $ 1,253 $ 1,278 $ 901 $ 100 $ 5,477 Current expected credit loss provision 161 842 1,109 (112) 1 2,001 Less write-offs charged against the allowance 53 1,091 94 71 1 1,310 At December 31, 2023 $ 2,053 $ 1,004 $ 2,293 $ 718 $ 100 $ 6,168
Inventories	Inventories at December 31 consisted of: 2023 2022 (In thousands) Finished products $ 225,319 $ 211,496 Raw materials 61,776 78,571 Supplies and parts 32,528 33,210 Total $ 319,623 $ 323,277
Schedule of Weighted Average Number of Shares	Basic and diluted earnings per share are calculated as follows, based on a reconciliation of the weighted-average common shares outstanding on a basic and diluted basis: 2023 2022 2021 (In thousands, except per share amounts) Net income $ 182,872 $ 116,220 $ 129,755 Weighted average common shares outstanding - basic 56,568 56,566 56,566 Effect of dilutive restricted stock units 100 — — Weighted average common shares outstanding - diluted 56,668 56,566 56,566 Shares excluded from the calculation of diluted earnings per share — — — Net income per share - basic $ 3.23 $ 2.05 $ 2.29 Net income per share - diluted $ 3.23 $ 2.05 $ 2.29

Disaggregation of Revenue (Tabl

Disaggregation of Revenue (Tables)	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The Company believes 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 15. Presented in the following tables are the 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 the contracting services to arrive at the external operating revenues. Due to the restructuring of segments the 2022 and 2021 information has been recast. Year ended December 31, 2023 Pacific Northwest Mountain Central Energy Services Corporate Services Total (In thousands) Aggregates $ 104,726 $ 189,946 $ 100,505 $ 152,691 $ — $ — $ 547,868 Ready-mix concrete 142,291 163,382 120,534 227,735 — — 653,942 Asphalt 32,178 103,327 112,897 204,018 — — 452,420 Liquid asphalt — — — — 253,196 — 253,196 Other 142,742 15,751 16 28,745 49,363 12,414 249,031 Contracting services publicsector 71,362 197,372 308,711 426,318 — — 1,003,763 Contracting services privatesector 54,978 103,011 124,282 21,276 — — 303,547 Internal sales (86,115) (109,108) (133,328) (235,875) (57,373) (11,618) (633,417) Revenues from contracts with customers $ 462,162 $ 663,681 $ 633,617 $ 824,908 $ 245,186 $ 796 $ 2,830,350 Year ended December 31, 2022 Pacific Northwest Mountain Central Energy Services Corporate Services Total (In thousands) Aggregates $ 92,266 $ 171,633 $ 83,343 $ 149,419 $ — $ — $ 496,661 Ready-mix concrete 127,569 157,951 106,654 217,335 — — 609,509 Asphalt 35,735 97,299 93,263 201,171 — — 427,468 Liquid asphalt — — — — 207,474 — 207,474 Other 114,079 14,844 36 24,956 45,245 618 199,778 Contracting services publicsector 81,989 173,981 249,573 412,487 — — 918,030 Contracting services privatesector 47,497 88,713 119,136 14,345 — — 269,691 Internal sales (81,105) (105,647) (110,095) (242,563) (54,006) (466) (593,882) Revenues from contracts with customers $ 418,030 $ 598,774 $ 541,910 $ 777,150 $ 198,713 $ 152 $ 2,534,729 Year ended December 31, 2021 Pacific Northwest Mountain Central Energy Services Corporate Services Total (In thousands) Aggregates $ 89,913 $ 135,182 $ 72,567 $ 146,348 $ — $ — $ 444,010 Ready-mix concrete 123,905 152,079 100,412 207,993 — — 584,389 Asphalt 26,348 78,937 69,310 165,251 — — 339,846 Liquid asphalt — — — — 166,052 — 166,052 Other 104,804 12,786 91 22,807 37,714 4 178,206 Contracting services publicsector 83,013 118,970 211,603 363,172 — — 776,758 Contracting services privatesector 44,603 68,171 112,058 15,881 — — 240,713 Internal sales (75,837) (91,184) (86,498) (200,681) (46,844) — (501,044) Revenues from contracts with customers $ 396,749 $ 474,941 $ 479,543 $ 720,771 $ 156,922 $ 4 $ 2,228,930

Uncompleted Contracts (Tables)

Uncompleted Contracts (Tables)	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Contract with Customer, Contract Asset, Contract Liability, and Receivable	Costs, estimated earnings, and billings on uncompleted contracts at December 31 are summarized as follows: 2023 2022 (In thousands) Costs incurred on uncompleted contracts $ 1,395,603 $ 1,217,480 Estimated earnings 208,926 153,317 1,604,529 1,370,797 Less billings to date (1,628,612) (1,379,495) Net contract liability $ (24,083) $ (8,698) Such amounts are included in the accompanying Consolidated Balance Sheets at December 31 under the following captions: 2023 2022 Change Location on Consolidated Balance Sheet (In thousands) Contract assets $ 27,293 $ 31,145 $ (3,852) Costs and estimated earnings in excess of billings on uncompleted contracts Contract liabilities (51,376) (39,843) (11,533) Billings in excess of costs and estimated earnings on uncompleted contracts Net contract liabilities $ (24,083) $ (8,698) $ (15,385) 2022 2021 Change Location on Consolidated Balance Sheet (In thousands) Contract assets $ 31,145 $ 22,005 $ 9,140 Costs and estimated earnings in excess of billings on uncompleted contracts Contract liabilities (39,843) (32,348) (7,495) Billings in excess of costs and estimated earnings on uncompleted contracts Net contract liabilities $ (8,698) $ (10,343) $ 1,645

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant and equipment at December 31 was as follows: 2023 2022 Weighted Average Depreciable Life in Years (In thousands) Land $ 154,475 $ 150,809 — Aggregate reserves 589,034 592,097 * Buildings and improvements 216,473 165,833 22.32 Machinery, vehicles and equipment 1,590,908 1,492,506 11.68 Construction in progress 28,844 88,163 — Less: accumulated depreciation and depletion 1,264,687 1,174,195 Net property, plant and equipment $ 1,315,047 $ 1,315,213 __________________ * Depleted on the units-of-production method based on proven and probable aggregate reserves.

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The changes in the carrying amount of goodwill were as follows: Balance at January 1, 2023 Goodwill Acquired Measurement Period 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 Balance at January 1, 2022 Goodwill Acquired During the Year Measurement Period Adjustments Reallocation of Goodwill Balance at December 31, 2022 (In thousands) Pacific $ 38,101 $ 238 $ — $ — $ 38,339 Northwest 93,102 — (2,124) — 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 $ 276,426 $ 238 $ (2,124) $ — $ 274,540
Schedule of Finite-Lived Intangible Assets	Other amortizable intangible assets at December 31, were as follows: Average Useful Life In Years 2023 2022 (In thousands) Customer relationships 2-7 $ 18,540 $ 18,540 Less accumulated amortization 9,102 7,367 9,438 11,173 Noncompete agreements 1-3 4,039 4,039 Less accumulated amortization 3,473 2,985 566 1,054 Other 15-20 2,479 5,279 Less accumulated amortization 1,662 4,076 817 1,203 Total $ 10,821 $ 13,430
Estimated Amortization Expense	Estimated amortization expense for identifiable intangible assets as of December 31, 2023, was: 2024 2025 2026 2027 2028 Thereafter (In thousands) Amortization expense $2,228 $1,919 $1,739 $1,716 $1,672 $1,547

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The Company’s assets measured at fair value on a recurring basis were as follows: Fair Value Measurements at December 31, 2023, Using Quoted Prices in Significant Other 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. Fair Value Measurements at December 31, 2022, Using Quoted Prices in Significant Other Significant Balance at December 31, 2022 (In thousands) Assets: Money market funds $ — $ 2,448 $ — $ 2,448 Insurance contracts* — 20,083 — 20,083 Total assets measured at fair value $ — $ 22,531 $ — $ 22,531 __________________ * The insurance contracts invest approximately 63 percent in fixed-income investments, 15 percent in common stock of large-cap companies, 8 percent in common stock of mid-cap companies, 6 percent in common stock of small-cap companies, 6 percent in target date investments and 2 percent in cash equivalents.
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments	The estimated fair value of the Company's Level 2 long-term debt was as follows: December 31, 2023 (In thousands) Carrying amount $ 696,985 Fair value $ 725,086

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Schedule of Long-Term Debt Instruments	Long-term Debt Outstanding Long-term debt outstanding was as follows: Weighted Average Interest Rate at December 31, 2023 December 31, 2023 (In thousands) Term loan agreement due on May 31, 2028 7.24 % $ 271,562 Senior notes due on May 1, 2031 7.75 % 425,000 Other notes due on January 1, 2061 — % 423 Less unamortized debt issuance costs 15,326 Total long-term debt 681,659 Less current maturities 7,082 Net long-term debt $ 674,577
Schedule of Maturities of Long-Term Debt	Schedule of Debt Maturities Long-term debt maturities, which excludes unamortized debt issuance costs, for the five years and thereafter following December 31, 2023, were as follows: 2024 2025 2026 2027 2028 Thereafter (In thousands) Long-term debt maturities $ 7,082 $ 10,520 $ 13,759 $ 17,187 $ 223,437 $ 425,000

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Summary of Operating Leases	The following tables provide information on the Company’s operating leases at and for the years ended December 31: 2023 2022 2021 (In thousands) Lease costs: Operating lease cost $ 18,199 $ 17,941 $ 21,914 Variable lease cost 383 98 84 Short-term lease cost 53,987 55,871 53,016 Total lease costs $ 72,569 $ 73,910 $ 75,014 2023 2022 (Dollars in thousands) Weighted average remaining lease term 1.62 years 2.03 years Weighted average discount rate 5.13 % 4.05 % Cash paid for amounts included in the measurement of lease liabilities $ 18,199 $ 17,941
Reconciliation of Future Undiscounted Cash Flows to Operating Lease Liabilities	The reconciliation of future undiscounted cash flows to operating lease liabilities presented on the Consolidated Balance Sheet at December 31, 2023, was as follows (in thousands): 2024 $ 14,128 2025 10,286 2026 7,207 2027 5,115 2028 3,174 Thereafter 13,329 Total 53,239 Less discount 8,533 Total operating lease liabilities $ 44,706

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2023
Asset Retirement Obligation Disclosure [Abstract]
Reconciliation of Asset Retirement Obligation	A reconciliation of the Company’s liability for the years ended December 31 was as follows: 2023 2022 (In thousands) Balance at beginning of year $ 37,361 $ 33,406 Liabilities incurred 5,190 4,657 Liabilities settled (2,726) (2,117) Accretion expense 1,957 1,415 Balance at end of year $ 41,782 $ 37,361

