Knife River (KNF) 10-Q 6 Nov 23 2023 Q3 Quarterly report Financial data

Cover page

Cover page - shares	9 Months Ended
	Sep. 30, 2023	Nov. 01, 2023
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 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 Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity common stock, shares outstanding		56,566,214
Entity Central Index Key	0001955520
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Amendment Flag	false

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenue:
Revenues	$ 1,090,372	$ 975,428	$ 2,183,462	$ 1,997,207
Cost of revenue:
Cost of Revenue	820,983	790,941	1,756,994	1,708,265
Gross profit	269,389	184,487	426,468	288,942
Selling, general and administrative expenses	59,168	41,572	167,276	130,223
Operating income	210,221	142,915	259,192	158,719
Interest expense	15,354	8,817	44,005	21,506
Other income (expense)	7	(1,277)	3,311	(6,056)
Income before income taxes	194,874	132,821	218,498	131,157
Income tax expense	48,219	33,164	56,327	32,947
Net income	$ 146,655	$ 99,657	$ 162,171	$ 98,210
Net income (loss) per share, basic
Income per share, Basic, Total	$ 2.59	$ 1.76	$ 2.87	$ 1.74
Net income (loss) per share, diluted
Income per share, Diluted, Total	$ 2.58	$ 1.76	$ 2.86	$ 1.74
Weighted Average Number of Shares Outstanding, Basic	56,566	56,566	56,566	56,566
Weighted Average Number of Shares Outstanding, Diluted	56,735	56,566	56,633	56,566
Construction materials
Revenue:
Revenues	$ 553,057	$ 483,221	$ 1,177,726	$ 1,060,051
Cost of revenue:
Cost of Revenue	346,298	340,609	856,606	846,965
Contracting services
Revenue:
Revenues	537,315	492,207	1,005,736	937,156
Cost of revenue:
Cost of Revenue	$ 474,685	$ 450,332	$ 900,388	$ 861,300

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Net Income (Loss)	$ 146,655	$ 99,657	$ 162,171	$ 98,210
Other comprehensive income:
Reclassification adjustment for loss on derivative instruments included in net income, tax	0	27	28	80
Reclassification adjustment for loss on derivative instruments included in net income, net of tax	0	82	90	246
Postretirement liability adjustment:
Postretirement liability gains (losses) arising during the period, tax	0	0	(6)	1,879
Postretirement liability gains (losses) arising during the period, net of tax	0	0	(17)	5,820
Amortization of postretirement liability losses included in net periodic benefit cost, tax	16	71	47	213
Amortization of postretirement liability losses included in net periodic benefit cost, net of tax	49	221	144	662
Postretirement liability adjustment	49	221	127	6,482
Other comprehensive income	49	303	217	6,728
Comprehensive income attributable to common stockholders	$ 146,704	$ 99,960	$ 162,388	$ 104,938

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash, cash equivalents and restricted cash	$ 116,159	$ 10,090
Receivables, net	491,866	210,157
Costs and estimated earnings in excess of billings on uncompleted contracts	50,545	31,145
Due from related-party	0	16,050
Inventories	314,711	323,277
Prepayments and other current assets	38,094	17,848
Total current assets	1,011,375	608,567
Noncurrent assets:
Property, plant and equipment	2,547,577	2,489,408
Less accumulated depreciation, depletion and amortization	1,248,042	1,174,195
Net property, plant and equipment	1,299,535	1,315,213
Goodwill	274,478	274,540
Other intangible assets, net	11,463	13,430
Operating lease right-of-use assets	44,309	45,873
Investments and other	39,722	36,696
Total noncurrent assets	1,669,507	1,685,752
Total assets	2,680,882	2,294,319
Current liabilities:
Long-term debt - current portion	7,082	211
Related-party notes payable - current portion	0	238,000
Accounts payable	148,977	87,370
Billings in excess of costs and estimated earnings on uncompleted contracts	58,785	39,843
Taxes payable	53,281	8,502
Accrued compensation	37,922	29,192
Due to related-party	0	20,286
Current operating lease liabilities	13,702	13,210
Other accrued liabilities	105,218	80,276
Total current liabilities	424,967	516,890
Noncurrent liabilities:
Long-term debt	675,649	427
Related-party notes payable	0	446,449
Deferred income taxes	173,989	175,804
Noncurrent operating lease liabilities	30,607	32,663
Other	132,652	93,497
Total liabilities	1,437,864	1,265,730
Stockholders' equity:
Common stock	570	800
Other paid-in capital	613,024	549,106
Retained earnings	645,185	494,661
MDU Resources Common Stock Held by Subsidiary at Cost, Value	0	(3,626)
Treasury Stock, Common, Value	(3,626)	0
Accumulated other comprehensive loss	(12,135)	(12,352)
Total stockholders' equity	1,243,018	1,028,589
Total liabilities and stockholders' equity	$ 2,680,882	$ 2,294,319
Common Stock, Shares Authorized	300,000,000	80,000
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 10
Common Stock, Shares, Issued		80,000
Common Stock, Shares, Outstanding	56,566,214	80,000
MDU Resources Common Stock Held by Subsidiary at Cost, Shares		(538,921)

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, Common	Accumulated other comprehensive loss
MDU Resources Common Stock Held by Subsidiary at Cost, Shares					(538,921)
Common stock balance (in shares) at Dec. 31, 2021		80,000
Balance at Dec. 31, 2021	$ 952,844	$ 800	$ 549,714	$ 430,446	$ (3,626)	$ 0	$ (24,490)
Treasury Stock, Common, Shares at Dec. 31, 2021						0
Net Income (Loss)	(40,010)			(40,010)
Other comprehensive income	303						303
APIC, Share-Based Payment Arrangement, Recognition and Exercise	306		333	(27)
Equity net transfers to (from) Parent	(16,408)		(3,432)	(12,976)
Common stock balance (in shares) at Mar. 31, 2022		80,000
Balance at Mar. 31, 2022	897,035	$ 800	546,615	377,433	(3,626)	$ 0	(24,187)
Treasury Stock, Common, Shares at Mar. 31, 2022						0
Common stock balance (in shares) at Dec. 31, 2021		80,000
Balance at Dec. 31, 2021	952,844	$ 800	549,714	430,446	(3,626)	$ 0	(24,490)
Treasury Stock, Common, Shares at Dec. 31, 2021						0
Net Income (Loss)	98,210
Other comprehensive income	6,728
Common stock balance (in shares) at Sep. 30, 2022		80,000
Balance at Sep. 30, 2022	1,011,316	$ 800	542,239	489,665	$ (3,626)	$ 0	(17,762)
Treasury Stock, Common, Shares at Sep. 30, 2022						0
MDU Resources Common Stock Held by Subsidiary at Cost, Shares					(538,921)
Common stock balance (in shares) at Mar. 31, 2022		80,000
Balance at Mar. 31, 2022	897,035	$ 800	546,615	377,433	$ (3,626)	$ 0	(24,187)
Treasury Stock, Common, Shares at Mar. 31, 2022						0
Net Income (Loss)	38,562			38,562
Other comprehensive income	6,122						6,122
APIC, Share-Based Payment Arrangement, Recognition and Exercise	306		333	(27)
Equity net transfers to (from) Parent	(18,037)		(5,063)	(12,974)
Common stock balance (in shares) at Jun. 30, 2022		80,000
Balance at Jun. 30, 2022	923,988	$ 800	541,885	402,994	$ (3,626)	$ 0	(18,065)
Treasury Stock, Common, Shares at Jun. 30, 2022						0
MDU Resources Common Stock Held by Subsidiary at Cost, Shares					(538,921)
Net Income (Loss)	99,657			99,657
Other comprehensive income	303						303
APIC, Share-Based Payment Arrangement, Recognition and Exercise	123		134	(11)
Equity net transfers to (from) Parent	(12,755)		220	(12,975)
Common stock balance (in shares) at Sep. 30, 2022		80,000
Balance at Sep. 30, 2022	$ 1,011,316	$ 800	542,239	489,665	$ (3,626)	$ 0	(17,762)
Treasury Stock, Common, Shares at Sep. 30, 2022						0
MDU Resources Common Stock Held by Subsidiary at Cost, Shares					(538,921)
MDU Resources Common Stock Held by Subsidiary at Cost, Shares	(538,921)				(538,921)
Common stock balance (in shares) at Dec. 31, 2022	80,000	80,000
Balance at Dec. 31, 2022	$ 1,028,589	$ 800	549,106	494,661	$ (3,626)	$ 0	(12,352)
Treasury Stock, Common, Shares at Dec. 31, 2022						0
Net Income (Loss)	(41,320)			(41,320)
Other comprehensive income	93						93
APIC, Share-Based Payment Arrangement, Recognition and Exercise	414		453	(39)
Equity net transfers to (from) Parent	(13,007)		(1,385)	(11,622)
Common stock balance (in shares) at Mar. 31, 2023		80,000
Balance at Mar. 31, 2023	$ 974,769	$ 800	548,174	441,680	(3,626)	$ 0	(12,259)
Treasury Stock, Common, Shares at Mar. 31, 2023						0
Common stock balance (in shares) at Dec. 31, 2022	80,000	80,000
Balance at Dec. 31, 2022	$ 1,028,589	$ 800	549,106	494,661	(3,626)	$ 0	(12,352)
Treasury Stock, Common, Shares at Dec. 31, 2022						0
Net Income (Loss)	162,171
Other comprehensive income	217
Common stock balance (in shares) at Sep. 30, 2023		56,997,350
Balance at Sep. 30, 2023	1,243,018	$ 570	613,024	645,185	$ 0	$ (3,626)	(12,135)
Treasury Stock, Common, Shares at Sep. 30, 2023						(431,136)
MDU Resources Common Stock Held by Subsidiary at Cost, Shares					(538,921)
Common stock balance (in shares) at Mar. 31, 2023		80,000
Balance at Mar. 31, 2023	974,769	$ 800	548,174	441,680	$ (3,626)	$ 0	(12,259)
Treasury Stock, Common, Shares at Mar. 31, 2023						0
Net Income (Loss)	56,836			56,836
Other comprehensive income	75						75
APIC, Share-Based Payment Arrangement, Recognition and Exercise	226		212	14
Transfer of parent stock held by subsidiary, shares					538,921
Transfer of parent stock held by subsidiary, Value	3,626				$ 3,626
Treasury Stock, Shares, Acquired						(431,136)
Treasury Stock, Value, Acquired, Cost Method	3,626					$ (3,626)
Stock Redeemed or Called During Period, Shares		(80,000)
Stock Redeemed or Called During Period, Value	0	$ (800)	(800)
Issuance of common stock (shares)		56,997,350
Stock Issued During Period, Value, New Issues	(26)	$ (570)	(596)
Equity net transfers to (from) Parent	62,972		62,972
Common stock balance (in shares) at Jun. 30, 2023		56,997,350
Balance at Jun. 30, 2023	1,094,852	$ 570	611,562	498,530	$ 0	$ (3,626)	(12,184)
Treasury Stock, Common, Shares at Jun. 30, 2023						(431,136)
MDU Resources Common Stock Held by Subsidiary at Cost, Shares					0
Net Income (Loss)	146,655			146,655
Other comprehensive income	49						49
APIC, Share-Based Payment Arrangement, Recognition and Exercise	1,462		1,462
Common stock balance (in shares) at Sep. 30, 2023		56,997,350
Balance at Sep. 30, 2023	$ 1,243,018	$ 570	$ 613,024	$ 645,185	$ 0	$ (3,626)	$ (12,135)
Treasury Stock, Common, Shares at Sep. 30, 2023						(431,136)
MDU Resources Common Stock Held by Subsidiary at Cost, Shares					0

