DEBT AND CREDIT FACILITIES (Tables)
   | 
6 Months Ended | 
Jun. 30, 2020  | 
| Debt Instrument, Redemption [Line Items] | 
 
 | 
| Schedule Of Long-Term Debt | 
 The following represents a summary of our long-term debt: 
 |  
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
(In Millions)  |  
June 30, 2020  |  
Debt Instrument  | 
   | 
Issuer1
  | 
   | 
 Annual Effective  
Interest Rate 
 | 
   | 
Total Principal Amount  | 
   | 
Debt Issuance Costs  | 
   | 
Unamortized Premiums (Discounts)  | 
   | 
Total Debt  | 
 
Senior Secured Notes:  | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
 
4.875% 2024 Senior Secured Notes  | 
   | 
Cliffs  | 
   | 
5.00%  | 
   | 
$  | 
394.5  | 
 
  | 
   | 
$  | 
(4.0  | 
)  | 
   | 
$  | 
(1.6  | 
)  | 
   | 
$  | 
388.9  | 
 
  | 
 
9.875% 2025 Senior Secured Notes  | 
   | 
Cliffs  | 
   | 
10.57%  | 
   | 
955.2  | 
 
  | 
   | 
(8.7  | 
)  | 
   | 
(26.7  | 
)  | 
   | 
919.8  | 
 
  | 
 
6.75% 2026 Senior Secured Notes  | 
   | 
Cliffs  | 
   | 
6.99%  | 
   | 
845.0  | 
 
  | 
   | 
(22.6  | 
)  | 
   | 
(9.4  | 
)  | 
   | 
813.0  | 
 
  | 
 
Senior Unsecured Notes:  | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
 
7.625% 2021 AK Senior Notes  | 
   | 
AK Steel  | 
   | 
7.33%  | 
   | 
33.5  | 
 
  | 
   | 
—  | 
 
  | 
   | 
0.1  | 
 
  | 
   | 
33.6  | 
 
  | 
 
7.50% 2023 AK Senior Notes  | 
   | 
AK Steel  | 
   | 
6.17%  | 
   | 
12.8  | 
 
  | 
   | 
—  | 
 
  | 
   | 
0.5  | 
 
  | 
   | 
13.3  | 
 
  | 
 
6.375% 2025 Senior Notes  | 
   | 
Cliffs  | 
   | 
8.11%  | 
   | 
64.3  | 
 
  | 
   | 
(0.2  | 
)  | 
   | 
(4.8  | 
)  | 
   | 
59.3  | 
 
  | 
 
6.375% 2025 AK Senior Notes  | 
   | 
AK Steel  | 
   | 
8.11%  | 
   | 
38.4  | 
 
  | 
   | 
—  | 
 
  | 
   | 
(2.9  | 
)  | 
   | 
35.5  | 
 
  | 
 
1.50% 2025 Convertible Senior Notes  | 
   | 
Cliffs  | 
   | 
6.26%  | 
   | 
296.3  | 
 
  | 
   | 
(3.9  | 
)  | 
   | 
(55.6  | 
)  | 
   | 
236.8  | 
 
  | 
 
5.75% 2025 Senior Notes  | 
   | 
Cliffs  | 
   | 
6.01%  | 
   | 
396.2  | 
 
  | 
   | 
(2.8  | 
)  | 
   | 
(4.3  | 
)  | 
   | 
389.1  | 
 
  | 
 
7.00% 2027 Senior Notes  | 
   | 
Cliffs  | 
   | 
9.24%  | 
   | 
88.0  | 
 
  | 
   | 
(0.3  | 
)  | 
   | 
(9.8  | 
)  | 
   | 
77.9  | 
 
  | 
 
7.00% 2027 AK Senior Notes  | 
   | 
AK Steel  | 
   | 
9.24%  | 
   | 
56.3  | 
 
  | 
   | 
—  | 
 
  | 
   | 
(6.2  | 
)  | 
   | 
50.1  | 
 
  | 
 
5.875% 2027 Senior Notes  | 
   | 
Cliffs  | 
   | 
6.49%  | 
   | 
555.5  | 
 
  | 
   | 
(4.5  | 
)  | 
   | 
(19.0  | 
)  | 
   | 
532.0  | 
 
  | 
 
6.25% 2040 Senior Notes  | 
   | 
Cliffs  | 
   | 
6.34%  | 
   | 
262.7  | 
 
  | 
   | 
(1.9  | 
)  | 
   | 
(2.8  | 
)  | 
   | 
258.0  | 
 
  | 
 
IRBs due 2024 to 2028  | 
   | 
AK Steel  | 
   | 
Various  | 
   | 
92.0  | 
 
  | 
   | 
—  | 
 
  | 
   | 
2.3  | 
 
  | 
   | 
94.3  | 
 
  | 
 
ABL Facility  | 
   | 
Cliffs2
  | 
   | 
2.79%  | 
   | 
2,000.0  | 
 
  | 
   | 
—  | 
 
  | 
   | 
—  | 
 
  | 
   | 
550.0  | 
 
  | 
 
Total long-term debt  | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
$  | 
4,451.6  | 
 
  | 
 
  
1 Unless otherwise noted, references in this column to "Cliffs" are to Cleveland-Cliffs Inc., and references to "AK Steel" are to AK Steel Corporation.
 
