v3.25.4
INCOME TAXES - Narrative Income Tax expense (Benefit) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Tax effect from change in tax rate $ (29) $ 370 $ 0
Net change in measurement of deferred tax assets (68) 182 (423)
Decrease through loss of control of subsidiary, deferred tax asset 552 563  
Effect of utilization of unrecognized tax losses carried forward     (366)
Increase (decrease) through derecognition of DTA on losses and deductible temporary differences     (109)
Tax effect of foreign tax rates 16 (21) (20)
Tax contingencies/settlements $ 97 $ 263 43
Kazakhstan Operations      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Expense non-deductible, impairment charges     900
Expense non-deductible, loss on disposal     1,500
ArcelorMittal USA LLC      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Decrease through loss of control of subsidiary, deferred tax asset     (292)
Calvert1      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Proportion of ownership interest in subsidiary (in percent) 50.00%    
Luxembourg      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Applicable tax rate (in percent) 23.87% 24.94%  
Decrease through loss of control of subsidiary, deferred tax asset $ (620)    
Future taxable income increase due to tax integration   $ (381) $ (314)
United States      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Tax contingencies/settlements $ 202    
Germany      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Applicable tax rate (in percent) 25.00% 30.30%