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Operating activities:
Net Income (Loss)	$ 162,171	$ 98,210
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	92,511	88,551
Deferred income taxes	(1,884)	5,043
Provision for credit losses	1,386	(296)
Amortization of debt issuance costs	2,425	355
Employee stock-based compensation costs	2,127	800
Pension and postretirement benefit plan net periodic benefit cost	889	981
Unrealized (gains) losses on investments	(685)	3,172
Gains on sales of assets	(3,806)	(3,575)
Changes in current assets and liabilities, net of acquisitions:
Receivables	(302,536)	(239,565)
Due from related-party	16,050	1,258
Inventories	8,566	(18,624)
Other current assets	(20,127)	835
Accounts payable	91,663	69,552
Due to related-party	(7,310)	9,829
Other current liabilities	78,006	21,786
Pension and postretirement benefit plan contributions	(1,611)	(313)
Other noncurrent changes	35,092	1,400
Net cash provided by operating activities	152,927	39,399
Investing activities:
Capital expenditures	(86,450)	(121,840)
Acquisitions, net of cash acquired	0	450
Net proceeds from sale or disposition of property and other	5,227	5,716
Investments	(1,764)	(2,226)
Net cash used in investing activities	(82,987)	(117,900)
Financing activities:
Issuance of current related-party notes, net	0	100,000
Issuance of long-term related-party notes, net	205,275	26,872
Issuance of long-term debt	700,000	0
Repayment of long-term debt	(1,891)	(206)
Debt issuance costs	(16,640)	(749)
Proceeds from issuance of common stock	(26)	0
Net transfers to Centennial	(850,589)	(42,236)
Net cash provided by financing activities	36,129	83,681
Increase in cash, cash equivalents and restricted cash	106,069	5,180
Cash, cash equivalents and restricted cash -- beginning of year	10,090	13,848
Cash, cash equivalents and restricted cash -- end of period	$ 116,159	$ 19,028

Background

Background	9 Months Ended
	Sep. 30, 2023
Restructuring and Related Activities [Abstract]
Background	BackgroundOn August 4, 2022, MDU Resources announced that its board of directors approved a plan to pursue the Separation of Knife River from MDU Resources. On May 31, 2023, the Separation was completed by a pro rata distribution of shares representing approximately 90 percent of Knife River's outstanding common stock to MDU Resources' stockholders. MDU Resources' stockholders received one share of Knife River common stock for every four shares of MDU Resources common stock held as of the close of business on May 22, 2023. MDU Resources retained approximately 10 percent of Knife River's common stock. The Distribution was tax-free to its stockholders for U. S. federal income tax purposes. At the time of the Separation, the net parent investment in Knife River held by Centennial was settled between the companies. As a result of the Separation, Knife River is now an independent public company trading on the New York Stock Exchange under the symbol "KNF." More information on the Separation and Distribution, as well as the Company's historical results, can be found within the Company's Registration Statement on Form 10.

Basis of presentation

Basis of presentation	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation [Text Block]	Basis of presentation The accompanying consolidated interim financial statements were prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Interim financial statements do not include all disclosures provided in annual financial statements and, accordingly, these financial statements should be read in conjunction with the Company's Registration Statement on Form 10. The information is unaudited but includes adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. On May 31, 2023, the Company became a stand-alone publicly traded company. Prior to the Separation on May 31, 2023, 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. These consolidated financial statements and footnotes reflect the historical financial position, results of operations and cash flows of the Company as historically managed within MDU Resources for the periods prior to the completion of the Separation and reflect the financial position, results of operations and cash flows as a stand-alone company for the period after the completion of the Separation. The historical consolidated financial statements and footnotes were prepared on a “carve-out” basis in connection with the Separation and were derived from the consolidated financial statements of MDU Resources as if the Company operated on a stand-alone basis during the periods presented, and were prepared utilizing the legal entity approach in conformity with GAAP. The results for the three and nine months ended September 30, 2022, vary from the previously reported MDU Resources' construction materials and contracting services segment due to an adjustment to a cost allocation for interim periods to conform with the Company's current year accounting. This adjustment does not impact the historical annual financial statements included in the Company's Registration Statement on Form 10. This adjustment increased cost of revenue for the three months ended September 30, 2022, by $4.4 million ($3.4 million after tax) and decreased cost of revenue for the nine months ended September 30, 2022, by $1.6 million ($1.2 million after tax). The adjustment is not considered material for the three or nine months ended September 30, 2022. The Company utilized allocations and carve-out methodologies to prepare its historical consolidated financial statements and footnotes. The consolidated financial statements and footnotes herein may not be indicative of the Company's future performance or actual expenses that would have been incurred as a stand-alone company for the periods presented. All revenues and costs, as well as assets and liabilities, directly associated with the business activity of the Company are included in the consolidated financial statements. In the periods prior to the Separation, the consolidated financial statements include expense allocations for certain functions provided by MDU Resources and Centennial, including, but not limited to certain general corporate expenses related to senior management, legal, human resources, finance and accounting, treasury, information technology, communications, procurement, tax, insurance and other shared services. These general corporate expenses are included in the Consolidated Statements of Operations within selling, general and administrative expenses and other income (expense). There were no amounts allocated to Knife River for the three months ended September 30, 2023, and $8.7 million was allocated for the nine months ended September 30, 2023. For the three and nine months ended September 30, 2022, there was $3.8 million and $13.4 million, respectively, allocated to Knife River. These expenses have been 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 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. Prior to the Separation, Knife River historically participated in Centennial’s centralized cash management program, including its overall financing arrangements. This arrangement is not reflective of the manner in which the Company would have been able to finance its operations had it been independent from MDU Resources for the period prior to the completion of the Separation. Knife River 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 Sheets as of December 31, 2022. 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 entered into debt agreements and subsequently paid a dividend of $825.0 million from the debt 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 reflected as "Net transfers from Centennial and MDU Resources including separation adjustments" in the Consolidated Statement of Equity. Interest expense in the Consolidated Statements of Operations includes the allocation of interest on borrowing and funding associated with the related-party note agreements for periods prior to the Separation. Prior to the Separation, income tax expense and tax balances in the consolidated financial statements were calculated on a separate tax return basis. The separate tax return method applies the accounting guidance for income taxes to the standalone financial statements as if the Company were a separate taxpayer and a standalone enterprise. Management believes the assumptions supporting the allocation and presentation of income taxes on a separate return basis are reasonable. As a stand-alone entity, the Company will file tax returns on its own behalf, and tax balances and effective income tax rate may differ from the amounts reported in the historical periods. Management has also evaluated the impact of events occurring after September 30, 2023, up to the date of issuance of these consolidated interim financial statements on November 6, 2023, that would require recognition or disclosure in the Consolidated Financial Statements. Principles of consolidation For the pre-Separation periods, the accompanying financial statements of the Company were derived from the consolidated financial statements and accounting records of MDU Resources as if the Company and its wholly owned subsidiaries operated on a stand-alone basis during the periods presented. The 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 consolidated financial statements. Related-party transactions between the Company and MDU Resources or Centennial for general operating activities and intercompany debt have been included in the consolidated financial statements for the pre-Separation periods. These related-party transactions were settled in cash and are reflected in the pre-Separation Consolidated Balance Sheets as “Due from related-party” or “Due to related-party” with the aggregate net effect reflected in the Consolidated Statements of Cash Flows within operating activities and “Related-party notes payable” with the aggregate net effect reflected in the Consolidated Statements of Cash Flows within financing activities. The aggregate net effect of related-party transactions not settled in cash as part of the Separation have been reflected in the pre-Separation Consolidated Balance Sheet within “Other paid-in capital”. See Note 18 for additional information on related-party transactions. 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 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 There have been no recent accounting standards that are expected to materially affect the Company. 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 September 30, 2023, the $116.2 million of cash, cash equivalents and restricted cash on the Consolidated Statements of Cash Flows is comprised of $84.0 million of cash and cash equivalents and $32.2 million of restricted cash. At September 30, 2022, the Company did not have any 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 as cash. Seasonality of operations Some of the Company's operations are seasonal and revenues from, and certain expenses for, such operations may fluctuate significantly among quarterly periods, with lower activity in the winter months and higher activity in the summer months. Accordingly, the interim results for particular segments, and for the Company as a whole, may not be indicative of results for the full fiscal year or other future periods.

Receivables and allowance for e

Receivables and allowance for expected credit losses	9 Months Ended
	Sep. 30, 2023
Credit Loss [Abstract]
Receivables and allowance for expected credit loss	Receivables and allowance for expected credit losses Receivables consist primarily of trade and contract receivables for the sale of goods and services net of expected credit losses. A majority of the Company's receivables are due in 30 days or less. The total balance of receivables past due 90 days or more was $14.4 million and $11.2 million at September 30, 2023 and December 31, 2022, respectively. Receivables were as follows: September 30, 2023 December 31, 2022 (In thousands) Trade receivables $ 236,373 $ 104,347 Contract receivables 223,874 82,428 Retention receivables 37,814 28,859 Receivables, gross 498,061 215,634 Less expected credit loss 6,195 5,477 Receivables, net $ 491,866 $ 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 North All Other Total (In thousands) At December 31, 2022 $ 2,045 $ 1,253 $ 1,278 $ 839 $ 62 $ 5,477 Current expected credit loss provision 45 313 164 (89) (1) 432 Less write-offs charged against the allowance 1 68 18 — — 87 At March 31, 2023 $ 2,089 $ 1,498 $ 1,424 $ 750 $ 61 $ 5,822 Current expected credit loss provision 9 74 631 (132) 1 583 Less write-offs charged against the allowance 18 512 3 — 2 535 At June 30, 2023 $ 2,080 $ 1,060 $ 2,052 $ 618 $ 60 $ 5,870 Current expected credit loss provision 46 242 (152) 215 20 371 Less write-offs charged against the allowance 26 4 13 3 — 46 At September 30, 2023 $ 2,100 $ 1,298 $ 1,887 $ 830 $ 80 $ 6,195 Pacific Northwest Mountain North All Other Total (In thousands) At December 31, 2021 $ 2,052 $ 512 $ 1,610 $ 1,152 $ 80 $ 5,406 Current expected credit loss provision 1 (125) (130) 6 (5) (253) Less write-offs charged against the allowance 1 20 3 1 1 26 At March 31, 2022 $ 2,052 $ 367 $ 1,477 $ 1,157 $ 74 $ 5,127 Current expected credit loss provision 11 58 (17) (37) (3) 12 Less write-offs charged against the allowance — 56 4 47 2 109 At June 30, 2022 $ 2,063 $ 369 $ 1,456 $ 1,073 $ 69 $ 5,030 Current expected credit loss provision (6) 194 (111) (141) 9 (55) Less write-offs charged against the allowance 9 7 40 4 16 76 At September 30, 2022 $ 2,048 $ 556 $ 1,305 $ 928 $ 62 $ 4,899

Inventories

Inventories	9 Months Ended
	Sep. 30, 2023
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories on the Consolidated Balance Sheets were as follows: September 30, 2023 December 31, 2022 (In thousands) Finished products $ 213,702 $ 211,496 Raw materials 63,156 78,571 Supplies and parts 37,853 33,210 Total $ 314,711 $ 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.

Earnings per share

Earnings per share	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Earnings per share	Earnings per share The calculation for basic and diluted earnings per share for any period presented prior to the Separation are based on 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 56,997,350 less shares held in treasury of 431,136, as described in Note 6. 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: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands, except per share amounts) Net income $ 146,655 $ 99,657 $ 162,171 $ 98,210 Weighted average common shares outstanding - basic 56,566 56,566 56,566 56,566 Effect of dilutive restricted stock units 169 — 67 — Weighted average common shares outstanding - diluted 56,735 56,566 56,633 56,566 Shares excluded from the calculation of diluted earnings per share — — — — Net income per share - basic $ 2.59 $ 1.76 $ 2.87 $ 1.74 Net income per share - diluted $ 2.58 $ 1.76 $ 2.86 $ 1.74

Equity

Equity	9 Months Ended
	Sep. 30, 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 Statement 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 subsidiary at cost of $3.6 million at September 30, 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 and will remain at the historical value since the exchange was between related parties. 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 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 award 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. The impact of this modification will be recorded over the remaining vesting periods and was not material to the Company's stock-based compensation expense for the three or nine months ended September 30, 2023.