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Disclosure of Share-Based Compensation Arrangements by Share-Based Payment Award	As of December 31, 2023, the outstanding restricted stock units were as follows: Grant Date Service Period Number of Shares Weighted Average Grant-Date Fair Value May 2023 2022-2024 66,887 $ 36.60 May 2023 2023-2025 82,680 $ 36.60 July 2023 2023-2025 71,650 $ 43.00 2022 2021 Weighted average grant date fair value $36.25 $37.96 Blended volatility range 24.07 % - 31.41 % 35.37 % - 46.35 % Risk-free interest rate range 0.71 % - 1.68 % 0.02 % - 0.20 % Weighted average discounted dividends per share $2.93 $3.16 For the year ended December 31, 2023, the following summarizes the activity of the performance share awards to the converted Knife River restricted stock units. Performance Share Awards Restricted Stock Units Number of Shares Weighted Average Grant-Date Fair Value Number of Shares Weighted Average Grant-Date Fair Value Nonvested at the beginning of period 69,601 $ 32.32 23,197 $ 27.54 Granted pre-Separation by MDU Resources — 81,507 $ 31.16 Adjustments for performance (13,261) $ 32.51 — Forfeited pre-Separation (4,510) $ 32.29 (4,941) $ 30.06 Nonvested pre-Separation 51,830 $ 32.27 99,763 $ 30.37 Conversion to Knife River restricted stock units (51,830) 125,050 Granted post Separation — 71,650 Vested shares — (53,958) Forfeited post Separation — (21,288) Nonvested at end of period — 221,217

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Unrealized Loss on Derivative Instruments Qualifying as Hedges Post-retirement Liability Adjustment Total Accumulated Other Comprehensive Loss (In thousands) At December 31, 2021 $ (418) $ (24,072) $ (24,490) Other comprehensive income before reclassifications — 10,935 10,935 Amounts reclassified from accumulated other comprehensive loss 328 875 1,203 Net current-period other comprehensive income 328 11,810 12,138 At December 31, 2022 (90) (12,262) (12,352) Other comprehensive income before reclassifications — 751 751 Amounts reclassified from accumulated other comprehensive loss 90 192 282 Net current-period other comprehensive income 90 943 1,033 At December 31, 2023 $ — $ (11,319) $ (11,319)
Reclassification out of Accumulated Other Comprehensive Income	The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parentheses indicate a decrease to net income on the Consolidated Statements of Operations. The reclassifications for the years ended December 31 were as follows: 2023 2022 2021 Location on Consolidated Statements of Income (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ (118) $ (435) $ (439) Interest expense 28 107 107 Income taxes (90) (328) (332) Amortization of postretirement liability losses included in net periodic benefit cost (256) (1,167) (1,453) Other income (expense) 64 292 363 Income taxes (192) (875) (1,090) Total reclassifications $ (282) $ (1,203) $ (1,422)

Cash Flow Information (Tables)

Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2023
Supplemental Cash Flow Information [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Cash expenditures for interest and income taxes for the years ended December 31 were as follows: 2023 2022 2021 (In thousands) Interest paid, net $ 54,925 $ 28,148 $ 19,121 Income taxes paid, net $ 76,689 $ 21,186 $ 34,784 Noncash investing and financing transactions at December 31 were as follows: 2023 2022 2021 (In thousands) Property, plant and equipment additions in accounts payable $ 12,672 $ 13,965 $ 15,840 Right-of-use assets obtained in exchange for new operating lease liabilities $ 14,967 $ 11,763 $ 11,497 Equity contribution from Centennial related to the Separation $ 64,724 $ — $ — Equity contribution to MDU Resources for asset/liability transfers related to the Separation $ (1,537) $ — $ — MDU Resources’ stock issued in connection with a business combination $ 383 $ 7,304 $ — Debt assumed in connection with a business combination $ — $ — $ 10 Accrual for holdback payment related to a business combination $ — $ 70 $ —

Business Segment Data (Tables)

Business Segment Data (Tables)	12 Months Ended
	Dec. 31, 2023
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Information on the Company’s segments as of December 31, and for the years then ended was as follows: 2023 2022 2021 (In thousands) External operating revenues: Pacific $ 462,162 $ 418,030 $ 396,749 Northwest 663,681 598,774 474,941 Mountain 633,617 541,910 479,543 Central 824,908 777,150 720,771 Energy Services 245,186 198,713 156,922 Corporate Services 796 152 4 Total external operating revenues $ 2,830,350 $ 2,534,729 $ 2,228,930 2023 2022 2021 (In thousands) Intersegment operating revenues: Pacific $ 86,115 $ 81,105 $ 75,837 Northwest 109,108 105,647 91,184 Mountain 133,328 110,095 86,498 Central 235,875 242,563 200,681 Energy Services 57,373 54,006 46,844 Corporate Services 11,618 466 — Total intersegment operating revenues $ 633,417 $ 593,882 $ 501,044 EBITDA: Pacific $ 56,206 $ 44,044 $ 57,915 Northwest 121,098 103,885 80,624 Mountain 103,142 72,604 65,017 Central 116,653 86,572 81,459 Energy Services 78,124 28,310 31,564 Corporate Services (53,219) (28,675) (23,173) Total segment EBITDA $ 422,004 $ 306,740 $ 293,406 Capital expenditures: Pacific $ 21,512 $ 31,462 $ 25,154 Northwest 31,653 60,697 278,946 Mountain 25,506 35,098 47,648 Central 39,302 46,574 51,144 Energy Services 4,099 5,651 4,577 Corporate Services 918 2,365 10,055 Total capital expenditures* $ 122,990 $ 181,847 $ 417,524 Assets: Pacific $ 432,820 $ 408,805 $ 384,573 Northwest 781,640 772,159 714,098 Mountain 315,661 293,121 278,608 Central 663,134 607,200 603,008 Energy Services 128,383 138,323 131,244 Corporate Services 278,175 74,711 70,293 Total assets $ 2,599,813 $ 2,294,319 $ 2,181,824 2023 2022 2021 (In thousands) Property, plant and equipment: Pacific $ 528,008 $ 517,794 $ 490,499 Northwest 839,060 813,513 759,482 Mountain 419,537 400,907 369,732 Central 646,929 615,893 594,330 Energy Services 102,844 98,698 93,272 Corporate Services 43,356 42,603 40,383 Less accumulated depreciation and depletion 1,264,687 1,174,195 1,097,388 Net property, plant and equipment $ 1,315,047 $ 1,315,213 $ 1,250,310 __________________ * Capital expenditures for 2023, 2022 and 2021 include noncash transactions for capital expenditure-related accounts payable, the issuance of equity securities in connection with an acquisition and accrual of a holdback payment in connection with an acquisition totaling $(910,000), $(5.4) million and $(8.1) million, respectively.
Reconciliation of Revenue from Segments to Consolidated	A reconciliation of reportable segment operating revenues to consolidated operating revenues is as follows: 2023 2022 2021 (In thousands) Total reportable segment operating revenues $ 3,451,353 $ 3,127,993 $ 2,729,970 Corporate Services revenue 12,414 618 4 Less: Elimination of intersegment operating revenues 633,417 593,882 501,044 Total consolidated operating revenues $ 2,830,350 $ 2,534,729 $ 2,228,930
Segment, Reconciliation of Other Items from Segments to Consolidated	A reconciliation of reportable segment assets to consolidated assets is as follows: 2023 2022 2021 (In thousands) Total assets for reportable segments $ 2,321,637 $ 2,219,608 $ 2,111,531 Other assets 4,049,800 3,439,435 3,239,393 Less: Elimination of intercompany receivables and investment in subsidiaries 3,771,624 3,364,724 3,169,100 Total consolidated assets $ 2,599,813 $ 2,294,319 $ 2,181,824 A reconciliation of reportable segment EBITDA to consolidated income before income taxes is as follows: 2023 2022 2021 (In thousands) Total EBITDA for reportable segments $ 475,223 $ 335,415 $ 316,579 Corporate Services EBITDA (53,219) (28,675) (23,173) Less: Depreciation, depletion and amortization 123,805 117,798 100,974 Interest expense, net* 52,891 30,121 19,218 Total consolidated income before income taxes $ 245,308 $ 158,821 $ 173,214 __________________ * Interest expense, net is interest expense net of interest income

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	Income tax expense on the Consolidated Statements of Operations for the years ended December 31 was as follows: 2023 2022 2021 (In thousands) Current: Federal $ 45,746 $ 27,293 $ 4,270 State 18,296 13,230 6,331 64,042 40,523 10,601 Deferred: Income taxes: Federal 263 1,715 26,793 State (1,869) 363 6,065 (1,606) 2,078 32,858 Total income tax expense $ 62,436 $ 42,601 $ 43,459
Schedule of Deferred Tax Assets and Liabilities	Components of deferred tax assets and deferred tax liabilities at December 31 were as follows: 2023 2022 (In thousands) Deferred tax assets: Deferred compensation/compensation related $ 22,358 $ 15,329 Operating lease liabilities 11,468 11,804 Asset retirement obligations 10,862 9,687 Net operating loss/credit carryforward 10,811 12,039 Accrued pension costs 10,556 11,070 Capitalized inventory overheads 7,388 7,260 Other 9,458 8,412 Total deferred tax assets $ 82,901 $ 75,601 2023 2022 (In thousands) Deferred tax liabilities: Basis differences on property, plant and equipment $ 206,507 $ 203,099 Intangible assets 12,220 10,975 Operating lease right-of-use-assets 11,468 11,804 Other 16,437 13,488 Total deferred tax liabilities 246,632 239,366 Valuation allowance 10,811 12,039 Net deferred income tax liability $ (174,542) $ (175,804)
Schedule of Net Deferred Income Tax Liability	The following table reconciles the change in the net deferred income tax liability from December 31, 2022, to December 31, 2023, to deferred income tax expense: 2023 2022 (In thousands) Change in net deferred income tax liability from the preceding table $ (1,262) $ 7,278 Deferred income taxes established due to an acquisition — (1,215) Deferred taxes associated with other comprehensive loss (344) (3,985) Deferred income tax expense for the period $ (1,606) $ 2,078
Schedule of Effective Income Tax Rate Reconciliation	Total income tax expense differs from the amount computed by applying the statutory federal income tax rate to income before taxes. The reasons for this difference were as follows: Years ended December 31, 2023 2022 2021 Amount % Amount % Amount % (Dollars in thousands) Computed tax at federal statutory rate $ 51,515 21.0 $ 33,353 21.0 $ 36,375 21.0 Increases (reductions) resulting from: State income taxes, net of federal income tax 12,756 5.2 9,702 6.1 9,429 5.4 Depletion allowance (2,756) (1.1) (2,123) (1.3) (1,893) (1.1) Other 921 0.4 1,669 1.0 (452) (0.2) Total income tax expense $ 62,436 25.5 $ 42,601 26.8 $ 43,459 25.1

