Annual report [Section 13 and 15(d), not S-K Item 405]

DEBT AND CREDIT FACILITIES - Debt Issuances and Terms (Details)

v3.25.4
DEBT AND CREDIT FACILITIES - Debt Issuances and Terms (Details) - USD ($)
12 Months Ended
Oct. 10, 2025
Oct. 03, 2025
Dec. 31, 2025
Sep. 08, 2025
Feb. 06, 2025
Dec. 31, 2024
Oct. 22, 2024
Debt Instrument [Line Items]              
Total debt     $ 7,330,000,000     $ 7,148,000,000  
7.625% 2034 Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Total debt $ 275,000,000     $ 850,000,000   0 $ 1,125,000,000
Stated interest rate     7.625% 7.625%      
Repurchase price if triggering event occurs     101.00%        
Redemption of debt   $ 73,000,000          
7.625% 2034 Senior Notes | Cleveland-Cliffs Inc. | Minimum              
Debt Instrument [Line Items]              
Redemption notice period     10 days        
7.625% 2034 Senior Notes | Cleveland-Cliffs Inc. | Maximum              
Debt Instrument [Line Items]              
Redemption notice period     60 days        
7.625% 2034 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One              
Debt Instrument [Line Items]              
Redemption price, percentage 102.75%   100.00%        
7.625% 2034 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One, Upon Equity Issuance              
Debt Instrument [Line Items]              
Redemption price, percentage     107.625%        
Restricted Amount (percent of original aggregate principal)     35.00%        
7.625% 2034 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Two              
Debt Instrument [Line Items]              
Redemption price, percentage     103.813%        
7.625% 2034 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Three              
Debt Instrument [Line Items]              
Redemption price, percentage     101.906%        
7.500% 2031 Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Total debt     $ 850,000,000   $ 850,000,000 0  
Stated interest rate     7.50%   7.50%    
Repurchase price if triggering event occurs     101.00%        
7.500% 2031 Senior Notes | Cleveland-Cliffs Inc. | Minimum              
Debt Instrument [Line Items]              
Redemption notice period     10 days        
7.500% 2031 Senior Notes | Cleveland-Cliffs Inc. | Maximum              
Debt Instrument [Line Items]              
Redemption notice period     60 days        
7.500% 2031 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One              
Debt Instrument [Line Items]              
Redemption price, percentage     100.00%        
7.500% 2031 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One, Upon Equity Issuance              
Debt Instrument [Line Items]              
Redemption price, percentage     107.50%        
Restricted Amount (percent of original aggregate principal)     35.00%        
7.500% 2031 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Two              
Debt Instrument [Line Items]              
Redemption price, percentage     103.75%        
7.500% 2031 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Three              
Debt Instrument [Line Items]              
Redemption price, percentage     101.875%        
4.625% 2029 Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Total debt     $ 368,000,000     368,000,000  
Stated interest rate     4.625%        
4.625% 2029 Senior Notes | Cleveland-Cliffs Inc. | Minimum              
Debt Instrument [Line Items]              
Redemption notice period     10 days        
4.625% 2029 Senior Notes | Cleveland-Cliffs Inc. | Maximum              
Debt Instrument [Line Items]              
Redemption notice period     60 days        
4.625% 2029 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Two              
Debt Instrument [Line Items]              
Redemption price, percentage     101.156%        
6.875% 2029 Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Total debt           900,000,000 900,000,000
Stated interest rate     6.875%        
Repurchase price if triggering event occurs     101.00%        
6.875% 2029 Senior Notes | Cleveland-Cliffs Inc. | Minimum              
Debt Instrument [Line Items]              
Redemption notice period     10 days        
6.875% 2029 Senior Notes | Cleveland-Cliffs Inc. | Maximum              
Debt Instrument [Line Items]              
Redemption notice period     60 days        
6.875% 2029 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One              
Debt Instrument [Line Items]              
Redemption price, percentage     100.00%        
6.875% 2029 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One, Upon Equity Issuance              
Debt Instrument [Line Items]              
Redemption price, percentage     106.875%        
Restricted Amount (percent of original aggregate principal)     35.00%        
6.875% 2029 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Two              
Debt Instrument [Line Items]              
Redemption price, percentage     103.438%        
6.750% 2030 Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Total debt     $ 750,000,000     750,000,000  
Stated interest rate     6.75%        
6.750% 2030 Senior Notes | Cleveland-Cliffs Inc. | Minimum              
Debt Instrument [Line Items]              
Redemption notice period     10 days        
6.750% 2030 Senior Notes | Cleveland-Cliffs Inc. | Maximum              
Debt Instrument [Line Items]              
Redemption notice period     60 days        
6.750% 2030 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One              
Debt Instrument [Line Items]              
Redemption price, percentage     100.00%        
6.750% 2030 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One, Upon Equity Issuance              
Debt Instrument [Line Items]              