Accumulated other comprehensive

Accumulated other comprehensive loss	9 Months Ended
	Sep. 30, 2023
Equity [Abstract]
Accumulated other comprehensive loss	Accumulated other comprehensive loss The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Unrealized Postretirement Total (In thousands) At December 31, 2022 $ (90) $ (12,262) $ (12,352) Amounts reclassified from accumulated other comprehensive loss 46 47 93 Net current-period other comprehensive income 46 47 93 At March 31, 2023 $ (44) $ (12,215) $ (12,259) Other comprehensive loss before reclassification — (17) (17) Amounts reclassified from accumulated other comprehensive loss 44 48 92 Net current-period other comprehensive income 44 31 75 At June 30, 2023 $ — $ (12,184) $ (12,184) Other comprehensive loss before reclassification — — — Amounts reclassified from accumulated other comprehensive loss — 49 49 Net current-period other comprehensive income — 49 49 At September 30, 2023 $ — $ (12,135) $ (12,135) Net Unrealized Postretirement Total (In thousands) At December 31, 2021 $ (418) $ (24,072) $ (24,490) Amounts reclassified from accumulated other comprehensive loss 82 221 303 Net current-period other comprehensive income 82 221 303 At March 31, 2022 $ (336) $ (23,851) $ (24,187) Other comprehensive income before reclassification — 5,820 5,820 Amounts reclassified from accumulated other comprehensive loss 82 220 302 Net current-period other comprehensive income 82 6,040 6,122 At June 30, 2022 $ (254) $ (17,811) $ (18,065) Amounts reclassified from accumulated other comprehensive loss 82 221 303 Net current-period other comprehensive income 82 221 303 At September 30, 2022 $ (172) $ (17,590) $ (17,762) The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Operations. The reclassifications were as follows: Three Months Ended Nine Months Ended Location on Consolidated Statements of Operations September 30, September 30, 2023 2022 2023 2022 (In thousands) Reclassification adjustment for loss on derivative income $ — $ (109) $ (118) $ (326) Interest expense — 27 28 80 Income taxes — (82) (90) (246) Amortization of postretirement liability losses included in net periodic benefit cost (65) (292) (191) (875) Other income 16 71 47 213 Income taxes (49) (221) (144) (662) Total reclassifications $ (49) $ (303) $ (234) $ (908)

Revenue from contracts with cus

Revenue from contracts with customers	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Revenue from contracts with customers	Revenue from contracts with customers Revenue is recognized when a performance obligation is satisfied by transferring control over a product or service to a customer. Revenue includes revenue from the sales of construction materials and contracting services. Revenue is measured based on consideration specified in a contract with a customer and excludes any sales incentives and amounts collected on behalf of third parties. 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. Revenue for construction materials is recognized at a point in time when delivery of the products has taken place. Contracting revenue is recognized over time using an input method based on the cost-to-cost measure of progress on a project. Disaggregation In the following tables, revenue is disaggregated by category for each segment and includes sales of materials to both third parties and internal customers. Due to consolidation requirements, the internal sales revenues must be eliminated against the construction materials product used in downstream materials and contracting services to arrive at the external operating revenues. 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. Three Months Ended September 30, 2023 Pacific Northwest Mountain North All Other Total (In thousands) Aggregates $ 33,624 $ 57,398 $ 39,519 $ 47,656 $ 15,388 $ 193,585 Ready-mix concrete 39,861 46,785 44,053 73,183 12,157 216,039 Asphalt 14,050 43,462 59,673 95,053 10,539 222,777 Other 81,081 4,497 11 10,211 118,312 214,112 Contracting services public-sector 32,632 68,316 135,700 181,779 23,483 441,910 Contracting services private-sector 17,745 25,144 43,944 8,526 46 95,405 Internal sales (37,566) (36,683) (68,178) (111,288) (39,741) (293,456) Revenues from contracts with customers $ 181,427 $ 208,919 $ 254,722 $ 305,120 $ 140,184 $ 1,090,372 Three Months Ended September 30, 2022 Pacific Northwest Mountain North All Other Total (In thousands) Aggregates $ 28,695 $ 52,614 $ 31,258 $ 45,039 $ 14,197 $ 171,803 Ready-mix concrete 35,395 45,600 37,334 64,496 16,082 198,907 Asphalt 10,935 45,110 45,553 96,830 7,133 205,561 Other 63,002 4,447 12 8,711 90,539 166,711 Contracting services public-sector 30,529 78,664 100,298 184,266 18,874 412,631 Contracting services private-sector 14,512 20,424 38,755 5,664 221 79,576 Internal sales (30,710) (42,627) (49,089) (110,700) (26,635) (259,761) Revenues from contracts with customers $ 152,358 $ 204,232 $ 204,121 $ 294,306 $ 120,411 $ 975,428 Nine Months Ended September 30, 2023 Pacific Northwest Mountain North All Other Total (In thousands) Aggregates $ 79,768 $ 147,937 $ 78,051 $ 81,999 $ 35,767 $ 423,522 Ready-mix concrete 106,531 125,273 92,929 139,369 33,604 497,706 Asphalt 21,640 84,908 89,955 141,942 22,888 361,333 Other 168,104 11,513 21 22,703 193,528 395,869 Contracting services public-sector 53,450 138,621 244,320 280,853 61,293 778,537 Contracting services private-sector 37,220 80,258 94,706 13,884 1,131 227,199 Internal sales (75,345) (84,937) (108,888) (167,055) (64,479) (500,704) Revenues from contracts with customers $ 391,368 $ 503,573 $ 491,094 $ 513,695 $ 283,732 $ 2,183,462 Nine Months Ended September 30, 2022 Pacific Northwest Mountain North All Other Total (In thousands) Aggregates $ 72,088 $ 129,752 $ 67,388 $ 75,718 $ 40,892 $ 385,838 Ready-mix concrete 98,520 121,079 84,950 124,026 46,959 475,534 Asphalt 26,909 79,801 77,021 141,595 19,886 345,212 Other 143,140 11,804 26 20,766 152,757 328,493 Contracting services public-sector 63,450 141,783 202,495 275,797 52,933 736,458 Contracting services private-sector 38,922 60,321 91,783 8,809 863 200,698 Internal Sales (76,911) (84,733) (90,654) (162,342) (60,386) (475,026) Revenues from contracts with customers $ 366,118 $ 459,807 $ 433,009 $ 484,369 $ 253,904 $ 1,997,207

Uncompleted Contracts

Uncompleted Contracts	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Uncompleted contracts	Uncompleted contracts The timing of revenue recognition may differ from the timing of invoicing to customers. The timing of invoicing to customers does not necessarily correlate with the timing of revenues being recognized under the cost-to-cost method of accounting. Contracts from contracting services are billed as work progresses in accordance with agreed upon contractual terms. Generally, billing to the customer occurs contemporaneous to revenue recognition. A variance in timing of the billings may result in a contract asset or a contract liability. A contract asset occurs when revenues are recognized under the cost-to-cost measure of progress, which exceeds amounts billed on uncompleted contracts. Such amounts will be billed as standard contract terms allow, usually based on various measures of performance or achievement. A contract liability occurs when there are billings in excess of revenues recognized under the cost-to-cost measure of progress on uncompleted contracts. Contract liabilities decrease as revenue is recognized from the satisfaction of the related performance obligation. The changes in contract assets and liabilities were as follows: September 30, 2023 December 31, 2022 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 50,545 $ 31,145 $ 19,400 Costs and estimated earnings in excess of billings on uncompleted contracts Contract liabilities (58,785) (39,843) (18,942) Billings in excess of costs and estimated earnings on uncompleted contracts Net contract liabilities $ (8,240) $ (8,698) $ 458 The Company recognized $3.4 million and $35.1 million in revenue for the three and nine months ended September 30, 2023, respectively, which was previously included in contract liabilities at December 31, 2022. The Company recognized $3.0 million and $29.2 million in revenue for the three and nine months ended September 30, 2022, respectively, which was previously included in contract liabilities at December 31, 2021. The Company recognized a net increase in revenues of $12.1 million and $10.6 million for the three and nine months ended September 30, 2023, respectively, from performance obligations satisfied in prior periods. The Company recognized a net increase in revenues of $4.9 million and $10.4 million for the three and nine months ended September 30, 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 September 30, 2023, the Company's remaining performance obligations were $732.2 million. The Company expects to recognize the following revenue amounts in future periods related to these remaining performance obligations: $677.7 million within the next 12 months or less; $38.5 million within the next 13 to 24 months; and $16.0 million in 25 months or more.

Goodwill and other intangible a

Goodwill and other intangible assets	9 Months Ended
	Sep. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and other intangible assets	Goodwill and other intangible assets The changes in the carrying amount of goodwill were as follows: Balance at January 1, 2023 Goodwill Acquired During the Year Measurement Balance at September 30, 2023 (In thousands) Pacific $ 38,339 $ — $ (62) $ 38,277 Northwest 90,978 — — 90,978 Mountain 26,816 — — 26,816 North Central 75,879 — — 75,879 All Other 42,528 — — 42,528 Total $ 274,540 $ — $ (62) $ 274,478 Other amortizable intangible assets were as follows: September 30, 2023 December 31, 2022 (In thousands) Customer relationships $ 18,540 $ 18,540 Less accumulated amortization 8,668 7,367 9,872 11,173 Noncompete agreements 4,039 4,039 Less accumulated amortization 3,358 2,985 681 1,054 Other 2,479 5,279 Less accumulated amortization 1,569 4,076 910 1,203 Total $ 11,463 $ 13,430 Amortization expense for amortizable intangible assets for the three and nine months ended September 30, 2023, was $647,000 and $2.0 million, respectively. Amortization expense for amortizable intangible assets for the three and nine months ended September 30, 2022, was $729,000 and $2.1 million, respectively. Estimated amortization expense for identifiable intangible assets as of September 30, 2023, was: Remainder of 2023 2024 2025 2026 2027 Thereafter (In thousands) Amortization expense $ 590 $ 2,157 $ 2,042 $ 1,739 $ 1,717 $ 3,218

Fair value measurements

Fair value measurements	9 Months Ended
	Sep. 30, 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 ASC 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. 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 $23.5 million and $20.1 million at September 30, 2023 and December 31, 2022, respectively, are classified as investments on the Consolidated Balance Sheets. The net unrealized loss on these investments was $597,000 for the three months ended September 30, 2023 and the net unrealized gain on these investments was $685,000 for the nine months ended September 30, 2023. The net unrealized loss on these investments was $541,000 and $3.2 million for the three and nine months ended September 30, 2022, respectively. 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 $4.8 million, which were used to purchase life insurance policies and re-invested in fixed-income and equity securities in the third quarter of 2023. The Company's assets measured at fair value on a recurring basis were as follows: Fair Value Measurements at September 30, 2023, Using Quoted Prices in Significant Significant Balance at September 30, 2023 (In thousands) Assets: Money market funds $ — $ 3,199 $ — $ 3,199 Insurance contracts* — 23,483 — 23,483 Total assets measured at fair value $ — $ 26,682 $ — $ 26,682 * The insurance contracts invest approximately 41 percent in fixed-income investments, 19 percent in cash equivalents, 18 percent in common stock of large-cap companies, 8 percent in common stock of mid-cap companies, 8 percent target date investments, 5 percent in common stock of small-cap companies and 1 percent in international investments. Fair Value Measurements at December 31, 2022, Using Quoted Prices in Significant 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. 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: September 30, 2023 (In thousands) Carrying amount $ 698,747 Fair value $ 700,687

Debt

Debt	9 Months Ended
	Sep. 30, 2023
Debt Disclosure [Abstract]
Debt	Debt Certain debt instruments of the Company contain restrictive covenants and cross-default provisions. In order to borrow under the debt agreements, 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 September 30, 2023. In the event the Company does not comply with the applicable covenants and other conditions, alternative sources of funding may need to be pursued. On April 25, 2023, the Company issued $425.0 million of 7.75 percent senior notes due May 1, 2031, pursuant to an indenture. On May 31, 2023, the Company entered into a senior secured credit agreement consisting of a $275.0 million term loan and a $350.0 million revolving credit facility. As of September 30, 2023, the Company had no outstanding borrowings against the revolving credit facility. Each debt facility has a SOFR-based interest rate and a maturity date of May 31, 2028. 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 EBITDA 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 EBITDA 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. Knife River's wholly owned subsidiary companies, subject to certain exclusions and exceptions, are named as subsidiary guarantors of the senior notes and the senior secured credit agreement. In addition, Knife River has pledged substantially all of its assets as collateral, subject to certain exclusions and exceptions, for the senior secured credit agreement. Long-term debt Long-term Debt Outstanding Long-term debt outstanding was as follows: Weighted Average Interest Rate at September 30, 2023 September 30, 2023 (In thousands) Term loan agreement due on May 31, 2028 7.52 % $ 273,281 Senior notes due on May 1, 2031 7.75 % 425,000 Other notes due on January 1, 2061 — % 466 Less unamortized debt issuance costs 16,016 Total long-term debt 682,731 Less current maturities 7,082 Net long-term debt $ 675,649 Schedule of Debt Maturities Long-term debt maturities, which excludes unamortized debt issuance costs, at September 30, 2023, were as follows: Remainder of 2023 2024 2025 2026 2027 Thereafter (In thousands) Long-term debt maturities $ 1,719 $ 7,082 $ 10,520 $ 13,802 $ 17,187 $ 648,437