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
Schedule of changes in benefit obligation and plan assets	Changes in benefit obligation and plan assets and amounts recognized in the Consolidated Balance Sheets at December 31, were as follows: Pension Benefits Other Postretirement Benefits 2023 2022 2023 2022 (In thousands) Change in benefit obligation: Benefit obligation at beginning of year $ 33,758 $ 44,363 $ 14,616 $ 19,480 Service cost — — 361 522 Interest cost 1,633 1,127 721 514 Plan participants’ contributions — — — 3 Actuarial (gain) loss 477 (9,174) (346) (5,319) Benefits paid (2,488) (2,558) (593) (584) Benefit obligation at end of year 33,380 33,758 14,759 14,616 Change in net plan assets: Fair value of plan assets at beginning of year 28,431 39,345 (314) 314 Actual return on plan assets 3,074 (8,356) 321 (473) Employer contribution 1,170 — 586 426 Plan participants’ contributions — — — 3 Benefits paid (2,488) (2,558) (593) (584) Fair value of net plan assets at end of year 30,187 28,431 — (314) Funded status - under $ (3,193) $ (5,327) $ (14,759) $ (14,930) Amounts recognized in the Consolidated Balance Sheets at December 31: Other accrued liabilities $ — $ — $ 699 $ 1,044 Noncurrent liabilities - other 3,193 5,327 14,060 13,886 Benefit obligation liabilities $ 3,193 $ 5,327 $ 14,759 $ 14,930 Amounts recognized in accumulated other comprehensive loss consist of: Actuarial (gain) loss $ 17,780 $ 19,087 $ (2,560) $ (2,057) Prior service credit — — (30) (109) Total $ 17,780 $ 19,087 $ (2,590) $ (2,166)
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets	The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for these plans at December 31, were as follows: 2023 2022 (In thousands) Projected benefit obligation $ 33,380 $ 33,758 Accumulated benefit obligation $ 33,380 $ 33,758 Fair value of plan assets $ 30,187 $ 28,431
Schedule of Net Benefit Costs	These components related to the Company’s pension and other postretirement benefit plans for the years ended December 31, were as follows: Pension Benefits Other Postretirement Benefits 2023 2022 2021 2023 2022 2021 (In thousands) Components of net periodic benefit cost (credit): Service cost $ — $ — $ — $ 361 $ 522 $ 567 Interest cost 1,633 1,127 1,053 721 514 492 Expected return on assets (1,800) (1,973) (2,028) 11 (12) (19) Amortization of prior service credit — — — (79) (79) (79) Amortization of actuarial gain (loss) 510 856 971 (175) 351 135 Net periodic benefit cost (credit) 343 10 (4) 839 1,296 1,096 Other changes in plan assets and benefit obligations recognized in accumulated other comprehensive loss: Net (gain) loss (797) 1,155 (162) (678) (4,833) (2,763) Amortization of actuarial gain (loss) (510) (856) (1,108) 175 (351) (135) Amortization of prior service credit — — — 79 79 90 Total recognized in accumulated other comprehensive loss (1,307) 299 (1,270) (424) (5,105) (2,808) Total recognized in net periodic benefit cost (credit) and accumulated other comprehensive loss $ (964) $ 309 $ (1,274) $ 415 $ (3,809) $ (1,712) The components of net periodic benefit cost are included in other income (expense) 2023 2022 2021 (In thousands) Components of net periodic benefit cost: Interest cost $ 765 $ 460 $ 407 Recognized net actuarial loss — 39 223 Net periodic benefit cost $ 765 $ 499 $ 630
Schedule of Defined Benefit Plans Disclosures	Weighted average assumptions used at December 31, were as follows: 2023 2022 Benefit obligation discount rate 4.74 % 4.97 % Benefit obligation rate of compensation increase N/A N/A Net periodic benefit cost discount rate 4.93 % 2.38 % Net periodic benefit cost rate of compensation increase N/A N/A
Schedule of Amounts Recognized in Other Comprehensive Income (Loss)	These components related to the Company’s pension and other postretirement benefit plans for the years ended December 31, were as follows: Pension Benefits Other Postretirement Benefits 2023 2022 2021 2023 2022 2021 (In thousands) Components of net periodic benefit cost (credit): Service cost $ — $ — $ — $ 361 $ 522 $ 567 Interest cost 1,633 1,127 1,053 721 514 492 Expected return on assets (1,800) (1,973) (2,028) 11 (12) (19) Amortization of prior service credit — — — (79) (79) (79) Amortization of actuarial gain (loss) 510 856 971 (175) 351 135 Net periodic benefit cost (credit) 343 10 (4) 839 1,296 1,096 Other changes in plan assets and benefit obligations recognized in accumulated other comprehensive loss: Net (gain) loss (797) 1,155 (162) (678) (4,833) (2,763) Amortization of actuarial gain (loss) (510) (856) (1,108) 175 (351) (135) Amortization of prior service credit — — — 79 79 90 Total recognized in accumulated other comprehensive loss (1,307) 299 (1,270) (424) (5,105) (2,808) Total recognized in net periodic benefit cost (credit) and accumulated other comprehensive loss $ (964) $ 309 $ (1,274) $ 415 $ (3,809) $ (1,712)
Defined Benefit Plan, Assumptions	Weighted average assumptions used to determine benefit obligations at December 31, were as follows: Pension Benefits Other Postretirement Benefits 2023 2022 2023 2022 Discount rate 4.83 % 5.06 % 4.84 % 5.07 % Expected return on plan assets 6.50 % 6.50 % — % 6.00 % Rate of compensation increase N/A N/A 4.00 % 3.00 % Weighted average assumptions used to determine net periodic benefit cost (credit) for the years ended December 31, were as follows: Pension Benefits Other Postretirement Benefits 2023 2022 2023 2022 Discount rate 5.06 % 2.62 % 5.06 % 2.69 % Expected return on plan assets 6.50 % 6.00 % 6.00 % 5.50 % Rate of compensation increase N/A N/A 3.00 % 3.00 %
Schedule of Health Care Cost Trend Rates	Health care rate assumptions for the Company’s other postretirement benefit plans as of December 31, were as follows: 2023 2022 Health care trend rate assumed for next year 7.5 % 7.5 % Health care cost trend rate – ultimate 4.5 % 4.5 % Year in which ultimate trend rate achieved 2034 2033
Schedule of Expected Benefit Payments	The following benefit payments, which reflect future service, as appropriate, at December 31, 2023, are as follows: Years Pension Benefits Other Postretirement Benefits (In thousands) 2024 $ 2,890 $ 695 2025 2,780 867 2026 2,740 1,053 2027 2,680 1,136 2028 2,620 1,235 2029-2033 12,200 6,507 The amount of future benefit payments for the unfunded, nonqualified defined benefit plans at December 31, 2023 are expected to aggregate as follows: 2024 2025 2026 2027 2028 2029-2033 (In thousands) Nonqualified benefits $ 1,620 $ 1,720 $ 1,700 $ 1,650 $ 1,690 $ 5,600
Schedule of Allocation of Plan Assets	The fair value of the Company’s pension plans’ assets by class were as follows: Fair Value Measurements at December 31, 2023, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at December 31, 2023 (In thousands) Assets: Cash equivalents $ — $ 1,021 $ — $ 1,021 Collective and mutual funds (a) 25,981 2,565 — 28,546 Investments measured at net asset value (b) — — — 620 Total assets measured at fair value $ 25,981 $ 3,586 $ — $ 30,187 __________________ (a) Collective and mutual funds invest approximately 33 percent in corporate bonds, 23 percent in U.S. Government securities, 15 percent in common stock of large-cap U.S. companies, 13 percent in other investments, 8 percent in common stock of international companies and 8 percent in cash and cash equivalents. (b) In accordance with ASC 820 - Fair Value, Measurements certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the Consolidated Balance Sheets. Fair Value Measurements at December 31, 2022, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at December 31, 2022 (In thousands) Assets: Cash equivalents $ — $ 859 $ — $ 859 Equity securities: U.S. companies 777 — — 777 International companies — 49 — 49 Collective and mutual funds (a) 12,729 3,508 — 16,237 Corporate bonds — 8,554 — 8,554 Municipal bonds — 621 — 621 U.S. Government securities 320 92 — 412 Pooled separate accounts (b) — 337 — 337 Investments measured at net asset value (c) — — — 585 Total assets measured at fair value $ 13,826 $ 14,020 $ — $ 28,431 __________________ (a) Collective and mutual funds invest approximately 29 percent in corporate bonds, 24 percent in common stock of large-cap U.S. companies, 16 percent in common stock of international companies, 7 percent in cash and cash equivalents, 7 percent in U.S. Government securities and 17 percent in other investments. (b) Pooled separate accounts are invested 100 percent in cash and cash equivalents. (c) In accordance with ASC 820 - Fair Value, Measurements certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the Consolidated Balance Sheets. The fair value of the Company’s other postretirement benefit plans’ assets (excluding cash) by asset class were as follows: Fair Value Measurements at December 31, 2022, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at December 31, 2022 (In thousands) Assets: Cash equivalents $ — $ (17) $ — $ (17) Equity securities: U.S. companies (11) — — (11) Insurance contract* — (286) — (286) Total assets measured at fair value $ (11) $ (303) $ — $ (314) __________________ *
Schedule of Accumulated and Projected Benefit Obligations	The projected benefit obligation and accumulated benefit obligation for the Company’s participants in these plans at December 31, were as follows: 2023 2022 (In thousands) Projected benefit obligation $ 15,873 $ 16,047 Accumulated benefit obligation $ 15,873 $ 16,047
Investment	The amount of investments that the Company anticipates using to satisfy obligations under these plans at December 31, was as follows: 2023 2022 (In thousands) Investments Insurance contract* $ 24,896 $ 20,083 Life insurance** 7,175 7,234 Other 3,241 2,448 Total investments $ 35,312 $ 29,765 __________________ * For more information on the insurance contract, see Note 7. ** Investments of life insurance are carried on plan participants (payable upon the employee’s death).
Multiemployer Plan	The Company’s participation in these plans is outlined in the following table. Unless otherwise noted, the most recent Pension Protection Act zone status available in 2023, 2022 and 2021 is for the plan’s year-end at December 31, 2022, December 31, 2021 and December 31, 2020, respectively. The zone status is based on information that the Company received from the plan and is certified by the plan’s actuary. Among other factors, plans in the “red zone,” or critical status, are generally less than 65 percent funded, plans in the “yellow zone,” or endangered status, are between 65 percent and 80 percent funded, and plans in the “green zone,” or healthy status, are at least 80 percent funded. Pension Fund EIN/Pension Plan Number Pension Protection Act Zone Status FIP/RP Status Pending/ Implemented Contributions Surcharge Imposed Expiration Date of Collective Bargaining Agreement 2023 2022 2023 2022 2021 (In thousands) Alaska Laborers Employer Retirement Fund 916028298-001 Red as of 6/30/22 Red as of 6/30/21 Implemented $ 887 $ 805 $ 737 No 12/31/2023 * Minnesota Teamsters Construction Division Pension Fund 416187751-001 Green Green No 418 644 713 No 4/30/2024 Pension Trust Fund for Operating Engineers 946090764-001 Yellow Yellow Implemented 2,476 2,484 2,495 No 3/31/2026- 6/30/2026 Western Conference of Teamsters Pension Plan 916145047-001 Green Green No 3,307 3,127 3,006 No 07/01/2023- 6/30/2026 * Other funds 5,653 5,938 5,519 Total contributions $ 12,741 $ 12,998 $ 12,470 __________________ * Plan includes contributions required by collective bargaining agreements which have expired but contain provisions automatically renewing their terms in the absence of a subsequent negotiated agreement. The Company was listed in the plans’ Forms 5500 as providing more than 5 percent of the total contributions for the following plans and plan years: Pension Fund Year Contributions to Plan Exceeded More Than 5 Percent of Total Contributions (as of December 31, of the Plan’s Year-End) DB Pension Plan of AGC-IUOE Local 701 Pension Trust Fund 2022 and 2021 Minnesota Teamsters Construction Division Pension Fund 2022 and 2021 Southwest Marine Pension Trust 2022 and 2021