Redemption price, percentage     106.75%        
Restricted Amount (percent of original aggregate principal)     35.00%        
6.750% 2030 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Two              
Debt Instrument [Line Items]              
Redemption price, percentage     103.375%        
6.750% 2030 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Three              
Debt Instrument [Line Items]              
Redemption price, percentage     101.688%        
4.875% 2031 Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Total debt     $ 325,000,000     325,000,000  
Stated interest rate     4.875%        
4.875% 2031 Senior Notes | Cleveland-Cliffs Inc. | Minimum              
Debt Instrument [Line Items]              
Redemption notice period     10 days        
4.875% 2031 Senior Notes | Cleveland-Cliffs Inc. | Maximum              
Debt Instrument [Line Items]              
Redemption notice period     60 days        
4.875% 2031 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One, Upon Equity Issuance              
Debt Instrument [Line Items]              
Redemption price, percentage     104.875%        
4.875% 2031 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Two              
Debt Instrument [Line Items]              
Redemption price, percentage     102.438%        
4.875% 2031 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Three              
Debt Instrument [Line Items]              
Redemption price, percentage     101.625%        
4.875% 2031 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Four              
Debt Instrument [Line Items]              
Redemption price, percentage     100.813%        
7.000% 2032 Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Total debt     $ 1,425,000,000     1,425,000,000  
Stated interest rate     7.00%        
Repurchase price if triggering event occurs     101.00%        
7.000% 2032 Senior Notes | Cleveland-Cliffs Inc. | Minimum              
Debt Instrument [Line Items]              
Redemption notice period     10 days        
7.000% 2032 Senior Notes | Cleveland-Cliffs Inc. | Maximum              
Debt Instrument [Line Items]              
Redemption notice period     60 days        
7.000% 2032 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One              
Debt Instrument [Line Items]              
Redemption price, percentage     100.00%        
7.000% 2032 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One, Upon Equity Issuance              
Debt Instrument [Line Items]              
Redemption price, percentage     107.00%        
Restricted Amount (percent of original aggregate principal)     35.00%        
7.000% 2032 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Two              
Debt Instrument [Line Items]              
Redemption price, percentage     103.50%        
7.000% 2032 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Three              
Debt Instrument [Line Items]              
Redemption price, percentage     101.75%        
7.375% 2033 Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Total debt           900,000,000 $ 900,000,000
Stated interest rate     7.375%        
Repurchase price if triggering event occurs     101.00%        
7.375% 2033 Senior Notes | Cleveland-Cliffs Inc. | Minimum              
Debt Instrument [Line Items]              
Redemption notice period     10 days        
7.375% 2033 Senior Notes | Cleveland-Cliffs Inc. | Maximum              
Debt Instrument [Line Items]              
Redemption notice period     60 days        
7.375% 2033 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One              
Debt Instrument [Line Items]              
Redemption price, percentage     100.00%        
7.375% 2033 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One, Upon Equity Issuance              
Debt Instrument [Line Items]              
Redemption price, percentage     107.375%        
Restricted Amount (percent of original aggregate principal)     35.00%        
7.375% 2033 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Two              
Debt Instrument [Line Items]              
Redemption price, percentage     103.688%        
6.250% 2040 Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Total debt     $ 235,000,000     235,000,000  
Stated interest rate     6.25%        
6.250% 2040 Senior Notes | Cleveland-Cliffs Inc. | Minimum              
Debt Instrument [Line Items]              
Redemption notice period     30 days        
6.250% 2040 Senior Notes | Cleveland-Cliffs Inc. | Maximum              
Debt Instrument [Line Items]              
Redemption notice period     60 days        
6.250% 2040 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period One              
Debt Instrument [Line Items]              
Redemption price, percentage     100.00%        
6.250% 2040 Senior Notes | Cleveland-Cliffs Inc. | Debt Instrument, Redemption, Period Two              
Debt Instrument [Line Items]              
Redemption price, percentage     0.40%        
Unsecured Debt | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Repurchase price if triggering event occurs     101.00%        
7.000% 2027 Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Total debt     $ 0     73,000,000  
Stated interest rate     7.00%        
Redemption of debt   556,000,000          
7.000% 2027 AK Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Redemption of debt   $ 56,000,000          
7.000% 2027 AK Senior Notes | AK Steel              
Debt Instrument [Line Items]              
Total debt     $ 0     56,000,000  
Stated interest rate     7.00%        
5.875% 2027 Senior Notes | Cleveland-Cliffs Inc.              
Debt Instrument [Line Items]              
Total debt     $ 0     $ 556,000,000  
Stated interest rate     5.875%