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Income Tax Disclosure	Income taxes Post-Separation, the income tax provisions are calculated based on Knife River's operating footprint, as well as tax return elections and assertions. Current income tax liabilities including amounts for unrecognized tax benefits related to the Company's activities included in MDU Resources' income tax returns were deemed to be immediately settled with MDU Resources' final settlement allocation process as dictated by the MDU Resources' Tax Sharing Agreement. Prior to the Separation, income tax expense and tax balances in the consolidated financial statements were calculated on a separate tax return basis. The separate tax return method applies the accounting guidance for income taxes to the stand-alone financial statements as if the Company were a separate taxpayer and a stand-alone enterprise. Management believes the assumptions supporting the allocation and presentation of income taxes on a separate return basis are reasonable. As a stand-alone entity, the Company will file tax returns on its own behalf, and tax balances and effective income tax rate may differ from the amounts reported in the historical periods. Income tax expense is based on reported income before income taxes. Deferred income taxes reflect the tax effect of temporary differences between asset and liability amounts that are recognized for financial reporting purposes and the amounts that are recognized for income tax purposes. These deferred taxes are measured by applying currently enacted tax laws. Valuation allowances are recognized to reduce deferred tax assets to the amount that will more likely than not be realized. In assessing the need for a valuation allowance, management considers all available evidence for each jurisdiction including past operating results, estimates of future taxable income and the feasibility of ongoing tax planning strategies and actions. When there is a change in determination as to the amount of deferred tax assets that can be realized, the valuation allowance is adjusted with a corresponding impact to provision for income taxes in the period in which such determination is made. The Company's cash tax payments for the year may vary significantly from prior years as a result of the timing of the Separation and the seasonality of the Company's business. Other Tax Matters Tax Matters Agreement In connection with the Separation, the Company entered into a tax matters agreement with MDU Resources. The tax matters agreement governs the respective rights, responsibilities, and obligations between the Company and MDU Resources after the Separation with respect to tax liabilities and benefits, tax attributes, tax returns, tax contests and other tax sharing regarding U.S. federal, state and local income taxes, other tax matters and related tax returns. Tax Refunds and Attributes The tax matters agreement provides for the allocation of certain pre-closing tax attributes between the Company and MDU Resources. Tax attributes will be allocated in accordance with the principles set forth in the MDU Resources' Tax Sharing Agreement, then existing, unless otherwise required by law. Under the tax matters agreement, the Company will be entitled to refunds for taxes for which the Company is responsible.

Cash flow information

Cash flow information	9 Months Ended
	Sep. 30, 2023
Supplemental Cash Flow Information [Abstract]
Cash flow information	Cash flow information Cash expenditures for interest and income taxes were as follows: Nine Months Ended September 30, 2023 2022 (In thousands) Interest paid, net $ 32,028 $ 19,472 Income taxes paid, net $ 22,183 $ 23,163 Noncash investing and financing transactions were as follows: Nine Months Ended September 30, 2023 2022 (In thousands) Right-of-use assets obtained in exchange for new operating lease liabilities $ 9,717 $ 5,851 Property, plant and equipment additions in accounts payable $ 2,832 $ 4,884 Equity contribution from Centennial related to the Separation $ 64,724 $ — Equity contribution to MDU Resources for asset/liability transfers related to the Separation $ (1,548) $ — MDU Resources' stock issued prior to spin in connection with a business combination $ 383 $ —

Business segment data

Business segment data	9 Months Ended
	Sep. 30, 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 organized by geographic region in the United States due to the cyclical nature of the construction work performed. The Company’s reportable segments are those that are based on the Company’s method of internal reporting and management of the business and are Pacific, Northwest, Mountain and North Central. The South and Energy Services operating segments do not meet the criteria to be reportable segments and, as such, are combined with its corporate services in All Other. Each segment is led by a segment president that reports to the Company’s chief operating officer. The chief operating officer works directly with the chief executive officer, the chief operating decision maker, to evaluate the performance of the segments using EBITDA and the allocation of resources. All of the reportable segments mine, process and sell construction aggregates (crushed stone and sand and gravel); produce and sell asphalt; and produce and sell ready-mix concrete, as well as in some segments the sale of merchandise and other building materials and related services, as well as vertically integrating their contracting services to support the aggregate-based product lines including heavy-civil construction, asphalt and concrete paving, and site development and grading, and in some segments the manufacturing of prestressed concrete products. The Pacific segment and All Other also produce and sell liquid asphalt products and the Pacific segment sells cement. Although not common to all locations, within All Other is the sale of merchandise and other building materials and related services . The information below follows the same accounting policies as described in the audited financial statements and notes included in the Company's Registration Statement on Form 10. Information on the Company's segments was as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) External operating revenues: Pacific $ 181,427 $ 152,358 $ 391,368 $ 366,118 Northwest 208,919 204,232 503,573 459,807 Mountain 254,722 204,121 491,094 433,009 North Central 305,120 294,306 513,695 484,369 All Other 140,184 120,411 283,732 253,904 Total external operating revenues $ 1,090,372 $ 975,428 $ 2,183,462 $ 1,997,207 Intersegment operating revenues: Pacific $ 37,566 $ 30,710 $ 75,345 $ 76,911 Northwest 36,683 42,627 84,937 84,733 Mountain 68,178 49,089 108,888 90,654 North Central 111,288 110,700 167,055 162,342 All Other 39,741 26,635 64,479 60,386 Total intersegment operating revenues $ 293,456 $ 259,761 $ 500,704 $ 475,026 EBITDA: Pacific $ 37,558 $ 24,563 $ 56,486 $ 45,194 Northwest 48,867 43,797 102,711 79,774 Mountain 60,473 39,644 86,486 60,244 North Central 70,508 58,584 71,402 50,424 All Other 23,994 5,500 35,323 5,578 Total segment EBITDA $ 241,400 $ 172,088 $ 352,408 $ 241,214 A reconciliation of reportable segment operating revenues to consolidated operating revenues is as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Total reportable segment operating revenues $ 1,203,903 $ 1,088,143 $ 2,335,955 $ 2,157,943 Other operating revenues 179,925 147,046 348,211 314,290 Less: Elimination of intersegment operating revenues 293,456 259,761 500,704 475,026 Total consolidated operating revenues $ 1,090,372 $ 975,428 $ 2,183,462 $ 1,997,207 A reconciliation of reportable segment EBITDA to consolidated income before income taxes is as follows: Three Months Ended Nine Months Ended Sept. 30, Sept. 30, 2023 2022 2023 2022 (In thousands) Total EBITDA for reportable segments $ 217,406 $ 166,588 $ 317,085 $ 235,636 Other EBITDA 23,994 5,500 35,323 5,578 Less: Depreciation, depletion and amortization 31,752 30,450 92,511 88,551 Interest expense, net* 14,774 8,817 41,399 21,506 Total consolidated income before income taxes $ 194,874 $ 132,821 $ 218,498 $ 131,157 * Interest, net is interest expense net of interest income.

Employee benefit plans

Employee benefit plans	9 Months Ended
	Sep. 30, 2023
Retirement Benefits [Abstract]
Employee benefit plans	Employee benefit plans The Company has noncontributory qualified defined benefit pension plans and other postretirement benefit plans for certain eligible employees. Prior to the Separation, Knife River was a participant in the MDU Resources postretirement benefit plan. The Company historically treated its share of the postretirement obligation under that plan as a single employer plan in accordance with ASC 715 - Compensation - Retirement Benefits and recorded the funded status and net periodic benefit cost associated with Knife River employees at Knife River. In connection with the Separation, effective June 1, 2023, Knife River established a new, stand-alone postretirement plan comparable to that of MDU Resources and transferred its obligations of $1.5 million for current participants (inclusive of employees that transferred to the Company from MDU Resources) to that plan. The Company's pension benefit plans were stand-alone for Knife River prior to the Separation. Components of net periodic benefit cost for the Company's pension benefit plans were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Components of net periodic benefit cost: Interest cost $ 408 $ 282 $ 1,224 $ 846 Expected return on assets (450) (493) (1,350) (1,479) Amortization of net actuarial loss 128 214 384 642 Net periodic benefit cost $ 86 $ 3 $ 258 $ 9 Components of net periodic benefit cost for the Company's other postretirement benefit plans were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Components of net periodic benefit cost: Service cost $ 91 $ 131 $ 270 $ 393 Interest cost 180 128 541 384 Expected return on assets — (3) 12 (9) Amortization of prior service credit (20) (20) (60) (60) Amortization of net actuarial (gain) loss (43) 88 (132) 264 Net periodic benefit cost $ 208 $ 324 $ 631 $ 972 The components of net periodic benefit cost, other than the service cost component, are included in other income on the Consolidated Statements of Operations. The service cost component is included in selling, general and administrative expenses on the Consolidated Statements of Operations.

Contingencies

Contingencies	9 Months Ended
	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Contingencies	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 September 30, 2023 and December 31, 2022, the Company accrued contingent liabilities as a result of litigation, which have not been discounted, of $645,000 and $1.0 million, respectively. At December 31, 2022, the Company also recorded corresponding insurance receivables of $325,000 related to the accrued liabilities. 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 The Company is a party to claims for the cleanup of a superfund site in Portland, Oregon. There were no material changes to the Company's environmental matters that were previously reported in the audited financial statements and notes included in the Company's Registration Statement on Form 10. Guarantees Certain subsidiaries of the Company have outstanding obligations to third parties where the Company has guaranteed their performance. These guarantees are related to contracts for contracting services and certain other guarantees. At September 30, 2023, the fixed maximum amounts guaranteed under these agreements aggregated to $11.5 million, all of which have no scheduled maturity date. Certain of the guarantees also have no fixed maximum amounts specified. There were no amounts outstanding under the previously mentioned guarantees at September 30, 2023. Certain subsidiaries of the Company have outstanding letters of credit to third parties related to insurance policies, cement purchases and other agreements. At September 30, 2023, the fixed maximum amounts guaranteed under these letters of credit aggregated $4.8 million. At September 30, 2023, the amounts of scheduled expiration of the maximum amounts guaranteed under these letters of credit aggregate to $4.0 million in 2023 and $771,000 in 2024. There were no amounts outstanding under the previously mentioned letters of credit at September 30, 2023. In the normal course of business, the Company has surety bonds related to contracts for contracting services, reclamation obligations and insurance policies 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 September 30, 2023, approximately $619.2 million of surety bonds were outstanding, which were not reflected on the Consolidated Balance Sheet.

Related Party Disclosures

Related Party Disclosures	9 Months Ended
	Sep. 30, 2023
Related Party Transactions [Abstract]
Related Party Transactions Disclosure	Related-party transactions 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 three and nine months ended September 30, 2023, the Company paid $1.3 million and $1.9 million, respectively, related to these activities, which were reflected in selling, general and administrative expenses on the Consolidated Statements of Operations. For the three and nine months ended September 30, 2023, the Company received $407,000 and $684,000, respectively, related to these activities, which were 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. 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 reflected as "Net transfers from Centennial and MDU Resources including separation adjustments" in the Consolidated Statement of Equity. Refer to Note 12 for additional information on the debt facilities entered into in connection with the Separation. For additional information on the presentation of related-party transactions, see Note 2.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Pay vs Performance Disclosure
Net Income (Loss)	$ 146,655	$ 56,836	$ (41,320)	$ 99,657	$ 38,562	$ (40,010)	$ 162,171	$ 98,210

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Sep. 30, 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