Commitment and Contingencies (T

Commitment and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Contractual Obligation, Fiscal Year Maturity	The commitments under these contracts as of December 31, 2023, were: 2024 2025 2026 2027 2028 Thereafter (In thousands) Purchase commitments $ 59,211 $ 27,758 $ 27,342 $ 2,028 $ 1,542 $ 8,212

Related-Party Transactions (Tab

Related-Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2023
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	Intercompany short-term and long-term borrowing arrangements at December 31, 2022 was as follows: Weighted average Interest rate at December 31, 2022 2022 (In thousands) Centennial term loan agreements with maturities ranging from March 17, 2023 to December 18, 2023 5.44 % $ 208,000 Centennial senior notes with maturities ranging from June 27, 2023 to April 4, 2034 4.34 % 410,000 Borrowing arrangements under Centennial commercial paper program, supported by Centennial’s credit agreements 5.27 % 66,449 Total long-term related-party notes payable 684,449 Less: current maturities 238,000 Net long-term related-party notes payable $ 446,449

Organization and Basis of Pre_2

Organization and Basis of Presentation (Details)	1 Months Ended	12 Months Ended
	Nov. 30, 2023 shares	Dec. 31, 2023 reportableSegment state $ / shares	May 31, 2023 $ / shares	Dec. 31, 2022 $ / shares
Organization [Line Items]
Number of states in which entity operates | state		14
Number of reportable segments | reportableSegment		5
Percent of outstanding shares distributed			90%
Common stock, par value (in dollars per share) | $ / shares		$ 0.01	$ 0.01	$ 10
Distribution ratio			0.25
Separation transaction, outstanding shares distributed (in shares) | shares	5,656,621
Knife River
Organization [Line Items]
Ownership percentage, noncontrolling owner			10%

Significant Accounting Polici_4

Significant Accounting Policies - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Significant Accounting Policies [Line Items]
Cash, cash equivalents and restricted cash	$ 262,320,000	$ 10,090,000	$ 13,848,000	$ 7,072,000
Cash and cash equivalents	219,300,000
Restricted cash	$ 43,000,000	0
Accounts receivable threshold period past due	30 days
Receivables past due 90 days	$ 16,700,000	11,200,000
Net asset book value	65,000,000
Long-lived asset impairment losses	$ 5,800,000	0	0
Impairment, Long-Lived Asset, Held-for-Use, Statement of Income or Comprehensive Income [Extensible Enumeration]	Selling, general and administrative expenses
Goodwill impairment losses	$ 0	0	0
Percentage interest held in joint venture	25%
Revenues	$ 2,830,350,000	2,534,729,000	2,228,930,000
Operating Income (Loss)	296,397,000	194,295,000	191,077,000
Assets from joint ventures	2,599,813,000	2,294,319,000	2,181,824,000
Investments in equity method joint ventures	68,000	13,000
Income (loss) from equity method joint ventures	$ 55,000	$ (426,000)	14,000
Common stock issued (in shares)	57,009,542	80,000
Treasury stock held at cost (in shares)	431,136
Joint Venture, Proportionate Consolidation
Significant Accounting Policies [Line Items]
Revenues	$ 4,900,000	$ 9,100,000	10,100,000
Operating Income (Loss)	(1,900,000)	823,000	1,300,000
Assets from joint ventures	$ 45,000	$ 912,000	$ 643,000

Significant Accounting Polici_5

Significant Accounting Policies - Components of Receivables, Net (Details) - Trade Accounts Receivable - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	$ 124,134	$ 104,347
Contract receivables	112,037	82,428
Retention receivables	36,782	28,859
Receivables, gross	272,953	215,634
Less expected credit loss	6,168	5,477	$ 5,406
Receivables, net	$ 266,785	$ 210,157

Significant Accounting Polici_6

Significant Accounting Policies - Details of Expected Credit Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Current expected credit loss provision	$ 2,001	$ 538	$ 48
Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	5,477	5,406
Current expected credit loss provision	2,001	538
Less write-offs charged against the allowance	1,310	467
Ending balance	6,168	5,477	5,406
Pacific | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,945	1,952
Current expected credit loss provision	161	21
Less write-offs charged against the allowance	53	28
Ending balance	2,053	1,945	1,952
Northwest | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,253	512
Current expected credit loss provision	842	946
Less write-offs charged against the allowance	1,091	205
Ending balance	1,004	1,253	512
Mountain | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,278	1,610
Current expected credit loss provision	1,109	(206)
Less write-offs charged against the allowance	94	126
Ending balance	2,293	1,278	1,610
North Central | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	901	1,232
Current expected credit loss provision	(112)	(229)
Less write-offs charged against the allowance	71	102
Ending balance	718	901	1,232
Corporate Services | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	100	100
Current expected credit loss provision	1	6
Less write-offs charged against the allowance	1	6
Ending balance	$ 100	$ 100	$ 100

Significant Accounting Polici_7

Significant Accounting Policies - Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Finished products	$ 225,319	$ 211,496
Raw materials	61,776	78,571
Supplies and parts	32,528	33,210
Total	$ 319,623	$ 323,277

Significant Accounting Polici_8

Significant Accounting Policies - Schedule of Earnings per Share Reconciliation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share [Abstract]
Net income	$ 182,872	$ 116,220	$ 129,755
Weighted average common shares outstanding – basic (in shares)	56,568,000	56,566,000	56,566,000
Effect of dilutive restricted stock units (in shares)	100,000	0	0
Diluted (in shares)	56,668,000	56,566,000	56,566,000
Shares excluded from the calculation of diluted earnings per share (in shares)	0	0	0
Net income (loss) per share – basic (in dollars per share)	$ 3.23	$ 2.05	$ 2.29
Net income (loss) per share – diluted (in dollars per share)	$ 3.23	$ 2.05	$ 2.29

Disaggregation of Revenue (Deta

Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 2,830,350	$ 2,534,729	$ 2,228,930
Aggregates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	547,868	496,661	444,010
Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	653,942	609,509	584,389
Asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	452,420	427,468	339,846
Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	253,196	207,474	166,052
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	249,031	199,778	178,206
Contracting services public­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,003,763	918,030	776,758
Contracting services private­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	303,547	269,691	240,713
Internal sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(633,417)	(593,882)	(501,044)
Pacific
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	462,162	418,030	396,749
Pacific | Aggregates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	104,726	92,266	89,913
Pacific | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	142,291	127,569	123,905
Pacific | Asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	32,178	35,735	26,348
Pacific | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Pacific | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	142,742	114,079	104,804
Pacific | Contracting services public­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	71,362	81,989	83,013
Pacific | Contracting services private­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	54,978	47,497	44,603
Pacific | Internal sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(86,115)	(81,105)	(75,837)
Northwest
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	663,681	598,774	474,941
Northwest | Aggregates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	189,946	171,633	135,182
Northwest | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	163,382	157,951	152,079
Northwest | Asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	103,327	97,299	78,937
Northwest | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Northwest | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	15,751	14,844	12,786
Northwest | Contracting services public­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	197,372	173,981	118,970
Northwest | Contracting services private­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	103,011	88,713	68,171
Northwest | Internal sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(109,108)	(105,647)	(91,184)
Mountain
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	633,617	541,910	479,543
Mountain | Aggregates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	100,505	83,343	72,567
Mountain | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	120,534	106,654	100,412
Mountain | Asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	112,897	93,263	69,310
Mountain | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Mountain | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	16	36	91
Mountain | Contracting services public­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	308,711	249,573	211,603
Mountain | Contracting services private­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	124,282	119,136	112,058
Mountain | Internal sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(133,328)	(110,095)	(86,498)
Central
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	824,908	777,150	720,771
Central | Aggregates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	152,691	149,419	146,348
Central | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	227,735	217,335	207,993
Central | Asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	204,018	201,171	165,251
Central | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Central | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	28,745	24,956	22,807
Central | Contracting services public­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	426,318	412,487	363,172
Central | Contracting services private­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	21,276	14,345	15,881
Central | Internal sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(235,875)	(242,563)	(200,681)
Energy Services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	245,186	198,713	156,922
Energy Services | Aggregates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Energy Services | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Energy Services | Asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Energy Services | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	253,196	207,474	166,052
Energy Services | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	49,363	45,245	37,714
Energy Services | Contracting services public­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Energy Services | Contracting services private­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Energy Services | Internal sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(57,373)	(54,006)	(46,844)
Corporate Services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	796	152	4
Corporate Services | Aggregates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Corporate Services | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Corporate Services | Asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Corporate Services | Liquid asphalt
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Corporate Services | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	12,414	618	4
Corporate Services | Contracting services public­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Corporate Services | Contracting services private­sector
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Corporate Services | Internal sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ (11,618)	$ (466)	$ 0

Uncompleted Contracts - Schedul

Uncompleted Contracts - Schedule of Costs, Estimated Earnings and Billings on Uncompleted Contracts (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Costs incurred on uncompleted contracts	$ 1,395,603	$ 1,217,480
Estimated earnings	208,926	153,317
Uncompleted contracts	1,604,529	1,370,797
Less billings to date	(1,628,612)	(1,379,495)
Net contract liability	$ (24,083)	$ (8,698)	$ (10,343)

Uncompleted Contracts - Sched_2

Uncompleted Contracts - Schedule of Contract Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Contract assets	$ 27,293	$ 31,145	$ 22,005
Change in contract assets	(3,852)	9,140
Contract liabilities	(51,376)	(39,843)	(32,348)
Change in contract liabilities	(11,533)	(7,495)
Net contract liabilities	(24,083)	(8,698)	$ (10,343)
Change in net contract assets (liabilities)	$ (15,385)	$ 1,645

Uncompleted Contracts - Narrati

Uncompleted Contracts - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Amounts included in contract liability at the beginning of the period	$ 37.5	$ 30.2
Contract with customer, performance obligation satisfied in previous period	12.3	$ 11
Remaining performance obligation	662.2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 610.8
Remaining performance obligation (in months)	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 37.1
Remaining performance obligation (in months)	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 14.3
Remaining performance obligation (in months)