2 Refers to Cleveland-Cliffs Inc. as borrower under our ABL Facility.
 
 |  
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
(In Millions)  |  
December 31, 2019  |  
Debt Instrument  | 
   | 
Issuer1
  | 
   | 
 Annual Effective  
Interest Rate 
 | 
   | 
Total Principal Amount  | 
   | 
Debt Issuance Costs  | 
   | 
Unamortized Discounts  | 
   | 
Total Debt  | 
 
Senior Secured Notes:  | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
 
4.875% 2024 Senior Notes  | 
   | 
Cliffs  | 
   | 
5.00%  | 
   | 
$  | 
400.0  | 
 
  | 
   | 
$  | 
(4.6  | 
)  | 
   | 
$  | 
(1.8  | 
)  | 
   | 
$  | 
393.6  | 
 
  | 
 
Senior Unsecured Notes:  | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
 
1.50% 2025 Convertible Senior Notes  | 
   | 
Cliffs  | 
   | 
6.26%  | 
   | 
316.3  | 
 
  | 
   | 
(4.6  | 
)  | 
   | 
(65.0  | 
)  | 
   | 
246.7  | 
 
  | 
 
5.75% 2025 Senior Notes  | 
   | 
Cliffs  | 
   | 
6.01%  | 
   | 
473.3  | 
 
  | 
   | 
(3.6  | 
)  | 
   | 
(5.5  | 
)  | 
   | 
464.2  | 
 
  | 
 
5.875% 2027 Senior Notes  | 
   | 
Cliffs  | 
   | 
6.49%  | 
   | 
750.0  | 
 
  | 
   | 
(6.3  | 
)  | 
   | 
(27.3  | 
)  | 
   | 
716.4  | 
 
  | 
 
6.25% 2040 Senior Notes  | 
   | 
Cliffs  | 
   | 
6.34%  | 
   | 
298.4  | 
 
  | 
   | 
(2.2  | 
)  | 
   | 
(3.3  | 
)  | 
   | 
292.9  | 
 
  | 
 
Former ABL Facility  | 
   | 
Cliffs2
  | 
   | 
N/A  | 
   | 
450.0  | 
 
  | 
   | 
N/A  | 
 
  | 
   | 
N/A  | 
 
  | 
   | 
—  | 
 
  | 
 
Total long-term debt  | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
$  | 
2,113.8  | 
 
  | 
 
  
 
 
1 Unless otherwise noted, references in this column to "Cliffs" are to Cleveland-Cliffs Inc.
 
2 Refers to Cleveland-Cliffs Inc. and certain of its subsidiaries as borrowers under our Former ABL Facility.
 
 | 
| Schedule of Extinguishment of Debt | 
 The following is a summary of the debt extinguished and the respective gain on extinguishment: 
 |  
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
   | 
   | 
(In Millions)  | 
 
   | 
   | 
Three Months Ended  June 30, 2020  | 
   | 
Six Months Ended June 30, 2020  | 
 
Debt Instrument  | 
   | 
Debt Extinguished  | 
   | 
Gain on Extinguishment  | 
   | 
Debt Extinguished  | 
   | 
Gain on Extinguishment  | 
 