Basis of presentation (Policies

Basis of presentation (Policies)	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	The accompanying consolidated interim financial statements were prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Interim financial statements do not include all disclosures provided in annual financial statements and, accordingly, these financial statements should be read in conjunction with the Company's Registration Statement on Form 10. The information is unaudited but includes adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. On May 31, 2023, the Company became a stand-alone publicly traded company. Prior to the Separation on May 31, 2023, 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. These consolidated financial statements and footnotes reflect the historical financial position, results of operations and cash flows of the Company as historically managed within MDU Resources for the periods prior to the completion of the Separation and reflect the financial position, results of operations and cash flows as a stand-alone company for the period after the completion of the Separation. The historical consolidated financial statements and footnotes were prepared on a “carve-out” basis in connection with the Separation and were derived from the consolidated financial statements of MDU Resources as if the Company operated on a stand-alone basis during the periods presented, and were prepared utilizing the legal entity approach in conformity with GAAP. The results for the three and nine months ended September 30, 2022, vary from the previously reported MDU Resources' construction materials and contracting services segment due to an adjustment to a cost allocation for interim periods to conform with the Company's current year accounting. This adjustment does not impact the historical annual financial statements included in the Company's Registration Statement on Form 10. This adjustment increased cost of revenue for the three months ended September 30, 2022, by $4.4 million ($3.4 million after tax) and decreased cost of revenue for the nine months ended September 30, 2022, by $1.6 million ($1.2 million after tax). The adjustment is not considered material for the three or nine months ended September 30, 2022. The Company utilized allocations and carve-out methodologies to prepare its historical consolidated financial statements and footnotes. The consolidated financial statements and footnotes herein may not be indicative of the Company's future performance or actual expenses that would have been incurred as a stand-alone company for the periods presented. All revenues and costs, as well as assets and liabilities, directly associated with the business activity of the Company are included in the consolidated financial statements. In the periods prior to the Separation, the consolidated financial statements include expense allocations for certain functions provided by MDU Resources and Centennial, including, but not limited to certain general corporate expenses related to senior management, legal, human resources, finance and accounting, treasury, information technology, communications, procurement, tax, insurance and other shared services. These general corporate expenses are included in the Consolidated Statements of Operations within selling, general and administrative expenses and other income (expense). There were no amounts allocated to Knife River for the three months ended September 30, 2023, and $8.7 million was allocated for the nine months ended September 30, 2023. For the three and nine months ended September 30, 2022, there was $3.8 million and $13.4 million, respectively, allocated to Knife River. These expenses have been 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 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. Prior to the Separation, Knife River historically participated in Centennial’s centralized cash management program, including its overall financing arrangements. This arrangement is not reflective of the manner in which the Company would have been able to finance its operations had it been independent from MDU Resources for the period prior to the completion of the Separation. Knife River 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 Sheets as of December 31, 2022. 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 entered into debt agreements and subsequently paid a dividend of $825.0 million from the debt 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 reflected as "Net transfers from Centennial and MDU Resources including separation adjustments" in the Consolidated Statement of Equity. Interest expense in the Consolidated Statements of Operations includes the allocation of interest on borrowing and funding associated with the related-party note agreements for periods prior to the Separation. Prior to the Separation, income tax expense and tax balances in the consolidated financial statements were calculated on a separate tax return basis. The separate tax return method applies the accounting guidance for income taxes to the standalone financial statements as if the Company were a separate taxpayer and a standalone enterprise. Management believes the assumptions supporting the allocation and presentation of income taxes on a separate return basis are reasonable. As a stand-alone entity, the Company will file tax returns on its own behalf, and tax balances and effective income tax rate may differ from the amounts reported in the historical periods. Management has also evaluated the impact of events occurring after September 30, 2023, up to the date of issuance of these consolidated interim financial statements on November 6, 2023, that would require recognition or disclosure in the Consolidated Financial Statements.
Consolidation, Policy	For the pre-Separation periods, the accompanying financial statements of the Company were derived from the consolidated financial statements and accounting records of MDU Resources as if the Company and its wholly owned subsidiaries operated on a stand-alone basis during the periods presented. The 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 consolidated financial statements. Related-party transactions between the Company and MDU Resources or Centennial for general operating activities and intercompany debt have been included in the consolidated financial statements for the pre-Separation periods. These related-party transactions were settled in cash and are reflected in the pre-Separation Consolidated Balance Sheets as “Due from related-party” or “Due to related-party” with the aggregate net effect reflected in the Consolidated Statements of Cash Flows within operating activities and “Related-party notes payable” with the aggregate net effect reflected in the Consolidated Statements of Cash Flows within financing activities. The aggregate net effect of related-party transactions not settled in cash as part of the Separation have been reflected in the pre-Separation Consolidated Balance Sheet within “Other paid-in capital”. See Note 18 for additional information on related-party transactions.
Use of Estimates, Policy	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 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	There have been no recent accounting standards that are expected to materially affect the Company.
Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy	The Company considers all highly liquid investments with an original maturity of three months or less, when purchased, to be cash and cash equivalents.
Seasonality of operations	Some of the Company's operations are seasonal and revenues from, and certain expenses for, such operations may fluctuate significantly among quarterly periods, with lower activity in the winter months and higher activity in the summer months.

Receivables and allowance for_2

Receivables and allowance for expected credit losses (Policies)	9 Months Ended
	Sep. 30, 2023
Credit Loss [Abstract]
Accounts receivable and allowance for doubtful accounts	Receivables consist primarily of trade and contract receivables for 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 loss	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.

Earnings per share (Policies)

Earnings per share (Policies)	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Earnings per share	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.

Revenue from contracts with c_2

Revenue from contracts with customers (Policies)	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Revenue from contracts with customers	Revenue is recognized when a performance obligation is satisfied by transferring control over a product or service to a customer. Revenue includes revenue from the sales of construction materials and contracting services. Revenue is measured based on consideration specified in a contract with a customer and excludes any sales incentives and amounts collected on behalf of third parties. 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. Revenue for construction materials is recognized at a point in time when delivery of the products has taken place. Contracting revenue is recognized over time using an input method based on the cost-to-cost measure of progress on a project.

Fair value disclosures (Policie

Fair value disclosures (Policies)	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Fair value measurements	The Company measures its investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income.

Income Taxes (Policies)

Income Taxes (Policies)	9 Months Ended
	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Income Tax, Policy	Income tax expense is based on reported income before income taxes. Deferred income taxes reflect the tax effect of temporary differences between asset and liability amounts that are recognized for financial reporting purposes and the amounts that are recognized for income tax purposes. These deferred taxes are measured by applying currently enacted tax laws.Valuation allowances are recognized to reduce deferred tax assets to the amount that will more likely than not be realized. In assessing the need for a valuation allowance, management considers all available evidence for each jurisdiction including past operating results, estimates of future taxable income and the feasibility of ongoing tax planning strategies and actions. When there is a change in determination as to the amount of deferred tax assets that can be realized, the valuation allowance is adjusted with a corresponding impact to provision for income taxes in the period in which such determination is made.

Business segment data (Policies

Business segment data (Policies)	9 Months Ended
	Sep. 30, 2023
Segment Reporting [Abstract]
Business segment data	The Company’s reportable segments are those that are based on the Company’s method of internal reporting and management of the business and are Pacific, Northwest, Mountain and North Central. The South and Energy Services operating segments do not meet the criteria to be reportable segments and, as such, are combined with its corporate services in All Other. Each segment is led by a segment president that reports to the Company’s chief operating officer. The chief operating officer works directly with the chief executive officer, the chief operating decision maker, to evaluate the performance of the segments using EBITDA and the allocation of resources.

Contingencies (Policies)

Contingencies (Policies)	9 Months Ended
	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
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.

Receivables and allowance for_3

Receivables and allowance for expected credit losses (Tables)	9 Months Ended
	Sep. 30, 2023
Credit Loss [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable	Receivables were as follows: September 30, 2023 December 31, 2022 (In thousands) Trade receivables $ 236,373 $ 104,347 Contract receivables 223,874 82,428 Retention receivables 37,814 28,859 Receivables, gross 498,061 215,634 Less expected credit loss 6,195 5,477 Receivables, net $ 491,866 $ 210,157
Accounts Receivable, Allowance for Credit Loss	Details of the Company's expected credit losses were as follows: Pacific Northwest Mountain North All Other Total (In thousands) At December 31, 2022 $ 2,045 $ 1,253 $ 1,278 $ 839 $ 62 $ 5,477 Current expected credit loss provision 45 313 164 (89) (1) 432 Less write-offs charged against the allowance 1 68 18 — — 87 At March 31, 2023 $ 2,089 $ 1,498 $ 1,424 $ 750 $ 61 $ 5,822 Current expected credit loss provision 9 74 631 (132) 1 583 Less write-offs charged against the allowance 18 512 3 — 2 535 At June 30, 2023 $ 2,080 $ 1,060 $ 2,052 $ 618 $ 60 $ 5,870 Current expected credit loss provision 46 242 (152) 215 20 371 Less write-offs charged against the allowance 26 4 13 3 — 46 At September 30, 2023 $ 2,100 $ 1,298 $ 1,887 $ 830 $ 80 $ 6,195 Pacific Northwest Mountain North All Other Total (In thousands) At December 31, 2021 $ 2,052 $ 512 $ 1,610 $ 1,152 $ 80 $ 5,406 Current expected credit loss provision 1 (125) (130) 6 (5) (253) Less write-offs charged against the allowance 1 20 3 1 1 26 At March 31, 2022 $ 2,052 $ 367 $ 1,477 $ 1,157 $ 74 $ 5,127 Current expected credit loss provision 11 58 (17) (37) (3) 12 Less write-offs charged against the allowance — 56 4 47 2 109 At June 30, 2022 $ 2,063 $ 369 $ 1,456 $ 1,073 $ 69 $ 5,030 Current expected credit loss provision (6) 194 (111) (141) 9 (55) Less write-offs charged against the allowance 9 7 40 4 16 76 At September 30, 2022 $ 2,048 $ 556 $ 1,305 $ 928 $ 62 $ 4,899

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2023
Inventory Disclosure [Abstract]
Inventories	Inventories on the Consolidated Balance Sheets were as follows: September 30, 2023 December 31, 2022 (In thousands) Finished products $ 213,702 $ 211,496 Raw materials 63,156 78,571 Supplies and parts 37,853 33,210 Total $ 314,711 $ 323,277

Earnings per share (Tables)

Earnings per share (Tables)	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Weighted average common shares outstanding	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: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands, except per share amounts) Net income $ 146,655 $ 99,657 $ 162,171 $ 98,210 Weighted average common shares outstanding - basic 56,566 56,566 56,566 56,566 Effect of dilutive restricted stock units 169 — 67 — Weighted average common shares outstanding - diluted 56,735 56,566 56,633 56,566 Shares excluded from the calculation of diluted earnings per share — — — — Net income per share - basic $ 2.59 $ 1.76 $ 2.87 $ 1.74 Net income per share - diluted $ 2.58 $ 1.76 $ 2.86 $ 1.74

Accumulated other comprehensi_2

Accumulated other comprehensive loss (Tables)	9 Months Ended
	Sep. 30, 2023
Equity [Abstract]
Accumulated comprehensive loss	The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Unrealized Postretirement Total (In thousands) At December 31, 2022 $ (90) $ (12,262) $ (12,352) Amounts reclassified from accumulated other comprehensive loss 46 47 93 Net current-period other comprehensive income 46 47 93 At March 31, 2023 $ (44) $ (12,215) $ (12,259) Other comprehensive loss before reclassification — (17) (17) Amounts reclassified from accumulated other comprehensive loss 44 48 92 Net current-period other comprehensive income 44 31 75 At June 30, 2023 $ — $ (12,184) $ (12,184) Other comprehensive loss before reclassification — — — Amounts reclassified from accumulated other comprehensive loss — 49 49 Net current-period other comprehensive income — 49 49 At September 30, 2023 $ — $ (12,135) $ (12,135) Net Unrealized Postretirement Total (In thousands) At December 31, 2021 $ (418) $ (24,072) $ (24,490) Amounts reclassified from accumulated other comprehensive loss 82 221 303 Net current-period other comprehensive income 82 221 303 At March 31, 2022 $ (336) $ (23,851) $ (24,187) Other comprehensive income before reclassification — 5,820 5,820 Amounts reclassified from accumulated other comprehensive loss 82 220 302 Net current-period other comprehensive income 82 6,040 6,122 At June 30, 2022 $ (254) $ (17,811) $ (18,065) Amounts reclassified from accumulated other comprehensive loss 82 221 303 Net current-period other comprehensive income 82 221 303 At September 30, 2022 $ (172) $ (17,590) $ (17,762)
Reclassification out of accumulated other comprehensive loss	The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Operations. The reclassifications were as follows: Three Months Ended Nine Months Ended Location on Consolidated Statements of Operations September 30, September 30, 2023 2022 2023 2022 (In thousands) Reclassification adjustment for loss on derivative income $ — $ (109) $ (118) $ (326) Interest expense — 27 28 80 Income taxes — (82) (90) (246) Amortization of postretirement liability losses included in net periodic benefit cost (65) (292) (191) (875) Other income 16 71 47 213 Income taxes (49) (221) (144) (662) Total reclassifications $ (49) $ (303) $ (234) $ (908)

