Quarterly report [Sections 13 or 15(d)]

DEBT AND CREDIT FACILITIES - Debt Redemption (Details)

v3.25.3
DEBT AND CREDIT FACILITIES - Debt Redemption (Details) - USD ($)
$ in Millions
9 Months Ended
Oct. 10, 2025
Sep. 30, 2025
Sep. 08, 2025
Feb. 06, 2025
Dec. 31, 2024
Debt Instrument, Redemption [Line Items]          
Aggregate principal amount   $ 8,135     $ 7,148
7.500% 2031 Senior Notes [Member] | Cleveland-Cliffs Inc.          
Debt Instrument, Redemption [Line Items]          
Aggregate principal amount   $ 850   $ 850 0
Stated interest rate   7.50%   7.50%  
Repurchase price if triggering event occurs   101.00%      
7.500% 2031 Senior Notes [Member] | Cleveland-Cliffs Inc. | Minimum          
Debt Instrument, Redemption [Line Items]          
Redemption notice period   10 days      
7.500% 2031 Senior Notes [Member] | Cleveland-Cliffs Inc. | Maximum          
Debt Instrument, Redemption [Line Items]          
Redemption notice period   60 days      
7.500% 2031 Senior Notes [Member] | Debt Instrument, Redemption, Period One | Cleveland-Cliffs Inc.          
Debt Instrument, Redemption [Line Items]          
Redemption price percentage   100.00%      
7.500% 2031 Senior Notes [Member] | Debt Instrument, Redemption, Period One, Upon Equity Issuance | Cleveland-Cliffs Inc.          
Debt Instrument, Redemption [Line Items]          
Redemption price percentage   107.50%      
Percentage of principal available for redemption   35.00%      
7.500% 2031 Senior Notes [Member] | Debt Instrument, Redemption, Period Two | Cleveland-Cliffs Inc.          
Debt Instrument, Redemption [Line Items]          
Redemption price percentage   103.75%      
7.500% 2031 Senior Notes [Member] | Debt Instrument, Redemption, Period Three | Cleveland-Cliffs Inc.          
Debt Instrument, Redemption [Line Items]          
Redemption price percentage   101.875%      
7.625% 2034 Senior Notes [Member] | Cleveland-Cliffs Inc.          
Debt Instrument, Redemption [Line Items]          
Aggregate principal amount   $ 850 $ 850   $ 0
Stated interest rate   7.625% 7.625%    
Repurchase price if triggering event occurs   101.00%      
7.625% 2034 Senior Notes [Member] | Cleveland-Cliffs Inc. | Subsequent Event          
Debt Instrument, Redemption [Line Items]          
Aggregate principal amount $ 275        
7.625% 2034 Senior Notes [Member] | Cleveland-Cliffs Inc. | Minimum          
Debt Instrument, Redemption [Line Items]          
Redemption notice period   10 days      
7.625% 2034 Senior Notes [Member] | Cleveland-Cliffs Inc. | Maximum          
Debt Instrument, Redemption [Line Items]          
Redemption notice period   60 days      
7.625% 2034 Senior Notes [Member] | Debt Instrument, Redemption, Period One | Cleveland-Cliffs Inc.          
Debt Instrument, Redemption [Line Items]          
Redemption price percentage   100.00%      
7.625% 2034 Senior Notes [Member] | Debt Instrument, Redemption, Period One | Cleveland-Cliffs Inc. | Subsequent Event          
Debt Instrument, Redemption [Line Items]          
Redemption price percentage 102.75%        
7.625% 2034 Senior Notes [Member] | Debt Instrument, Redemption, Period One, Upon Equity Issuance | Cleveland-Cliffs Inc.          
Debt Instrument, Redemption [Line Items]          
Redemption price percentage   107.625%      
Percentage of principal available for redemption   35.00%      
7.625% 2034 Senior Notes [Member] | Debt Instrument, Redemption, Period Two | Cleveland-Cliffs Inc.          
Debt Instrument, Redemption [Line Items]          
Redemption price percentage   103.813%      
7.625% 2034 Senior Notes [Member] | Debt Instrument, Redemption, Period Three | Cleveland-Cliffs Inc.          
Debt Instrument, Redemption [Line Items]          
Redemption price percentage   101.906%