Organization and Basis of Presentation	12 Months Ended
Organization and Basis of Presentation	Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation At Knife River, we are a people-first construction materials and contracting services company. We provide construction materials and contracting services to build safe roads, bridges, airport runways and other critical infrastructure needs that connect people with where they want to go and with the supplies they need. We are one of the leading providers of crushed stone and sand and gravel in the United States and operate across 14 states. We conduct our operations through four reportable segments: West, Mountain, Central and Energy Services. In January 2025, we made a change to our organizational structure to better align with our business strategy. We reorganized our business segments to reflect changes in the way our chief operating decision maker evaluates performance, makes operating decisions and allocates resources. Our former Pacific and Northwest operating segments were combined to form the new West operating segment. Our former North Central and South operating segments were combined to form the new Central operating segment. The reorganization resulted in four operating segments: West, Mountain, Central and Energy Services, each of which is also a reportable segment. Each segment’s performance is evaluated based on segment results without allocating corporate expenses, which include corporate costs associated with accounting, legal, treasury, business development, information technology, human resources, and other corporate expenses that support the operating segments. Prior periods have been recast to conform to the current reportable segment presentation. On March 7, 2025, we acquired Strata Corporation (Strata), a leading construction materials and contracting services provider in North Dakota and northwestern Minnesota. The purchase price for Strata totaled $454.0 million and was subject to post-closing adjustments. The results of operations and balance sheet accounts for Strata are included in the consolidated financial statements from the date of acquisition. For more information, see Note 3. In July 2025, House Bill 1, known as the One Big Beautiful Bill Act ("OBBBA"), was enacted. The OBBBA includes significant provisions that, among other provisions, makes 100% bonus depreciation permanent and restores the ability to expense domestic research expenditures. The OBBBA did not have a material impact on the Company’s annual estimated income tax rate, but did result in a reclassification between current taxes payable and deferred tax liabilities. In December 2025, we reclassified our retention receivables of $42.8 million on a contract-by-contract basis from accounts receivable. The reclassification resulted in an increase to contract assets of $31.8 million and a decrease to contract liabilities of $11.0 million due to FASB’s clarification of retention receivables under ASC 606. Prior years were not revised. Separation from MDU Resources On May 31, 2023, MDU Resources completed the separation of Knife River through the distribution of approximately 90 percent of the outstanding shares of common stock, par value $.01 per share, of Knife River to the stockholders of record of MDU Resources as of the close of business on May 22, 2023. MDU Resources retained approximately 10 percent of the outstanding shares of Knife River common stock. The Distribution was structured as a pro rata distribution of one share of Knife River common stock for every four shares of MDU Resources common stock. In November 2023, MDU Resources disposed of all 5,656,621 retained shares of Knife River common stock in an underwritten public offering. As a result of the Distribution, Knife River is now an independent public company and its common stock is listed under the symbol “KNF” on the New York Stock Exchange. The Separation was completed pursuant to a separation and distribution agreement and other agreements with MDU Resources related to the Separation, including, but not limited to, a tax matters agreement, an employee matters agreement and a transition services agreement. For an interim period following the Separation, certain functions continued to be provided by MDU Resources under a transition services agreement. For more information on the transition services agreement, see Note 19. Basis of Presentation Prior to the Separation, we operated as a wholly owned subsidiary of Centennial and an indirect, wholly owned subsidiary of MDU Resources and not as a stand-alone company. The accompanying audited consolidated financial statements and footnotes for the periods prior to the Separation were prepared on a “carve-out” basis using a legal entity approach in conformity with GAAP and were derived from the audited consolidated financial statements of MDU Resources as if we operated on a stand-alone basis during these periods. All revenues and costs as well as assets and liabilities directly associated with the business activity of Knife River are included in the financial statements. In the periods prior to the Separation, the audited consolidated financial statements include expense allocations for certain functions provided by MDU Resources and Centennial, including, but not limited to certain general corporate expenses related to senior management, legal, human resources, finance and accounting, treasury, information technology, communications, procurement, tax, insurance and other shared services. These general corporate expenses are included in the Consolidated Statements of Operations within selling, general and administrative expenses and other income (expense). The amount allocated to us was $10.7 million for the year ended December 31, 2023. These expenses were allocated to us on the basis of direct usage when identifiable, with the remainder principally allocated on the basis of percent of total capital invested or other allocation methodologies that were considered to be a reasonable reflection of the utilization of the services provided to the benefits received, including the following: number of employees paid and stated as cost per check; number of employees served; weighted factor of travel, managed units, national account spending equipment and fleet acquisitions; purchase order dollars spent and purchase order line count; number of payments; vouchers or unclaimed property reports; labor hours; time tracked; and projected workload. The allocations may not, however, reflect the expense we would have incurred as a stand-alone company for the periods presented. These costs also may not be indicative of the expenses that we will incur in the future or would have incurred if we had obtained these services from a third party. Prior to the Separation, we participated in Centennial’s centralized cash management program, including its overall financing arrangements. Interest expense in the Consolidated Statements of Operations for the periods prior to the Separation reflects the allocation of interest on borrowing and funding associated with the related-party note agreements. Upon the completion of the Separation, we implemented our own financing agreements with lenders. For additional information on our current debt financing, see Note 9. Related-party transactions between us and MDU Resources or Centennial for general operating activities and intercompany debt have been included in the audited consolidated financial statements for periods prior to the Separation. The cash settlement of these transactions are included in the Consolidated Statements of Cash Flows as operating or financing activities following the nature of the transactions. The aggregate net effect of related-party transactions not settled in cash as part of the Separation have been reflected in the Consolidated Balance Sheets and Statements of Stockholders’ Equity within “Other paid-in capital” and within the Consolidated Statements of Cash Flows following the nature of the transactions with a majority included in the financing section. See Note 19 for additional information on related-party transactions. Management has also evaluated the impact of events occurring after December 31, 2025, up to the date of issuance of these audited consolidated financial statements on February 20, 2026, that would require recognition or disclosure in the audited Consolidated Financial Statements. Principles of consolidation For all periods, the audited consolidated financial statements were prepared in accordance with GAAP and include the accounts of Knife River and our wholly owned subsidiaries. All intercompany accounts and transactions between our businesses have been eliminated in the accompanying audited consolidated financial statements. Use of estimates The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, at the date of the audited consolidated financial statements, as well as the reported amounts of revenues and expenses during the reporting period. Estimates are used for items such as long-lived assets and goodwill; fair values of acquired assets and liabilities under the acquisition method of accounting; aggregate reserves; property depreciable lives; tax provisions; revenue recognized using the cost-to-cost measure of progress for contracts; expected credit losses; environmental and other loss contingencies; costs on contracting services contracts; actuarially determined benefit costs; asset retirement obligations; present value of right-of-use assets and lease liabilities; and the valuation of stock-based compensation. These estimates are based on management’s best knowledge of current events, historical experience, actions that we may undertake in the future and on various other assumptions that are believed to be reasonable under the circumstances. As additional information becomes available, or actual amounts are determinable, the recorded estimates are revised. Consequently, operating results can be affected by revisions to prior accounting estimates.