Revenue from contracts with c_3

Revenue from contracts with customers (Tables)	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Disaggregation of revenue	In the following tables, revenue is disaggregated by category for each segment and includes sales of materials to both third parties and internal customers. Due to consolidation requirements, the internal sales revenues must be eliminated against the construction materials product used in downstream materials and contracting services to arrive at the external operating revenues. 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. Three Months Ended September 30, 2023 Pacific Northwest Mountain North All Other Total (In thousands) Aggregates $ 33,624 $ 57,398 $ 39,519 $ 47,656 $ 15,388 $ 193,585 Ready-mix concrete 39,861 46,785 44,053 73,183 12,157 216,039 Asphalt 14,050 43,462 59,673 95,053 10,539 222,777 Other 81,081 4,497 11 10,211 118,312 214,112 Contracting services public-sector 32,632 68,316 135,700 181,779 23,483 441,910 Contracting services private-sector 17,745 25,144 43,944 8,526 46 95,405 Internal sales (37,566) (36,683) (68,178) (111,288) (39,741) (293,456) Revenues from contracts with customers $ 181,427 $ 208,919 $ 254,722 $ 305,120 $ 140,184 $ 1,090,372 Three Months Ended September 30, 2022 Pacific Northwest Mountain North All Other Total (In thousands) Aggregates $ 28,695 $ 52,614 $ 31,258 $ 45,039 $ 14,197 $ 171,803 Ready-mix concrete 35,395 45,600 37,334 64,496 16,082 198,907 Asphalt 10,935 45,110 45,553 96,830 7,133 205,561 Other 63,002 4,447 12 8,711 90,539 166,711 Contracting services public-sector 30,529 78,664 100,298 184,266 18,874 412,631 Contracting services private-sector 14,512 20,424 38,755 5,664 221 79,576 Internal sales (30,710) (42,627) (49,089) (110,700) (26,635) (259,761) Revenues from contracts with customers $ 152,358 $ 204,232 $ 204,121 $ 294,306 $ 120,411 $ 975,428 Nine Months Ended September 30, 2023 Pacific Northwest Mountain North All Other Total (In thousands) Aggregates $ 79,768 $ 147,937 $ 78,051 $ 81,999 $ 35,767 $ 423,522 Ready-mix concrete 106,531 125,273 92,929 139,369 33,604 497,706 Asphalt 21,640 84,908 89,955 141,942 22,888 361,333 Other 168,104 11,513 21 22,703 193,528 395,869 Contracting services public-sector 53,450 138,621 244,320 280,853 61,293 778,537 Contracting services private-sector 37,220 80,258 94,706 13,884 1,131 227,199 Internal sales (75,345) (84,937) (108,888) (167,055) (64,479) (500,704) Revenues from contracts with customers $ 391,368 $ 503,573 $ 491,094 $ 513,695 $ 283,732 $ 2,183,462 Nine Months Ended September 30, 2022 Pacific Northwest Mountain North All Other Total (In thousands) Aggregates $ 72,088 $ 129,752 $ 67,388 $ 75,718 $ 40,892 $ 385,838 Ready-mix concrete 98,520 121,079 84,950 124,026 46,959 475,534 Asphalt 26,909 79,801 77,021 141,595 19,886 345,212 Other 143,140 11,804 26 20,766 152,757 328,493 Contracting services public-sector 63,450 141,783 202,495 275,797 52,933 736,458 Contracting services private-sector 38,922 60,321 91,783 8,809 863 200,698 Internal Sales (76,911) (84,733) (90,654) (162,342) (60,386) (475,026) Revenues from contracts with customers $ 366,118 $ 459,807 $ 433,009 $ 484,369 $ 253,904 $ 1,997,207

Uncompleted contracts (Tables)

Uncompleted contracts (Tables)	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Contract balances	The changes in contract assets and liabilities were as follows: September 30, 2023 December 31, 2022 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 50,545 $ 31,145 $ 19,400 Costs and estimated earnings in excess of billings on uncompleted contracts Contract liabilities (58,785) (39,843) (18,942) Billings in excess of costs and estimated earnings on uncompleted contracts Net contract liabilities $ (8,240) $ (8,698) $ 458

Goodwill and other intangible_2

Goodwill and other intangible assets (Tables)	9 Months Ended
	Sep. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the carrying amount of goodwill	The changes in the carrying amount of goodwill were as follows: Balance at January 1, 2023 Goodwill Acquired During the Year Measurement Balance at September 30, 2023 (In thousands) Pacific $ 38,339 $ — $ (62) $ 38,277 Northwest 90,978 — — 90,978 Mountain 26,816 — — 26,816 North Central 75,879 — — 75,879 All Other 42,528 — — 42,528 Total $ 274,540 $ — $ (62) $ 274,478
Other amortizable intangible assets	Other amortizable intangible assets were as follows: September 30, 2023 December 31, 2022 (In thousands) Customer relationships $ 18,540 $ 18,540 Less accumulated amortization 8,668 7,367 9,872 11,173 Noncompete agreements 4,039 4,039 Less accumulated amortization 3,358 2,985 681 1,054 Other 2,479 5,279 Less accumulated amortization 1,569 4,076 910 1,203 Total $ 11,463 $ 13,430
Estimated amortization expense	Estimated amortization expense for identifiable intangible assets as of September 30, 2023, was: Remainder of 2023 2024 2025 2026 2027 Thereafter (In thousands) Amortization expense $ 590 $ 2,157 $ 2,042 $ 1,739 $ 1,717 $ 3,218

Fair value measurements (Tables

Fair value measurements (Tables)	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Assets and liabilities measured at fair value on a recurring basis	The Company's assets measured at fair value on a recurring basis were as follows: Fair Value Measurements at September 30, 2023, Using Quoted Prices in Significant Significant Balance at September 30, 2023 (In thousands) Assets: Money market funds $ — $ 3,199 $ — $ 3,199 Insurance contracts* — 23,483 — 23,483 Total assets measured at fair value $ — $ 26,682 $ — $ 26,682 * The insurance contracts invest approximately 41 percent in fixed-income investments, 19 percent in cash equivalents, 18 percent in common stock of large-cap companies, 8 percent in common stock of mid-cap companies, 8 percent target date investments, 5 percent in common stock of small-cap companies and 1 percent in international investments. Fair Value Measurements at December 31, 2022, Using Quoted Prices in Significant 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.
Fair Value, by Balance Sheet Grouping	The estimated fair value of the Company's Level 2 long-term debt was as follows: September 30, 2023 (In thousands) Carrying amount $ 698,747 Fair value $ 700,687

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2023
Debt Disclosure [Abstract]
Long-term debt outstanding	Long-term debt outstanding was as follows: Weighted Average Interest Rate at September 30, 2023 September 30, 2023 (In thousands) Term loan agreement due on May 31, 2028 7.52 % $ 273,281 Senior notes due on May 1, 2031 7.75 % 425,000 Other notes due on January 1, 2061 — % 466 Less unamortized debt issuance costs 16,016 Total long-term debt 682,731 Less current maturities 7,082 Net long-term debt $ 675,649
Schedule of debt maturities	Long-term debt maturities, which excludes unamortized debt issuance costs, at September 30, 2023, were as follows: Remainder of 2023 2024 2025 2026 2027 Thereafter (In thousands) Long-term debt maturities $ 1,719 $ 7,082 $ 10,520 $ 13,802 $ 17,187 $ 648,437

Cash flow information (Tables)

Cash flow information (Tables)	9 Months Ended
	Sep. 30, 2023
Supplemental Cash Flow Information [Abstract]
Cash expenditures for interest and income taxes and noncash investing and financing transactions	Cash expenditures for interest and income taxes were as follows: Nine Months Ended September 30, 2023 2022 (In thousands) Interest paid, net $ 32,028 $ 19,472 Income taxes paid, net $ 22,183 $ 23,163 Noncash investing and financing transactions were as follows: Nine Months Ended September 30, 2023 2022 (In thousands) Right-of-use assets obtained in exchange for new operating lease liabilities $ 9,717 $ 5,851 Property, plant and equipment additions in accounts payable $ 2,832 $ 4,884 Equity contribution from Centennial related to the Separation $ 64,724 $ — Equity contribution to MDU Resources for asset/liability transfers related to the Separation $ (1,548) $ — MDU Resources' stock issued prior to spin in connection with a business combination $ 383 $ —

Business segment data (Tables)

Business segment data (Tables)	9 Months Ended
	Sep. 30, 2023
Segment Reporting [Abstract]
Information on the Company's businesses	Information on the Company's segments was as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) External operating revenues: Pacific $ 181,427 $ 152,358 $ 391,368 $ 366,118 Northwest 208,919 204,232 503,573 459,807 Mountain 254,722 204,121 491,094 433,009 North Central 305,120 294,306 513,695 484,369 All Other 140,184 120,411 283,732 253,904 Total external operating revenues $ 1,090,372 $ 975,428 $ 2,183,462 $ 1,997,207 Intersegment operating revenues: Pacific $ 37,566 $ 30,710 $ 75,345 $ 76,911 Northwest 36,683 42,627 84,937 84,733 Mountain 68,178 49,089 108,888 90,654 North Central 111,288 110,700 167,055 162,342 All Other 39,741 26,635 64,479 60,386 Total intersegment operating revenues $ 293,456 $ 259,761 $ 500,704 $ 475,026 EBITDA: Pacific $ 37,558 $ 24,563 $ 56,486 $ 45,194 Northwest 48,867 43,797 102,711 79,774 Mountain 60,473 39,644 86,486 60,244 North Central 70,508 58,584 71,402 50,424 All Other 23,994 5,500 35,323 5,578 Total segment EBITDA $ 241,400 $ 172,088 $ 352,408 $ 241,214
Reconciliation of Revenue from Segments to Consolidated	A reconciliation of reportable segment operating revenues to consolidated operating revenues is as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Total reportable segment operating revenues $ 1,203,903 $ 1,088,143 $ 2,335,955 $ 2,157,943 Other operating revenues 179,925 147,046 348,211 314,290 Less: Elimination of intersegment operating revenues 293,456 259,761 500,704 475,026 Total consolidated operating revenues $ 1,090,372 $ 975,428 $ 2,183,462 $ 1,997,207
Segment, Reconciliation of Other Items from Segments to Consolidated	A reconciliation of reportable segment EBITDA to consolidated income before income taxes is as follows: Three Months Ended Nine Months Ended Sept. 30, Sept. 30, 2023 2022 2023 2022 (In thousands) Total EBITDA for reportable segments $ 217,406 $ 166,588 $ 317,085 $ 235,636 Other EBITDA 23,994 5,500 35,323 5,578 Less: Depreciation, depletion and amortization 31,752 30,450 92,511 88,551 Interest expense, net* 14,774 8,817 41,399 21,506 Total consolidated income before income taxes $ 194,874 $ 132,821 $ 218,498 $ 131,157 * Interest, net is interest expense net of interest income.

Employee benefit plans (Tables)

Employee benefit plans (Tables)	9 Months Ended
	Sep. 30, 2023
Retirement Benefits [Abstract]
Schedule of net benefit costs	Components of net periodic benefit cost for the Company's pension benefit plans were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Components of net periodic benefit cost: Interest cost $ 408 $ 282 $ 1,224 $ 846 Expected return on assets (450) (493) (1,350) (1,479) Amortization of net actuarial loss 128 214 384 642 Net periodic benefit cost $ 86 $ 3 $ 258 $ 9 Components of net periodic benefit cost for the Company's other postretirement benefit plans were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Components of net periodic benefit cost: Service cost $ 91 $ 131 $ 270 $ 393 Interest cost 180 128 541 384 Expected return on assets — (3) 12 (9) Amortization of prior service credit (20) (20) (60) (60) Amortization of net actuarial (gain) loss (43) 88 (132) 264 Net periodic benefit cost $ 208 $ 324 $ 631 $ 972

Background (Details)

Background (Details)	May 31, 2023
Restructuring and Related Activities [Abstract]
Percent of Shares Distributed in Conjunction with Spinoff	90%
Percent of Shares, Retained by Parent, in Conjunction with Spinoff	10%

Basis of presentation (Details)

Basis of presentation (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	May 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Form 10 Separation Adjustments to Costs of Goods Sold			$ 4.4		$ (1.6)
Form 10 Separation Adjustments to Net Income			3.4		(1.2)
Costs and Expenses, Related Party		$ 0	$ 3.8	$ 8.7	$ 13.4
Related-party notes payable to Centennial	$ 889.7
Dividend paid from debt proceeds to Centennial	825
Net contribution from Centennial after repayment of notes	$ 64.7

Basis of presentation (Details

Basis of presentation (Details 2) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash, cash equivalents and restricted cash	$ 116,159	$ 10,090	$ 19,028	$ 13,848
Cash and cash equivalents	84,000
Restricted cash	$ 32,200		$ 0

