Quarterly report pursuant to Section 13 or 15(d)

SUBSEQUENT EVENTS (Details)

v3.24.3
SUBSEQUENT EVENTS (Details)
Nov. 01, 2024
USD ($)
shares
Jul. 12, 2024
USD ($)
Nov. 01, 2024
$ / shares
Oct. 22, 2024
USD ($)
Sep. 30, 2024
USD ($)
Sep. 13, 2024
USD ($)
Dec. 31, 2023
USD ($)
Subsequent Events [Abstract]              
Long-term Debt, Gross         $ 3,835,000,000   $ 3,192,000,000
Subsequent Event [Line Items]              
Long-term Debt, Gross         3,835,000,000   $ 3,192,000,000
Stelco Holdings Inc              
Subsequent Event [Line Items]              
Expected enterprise value of acquisition   $ 2,500,000,000          
Subsequent Event | Stelco Holdings Inc              
Subsequent Event [Line Items]              
Shares of Cliffs common shares issued to Stelco Holdings stockholders (in shares) | shares 0.454            
Expected enterprise value of acquisition $ 3,200,000,000            
Subsequent Event | Stelco Holdings Inc | Stelco Holdings Inc              
Subsequent Event [Line Items]              
Price per share (in dollars per share) | $ / shares     $ 60.00        
7.375% 2033 Senior Guaranteed Note | Subsequent Event              
Subsequent Events [Abstract]              
Long-term Debt, Gross       $ 900,000,000      
Subsequent Event [Line Items]              
Long-term Debt, Gross       $ 900,000,000      
Stated interest rate       7.375%      
6.875% 2029 Senior Guaranteed Note | Subsequent Event              
Subsequent Events [Abstract]              
Long-term Debt, Gross       $ 900,000,000      
Subsequent Event [Line Items]              
Long-term Debt, Gross       $ 900,000,000      
Stated interest rate       6.875%      
Bridge Loan | Line of Credit              
Subsequent Event [Line Items]              
Maximum borrowing capacity         $ 3,300,000,000 $ 2,400,000,000  
Bridge Loan | Subsequent Event | Line of Credit              
Subsequent Event [Line Items]              
Maximum borrowing capacity       $ 1,800,000,000