v3.26.1
Organization and basis of presentation - Narrative (Details)
$ in Millions
3 Months Ended
Mar. 31, 2026
segment
shares
Mar. 31, 2025
USD ($)
Dec. 31, 2025
shares
Jun. 23, 2025
shares
Business Combination [Line Items]        
Number of reportable segments | segment 2      
Common stock, outstanding (in shares) 553,515,402   553,082,525 566,875,513
Treasury stock (in shares) 13,360,111   13,792,988 13,793,444
Related Party        
Business Combination [Line Items]        
Various transaction costs | $   $ 5    
Holcim Ltd | Amrize Ltd | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff        
Business Combination [Line Items]        
Equity interest disposed       100.00%
Number of shares issued (in shares)       553,082,069