Property, Plant and Equipment -

Property, Plant and Equipment - Details of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation and depletion	$ 1,264,687	$ 1,174,195	$ 1,097,388
Net property, plant and equipment	1,315,047	1,315,213	$ 1,250,310
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment:	154,475	150,809
Aggregate reserves
Property, Plant and Equipment [Line Items]
Property, plant and equipment:	589,034	592,097
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment:	$ 216,473	165,833
Weighted Average Depreciable Life in Years	22 years 3 months 25 days
Machinery, vehicles and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment:	$ 1,590,908	1,492,506
Weighted Average Depreciable Life in Years	11 years 8 months 4 days
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment:	$ 28,844	$ 88,163

Property, Plant and Equipment_2

Property, Plant and Equipment - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation	$ 119.2	$ 113.6	$ 93.9

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Goodwill [Line Items]
Reallocation of goodwill	$ 0	$ 0
Amortization of intangible assets	2,600	2,800	$ 2,600
Energy Services
Goodwill [Line Items]
Reallocation of goodwill	$ 5,656	$ 0

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Changes in the Carrying Amount (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Goodwill [Roll Forward]
Balance at beginning of period	$ 274,540	$ 276,426
Goodwill Acquired During the Year	0	238
Measurement Period Adjustments	(62)	(2,124)
Reallocation of Goodwill	0	0
Balance at end of period	274,478	274,540
Pacific
Goodwill [Roll Forward]
Balance at beginning of period	38,339	38,101
Goodwill Acquired During the Year	0	238
Measurement Period Adjustments	(62)	0
Reallocation of Goodwill	(5,656)	0
Balance at end of period	32,621	38,339
Northwest
Goodwill [Roll Forward]
Balance at beginning of period	90,978	93,102
Goodwill Acquired During the Year	0	0
Measurement Period Adjustments	0	(2,124)
Reallocation of Goodwill	0	0
Balance at end of period	90,978	90,978
Mountain
Goodwill [Roll Forward]
Balance at beginning of period	26,816	26,816
Goodwill Acquired During the Year	0	0
Measurement Period Adjustments	0	0
Reallocation of Goodwill	0	0
Balance at end of period	26,816	26,816
North Central
Goodwill [Roll Forward]
Balance at beginning of period	75,879	75,879
Goodwill Acquired During the Year	0	0
Measurement Period Adjustments	0	0
Reallocation of Goodwill	0	0
Balance at end of period	75,879	75,879
South
Goodwill [Roll Forward]
Balance at beginning of period	38,708	38,708
Goodwill Acquired During the Year	0	0
Measurement Period Adjustments	0	0
Reallocation of Goodwill	0	0
Balance at end of period	38,708	38,708
Energy Services
Goodwill [Roll Forward]
Balance at beginning of period	3,820	3,820
Goodwill Acquired During the Year	0	0
Measurement Period Adjustments	0	0
Reallocation of Goodwill	5,656	0
Balance at end of period	$ 9,476	$ 3,820

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Other Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Total	$ 10,821	$ 13,430
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	18,540	18,540
Less accumulated amortization	9,102	7,367
Total	$ 9,438	11,173
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Average Useful Life In Years	2 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Average Useful Life In Years	7 years
Noncompete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 4,039	4,039
Less accumulated amortization	3,473	2,985
Total	$ 566	1,054
Noncompete agreements | Minimum
Finite-Lived Intangible Assets [Line Items]
Average Useful Life In Years	1 year
Noncompete agreements | Maximum
Finite-Lived Intangible Assets [Line Items]
Average Useful Life In Years	3 years
Other
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 2,479	5,279
Less accumulated amortization	1,662	4,076
Total	$ 817	$ 1,203
Other | Minimum
Finite-Lived Intangible Assets [Line Items]
Average Useful Life In Years	15 years
Other | Maximum
Finite-Lived Intangible Assets [Line Items]
Average Useful Life In Years	20 years

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets - Schedule of Estimated Amortization Expense (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2024	$ 2,228
2025	1,919
2026	1,739
2027	1,716
2028	1,672
Thereafter	$ 1,547

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Net unrealized gain (loss) on investments used to satisfy obligations under nonqualified benefit plans	$ 1.9	$ (2.8)	$ 1.4
Payment to acquire life insurance policy	$ 5.3

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Assets Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Concentration risks, percentage [Abstract]
Percentage in fixed-income and other investments	40%	63%
Percentage investment in common stock of large-cap companies	19%	15%
Percentage investment in cash equivalents of mid-cap companies	18%
Percentage investment in target date investments of mid-cap companies	8%
Percentage investment in common stock of mid-cap companies	8%	8%
Percentage investment in common stock of small-cap companies	6%	6%
Percentage investment in international investments	1%
Percentage investment in target date investments		6%
Percentage investment in cash and cash equivalents		2%
Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 28,137	$ 22,531
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	0	0
Significant Other Observable Inputs (Level 2) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	28,137	22,531
Significant Unobservable Inputs (Level 3) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	0	0
Money market funds | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	3,241	2,448
Money market funds | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	0	0
Money market funds | Significant Other Observable Inputs (Level 2) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	3,241	2,448
Money market funds | Significant Unobservable Inputs (Level 3) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	0	0
Insurance contracts | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	24,896	20,083
Insurance contracts | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	0	0
Insurance contracts | Significant Other Observable Inputs (Level 2) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	24,896	20,083
Insurance contracts | Significant Unobservable Inputs (Level 3) | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 0	$ 0

Fair Value Measurements - Long-

Fair Value Measurements - Long-term Debt at Fair Value (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Carrying amount
Fair value measurements [Line Items]
Fair value	$ 696,985
Fair value
Fair value measurements [Line Items]
Fair value	$ 725,086

Debt - Schedule of Long-term De

Debt - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Apr. 25, 2023	Dec. 31, 2022
Long-term debt outstanding [Line Items]
Unamortized debt issuance costs	$ 15,326
Total long-term debt	681,659
Long-term debt - current portion	7,082		$ 211
Long-term debt	674,577		$ 427
Line of Credit | Term loan agreement due on May 31, 2028
Long-term debt outstanding [Line Items]
Total long-term debt	$ 271,562
Debt instrument, interest rate	7.24%
Senior Notes | Senior notes due on May 1, 2031
Long-term debt outstanding [Line Items]
Total long-term debt	$ 425,000
Debt instrument, interest rate	7.75%	7.75%
Other Notes | Other notes due on January 1, 2061
Long-term debt outstanding [Line Items]
Total long-term debt	$ 423
Debt instrument, interest rate	0%

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($)		12 Months Ended
	May 31, 2023	Dec. 31, 2023	Apr. 25, 2023
Long-term debt outstanding [Line Items]
Outstanding letters of credit		$ 0
Mandatory annual amortization, years one and two		2.50%
Mandatory annual amortization, years three and four		5%
Mandatory annual amortization, years five and thereafter		7.50%
Letter of Credit
Long-term debt outstanding [Line Items]
Line of credit, maximum borrowing capacity		$ 21,000,000
Senior notes due on May 1, 2031 | Senior Notes
Long-term debt outstanding [Line Items]
Debt instrument, face amount			$ 425,000,000
Debt instrument, interest rate		7.75%	7.75%
Credit Agreement | Line of Credit
Long-term debt outstanding [Line Items]
Debt instrument, term	5 years
Credit Agreement | Line of Credit | Fed funds rate
Long-term debt outstanding [Line Items]
Debt instrument, basis spread on variable rate		0.50%
Credit Agreement | Line of Credit | SOFR
Long-term debt outstanding [Line Items]
Debt instrument, basis spread on variable rate		1.10%
Credit Agreement | Line of Credit | SOFR Plus 1.1% | Minimum
Long-term debt outstanding [Line Items]
Debt instrument, basis spread on variable rate		0.75%
Credit Agreement | Line of Credit | SOFR Plus 1.1% | Maximum
Long-term debt outstanding [Line Items]
Debt instrument, basis spread on variable rate		1.50%
Credit Agreement | Line of Credit | SOFR Plus Rate Determined by Interest Period | Minimum
Long-term debt outstanding [Line Items]
Debt instrument, basis spread on variable rate		1.75%
Credit Agreement | Line of Credit | SOFR Plus Rate Determined by Interest Period | Maximum
Long-term debt outstanding [Line Items]
Debt instrument, basis spread on variable rate		2.50%
Credit Agreement | Line of Credit | Term Loan
Long-term debt outstanding [Line Items]
Debt instrument, face amount	$ 275,000,000
Long-term line of credit		$ 0
Debt instrument, covenant, total debt ratio, minimum		475%
Debt instrument, covenant, interest coverage ratio, minimum		225%
Credit Agreement | Line of Credit | Revolving Credit Facility
Long-term debt outstanding [Line Items]
Line of credit, maximum borrowing capacity	350,000,000
Long-term line of credit	$ 190,000,000
Line of credit facility, remaining borrowing capacity		$ 329,000,000
Credit Agreement | Line of Credit | Revolving Credit Facility | Minimum
Long-term debt outstanding [Line Items]
Line of credit facility, unused capacity, commitment fee percentage		0.25%
Credit Agreement | Line of Credit | Revolving Credit Facility | Maximum
Long-term debt outstanding [Line Items]
Line of credit facility, unused capacity, commitment fee percentage		0.50%
Credit Agreement | Line of Credit | Letter of Credit
Long-term debt outstanding [Line Items]
Outstanding letters of credit		$ 21,000,000

Debt - Schedule of Maturity of

Debt - Schedule of Maturity of Long-term Debt (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Debt Disclosure [Abstract]
2024	$ 7,082
2025	10,520
2026	13,759
2027	17,187
2028	223,437
Thereafter	$ 425,000

Leases - Narrative (Details)

Leases - Narrative (Details)	Dec. 31, 2023
Vehicles | Maximum
Lessee, Lease, Description [Line Items]
Lease term	5 years
Equipment | Maximum
Lessee, Lease, Description [Line Items]
Lease term	5 years
Buildings | Minimum
Lessee, Lease, Description [Line Items]
Lease term	35 years

Leases - Summary of Operating L

Leases - Summary of Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lease costs:
Operating lease cost	$ 18,199	$ 17,941	$ 21,914
Variable lease cost	383	98	84
Short-term lease cost	53,987	55,871	53,016
Total lease costs	$ 72,569	$ 73,910	$ 75,014
Weighted average remaining lease term	1 year 7 months 13 days	2 years 10 days
Weighted average discount rate	5.13%	4.05%
Cash paid for amounts included in the measurement of lease liabilities	$ 18,199	$ 17,941

Leases - Reconciliation of Futu

Leases - Reconciliation of Future Undiscounted Cash Flows to Operating Lease Liabilities (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Leases [Abstract]
2024	$ 14,128
2025	10,286
2026	7,207
2027	5,115
2028	3,174
Thereafter	13,329
Total	53,239
Less discount	8,533
Total operating lease liabilities	$ 44,706