Receivables and allowance for_4

Receivables and allowance for expected credit losses (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Credit Loss [Abstract]
Accounts Receivable, Noncurrent, 90 Days or More Past Due, Still Accruing	$ 14.4	$ 11.2

Receivables and allowance for_5

Receivables and allowance for expected credit losses (Details 2) - Trade Accounts Receivable - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	$ 236,373			$ 104,347
Contract receivables	223,874			82,428
Retention receivables	37,814			28,859
Receivables, gross	498,061			215,634
Less expected credit loss	6,195	$ 5,870	$ 5,822	5,477	$ 4,899	$ 5,030	$ 5,127	$ 5,406
Receivables, net	$ 491,866			$ 210,157

Receivables and allowance for_6

Receivables and allowance for expected credit losses (Details 3) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses							$ 1,386	$ (296)
Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	$ 5,870	$ 5,822	$ 5,477	$ 5,030	$ 5,127	$ 5,406	5,477	5,406
Provision for credit losses	371	583	432	(55)	12	(253)
Less write-offs charged against the allowance	46	535	87	76	109	26
Balance	6,195	5,870	5,822	4,899	5,030	5,127	6,195	4,899
Pacific | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	2,080	2,089	2,045	2,063	2,052	2,052	2,045	2,052
Provision for credit losses	46	9	45	(6)	11	1
Less write-offs charged against the allowance	26	18	1	9	0	1
Balance	2,100	2,080	2,089	2,048	2,063	2,052	2,100	2,048
Northwest | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	1,060	1,498	1,253	369	367	512	1,253	512
Provision for credit losses	242	74	313	194	58	(125)
Less write-offs charged against the allowance	4	512	68	7	56	20
Balance	1,298	1,060	1,498	556	369	367	1,298	556
Mountain | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	2,052	1,424	1,278	1,456	1,477	1,610	1,278	1,610
Provision for credit losses	(152)	631	164	(111)	(17)	(130)
Less write-offs charged against the allowance	13	3	18	40	4	3
Balance	1,887	2,052	1,424	1,305	1,456	1,477	1,887	1,305
North Central | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	618	750	839	1,073	1,157	1,152	839	1,152
Provision for credit losses	215	(132)	(89)	(141)	(37)	6
Less write-offs charged against the allowance	3	0	0	4	47	1
Balance	830	618	750	928	1,073	1,157	830	928
All Other | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	60	61	62	69	74	80	62	80
Provision for credit losses	20	1	(1)	9	(3)	(5)
Less write-offs charged against the allowance	0	2	0	16	2	1
Balance	$ 80	$ 60	$ 61	$ 62	$ 69	$ 74	$ 80	$ 62

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Inventory Disclosure [Abstract]
Finished products	$ 213,702	$ 211,496
Raw materials	63,156	78,571
Supplies and parts	37,853	33,210
Total	$ 314,711	$ 323,277

Earnings per share (Details 1)

Earnings per share (Details 1) - shares	May 31, 2023	Dec. 31, 2022
Earnings Per Share [Abstract]
Common Stock, Shares, Issued	56,997,350	80,000
Treasury Stock, Common, Shares	(431,136)

Earnings per share (Details 2)

Earnings per share (Details 2) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Net Income (Loss)	$ 146,655	$ 56,836	$ (41,320)	$ 99,657	$ 38,562	$ (40,010)	$ 162,171	$ 98,210
Weighted Average Number of Shares Outstanding, Basic	56,566			56,566			56,566	56,566
Effect of dilutive restricted stock units	169			0			67	0
Weighted average common shares outstanding - diluted	56,735			56,566			56,633	56,566
Shares excluded from the calculation of diluted earnings per share	0			0			0	0
Income per share, Basic, Total	$ 2.59			$ 1.76			$ 2.87	$ 1.74
Income per share, Diluted, Total	$ 2.58			$ 1.76			$ 2.86	$ 1.74

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	May 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Class of Stock [Line Items]
Common Stock, Shares, Issued			56,997,350		80,000
Common Stock, Par or Stated Value Per Share	$ 0.01		$ 0.01		$ 10
MDU Resources Common Stock Held by Subsidiary at Cost, Shares			538,921		(538,921)
Treasury Stock, Common, Shares			431,136
Total stockholders' equity	$ 1,243,018	$ 1,094,852		$ 974,769	$ 1,028,589	$ 1,011,316	$ 923,988	$ 897,035	$ 952,844
MDU Resources' Common Stock Held by Subsidiary
Class of Stock [Line Items]
Total stockholders' equity	$ 3,600

Accumulated other comprehensi_3

Accumulated other comprehensive loss (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Accumulated other comprehensive loss [Roll Forward]
Balance	$ 1,094,852	$ 974,769	$ 1,028,589	$ 923,988	$ 897,035	$ 952,844	$ 1,028,589	$ 952,844
Net current-period other comprehensive income	49	75	93	303	6,122	303	217	6,728
Balance	1,243,018	1,094,852	974,769	1,011,316	923,988	897,035	1,243,018	1,011,316
Net unrealized loss on derivative instruments qualifying as hedges
Accumulated other comprehensive loss [Roll Forward]
Balance	0	(44)	(90)	(254)	(336)	(418)	(90)	(418)
Amounts reclassified from accumulated other comprehensive loss	0	44	46	82	82	82
Other comprehensive income (loss) before reclassifications	0	0			0
Net current-period other comprehensive income	0	44	46	82	82	82
Balance	0	0	(44)	(172)	(254)	(336)	0	(172)
Postretirement liability adjustment
Accumulated other comprehensive loss [Roll Forward]
Balance	(12,184)	(12,215)	(12,262)	(17,811)	(23,851)	(24,072)	(12,262)	(24,072)
Amounts reclassified from accumulated other comprehensive loss	49	48	47	221	220	221
Other comprehensive income (loss) before reclassifications	0	(17)			5,820
Net current-period other comprehensive income	49	31	47	221	6,040	221
Balance	(12,135)	(12,184)	(12,215)	(17,590)	(17,811)	(23,851)	(12,135)	(17,590)
Total accumulated other comprehensive loss
Accumulated other comprehensive loss [Roll Forward]
Balance	(12,184)	(12,259)	(12,352)	(18,065)	(24,187)	(24,490)	(12,352)	(24,490)
Amounts reclassified from accumulated other comprehensive loss	49	92	93	303	302	303
Other comprehensive income (loss) before reclassifications	0	(17)			5,820
Net current-period other comprehensive income	49	75	93	303	6,122	303
Balance	$ (12,135)	$ (12,184)	$ (12,259)	$ (17,762)	$ (18,065)	$ (24,187)	$ (12,135)	$ (17,762)

Reclassification out of accumul

Reclassification out of accumulated other comprehensive loss (Details 2) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Interest expense	$ (15,354)			$ (8,817)			$ (44,005)	$ (21,506)
Income tax expense	(48,219)			(33,164)			(56,327)	(32,947)
Other income	7			(1,277)			3,311	(6,056)
Net Income (Loss)	146,655	$ 56,836	$ (41,320)	99,657	$ 38,562	$ (40,010)	162,171	98,210
Reclassification out of accumulated other comprehensive loss
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Net Income (Loss)	(49)			(303)			(234)	(908)
Reclassification adjustment for loss on derivative income | Reclassification out of accumulated other comprehensive loss | Interest rate contract
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Interest expense	0			(109)			(118)	(326)
Income tax expense	0			27			28	80
Net Income (Loss)	0			(82)			(90)	(246)
Amortization of postretirement liability losses included in net periodic benefit cost | Reclassification out of accumulated other comprehensive loss
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Income tax expense	16			71			47	213
Other income	(65)			(292)			(191)	(875)
Net Income (Loss)	$ (49)			$ (221)			$ (144)	$ (662)

Disaggregation of revenue (Deta

Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenues	$ 1,090,372	$ 975,428	$ 2,183,462	$ 1,997,207
Aggregates
Disaggregation of Revenue [Line Items]
Revenues	193,585	171,803	423,522	385,838
Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	216,039	198,907	497,706	475,534
Asphalt
Disaggregation of Revenue [Line Items]
Revenues	222,777	205,561	361,333	345,212
Other
Disaggregation of Revenue [Line Items]
Revenues	214,112	166,711	395,869	328,493
Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	441,910	412,631	778,537	736,458
Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	95,405	79,576	227,199	200,698
Internal sales
Disaggregation of Revenue [Line Items]
Revenues	(293,456)	(259,761)	(500,704)	(475,026)
Pacific
Disaggregation of Revenue [Line Items]
Revenues	181,427	152,358	391,368	366,118
Pacific | Aggregates
Disaggregation of Revenue [Line Items]
Revenues	33,624	28,695	79,768	72,088
Pacific | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	39,861	35,395	106,531	98,520
Pacific | Asphalt
Disaggregation of Revenue [Line Items]
Revenues	14,050	10,935	21,640	26,909
Pacific | Other
Disaggregation of Revenue [Line Items]
Revenues	81,081	63,002	168,104	143,140
Pacific | Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	32,632	30,529	53,450	63,450
Pacific | Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	17,745	14,512	37,220	38,922
Pacific | Internal sales
Disaggregation of Revenue [Line Items]
Revenues	(37,566)	(30,710)	(75,345)	(76,911)
Northwest
Disaggregation of Revenue [Line Items]
Revenues	208,919	204,232	503,573	459,807
Northwest | Aggregates
Disaggregation of Revenue [Line Items]
Revenues	57,398	52,614	147,937	129,752
Northwest | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	46,785	45,600	125,273	121,079
Northwest | Asphalt
Disaggregation of Revenue [Line Items]
Revenues	43,462	45,110	84,908	79,801
Northwest | Other
Disaggregation of Revenue [Line Items]
Revenues	4,497	4,447	11,513	11,804
Northwest | Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	68,316	78,664	138,621	141,783
Northwest | Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	25,144	20,424	80,258	60,321
Northwest | Internal sales
Disaggregation of Revenue [Line Items]
Revenues	(36,683)	(42,627)	(84,937)	(84,733)
Mountain
Disaggregation of Revenue [Line Items]
Revenues	254,722	204,121	491,094	433,009
Mountain | Aggregates
Disaggregation of Revenue [Line Items]
Revenues	39,519	31,258	78,051	67,388
Mountain | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	44,053	37,334	92,929	84,950
Mountain | Asphalt
Disaggregation of Revenue [Line Items]
Revenues	59,673	45,553	89,955	77,021
Mountain | Other
Disaggregation of Revenue [Line Items]
Revenues	11	12	21	26
Mountain | Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	135,700	100,298	244,320	202,495
Mountain | Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	43,944	38,755	94,706	91,783
Mountain | Internal sales
Disaggregation of Revenue [Line Items]
Revenues	(68,178)	(49,089)	(108,888)	(90,654)
North Central
Disaggregation of Revenue [Line Items]
Revenues	305,120	294,306	513,695	484,369
North Central | Aggregates
Disaggregation of Revenue [Line Items]
Revenues	47,656	45,039	81,999	75,718
North Central | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	73,183	64,496	139,369	124,026
North Central | Asphalt
Disaggregation of Revenue [Line Items]
Revenues	95,053	96,830	141,942	141,595
North Central | Other
Disaggregation of Revenue [Line Items]
Revenues	10,211	8,711	22,703	20,766
North Central | Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	181,779	184,266	280,853	275,797
North Central | Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	8,526	5,664	13,884	8,809
North Central | Internal sales
Disaggregation of Revenue [Line Items]
Revenues	(111,288)	(110,700)	(167,055)	(162,342)
All Other
Disaggregation of Revenue [Line Items]
Revenues	140,184	120,411	283,732	253,904
All Other | Aggregates
Disaggregation of Revenue [Line Items]
Revenues	15,388	14,197	35,767	40,892
All Other | Ready-mix concrete
Disaggregation of Revenue [Line Items]
Revenues	12,157	16,082	33,604	46,959
All Other | Asphalt
Disaggregation of Revenue [Line Items]
Revenues	10,539	7,133	22,888	19,886
All Other | Other
Disaggregation of Revenue [Line Items]
Revenues	118,312	90,539	193,528	152,757
All Other | Contracting services public-sector
Disaggregation of Revenue [Line Items]
Revenues	23,483	18,874	61,293	52,933
All Other | Contracting services private-sector
Disaggregation of Revenue [Line Items]
Revenues	46	221	1,131	863
All Other | Internal sales
Disaggregation of Revenue [Line Items]
Revenues	$ (39,741)	$ (26,635)	$ (64,479)	$ (60,386)

Contract Balances (Details)

