Quarterly report pursuant to Section 13 or 15(d)

DEBT AND CREDIT FACILITIES - Narrative (Details)

v3.20.2
DEBT AND CREDIT FACILITIES - Narrative (Details) - USD ($)
$ in Millions
6 Months Ended
Jun. 30, 2020
Jun. 19, 2020
Apr. 24, 2020
Apr. 17, 2020
Mar. 16, 2020
Mar. 13, 2020
Debt Instrument [Line Items]            
Long-term Debt, Gross $ 4,640.7          
6.375% 2025 Senior Notes [Member]            
Debt Instrument [Line Items]            
Long-term Debt, Gross         $ 231.8  
Debt Instrument, Interest Rate, Stated Percentage 6.375%          
Repurchase price if triggering event occurs 101.00%          
Debt Issuance Costs, Gross $ 0.9          
7.00% 2027 Senior Notes [Member]            
Debt Instrument [Line Items]            
Long-term Debt, Gross         $ 335.4  
Debt Instrument, Interest Rate, Stated Percentage 7.00%          
Debt Issuance Costs, Gross $ 1.3          
9.875% 2025 Senior Secured Notes [Member]            
Debt Instrument [Line Items]            
Long-term Debt, Gross     $ 555.2 $ 400.0    
Debt issuance, discount rate     99.00% 94.50%    
Debt Instrument, Interest Rate, Stated Percentage 9.875%          
Repurchase price if triggering event occurs 101.00%          
Debt Issuance Costs, Gross $ 9.1          
6.75% 2026 Senior Secured Notes [Member]            
Debt Instrument [Line Items]            
Long-term Debt, Gross   $ 120.0       $ 725.0
Debt issuance, discount rate   99.25%       98.783%
Debt Instrument, Interest Rate, Stated Percentage 6.75%          
Repurchase price if triggering event occurs 101.00%          
Debt Issuance Costs, Gross $ 23.7          
Cleveland-Cliffs Inc. [Member] | 6.375% 2025 Senior Notes [Member]            
Debt Instrument [Line Items]            
Long-term Debt, Gross 64.3          
Cleveland-Cliffs Inc. [Member] | 7.00% 2027 Senior Notes [Member]            
Debt Instrument [Line Items]            
Long-term Debt, Gross $ 88.0          
Repurchase price if triggering event occurs 101.00%          
Cleveland-Cliffs Inc. [Member] | 9.875% 2025 Senior Secured Notes [Member]            
Debt Instrument [Line Items]            
Long-term Debt, Gross $ 955.2          
Cleveland-Cliffs Inc. [Member] | 6.75% 2026 Senior Secured Notes [Member]            
Debt Instrument [Line Items]            
Long-term Debt, Gross 845.0          
AK Steel Holding Corporation [Member]            
Debt Instrument [Line Items]            
Unsecured Long-term Debt, Noncurrent 141.0          
AK Steel Holding Corporation [Member] | Unsecured Industrial Revenue Bonds [Member]            
Debt Instrument [Line Items]            
Long-term Debt, Gross $ 66.0          
Debt, Weighted Average Interest Rate 6.86%          
AK Steel Holding Corporation [Member] | Secured Industrial Revenue Bonds [Member]            
Debt Instrument [Line Items]            
Long-term Debt, Gross $ 26.0