Annual report pursuant to Section 13 and 15(d)

CAPITAL STOCK - Narrative (Details)

v3.22.0.1
CAPITAL STOCK - Narrative (Details)
$ / shares in Units, $ in Millions
3 Months Ended 12 Months Ended
Mar. 11, 2021
USD ($)
Dec. 09, 2020
shares
Apr. 24, 2020
USD ($)
Mar. 13, 2020
USD ($)
Sep. 30, 2021
USD ($)
shares
Jun. 30, 2021
USD ($)
Dec. 31, 2021
USD ($)
$ / shares
shares
Dec. 31, 2020
USD ($)
$ / shares
shares
Dec. 31, 2019
USD ($)
Apr. 29, 2021
shares
Mar. 31, 2021
shares
Feb. 11, 2021
$ / shares
shares
Class of Stock [Line Items]                        
Common shares, issued (in shares)             506,832,537 506,832,537       20,000,000
Common Stock, Shares, Sold                       40,000,000
Common stock, shares issued, price per share | $ / shares                       $ 16.12
Debt Extinguished | $     $ 736       $ 1,306 $ 1,513 $ 724      
Common shares, par value (in dollars per share) | $ / shares             $ 0.125 $ 0.125        
Redeemable preferred stock, issued (in shares)             0 583,273        
Redeemable preferred stock, outstanding (in shares)             0 583,273        
Common shares, authorized (in shares)             1,200,000,000 600,000,000   1,200,000,000 600,000,000  
Repurchase of common shares | $             $ 0 $ 0 $ 253      
9.875% 2025 Senior Secured Notes                        
Class of Stock [Line Items]                        
Debt Extinguished | $ $ 322         $ 25 $ 347          
ArcelorMittal                        
Class of Stock [Line Items]                        
Common Stock, Shares, Sold                       40,000,000
Cleveland-Cliffs Inc. | 9.875% 2025 Senior Secured Notes                        
Class of Stock [Line Items]                        
Stated interest rate             9.875% 9.875%        
AK Steel                        
Class of Stock [Line Items]                        
Exchange ratio       0.400                
Common Stock                        
Class of Stock [Line Items]                        
Common shares, par value (in dollars per share) | $ / shares             $ 0.125          
Stock Repurchased During Period, Shares               24,000,000        
Common Stock | ArcelorMittal USA                        
Class of Stock [Line Items]                        
Acquisition (in shares)   78,186,671                    
Common Stock | AK Steel                        
Class of Stock [Line Items]                        
Acquisition (in shares)             127,000,000          
Exchange ratio             0.400          
Fair value of Cliffs common shares issued for outstanding AK Steel common stock | $       $ 618                
Series B Preferred Stock                        
Class of Stock [Line Items]                        
Stock Redeemed or Called During Period, Shares         583,273              
Stock Redeemed or Called During Period, Value | $         $ 1,300              
Preferred Stock, Shares Authorized             4,000,000          
Preferred Stock, Shares Issued             0          
Preferred Stock, Shares Outstanding             0          
Series B Preferred Stock | ArcelorMittal USA                        
Class of Stock [Line Items]                        
Acquisition (in shares)   583,273         583,273          
Series A Preferred Stock                        
Class of Stock [Line Items]                        
Preferred Stock, Shares Authorized             3,000,000          
Preferred Stock, Shares Issued             0          
Preferred Stock, Shares Outstanding             0