Annual report pursuant to Section 13 and 15(d)

DEBT AND CREDIT FACILITIES - Debt Extinguishments (Details)

v3.20.4
DEBT AND CREDIT FACILITIES - Debt Extinguishments (Details) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 12, 2021
Mar. 11, 2021
Apr. 24, 2020
Mar. 27, 2020
Mar. 13, 2020
Mar. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Apr. 17, 2020
Mar. 16, 2020
Extinguishment of Debt [Line Items]                      
Debt Extinguished     $ 736       $ 1,513 $ 724 $ 227    
Gain (loss) on extinguishment of debt             130 (18) (7)    
Debt Instrument, Par Value             5,595        
Reduction of Principal Long-Term Debt     181                
AK Steel [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             132        
Senior Notes [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished             35        
Unsecured Industrial Revenue Bonds | AK Steel [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished             7        
7.625% 2021 AK Senior Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished       $ 9 $ 364   373        
Gain (loss) on extinguishment of debt             0        
7.625% 2021 AK Senior Notes | AK Steel [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             34        
7.625% 2021 AK Senior Notes | AK Steel [Member] | Subsequent Event [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished $ 34                    
7.50% 2023 AK Senior Notes [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished       $ 56 $ 311   367        
Gain (loss) on extinguishment of debt             3        
7.50% 2023 AK Senior Notes [Member] | AK Steel [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             13        
7.50% 2023 AK Senior Notes [Member] | AK Steel [Member] | Subsequent Event [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished 13                    
4.875% 2024 Senior Secured Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished             6        
Gain (loss) on extinguishment of debt             1        
4.875% 2024 Senior Secured Notes | Cleveland-Cliffs Inc. [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             395 400      
4.875% 2024 Senior Secured Notes | Cleveland-Cliffs Inc. [Member] | Subsequent Event [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished 395                    
6.375% 2025 Senior Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished             168        
Gain (loss) on extinguishment of debt             21        
6.375% 2025 Senior Notes | Cleveland-Cliffs Inc. [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             64       $ 232
6.375% 2025 Senior Notes | Cleveland-Cliffs Inc. [Member] | Subsequent Event [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished 64                    
1.50% 2025 Convertible Senior Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished             20        
Gain (loss) on extinguishment of debt             1        
1.50% 2025 Convertible Senior Notes | Cleveland-Cliffs Inc. [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             296 316      
5.75% 2025 Senior Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished             77 600 2    
Gain (loss) on extinguishment of debt             16 (13) 0    
5.75% 2025 Senior Notes | Cleveland-Cliffs Inc. [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             396 473      
7.00% 2027 Senior Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished             262        
Gain (loss) on extinguishment of debt             27        
7.00% 2027 Senior Notes | Cleveland-Cliffs Inc. [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             73       $ 335
5.875% 2027 Senior Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished             195        
Gain (loss) on extinguishment of debt             49        
5.875% 2027 Senior Notes | Cleveland-Cliffs Inc. [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             556 750      
6.25% 2040 Senior Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished             36        
Gain (loss) on extinguishment of debt             13        
6.25% 2040 Senior Notes | Cleveland-Cliffs Inc. [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             263 298      
6.375% 2025 AK Senior Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished             9        
Gain (loss) on extinguishment of debt             (1)        
6.375% 2025 AK Senior Notes | AK Steel [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             29        
6.375% 2025 AK Senior Notes | AK Steel [Member] | Subsequent Event [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished $ 29                    
4.875% 2021 Senior Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished               124 14    
Gain (loss) on extinguishment of debt               $ (5) 0    
5.90% 2020 Senior Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished                 89    
Gain (loss) on extinguishment of debt                 (3)    
4.80% 2020 Senior Notes                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished                 122    
Gain (loss) on extinguishment of debt                 $ (4)    
9.875% 2025 Senior Secured Notes | Subsequent Event [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished   $ 334       $ 334          
9.875% 2025 Senior Secured Notes | Cleveland-Cliffs Inc. [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value     $ 555       955     $ 400  
9.875% 2025 Senior Secured Notes | Cleveland-Cliffs Inc. [Member] | Subsequent Event [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Extinguished   $ 322                  
Unsecured Industrial Revenue Bonds | AK Steel [Member]                      
Extinguishment of Debt [Line Items]                      
Debt Instrument, Par Value             $ 66