v3.25.4
PERSONNEL EXPENSES AND DEFERRED EMPLOYEE BENEFITS - Deferred Employee Benefits - Narrative (Details) - USD ($)
$ in Millions
 1 Months Ended 3 Months Ended 12 Months Ended 108 Months Ended
Jan. 31, 2025
Feb. 28, 2016
Dec. 31, 2015
Sep. 30, 2014
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of defined benefit plans [line items]              
Deferred employee benefits         $ 2,526 $ 2,338  
Belgium              
Disclosure of defined benefit plans [line items]              
Rates of return of insured plans on employer contributions (in percent)     3.25%        
Rates of return of insured plans on employee contributions (in percent)     3.75%        
Minimum guaranteed rate of return of insured plans (in percent)           1.75%  
Belgium | Forecast              
Disclosure of defined benefit plans [line items]              
Minimum guaranteed rate of return of insured plans (in percent) 2.50%            
Collective labor agreement | Canada              
Disclosure of defined benefit plans [line items]              
Term of collective labor agreement   6 years   6 years      
Fully funded pension plans | Canada | ArcelorMittal Dofasco G.P.              
Disclosure of defined benefit plans [line items]              
Deferred employee benefits         126 $ 356 $ 352
Fully funded pension plans | Canada | ArcelorMittal Mining Canada G.P. and ArcelorMittal Infrastructure Canada G.P. ("AMMC")              
Disclosure of defined benefit plans [line items]              
Deferred employee benefits         171   $ 171
Pension plan benefits              
Disclosure of defined benefit plans [line items]              
Deferred employee benefits         1,448 1,310  
Pension plan benefits | ArcelorMittal Bremen GmbH | Present value of defined benefit obligation              
Disclosure of defined benefit plans [line items]              
Past service cost, net defined benefit liability (asset)         44    
Pension plan benefits | Canada              
Disclosure of defined benefit plans [line items]              
Deferred employee benefits         $ 18 $ 26