v3.25.4
Debt - Narrative (Details)
$ in Millions, $ in Millions
12 Months Ended
Apr. 08, 2025
USD ($)
Apr. 07, 2025
USD ($)
tranche
Mar. 24, 2025
USD ($)
Dec. 31, 2025
USD ($)
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Dec. 31, 2025
CAD ($)
Jun. 18, 2025
USD ($)
May 19, 2025
USD ($)
May 15, 2025
USD ($)
Sep. 22, 2016
USD ($)
Debt Instrument [Line Items]                      
Interest expense, debt       $ 216 $ 43 $ 49          
Net proceeds from note offering after deductions for discounts and related debt issuance costs       3,395 0 0          
Debt issuance costs       $ 24 0 $ 0          
Debt instrument, covenant, leverage ratio, maximum       3.75     3.75        
Nonrelated Party                      
Debt Instrument [Line Items]                      
Deduction for fees and discounts       $ (2) 13            
Line of Credit                      
Debt Instrument [Line Items]                      
Line of credit facility, maximum borrowing capacity       60     $ 40        
Standby Letters of Credit                      
Debt Instrument [Line Items]                      
Remaining borrowing capacity       129 $ 213            
The Commerical Paper Program | Commercial Paper                      
Debt Instrument [Line Items]                      
Line of credit facility, maximum borrowing capacity                   $ 2,000  
The Bridge Loan | Bridge Loan                      
Debt Instrument [Line Items]                      
Debt instrument, term     364 days                
Line of credit facility, maximum borrowing capacity     $ 5,100                
Remaining borrowing capacity $ 1,700                    
Level 1                      
Debt Instrument [Line Items]                      
Long-term debt, fair value       5,047              
Other long-term debt, fair value       $ 58              
Senior Notes | 3.500% Unsecured Notes due 2026 | Amrize Finance US LLC                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate                 3.50%    
Senior Notes | 3.500% New Exchange Notes | Amrize Finance US LLC                      
Debt Instrument [Line Items]                      
Debt face amount                 $ 400    
Senior Notes | 4.750% Unsecured Notes due 2046 | Amrize Finance US LLC                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate                 4.75%    
Senior Notes | 4.750% New Exchange Notes | Amrize Finance US LLC                      
Debt Instrument [Line Items]                      
Debt face amount                 $ 590    
Senior Notes | 7.125% New Exchange Notes | Subsidiary of Parent                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate                 7.125%    
Debt face amount                 $ 483    
Senior Notes | 4.200% New Exchange Notes | Subsidiary of Parent                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate                 4.20%    
Debt face amount                 $ 50    
Senior Notes | 6.875% New Exchange Notes | Subsidiary of Parent                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate                 6.875%    
Debt face amount                 $ 250    
Senior Notes | 6.500% New Exchange Notes | Subsidiary of Parent                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate                 6.50%    
Debt face amount                 $ 250    
Senior Notes | Original Exchange Notes | Amrize Finance US LLC                      
Debt Instrument [Line Items]                      
Debt face amount               $ 880      
Senior Notes | Original Exchange Notes | Subsidiary of Parent                      
Debt Instrument [Line Items]                      
Debt face amount               925      
Senior Notes | New Exchange Notes                      
Debt Instrument [Line Items]                      
Debt face amount               1,805      
Senior Notes | Bonds Due 2031                      
Debt Instrument [Line Items]                      
Debt face amount                 $ 50    
Senior Notes | Senior Unsecured Notes "Notes"                      
Debt Instrument [Line Items]                      
Net proceeds from note offering after deductions for discounts and related debt issuance costs $ 3,400                    
Senior Notes | Senior Unsecured Notes "Notes" | Amrize Finance US LLC                      
Debt Instrument [Line Items]                      
Debt face amount   $ 3,400                  
Debt instrument, number of tranches | tranche   4                  
Net proceeds from note offering after deductions for discounts and related debt issuance costs   $ 3,381                  
Deduction for fees and discounts   6                  
Debt issuance costs   $ 13                  
Senior Notes | 4.600% Unsecured Notes due 2027 | Amrize Finance US LLC                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate   4.60%                  
Debt face amount   $ 700                  
Debt instrument, term   2 years                  
Senior Notes | 4.700% Unsecured Notes due 2028 | Amrize Finance US LLC                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate   4.70%                  
Debt face amount   $ 700                  
Debt instrument, term   3 years                  
Senior Notes | 4.950% Unsecured Notes due 2030 | Amrize Finance US LLC                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate   4.95%                  
Debt face amount   $ 1,000                  
Debt instrument, term   5 years                  
Senior Notes | 5.400% Unsecured Notes due 2035 | Amrize Finance US LLC                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate   5.40%                  
Debt face amount   $ 1,000                  
Debt instrument, term   10 years                  
Unsecured Debt | 3.500% Unsecured Notes due 2026                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate       3.50%     3.50%       3.50%
Debt face amount                     $ 400
Unsecured Debt | 4.750% Unsecured Notes due 2046                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate       4.75%     4.75%       4.75%
Debt face amount                     $ 590
Unsecured Debt | Original Exchange Notes | Amrize Finance US LLC                      
Debt Instrument [Line Items]                      
Debt face amount               $ 880      
Unsecured Debt | 4.600% Unsecured Notes due 2027                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate       4.60%     4.60%        
Unsecured Debt | 4.700% Unsecured Notes due 2028                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate       4.70%     4.70%        
Unsecured Debt | 4.950% Unsecured Notes due 2030                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate       4.95%     4.95%        
Unsecured Debt | 5.400% Unsecured Notes due 2035                      
Debt Instrument [Line Items]                      
Debt instrument, interest rate       5.40%     5.40%        
Unsecured Debt | Level 1                      
Debt Instrument [Line Items]                      
Long-term debt, fair value       $ 4,989              
Line of Credit | The Revolving Credit Facility | Revolving Credit Facility                      
Debt Instrument [Line Items]                      
Debt instrument, term     5 years                
Line of credit facility, maximum borrowing capacity     $ 2,000                
Line of Credit | The Revolving Credit Facility | Revolving Credit Facility | Fed Funds Effective Rate Overnight Index Swap Rate                      
Debt Instrument [Line Items]                      
Debt instrument, basis spread on variable rate     0.50%                
Line of Credit | The Revolving Credit Facility | Revolving Credit Facility | Overnight Bank Funding Rate                      
Debt Instrument [Line Items]                      
Debt instrument, basis spread on variable rate     0.50%                
Line of Credit | The Revolving Credit Facility | Revolving Credit Facility | Secured Overnight Financing Rate (SOFR)                      
Debt Instrument [Line Items]                      
Debt instrument, basis spread on variable rate     1.00%                
Debt instrument, variable rate, floor     0.00%                
Line of Credit | The Revolving Credit Facility | Revolving Credit Facility | Canadian Overnight Repo Rate Average                      
Debt Instrument [Line Items]                      
Debt instrument, variable rate, floor     0.00%