Asset Retirement Obligations -

Asset Retirement Obligations - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Asset Retirement Obligation Disclosure [Abstract]
Asset retirement obligation, current	$ 6.9	$ 4.4
Asset retirement obligation, noncurrent	34.9	33
Accretion and depreciation expense	$ 2.6	$ 2.1	$ 2.1

Asset Retirement Obligations _2

Asset Retirement Obligations - Reconciliation of asset retirement obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	$ 37,361	$ 33,406
Liabilities incurred	5,190	4,657
Liabilities settled	(2,726)	(2,117)
Accretion expense	1,957	1,415
Balance at end of year	$ 41,782	$ 37,361

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Millions	May 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Equity [Abstract]
Issuance of common stock in connection with the Separation (in shares)	56,997,350
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 10
Common stock held by subsidiary (in shares)			538,921
Treasury stock held at cost (in shares)		431,136
Common stock held by subsidiary at cost		$ 3.6

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($)		5 Months Ended	12 Months Ended
	May 31, 2023	May 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock-based compensation expense			$ 2,700,000	$ 1,200,000	$ 1,400,000
Remaining unrecognized compensation expense			$ 5,000,000
Remaining unrecognized compensation expense, weighted average amortization period (in years)			1 year 9 months 18 days
Historical volatility rate				50%
Implied volatility rate				50%
Issuance of common stock to directors for services			$ 702,000
Restricted Stock Units (RSUs)
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Incremental compensation cost	$ 194,000
Award vesting period (in years)			3 years
Weighted average grant-date fair value (in dollars per share)		$ 31.16
Performance Share Awards
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Incremental compensation cost	$ 0
Fair value of shares vested				$ 962,000	$ 1,700,000
Award vesting period (in years)				3 years
Weighted average grant-date fair value (in dollars per share)				$ 36.25	$ 37.96
Restricted Stock Units and Other Stock Awards
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Authorized to grant (in shares)			2,500,000
Number of shares available for grant (in shares)			2,400,000
Share-Based Payment Arrangement
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Issuance of common stock to directors for services (in shares)			12,192
Issuance of common stock to directors for services			$ 702,000
Performance Shares, Performance Conditions
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted average grant-date fair value (in dollars per share)				$ 27.73	$ 27.35
Performance Shares, Performance Conditions | Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Performance award, percent of target				0%
Performance Shares, Performance Conditions | Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Performance award, percent of target				200%
Performance Shares, Market Conditions | Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Performance award, percent of target				0%
Performance Shares, Market Conditions | Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Performance award, percent of target				200%

Stock-Based Compensation - Outs

Stock-Based Compensation - Outstanding Restricted Stock (Details) - Restricted Stock Units (RSUs) - $ / shares	Dec. 31, 2023	May 30, 2023	Dec. 31, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Outstanding (in shares)	221,217	99,763	23,197
Outstanding (in dollars per share)		$ 30.37	$ 27.54
2022-2024, May 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Outstanding (in shares)	66,887
Outstanding (in dollars per share)	$ 36.60
2023-2025, May 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Outstanding (in shares)	82,680
Outstanding (in dollars per share)	$ 36.60
2023-2025, July 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Outstanding (in shares)	71,650
Outstanding (in dollars per share)	$ 43

Stock-Based Compensation - Perf

Stock-Based Compensation - Performance Share Assumptions (Details) - Performance Share Awards - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted average grant-date fair value (in dollars per share)	$ 36.25	$ 37.96
Risk-free interest rate range, minimum	0.71%	0.02%
Risk-free interest rate range, maximum	1.68%	0.20%
Weighted average discounted dividends per share (in dollars per share)	$ 2.93	$ 3.16
Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Blended volatility range	24.07%	35.37%
Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Blended volatility range	31.41%	46.35%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Performance Share Awards Converted to Restricted Stock Units (Details) - $ / shares	5 Months Ended	7 Months Ended	12 Months Ended
	May 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Performance Share Awards
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested at beginning of period (in shares)	69,601	51,830
Granted (in shares)	0	0
Adjustments for performance (in shares)	(13,261)
Forfeited (in shares)	(4,510)	0
Conversion to Knife River restricted stock units (in shares)		(51,830)
Vested (in shares)		0
Nonvested at end of period (in shares)	51,830	0	69,601
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested at beginning of period (in dollars per share)	$ 32.32	$ 32.27
Granted (in dollars per share)			$ 36.25	$ 37.96
Adjustments for performance (in dollars per share)	32.51
Forfeited (in dollars per share)	32.29
Nonvested at end of period (in dollars per share)	$ 32.27		$ 32.32
Restricted Stock Units (RSUs)
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested at beginning of period (in shares)	23,197	99,763
Granted (in shares)	81,507	71,650
Adjustments for performance (in shares)	0
Forfeited (in shares)	(4,941)	(21,288)
Conversion to Knife River restricted stock units (in shares)		125,050
Vested (in shares)		(53,958)
Nonvested at end of period (in shares)	99,763	221,217	23,197
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested at beginning of period (in dollars per share)	$ 27.54	$ 30.37
Granted (in dollars per share)	31.16
Forfeited (in dollars per share)	30.06
Nonvested at end of period (in dollars per share)	$ 30.37		$ 27.54

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss - After-Tax Changes in the Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated other comprehensive loss [Roll Forward]
Beginning balance	$ 1,028,589	$ 952,844	$ 878,244
Other comprehensive income before reclassifications	751	10,935
Amounts reclassified from accumulated other comprehensive loss	282	1,203
Net current-period other comprehensive income	1,033	12,138	4,463
Ending balance	1,266,012	1,028,589	952,844
Net Unrealized Loss on Derivative Instruments Qualifying as Hedges
Accumulated other comprehensive loss [Roll Forward]
Beginning balance	(90)	(418)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	90	328
Net current-period other comprehensive income	90	328
Ending balance	0	(90)	(418)
Post-retirement Liability Adjustment
Accumulated other comprehensive loss [Roll Forward]
Beginning balance	(12,262)	(24,072)
Other comprehensive income before reclassifications	751	10,935
Amounts reclassified from accumulated other comprehensive loss	192	875
Net current-period other comprehensive income	943	11,810
Ending balance	(11,319)	(12,262)	(24,072)
Total Accumulated Other Comprehensive Loss
Accumulated other comprehensive loss [Roll Forward]
Beginning balance	(12,352)	(24,490)	(28,953)
Net current-period other comprehensive income	1,033	12,138	4,463
Ending balance	$ (11,319)	$ (12,352)	$ (24,490)

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Loss - Reclassification Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Interest expense	$ (58,096)	$ (30,121)	$ (19,218)
Income taxes	(62,436)	(42,601)	(43,459)
Other income (expense)	7,007	(5,353)	1,355
Net income	182,872	116,220	129,755
Reclassification out of accumulated other comprehensive loss
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Net income	(282)	(1,203)	(1,422)
Net Unrealized Loss on Derivative Instruments Qualifying as Hedges | Interest rate contract
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Interest expense	(118)	(435)	(439)
Income taxes	28	107	107
Net income	(90)	(328)	(332)
Amortization of postretirement liability losses included in net periodic benefit cost
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Income taxes	64	292	363
Net income	(192)	(875)	(1,090)
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]
Other income (expense)	$ (256)	$ (1,167)	$ (1,453)

Cash Flow Information (Details)

Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Supplemental Cash Flow Information [Abstract]
Interest paid, net	$ 54,925	$ 28,148	$ 19,121
Income taxes paid, net	76,689	21,186	34,784
Property, plant and equipment additions in accounts payable	12,672	13,965	15,840
Right-of-use assets obtained in exchange for new operating lease liabilities	14,967	11,763	11,497
Equity contribution from Centennial related to the Separation	64,724	0	0
Equity contribution to MDU Resources for asset/liability transfers related to the Separation	(1,537)	0	0
MDU Resources’ stock issued in connection with a business combination	383	7,304	0
Debt assumed in connection with a business combination	0	0	10
Accrual for holdback payment related to a business combination	$ 0	$ 70	$ 0

Business Segment Data - Narrati

Business Segment Data - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 reportableSegment state
Segment Reporting [Abstract]
Number of states in which entity operates | state	14
Number of reportable segments | reportableSegment	5

Business Segment Data - Informa

Business Segment Data - Information on the Company's Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Revenues	$ 2,830,350	$ 2,534,729	$ 2,228,930
EBITDA:	422,004	306,740	293,406
Capital expenditures:	122,990	181,847	417,524
Assets:	2,599,813	2,294,319	2,181,824
Less: accumulated depreciation and depletion	1,264,687	1,174,195	1,097,388
Net property, plant and equipment	1,315,047	1,315,213	1,250,310
Noncash transactions in capital expenditures	(910)	(5,400)	(8,100)
Corporate Services
Segment Reporting Information [Line Items]
Revenues	12,414	618	4
EBITDA:	(53,219)	(28,675)	(23,173)
External operating revenues:
Segment Reporting Information [Line Items]
Revenues	3,451,353	3,127,993	2,729,970
EBITDA:	475,223	335,415	316,579
Assets:	2,321,637	2,219,608	2,111,531
External operating revenues: | Pacific
Segment Reporting Information [Line Items]
Revenues	462,162	418,030	396,749
EBITDA:	56,206	44,044	57,915
Capital expenditures:	21,512	31,462	25,154
Assets:	432,820	408,805	384,573
Property, plant and equipment:	528,008	517,794	490,499
External operating revenues: | Northwest
Segment Reporting Information [Line Items]
Revenues	663,681	598,774	474,941
EBITDA:	121,098	103,885	80,624
Capital expenditures:	31,653	60,697	278,946
Assets:	781,640	772,159	714,098
Property, plant and equipment:	839,060	813,513	759,482
External operating revenues: | Mountain
Segment Reporting Information [Line Items]
Revenues	633,617	541,910	479,543
EBITDA:	103,142	72,604	65,017
Capital expenditures:	25,506	35,098	47,648
Assets:	315,661	293,121	278,608
Property, plant and equipment:	419,537	400,907	369,732
External operating revenues: | Central
Segment Reporting Information [Line Items]
Revenues	824,908	777,150	720,771
EBITDA:	116,653	86,572	81,459
Capital expenditures:	39,302	46,574	51,144
Assets:	663,134	607,200	603,008
Property, plant and equipment:	646,929	615,893	594,330
External operating revenues: | Energy Services
Segment Reporting Information [Line Items]
Revenues	245,186	198,713	156,922
EBITDA:	78,124	28,310	31,564
Capital expenditures:	4,099	5,651	4,577
Assets:	128,383	138,323	131,244
Property, plant and equipment:	102,844	98,698	93,272
External operating revenues: | Corporate Services
Segment Reporting Information [Line Items]
Revenues	796	152	4
EBITDA:	(53,219)	(28,675)	(23,173)
Capital expenditures:	918	2,365	10,055
Assets:	278,175	74,711	70,293
Property, plant and equipment:	43,356	42,603	40,383
Intersegment operating revenues:
Segment Reporting Information [Line Items]
Revenues	633,417	593,882	501,044
Intersegment operating revenues: | Pacific
Segment Reporting Information [Line Items]
Revenues	86,115	81,105	75,837
Intersegment operating revenues: | Northwest
Segment Reporting Information [Line Items]
Revenues	109,108	105,647	91,184
Intersegment operating revenues: | Mountain
Segment Reporting Information [Line Items]
Revenues	133,328	110,095	86,498
Intersegment operating revenues: | Central
Segment Reporting Information [Line Items]
Revenues	235,875	242,563	200,681
Intersegment operating revenues: | Energy Services
Segment Reporting Information [Line Items]
Revenues	57,373	54,006	46,844
Intersegment operating revenues: | Corporate Services
Segment Reporting Information [Line Items]
Revenues	$ 11,618	$ 466	$ 0