Contract Balances (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Contract assets	$ 50,545		$ 50,545		$ 31,145
Change in contract assets			19,400
Contract liabilities	(58,785)		(58,785)		(39,843)
Contract with Customer, Liability, Current Change			(18,942)
Net contract liabilities	(8,240)		(8,240)		$ (8,698)
Change in net contract assets (liabilities)			458
Amounts included in contract liability at the beginning of the period	3,400	$ 3,000	35,100	$ 29,200
Contract with customer, performance obligation satisfied in previous period	$ 12,100	$ 4,900	$ 10,600	$ 10,400

Uncompleted contracts remaining

Uncompleted contracts remaining performance obligations (Details 2) $ in Millions	Sep. 30, 2023 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 732.2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 677.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 38.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	13 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 16
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	25 months

Goodwill rollforward (Details)

Goodwill rollforward (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2023 USD ($)
Goodwill [Roll Forward]
Balance at beginning of period	$ 274,540
Goodwill acquired during the year	0
Measurement period adjustments	(62)
Balance at end of period	274,478
Pacific
Goodwill [Roll Forward]
Balance at beginning of period	38,339
Goodwill acquired during the year	0
Measurement period adjustments	(62)
Balance at end of period	38,277
Northwest
Goodwill [Roll Forward]
Balance at beginning of period	90,978
Goodwill acquired during the year	0
Measurement period adjustments	0
Balance at end of period	90,978
Mountain
Goodwill [Roll Forward]
Balance at beginning of period	26,816
Goodwill acquired during the year	0
Measurement period adjustments	0
Balance at end of period	26,816
North Central
Goodwill [Roll Forward]
Balance at beginning of period	75,879
Goodwill acquired during the year	0
Measurement period adjustments	0
Balance at end of period	75,879
All Other
Goodwill [Roll Forward]
Balance at beginning of period	42,528
Goodwill acquired during the year	0
Measurement period adjustments	0
Balance at end of period	$ 42,528

Other intangible assets (Detail

Other intangible assets (Details 2) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	$ 11,463,000		$ 11,463,000		$ 13,430,000
Amortization of intangible assets	647,000	$ 729,000	2,000,000	$ 2,100,000
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	18,540,000		18,540,000		18,540,000
Intangible assets, less accumulated amortization	8,668,000		8,668,000		7,367,000
Intangible assets, net (excluding goodwill)	9,872,000		9,872,000		11,173,000
Noncompete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	4,039,000		4,039,000		4,039,000
Intangible assets, less accumulated amortization	3,358,000		3,358,000		2,985,000
Intangible assets, net (excluding goodwill)	681,000		681,000		1,054,000
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	2,479,000		2,479,000		5,279,000
Intangible assets, less accumulated amortization	1,569,000		1,569,000		4,076,000
Intangible assets, net (excluding goodwill)	$ 910,000		$ 910,000		$ 1,203,000

Future amortization expense (De

Future amortization expense (Details 3) $ in Thousands	Sep. 30, 2023 USD ($)
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Remainder of 2023	$ 590
2024	2,157
2025	2,042
2026	1,739
2027	1,717
Thereafter	$ 3,218

Fair value measurements insuran

Fair value measurements insurance contracts (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Investments used to satisfy nonqualified benefit plans obligations	$ 23,500,000		$ 23,500,000		$ 20,100,000
Net unrealized gain (loss) on investments used to satisfy obligations under nonqualified benefit plans	(597,000)	$ (541,000)	685,000	$ (3,200,000)
Proceeds from Retired Contracts as part of the Separation	$ 4,800,000		$ 4,800,000

Fair value measurements (Detail

Fair value measurements (Details 2) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Concentration risks, percentage [Abstract]
Percentage in fixed-income and other investments	41%	63%
Percentage investment in cash and cash equivalents	19%	2%
Percentage investment in common stock of large-cap companies	18%	15%
Percentage investment in common stock of mid-cap companies	8%	8%
Percentage investment in target date investments	8%	6%
Percentage investment in common stock of small-cap companies	5%	6%
Percentage investment in international investments	1%
Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 26,682	$ 22,531
Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	26,682	22,531
Money market funds | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	3,199	2,448
Money market funds | Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	3,199	2,448
Insurance contracts* | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	23,483	20,083
Insurance contracts* | Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 23,483	$ 20,083

Fair value measures and disclos

Fair value measures and disclosures (Details 3) $ in Thousands	Sep. 30, 2023 USD ($)
Fair value, balance sheet grouping [Line Items]
Long-term debt	$ 682,731
Reported Value Measurement [Member]
Fair value, balance sheet grouping [Line Items]
Long-term debt	698,747
Estimate of Fair Value Measurement [Member]
Fair value, balance sheet grouping [Line Items]
Long-term debt, fair value	$ 700,687

Long-term debt outstanding (Det

Long-term debt outstanding (Details 1) - USD ($) $ in Thousands		9 Months Ended
	May 31, 2023	Sep. 30, 2023	Apr. 25, 2023	Dec. 31, 2022
Long-term debt outstanding [Line Items]
Long-term debt		$ 682,731
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%
Maximum Distributions To The Company As A Ratio Of Average Consolidated Indebtedness To Consolidated EBITDA		4.75%
Minimum Interest Coverage To The Company As A Ratio Of Average Interest Expense To Consolidated EBITDA		2.25%
Long-term debt - current portion		$ 7,082		$ 211
Long-Term Debt, Excluding Current Maturities		675,649		$ 427
Senior Notes
Long-term debt outstanding [Line Items]
Long-term debt		$ 425,000	$ 425,000
Long-Term Debt, Percentage Bearing Fixed Interest, Percentage Rate			7.75%
Weighted Average Interest Rate		7.75%
Loans Payable
Long-term debt outstanding [Line Items]
Long-term debt	$ 275,000	$ 273,281
Weighted Average Interest Rate		7.52%
Revolving Credit Facility
Long-term debt outstanding [Line Items]
Long-term debt	350,000
Draw Down on Revolver	$ 190,000
Other Notes
Long-term debt outstanding [Line Items]
Long-term debt		$ 466
Weighted Average Interest Rate		0%
Long-term Debt
Long-term debt outstanding [Line Items]
Unamortized Debt Issuance Costs		$ 16,016

Schedule of debt maturities (De

Schedule of debt maturities (Details 2) $ in Thousands	Sep. 30, 2023 USD ($)
Long-term debt maturities [Line Items]
Remainder of 2023	$ 1,719
2024	7,082
2025	10,520
2026	13,802
2027	17,187
Thereafter	$ 648,437

Cash flow information (Details)

Cash flow information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Supplemental Cash Flow Information [Abstract]
Interest paid, net	$ 32,028	$ 19,472
Income taxes paid, net	22,183	23,163
Right-of-use assets obtained in exchange for new operating lease liabilities	9,717	5,851
Property, plant and equipment additions in accounts payable	2,832	4,884
Equity contribution from Centennial related to the Separation	64,724	0
Equity contribution to MDU Resources for asset/liability transfers related to the Separation	(1,548)	0
MDU Resources' stock issued prior to spin in connection with a business combination	$ 383	$ 0

Business segment data (Details)

Business segment data (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Revenues	$ 1,090,372	$ 975,428	$ 2,183,462	$ 1,997,207
EBITDA:	241,400	172,088	352,408	241,214
Pacific
Segment Reporting Information [Line Items]
Revenues	181,427	152,358	391,368	366,118
EBITDA:	37,558	24,563	56,486	45,194
Northwest
Segment Reporting Information [Line Items]
Revenues	208,919	204,232	503,573	459,807
EBITDA:	48,867	43,797	102,711	79,774
Mountain
Segment Reporting Information [Line Items]
Revenues	254,722	204,121	491,094	433,009
EBITDA:	60,473	39,644	86,486	60,244
North Central
Segment Reporting Information [Line Items]
Revenues	305,120	294,306	513,695	484,369
EBITDA:	70,508	58,584	71,402	50,424
All Other
Segment Reporting Information [Line Items]
Revenues	140,184	120,411	283,732	253,904
EBITDA:	23,994	5,500	35,323	5,578
Intersegment eliminations | Pacific
Segment Reporting Information [Line Items]
Revenues	37,566	30,710	75,345	76,911
Intersegment eliminations | Northwest
Segment Reporting Information [Line Items]
Revenues	36,683	42,627	84,937	84,733
Intersegment eliminations | Mountain
Segment Reporting Information [Line Items]
Revenues	68,178	49,089	108,888	90,654
Intersegment eliminations | North Central
Segment Reporting Information [Line Items]
Revenues	111,288	110,700	167,055	162,342
Intersegment eliminations | All Other
Segment Reporting Information [Line Items]
Revenues	39,741	26,635	64,479	60,386
Total intersegment operating revenues | Parent Company
Segment Reporting Information [Line Items]
Revenues	$ 293,456	$ 259,761	$ 500,704	$ 475,026

Business segment data operating

Business segment data operating revenues reconciliation (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 1,090,372	$ 975,428	$ 2,183,462	$ 1,997,207
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,203,903	1,088,143	2,335,955	2,157,943
Corporate, Non-Segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	179,925	147,046	348,211	314,290
Elimination of intersegment operating revenues | Parent Company
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 293,456	$ 259,761	$ 500,704	$ 475,026

Business segment data EBITDA re

Business segment data EBITDA reconciliation (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
EBITDA:	$ 241,400	$ 172,088	$ 352,408	$ 241,214
Depreciation, depletion and amortization	31,752	30,450	92,511	88,551
Interest expense, net	14,774	8,817	41,399	21,506
Total consolidated income before income taxes	194,874	132,821	218,498	131,157
Operating Segments
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
EBITDA:	217,406	166,588	317,085	235,636
Corporate, Non-Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
EBITDA:	$ 23,994	$ 5,500	$ 35,323	$ 5,578

Employee benefit plans (Details

Employee benefit plans (Details) $ in Millions	Jun. 01, 2023 USD ($)
Qualified plan | Unfunded plan | Other postretirement benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined Benefit Plan, Benefit Obligation Transferred in Connection with Spinoff	$ 1.5

Employee benefit plans (Detai_2

Employee benefit plans (Details 2) - Qualified plan - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Underfunded plan | Pension benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Interest cost	$ 408	$ 282	$ 1,224	$ 846
Expected return on assets	(450)	(493)	(1,350)	(1,479)
Amortization of net actuarial (gain) loss	128	214	384	642
Net periodic benefit cost	86	3	258	9
Unfunded plan | Other postretirement benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Service cost	91	131	270	393
Interest cost	180	128	541	384
Expected return on assets	0	(3)	12	(9)
Amortization of prior service credit	(20)	(20)	(60)	(60)
Amortization of net actuarial (gain) loss	(43)	88	(132)	264
Net periodic benefit cost	$ 208	$ 324	$ 631	$ 972

Litigation (Details)

Litigation (Details) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Loss Contingencies [Line Items]
Potential liabilities related to litigation and environmental matters	$ 645,000	$ 1,000,000
Insurance Receivable		$ 325,000

Guarantees (Details 2)

Guarantees (Details 2)	Sep. 30, 2023 USD ($)
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 11,500,000
Amount outstanding under guarantees that is reflected on balance sheet	0
Letters of credit	4,800,000
Letters of credit set to expire - 2023	4,000,000
Letters of credit set to expire - 2024	771,000
Outstanding letters of credit	0
Amount of surety bonds outstanding	$ 619,200,000

Related Party Disclosures (Deta

Related Party Disclosures (Details 1) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023
Related Party Transactions [Abstract]
Transition Services Agreement Payable	$ 1,300,000	$ 1,900,000
Transition Services Agreement Receivable	$ 407,000	$ 684,000

Related Party Disclosures (De_2

Related Party Disclosures (Details 2) - USD ($) $ in Thousands	May 31, 2023	May 30, 2023	Sep. 30, 2023	Apr. 25, 2023
Related Party Transaction [Line Items]
Related-party notes payable to Centennial		$ 889,700
Long-term debt			$ 682,731
Dividend paid from debt proceeds to Centennial		825,000
Net contribution from Centennial after repayment of notes		$ 64,700
Senior Notes
Related Party Transaction [Line Items]
Long-term debt			425,000	$ 425,000
Long-Term Debt, Percentage Bearing Fixed Interest, Percentage Rate				7.75%
Loans Payable
Related Party Transaction [Line Items]
Long-term debt	$ 275,000		$ 273,281
Revolving Credit Facility
Related Party Transaction [Line Items]
Long-term debt	350,000
Draw Down on Revolver	$ 190,000