Summary of significant accounting policies (Policies)	6 Months Ended
Jun. 30, 2025
Accounting Policies [Abstract]
Basis of presentation and use of estimates	Basis of presentation and use of estimates The accompanying unaudited Condensed Consolidated Financial Statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) for interim financial information and with the instructions to the Quarterly Report on Form 10-Q and in Article 10 of Regulation S-X. The Company has continued to follow the accounting policies set forth in the audited Consolidated Financial Statements and related notes thereto included in the Company’s 2024 Form 10-K. In the opinion of our management, these statements reflect all adjustments, consisting of only normal recurring adjustments, necessary for a fair statement of our results of operations and financial condition for the periods and at the dates presented. Operating results for the three and six months ended June 30, 2025 are not necessarily indicative of the results that may be expected for the year ending December 31, 2025. The Condensed Consolidated Balance Sheet at December 31, 2024 has been derived from the audited Consolidated Financial Statements at that date but does not include all of the information and notes required by U.S. GAAP for complete financial statements. These Condensed Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and notes thereto included in the Company’s 2024 Form 10-K. The preparation of the Company's Condensed Consolidated Financial Statements requires management to make certain estimates and assumptions about future events. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities and reported amounts of revenues and expenses. Such estimates include impairment of long-lived assets, impairment of goodwill, pension and other postretirement benefits, tax matters and litigation, including insurance and environmental compliance costs. These estimates and assumptions are based on management’s judgment.
Use of estimates	Estimates and underlying assumptions are reviewed on an ongoing basis. Changes in accounting estimates may be necessary if there are changes in the circumstances or experiences on which the estimate was based or as a result of new information. Changes in estimates, including those resulting from changes in the economic environment, are reflected in the period in which the change in estimate occurs.
Cash and cash equivalents and restricted cash	Cash and cash equivalents and restricted cash The Company had restricted cash of $6 million at June 30, 2025, December 31, 2024, and June 30, 2024, respectively, included within Cash and cash equivalents in the Condensed Consolidated Balance Sheets. The Company is restricted from utilizing the cash for purposes other than with government approval as it is linked to the awarding of government licenses for quarrying. Restricted cash of $39 million and $869 million as separately presented in the Condensed Consolidated Balance Sheets at December 31, 2024, and June 30, 2024, respectively, consists of amounts held in escrow which at December 31, 2024 were primarily designated for exchange of assets under Section 1031 of the U.S. Internal Revenue Code of 1986, as amended and at June 30, 2024 were primarily related to amounts payable for the acquisition of Adbri Ltd (Adbri).
New accounting standards	New accounting standards Refer to Note 1.25 in the 2024 Form 10-K for impacts of new accounting standards. There were no material impacts from the adoption of new accounting standards for the six months ended June 30, 2025.

Summary of significant accounting policies (Policies)

6 Months Ended

Jun. 30, 2025

Basis of presentation and use of estimates

The accompanying unaudited Condensed Consolidated Financial Statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) for interim financial information and with the instructions to the Quarterly Report on Form 10-Q and in Article 10 of Regulation S-X. The Company has continued to follow the accounting policies set forth in the audited Consolidated Financial Statements and related notes thereto included in the Company’s 2024 Form 10-K. In the opinion of our management, these statements reflect all adjustments, consisting of only normal recurring adjustments, necessary for a fair statement of our results of operations and financial condition for the periods and at the dates presented. Operating results for the three and six months ended June 30, 2025 are not necessarily indicative of the results that may be expected for the year ending December 31, 2025. The Condensed Consolidated Balance Sheet at December 31, 2024 has been derived from the audited Consolidated Financial Statements at that date but does not include all of the information and notes required by U.S. GAAP for complete financial statements. These Condensed Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and notes thereto included in the Company’s 2024 Form 10-K.

The preparation of the Company's Condensed Consolidated Financial Statements requires management to make certain estimates and assumptions about future events. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities and reported amounts of revenues and expenses. Such estimates include impairment of long-lived assets, impairment of goodwill, pension and other postretirement benefits, tax matters and litigation, including insurance and environmental compliance costs. These estimates and assumptions are based on management’s judgment.

Use of estimates

Estimates and underlying assumptions are reviewed on an ongoing basis. Changes in accounting estimates may be necessary if there are changes in the circumstances or experiences on which the estimate was based or as a result of new information.

Changes in estimates, including those resulting from changes in the economic environment, are reflected in the period in which the change in estimate occurs.

Cash and cash equivalents and restricted cash

The Company had restricted cash of $6 million at June 30, 2025, December 31, 2024, and June 30, 2024, respectively, included within Cash and cash equivalents in the Condensed Consolidated Balance Sheets. The Company is restricted from utilizing the cash for purposes other than with government approval as it is linked to the awarding of government licenses for quarrying.

Restricted cash of $39 million and $869 million as separately presented in the Condensed Consolidated Balance Sheets at December 31, 2024, and June 30, 2024, respectively, consists of amounts held in escrow which at December 31, 2024 were primarily designated for exchange of assets under Section 1031 of the U.S. Internal Revenue Code of 1986, as amended and at June 30, 2024 were primarily related to amounts payable for the acquisition of Adbri Ltd (Adbri).

New accounting standards

Refer to Note 1.25 in the 2024 Form 10-K for impacts of new accounting standards. There were no material impacts from the adoption of new accounting standards for the six months ended June 30, 2025.