Business Segment Data - Reconci

Business Segment Data - Reconciliation of Segment Information to Consolidated Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 2,830,350	$ 2,534,729	$ 2,228,930
Other assets	4,049,800	3,439,435	3,239,393
Assets:	(2,599,813)	(2,294,319)	(2,181,824)
Corporate Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	12,414	618	4
External operating revenues:
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	3,451,353	3,127,993	2,729,970
Assets:	(2,321,637)	(2,219,608)	(2,111,531)
External operating revenues: | Corporate Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	796	152	4
Assets:	(278,175)	(74,711)	(70,293)
Total intersegment operating revenues
Segment Reporting, Revenue Reconciling Item [Line Items]
Assets:	$ 3,771,624	$ 3,364,724	$ 3,169,100

Business Segment Data - Recon_2

Business Segment Data - Reconciliation of Segment EBITDA to Consolidated EBITDA (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
EBITDA:	$ 422,004	$ 306,740	$ 293,406
Depreciation, depletion and amortization	123,805	117,798	100,974
Interest expense, net	52,891	30,121	19,218
Total consolidated income before income taxes	245,308	158,821	173,214
Corporate Services
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
EBITDA:	(53,219)	(28,675)	(23,173)
External operating revenues:
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
EBITDA:	475,223	335,415	316,579
External operating revenues: | Corporate Services
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
EBITDA:	$ (53,219)	$ (28,675)	$ (23,173)

Income Taxes - Summary of Incom

Income Taxes - Summary of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current:
Federal	$ 45,746	$ 27,293	$ 4,270
State	18,296	13,230	6,331
Current income tax expense	64,042	40,523	10,601
Deferred:
Federal	263	1,715	26,793
State	(1,869)	363	6,065
Deferred income tax expense for the period	(1,606)	2,078	32,858
Total income tax expense	$ 62,436	$ 42,601	$ 43,459

Income Taxes - Net Deferred Tax

Income Taxes - Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Deferred compensation/compensation related	$ 22,358	$ 15,329
Operating lease liabilities	11,468	11,804
Accrued pension costs	10,556	11,070
Asset retirement obligations	10,862	9,687
Net operating loss/credit carryforward	10,811	12,039
Capitalized inventory overheads	7,388	7,260
Other	9,458	8,412
Total deferred tax assets	82,901	75,601
Deferred tax liabilities:
Basis differences on property, plant and equipment	206,507	203,099
Intangible assets	12,220	10,975
Operating lease right-of-use-assets	11,468	11,804
Other	16,437	13,488
Total deferred tax liabilities	246,632	239,366
Valuation allowance	10,811	12,039
Net deferred income tax liability	$ (174,542)	$ (175,804)

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 591	$ 591
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 133,600	$ 160,100

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Deferred Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Change in net deferred income tax liability from the preceding table	$ (1,262)	$ 7,278
Deferred income taxes established due to an acquisition	0	(1,215)
Deferred taxes associated with other comprehensive loss	(344)	(3,985)
Deferred income tax expense for the period	$ (1,606)	$ 2,078	$ 32,858

Income Taxes - Income Tax Expen

Income Taxes - Income Tax Expense Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Amount
Computed tax at federal statutory rate	$ 51,515	$ 33,353	$ 36,375
State income taxes, net of federal income tax	12,756	9,702	9,429
Depletion allowance	(2,756)	(2,123)	(1,893)
Other	921	1,669	(452)
Total income tax expense	$ 62,436	$ 42,601	$ 43,459
Percent
Computed tax at federal statutory rate	21%	21%	21%
State income taxes, net of federal income tax	5.20%	6.10%	5.40%
Depletion allowance	(1.10%)	(1.30%)	(1.10%)
Other	0.40%	1%	(0.20%)
Total income tax expense	25.50%	26.80%	25.10%

Employee Benefit Plans - Narrat

Employee Benefit Plans - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Jan. 01, 2011
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Plan participant age	65 years
Qualified plan | Minimum | Defined Benefit Plan, Equity Securities
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Targeted allocation percentages	40%
Qualified plan | Minimum | Fixed Income Securities
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Targeted allocation percentages	50%
Qualified plan | Maximum | Defined Benefit Plan, Equity Securities
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Targeted allocation percentages	50%
Qualified plan | Maximum | Fixed Income Securities
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Targeted allocation percentages	60%
Qualified plan | Unfunded plan | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Excess percentage of unrecognized pension actuarial gains and losses	10%
Market-related value of assets, average of assets (in years)	5 years
Qualified plan | Underfunded plan | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Expected employer contributions in next fiscal year	$ 700
Qualified plan | Underfunded plan | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Expected employer contributions in next fiscal year	$ 912
Nonqualified Plan | Underfunded plan | Postretirement Health Coverage
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Plan participant age		55 years
Plan participant age, all other employees		60 years
Years of continuous service		10 years

Employee Benefit Plans - Change

Employee Benefit Plans - Change in Benefit Obligation and Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pension Benefits
Change in benefit obligation:
Benefit obligation at beginning of year	$ 33,758	$ 44,363
Service cost	0	0
Interest cost	1,633	1,127
Plan participants’ contributions	0	0
Actuarial (gain) loss	477	(9,174)
Benefits paid	(2,488)	(2,558)
Benefit obligation at end of year	33,380	33,758
Change in net plan assets:
Fair value of plan assets at beginning of year	28,431	39,345
Actual return on plan assets	3,074	(8,356)
Employer contribution	1,170	0
Plan participants’ contributions	0	0
Benefits paid	(2,488)	(2,558)
Fair value of net plan assets at end of year	30,187	28,431
Funded status - under	(3,193)	(5,327)
Amounts recognized in the Consolidated Balance Sheets at December 31:
Other accrued liabilities	0	0
Noncurrent liabilities - other	3,193	5,327
Benefit obligation liabilities	3,193	5,327
Amounts recognized in accumulated other comprehensive loss consist of:
Actuarial (gain) loss	17,780	19,087
Prior service credit	0	0
Total	17,780	19,087
Other Postretirement Benefits
Change in benefit obligation:
Benefit obligation at beginning of year	14,616	19,480
Service cost	361	522
Interest cost	721	514
Plan participants’ contributions	0	3
Actuarial (gain) loss	(346)	(5,319)
Benefits paid	(593)	(584)
Benefit obligation at end of year	14,759	14,616
Change in net plan assets:
Fair value of plan assets at beginning of year	(314)	314
Actual return on plan assets	321	(473)
Employer contribution	586	426
Plan participants’ contributions	0	3
Benefits paid	(593)	(584)
Fair value of net plan assets at end of year	0	(314)
Funded status - under	(14,759)	(14,930)
Amounts recognized in the Consolidated Balance Sheets at December 31:
Other accrued liabilities	699	1,044
Noncurrent liabilities - other	14,060	13,886
Benefit obligation liabilities	14,759	14,930
Amounts recognized in accumulated other comprehensive loss consist of:
Actuarial (gain) loss	(2,560)	(2,057)
Prior service credit	(30)	(109)
Total	$ (2,590)	$ (2,166)

Employee Benefit Plans - Schedu

Employee Benefit Plans - Schedule of Accumulated Benefit Obligations in Excess of Plan Assets (Details) - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Projected benefit obligation	$ 33,380	$ 33,758
Accumulated benefit obligation	33,380	33,758
Fair value of plan assets	$ 30,187	$ 28,431

Employee Benefit Plans - Compon

Employee Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Benefits
Components of net periodic benefit cost (credit):
Service cost	$ 0	$ 0
Interest cost	1,633	1,127
Other Postretirement Benefits
Components of net periodic benefit cost (credit):
Service cost	361	522
Interest cost	721	514
Underfunded plan | Pension Benefits
Components of net periodic benefit cost (credit):
Service cost	0	0	$ 0
Interest cost	1,633	1,127	1,053
Expected return on assets	(1,800)	(1,973)	(2,028)
Amortization of prior service credit	0	0	0
Amortization of actuarial gain (loss)	510	856	971
Net periodic benefit cost (credit)	343	10	(4)
Underfunded plan | Other Postretirement Benefits
Components of net periodic benefit cost (credit):
Service cost	361	522	567
Interest cost	721	514	492
Expected return on assets	11	(12)	(19)
Amortization of prior service credit	(79)	(79)	(79)
Amortization of actuarial gain (loss)	(175)	351	135
Net periodic benefit cost (credit)	839	1,296	1,096
Unfunded plan | Pension Benefits
Other changes in plan assets and benefit obligations recognized in accumulated other comprehensive loss:
Net (gain) loss	(797)	1,155	(162)
Amortization of actuarial gain (loss)	(510)	(856)	(1,108)
Amortization of prior service credit	0	0	0
Total recognized in accumulated other comprehensive loss	(1,307)	299	(1,270)
Total recognized in net periodic benefit cost (credit) and accumulated other comprehensive loss	(964)	309	(1,274)
Unfunded plan | Other Postretirement Benefits
Other changes in plan assets and benefit obligations recognized in accumulated other comprehensive loss:
Net (gain) loss	(678)	(4,833)	(2,763)
Amortization of actuarial gain (loss)	175	(351)	(135)
Amortization of prior service credit	79	79	90
Total recognized in accumulated other comprehensive loss	(424)	(5,105)	(2,808)
Total recognized in net periodic benefit cost (credit) and accumulated other comprehensive loss	$ 415	$ (3,809)	$ (1,712)

Employee Benefit Plans - Weight

Employee Benefit Plans - Weighted Average Assumptions (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pension Benefits | Underfunded plan
Benefit obligation:
Discount rate	4.83%	5.06%
Expected return on plan assets	6.50%	6.50%
Net periodic benefit cost:
Discount rate	5.06%	2.62%
Expected return on plan assets	6.50%	6%
Other Postretirement Benefits | Qualified plan
Benefit obligation:
Discount rate	4.84%	5.07%
Expected return on plan assets	0%	6%
Rate of compensation increase	4%	3%
Net periodic benefit cost:
Discount rate	5.06%	2.69%
Expected return on plan assets	6%	5.50%
Rate of compensation increase	3%	3%

Employee Benefit Plans - Health

Employee Benefit Plans - Health Care Cost Assumptions (Details) - Postretirement Health Coverage	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Health care trend rate assumed for next year	7.50%	7.50%
Health care cost trend rate – ultimate	4.50%	4.50%
Year in which ultimate trend rate achieved	2034	2033

