Annual report pursuant to Section 13 and 15(d)

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

v3.20.4
DEBT AND CREDIT FACILITIES - Debt Issuances and Terms (Details)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2020
USD ($)
$ / shares
Dec. 31, 2018
Jun. 19, 2020
USD ($)
Apr. 24, 2020
USD ($)
Apr. 17, 2020
USD ($)
Mar. 16, 2020
USD ($)
Mar. 13, 2020
USD ($)
Dec. 31, 2019
USD ($)
Debt Instrument [Line Items]                
Debt Instrument, Par Value $ 5,595              
Common shares, par value | $ / shares $ 0.125              
AK Steel [Member]                
Debt Instrument [Line Items]                
Debt Instrument, Par Value $ 132              
9.875% 2025 Senior Secured Notes | Cleveland-Cliffs Inc. [Member]                
Debt Instrument [Line Items]                
Debt Instrument, Par Value $ 955     $ 555 $ 400      
Debt issuance, discount rate       99.00% 94.50%      
Repurchase price if triggering event occurs 101.00%              
6.75% 2026 Senior Secured Notes | Cleveland-Cliffs Inc. [Member]                
Debt Instrument [Line Items]                
Debt Instrument, Par Value $ 845   $ 120       $ 725  
Debt issuance, discount rate     99.25%       98.783%  
Repurchase price if triggering event occurs 101.00%              
6.375% 2025 Senior Notes | Cleveland-Cliffs Inc. [Member]                
Debt Instrument [Line Items]                
Debt Instrument, Par Value $ 64         $ 232    
Repurchase price if triggering event occurs 101.00%              
7.00% 2027 Senior Notes | Cleveland-Cliffs Inc. [Member]                
Debt Instrument [Line Items]                
Debt Instrument, Par Value $ 73         $ 335    
Repurchase price if triggering event occurs 101.00%              
1.50% 2025 Convertible Senior Notes                
Debt Instrument [Line Items]                
Debt Instrument, Convertible, Conversion Ratio 129.2985 122.4365            
Convertible debt, initial conversion price | $ / shares $ 8.17              
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger, Five-Day Trading 0.98              
Convertible debt, equity component $ 86              
Debt Instrument, Redemption Price, Percentage 100.00%              
1.50% 2025 Convertible Senior Notes | Minimum [Member]                
Debt Instrument [Line Items]                
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger 130.00%              
1.50% 2025 Convertible Senior Notes | Cleveland-Cliffs Inc. [Member]                
Debt Instrument [Line Items]                
Debt Instrument, Par Value $ 296             $ 316
5.875% 2027 Senior Notes | Cleveland-Cliffs Inc. [Member]                
Debt Instrument [Line Items]                
Debt Instrument, Par Value $ 556             750
Repurchase price if triggering event occurs 101.00%              
6.25% 2040 Senior Notes | Cleveland-Cliffs Inc. [Member]                
Debt Instrument [Line Items]                
Debt Instrument, Par Value $ 263             298
Repurchase price if triggering event occurs 101.00%              
5.75% 2025 Senior Notes | Cleveland-Cliffs Inc. [Member]                
Debt Instrument [Line Items]                
Debt Instrument, Par Value $ 396             473
Repurchase price if triggering event occurs 101.00%              
4.875% 2024 Senior Secured Notes | Cleveland-Cliffs Inc. [Member]                
Debt Instrument [Line Items]                
Debt Instrument, Par Value $ 395             $ 400
Repurchase price if triggering event occurs 101.00%