Annual report pursuant to Section 13 and 15(d)

ACQUISITIONS - Preliminary purchase price allocation (Details)

v3.20.4
ACQUISITIONS - Preliminary purchase price allocation (Details) - USD ($)
$ in Millions
 10 Months Ended 12 Months Ended
Dec. 31, 2020
Dec. 31, 2020
Mar. 13, 2020
Dec. 31, 2019
Business Acquisition [Line Items]        
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Current Assets, Income Tax Receivable $ 12 $ 12 $ 3  
Goodwill 1,406 1,406   $ 2
ArcelorMittal USA [Member]        
Business Acquisition [Line Items]        
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents 35 35    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables 349 349    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory 2,115 2,115    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other 22 22    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment 4,017 4,017    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets 158 158    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable (758) (758)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accrued Employment Costs (271) (271)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, State and Local Taxes (76) (76)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Pension and OPEB Liabilities (109) (109)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other (322) (322)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Pension and OPEB Liabilities (3,195) (3,195)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other (598) (598)    
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value (13) (13)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net 1,366 1,366    
Goodwill 1,230 1,230    
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest 2,596 2,596    
AK Steel [Member]        
Business Acquisition [Line Items]        
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents 39 39 38  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables 664 664 666  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory 1,320 1,320 1,563  
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Current Assets, Income Tax Receivable 3 3    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other 49 49 65  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment 2,312 2,312 2,184  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Income Taxes 30 30 0  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets 472 472 475  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable (644) (644) (636)  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accrued Employment Costs (93) (93) (94)  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, State and Local Taxes (31) (31) (35)  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Pension and OPEB Liabilities (78) (78) (75)  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other (196) (196) (201)  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt 1,179 1,179 1,179  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Pension and OPEB Liabilities (871) (871) (873)  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other (435) (435) (507)  
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value (1) (1) 0  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net 1,361 1,361 1,394  
Goodwill 174 174 141  
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest 1,535 1,535 $ 1,535  
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Cash and Cash Equivalents 1      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Accounts Receivable (2)      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory (243)      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Income Tax Receivables 0      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Other Current Assets (16)      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment 128      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Deferred Income Taxes 30      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Other Noncurrent Assets (3)      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Accounts Payable (8)      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Accrued Employment Cost 1      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, State and Local Income Taxes 4      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Retirement Benefit Liabilities (3)      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Other Current Liabilities 5      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Long-term Debt 0      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Retirement Benefit Liabilities, Noncurrent 2      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Other Noncurrent Liabilities 72      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Noncontrlling Interest (1)      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Net Identifiable Assets (33)      
Goodwill, Purchase Accounting Adjustments 33      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Consideration Transferred $ 0      
AK Steel [Member] | Inventories [Member]        
Business Acquisition [Line Items]        
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory   243    
AK Steel [Member] | Cost of goods sold        
Business Acquisition [Line Items]        
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments Related to Previous Period   $ 8