Employee Benefit Plans - Expect

Employee Benefit Plans - Expected Benefit Payments (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Qualified plan | Pension Benefits
Pension and Other Postretirement Benefits
2024	$ 2,890
2025	2,780
2026	2,740
2027	2,680
2028	2,620
2029-2033	12,200
Nonqualified Plan | Other Postretirement Benefits
Pension and Other Postretirement Benefits
2024	695
2025	867
2026	1,053
2027	1,136
2028	1,235
2029-2033	$ 6,507

Employee Benefit Plans - Fair V

Employee Benefit Plans - Fair Value of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	$ 30,187	$ 28,431	$ 39,345
Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	0	(314)	$ 314
Fair value, measurements, recurring | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	30,187	28,431
Fair value, measurements, recurring | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		(314)
Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	25,981	13,826
Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		(11)
Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	3,586	14,020
Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		(303)
Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	$ 0	0
Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
Cash equivalents | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, plan assets, investment within plan asset category, percentage	8%
Cash equivalents | Fair value, measurements, recurring | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	$ 1,021	859
Cash equivalents | Fair value, measurements, recurring | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		(17)
Cash equivalents | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	0	0
Cash equivalents | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
Cash equivalents | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	1,021	859
Cash equivalents | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		(17)
Cash equivalents | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	$ 0	0
Cash equivalents | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
U.S. companies | Fair value, measurements, recurring | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		777
U.S. companies | Fair value, measurements, recurring | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		(11)
U.S. companies | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		777
U.S. companies | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		(11)
U.S. companies | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
U.S. companies | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
U.S. companies | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
U.S. companies | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		$ 0
International companies | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, plan assets, investment within plan asset category, percentage	8%	24%
International companies | Fair value, measurements, recurring | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		$ 49
International companies | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
International companies | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		49
International companies | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
Collective and mutual funds | Fair value, measurements, recurring | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	$ 28,546	16,237
Collective and mutual funds | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	25,981	12,729
Collective and mutual funds | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	2,565	3,508
Collective and mutual funds | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	$ 0	$ 0
Corporate bonds | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, plan assets, investment within plan asset category, percentage	33%	29%
Corporate bonds | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, plan assets, investment within plan asset category, percentage		69%
Corporate bonds | Fair value, measurements, recurring | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		$ 8,554
Corporate bonds | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
Corporate bonds | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		8,554
Corporate bonds | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
Municipal bonds | Fair value, measurements, recurring | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		621
Municipal bonds | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
Municipal bonds | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		621
Municipal bonds | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
U.S. Government securities | Fair value, measurements, recurring | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		412
U.S. Government securities | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		320
U.S. Government securities | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		92
U.S. Government securities | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
Pooled separate accounts | Fair value, measurements, recurring | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		337
Pooled separate accounts | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
Pooled separate accounts | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		337
Pooled separate accounts | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		$ 0
Other | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, plan assets, investment within plan asset category, percentage	13%	17%
Other | Fair value, measurements, recurring | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	$ 620	$ 585
Other | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	0	0
Other | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	0	0
Other | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value	$ 0	$ 0
U.S. Government securities | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, plan assets, investment within plan asset category, percentage	23%	7%
U.S. Government securities | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, plan assets, investment within plan asset category, percentage		14%
Common stock of large-cap U.S. companies | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, plan assets, investment within plan asset category, percentage	15%	16%
Common stock of large-cap U.S. companies | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, plan assets, investment within plan asset category, percentage		13%
Pooled separate accounts, cash and cash equivalents | Pension Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, plan assets, investment within plan asset category, percentage		7%
Insurance contract | Fair value, measurements, recurring | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		$ (286)
Insurance contract | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		0
Insurance contract | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		(286)
Insurance contract | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3) | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total assets measured at fair value		$ 0
Common stock of small-cap U.S. companies | Other Postretirement Benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, plan assets, investment within plan asset category, percentage		4%

Employee Benefit Plans - Nonqua

Employee Benefit Plans - Nonqualified Benefit Plans, Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Plan participant age	65 years
Benefit period	15 years
Defined contribution plan, contribution cost	$ 31,100	$ 27,600	$ 26,600
Nonqualified Plan
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined contribution plan, contribution cost	$ 1,500	$ 1,200	$ 900

Employee Benefit Plans - Nonq_2

Employee Benefit Plans - Nonqualified Benefit Plans, Projected and Accumulated Benefit Obligation (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Projected benefit obligation	$ 15,873	$ 16,047
Accumulated benefit obligation	$ 15,873	$ 16,047

Employee Benefit Plans - Nonq_3

Employee Benefit Plans - Nonqualified Benefit Plans, Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)
Supplemental Employee Retirement Plan
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Interest cost	$ 765	$ 460	$ 407
Recognized net actuarial loss	0	39	223
Net periodic benefit cost (credit)	$ 765	$ 499	$ 630

Employee Benefit Plans - Nonq_4

Employee Benefit Plans - Nonqualified Benefit Plans, Weighted Average Assumptions (Details) - Supplemental Employee Retirement Plan	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Benefit obligation discount rate	4.74%	4.97%
Net periodic benefit cost discount rate	4.93%	2.38%

Employee Benefit Plans - Nonq_5

Employee Benefit Plans - Nonqualified Benefit Plans, Future Benefit Payments (Details) - Supplemental Employee Retirement Plan $ in Thousands	Dec. 31, 2023 USD ($)
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
2024	$ 1,620
2025	1,720
2026	1,700
2027	1,650
2028	1,690
2029-2033	$ 5,600

Employee Benefit Plans - Nonq_6

Employee Benefit Plans - Nonqualified Benefit Plans, Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total investments	$ 35,312	$ 29,765
Insurance contract
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total investments	24,896	20,083
Life insurance
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total investments	7,175	7,234
Other
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Total investments	$ 3,241	$ 2,448

Employee Benefit Plans - Define

Employee Benefit Plans - Defined Contribution Plans and Multiemployer Plans, Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Multiemployer Plan [Line Items]
Defined contribution plan, contribution cost	$ 31,100	$ 27,600	$ 26,600
Multiemployer plan, contribution cost	12,741	12,998	12,470
Other Postretirement Benefits
Multiemployer Plan [Line Items]
Multiemployer plan, contribution cost	$ 1,800	$ 1,800	$ 3,200

Employee Benefit Plans - Defi_2

Employee Benefit Plans - Defined Contribution Plans and Multiemployer Plans, Company Participation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Multiemployer Plan [Line Items]
Other funds	$ 5,653	$ 5,938	$ 5,519
Contributions	12,741	12,998	12,470
Alaska Laborers Employer Retirement Fund
Multiemployer Plan [Line Items]
Contributions, excluding other funds	887	805	737
Minnesota Teamsters Construction Division Pension Fund
Multiemployer Plan [Line Items]
Contributions, excluding other funds	418	644	713
Pension Trust Fund for Operating Engineers
Multiemployer Plan [Line Items]
Contributions, excluding other funds	2,476	2,484	2,495
Western Conference of Teamsters Pension Plan
Multiemployer Plan [Line Items]
Contributions, excluding other funds	$ 3,307	$ 3,127	$ 3,006

Commitments and Contingencies -

Commitments and Contingencies - Litigation (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Potential liabilities related to litigation and environmental matters	$ 873	$ 1,000
Insurance receivables	$ 42	$ 325

Commitments and Contingencies_2

Commitments and Contingencies - Environmental Matters (Details)	Dec. 31, 2016 USD ($)	Dec. 31, 2023	Dec. 31, 2020 responsibleParty	Jan. 31, 2017 USD ($)
Other Commitments [Line Items]
Number of other responsible parties | responsibleParty			100
Environmental remediation period (in years)				13 years
Environmental remediation, estimated present value of expected costs				$ 1,000,000,000
Environmental remediation, percent of site to be remediated		100%
Lower Willamette Group
Other Commitments [Line Items]
Incurred investigation related costs (over)	$ 115,000,000

Commitments and Contingencies_3

Commitments and Contingencies - Purchase Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Maximum commitment terms (in years)	25 years
Purchase commitments
2024	$ 59,211
2025	27,758
2026	27,342
2027	2,028
2028	1,542
Thereafter	8,212
Purchased under various commitments during the year	$ 128,700	$ 167,600	$ 137,400

Commitments and Contingencies_4

Commitments and Contingencies - Guarantees (Details)	Dec. 31, 2023 USD ($)
Other Commitments [Line Items]
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 - 2024	20,700,000
Letters of credit set to expire - 2025	300,000
Outstanding letters of credit	$ 0
Surety bond expiration period	12 months
Amount of surety bonds outstanding	$ 597,500,000
Letter of Credit
Other Commitments [Line Items]
Line of credit, maximum borrowing capacity	$ 21,000,000

Related-Party Transactions - Na

Related-Party Transactions - Narrative (Details) - USD ($)		12 Months Ended
	May 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	May 30, 2023	Apr. 25, 2023
Related Party Transaction [Line Items]
Net transfers from Centennial and MDU Resources including Separation adjustments		$ 62,972,000
Selling, general and administrative expenses		242,538,000	$ 166,599,000	$ 155,872,000
Other income (expense)		7,007,000	(5,353,000)	1,355,000
Senior Notes | Senior notes due on May 1, 2031
Related Party Transaction [Line Items]
Debt instrument, face amount						$ 425,000,000
Line of Credit | Credit Agreement | Term Loan
Related Party Transaction [Line Items]
Debt instrument, face amount	$ 275,000,000
Long-term line of credit		0
Line of Credit | Credit Agreement | Revolving Credit Facility
Related Party Transaction [Line Items]
Line of credit, maximum borrowing capacity	350,000,000
Long-term line of credit	190,000,000
Related Party
Related Party Transaction [Line Items]
Costs and expenses, related party		10,700,000	$ 18,000,000	$ 15,600,000
Net transfers from Centennial and MDU Resources including Separation adjustments	64,700,000
Selling, general and administrative expenses		3,000,000
Other income (expense)		$ 824,000
Related Party | Centennial
Related Party Transaction [Line Items]
Notes payable					$ 889,700,000
Dividends	$ 825,000,000

Related-Party Transactions - Sc

Related-Party Transactions - Schedule of Intercompany Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Total long-term debt	$ 681,659
Long-term debt - current portion	7,082	$ 211
Long-term debt	$ 674,577	427
Related Party
Related Party Transaction [Line Items]
Total long-term debt		684,449
Long-term debt - current portion		238,000
Long-term debt		$ 446,449
Related Party | Centennial Term Loan Agreements
Related Party Transaction [Line Items]
Weighted average interest rate, at point in time		5.44%
Total long-term debt		$ 208,000
Related Party | Centennial Senior Notes
Related Party Transaction [Line Items]
Weighted average interest rate, at point in time		4.34%
Total long-term debt		$ 410,000
Related Party | Borrowing Arrangements
Related Party Transaction [Line Items]
Weighted average interest rate, at point in time		5.27%
Total long-term debt		$ 66,449