7.625% 2021 AK Senior Notes  | 
   | 
$  | 
—  | 
 
  | 
   | 
$  | 
—  | 
 
  | 
   | 
$  | 
372.7  | 
 
  | 
   | 
$  | 
0.4  | 
 
  | 
 
7.50% 2023 AK Senior Notes  | 
   | 
—  | 
 
  | 
   | 
—  | 
 
  | 
   | 
367.2  | 
 
  | 
   | 
2.8  | 
 
  | 
 
4.875% 2024 Senior Secured Notes  | 
   | 
5.5  | 
 
  | 
   | 
0.5  | 
 
  | 
   | 
5.5  | 
 
  | 
   | 
0.5  | 
 
  | 
 
6.375% 2025 Senior Notes  | 
   | 
167.5  | 
 
  | 
   | 
21.3  | 
 
  | 
   | 
167.5  | 
 
  | 
   | 
21.3  | 
 
  | 
 
1.50% 2025 Convertible Senior Notes  | 
   | 
20.0  | 
 
  | 
   | 
1.3  | 
 
  | 
   | 
20.0  | 
 
  | 
   | 
1.3  | 
 
  | 
 
5.75% 2025 Senior Notes  | 
   | 
77.1  | 
 
  | 
   | 
16.3  | 
 
  | 
   | 
77.1  | 
 
  | 
   | 
16.3  | 
 
  | 
 
7.00% 2027 Senior Notes  | 
   | 
247.3  | 
 
  | 
   | 
28.4  | 
 
  | 
   | 
247.3  | 
 
  | 
   | 
28.4  | 
 
  | 
 
5.875% 2027 Senior Notes  | 
   | 
194.5  | 
 
  | 
   | 
48.7  | 
 
  | 
   | 
194.5  | 
 
  | 
   | 
48.7  | 
 
  | 
 
6.25% 2040 Senior Notes  | 
   | 
35.7  | 
 
  | 
   | 
12.9  | 
 
  | 
   | 
35.7  | 
 
  | 
   | 
12.9  | 
 
  | 
 
   | 
   | 
$  | 
747.6  | 
 
  | 
   | 
$  | 
129.4  | 
 
  | 
   | 
$  | 
1,487.5  | 
 
  | 
   | 
$  | 
132.6  | 
 
  | 
 
  
 
 
Debt Extinguishments - 2019 
The following is a summary of the debt extinguished with cash and the respective loss on extinguishment: 
 |  
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
   | 
   | 
(In Millions)  | 
 
   | 
   | 
 Three Months Ended  
June 30, 2019 
 | 
   | 
 Six Months Ended  
June 30, 2019 
 | 
 
Debt Instrument  | 
   | 
Debt Extinguished  | 
   | 
(Loss) on Extinguishment  | 
   | 
Debt Extinguished  | 
   | 
(Loss) on Extinguishment  | 
 
4.875% 2021 Senior Notes  | 
   | 
$  | 
114.0  | 
 
  | 
   | 
$  | 
(5.0  | 
)  | 
   | 
$  | 
124.0  | 
 
  | 
   | 
$  | 
(5.3  | 
)  | 
 
5.75% 2025 Senior Notes  | 
   | 
600.0  | 
 
  | 
   | 
(12.9  | 
)  | 
   | 
600.0  | 
 
  | 
   | 
(12.9  | 
)  | 
 
   | 
   | 
$  | 
714.0  | 
 
  | 
   | 
$  | 
(17.9  | 
)  | 
   | 
$  | 
724.0  | 
 
  | 
   | 
$  | 
(18.2  | 
)  | 
 
  
 
 
 | 
| Schedule of Line of Credit Facilities | 
 The following represents a summary of our borrowing capacity under the ABL Facility: 
 |  
 | 
 | 
 | 
 | 
 | 
 
   | 
   | 
(In Millions)  | 
 
   | 
   | 
June 30,  2020  | 
 
Available borrowing base on ABL Facility1
  | 
   | 
$  | 
1,652.1  | 
 
  | 
 
Borrowings  | 
   | 
(550.0  | 
)  | 
 
Letter of credit obligations2
  | 
   | 
(198.5  | 
)  | 
 
Borrowing capacity available  | 
   | 
$  | 
903.6  | 
 
  | 
 
  
 
 
1 As of June 30, 2020, the ABL Facility has a maximum borrowing base of $2.0 billion.  The available borrowing base is determined by applying customary advance rates to eligible accounts receivable, inventory and certain mobile equipment.
 
2 We issued standby letters of credit with certain financial institutions in order to support business obligations including, but not limited to, workers' compensation, employee severance, IRBs and environmental obligations.
 
 | 
| Schedule of Maturities of Long-term Debt | 
 
The following represents a summary of our maturities of debt instruments based on the principal amounts outstanding at June 30, 2020: 
 
 |  
 | 
 | 
 | 
 | 
 | 
 
   | 
   | 
(In Millions)  | 
 
   | 
   | 
Maturities of Debt  | 
 
2020 (remaining period of year)  | 
   | 
$  | 
—  | 
 
  | 
 
2021  | 
   | 
33.5  | 
 
  | 
 
2022  | 
   | 
—  | 
 
  | 
 
2023  | 
   | 
12.8  | 
 
  | 
 
2024  | 
   | 
456.5  | 
 
  | 
 
Thereafter  | 
   | 
4,137.9  | 
 
  | 
 
Total maturities of debt  | 
   | 
$  | 
4,640.7  | 
 
  | 
 
  
 
 
 | 
| 9.875% 2025 Senior Secured Notes [Member] | 
 
 | 
| Debt Instrument, Redemption [Line Items] | 
 
 | 
| Debt Instrument Redemption | 
The following is a summary of redemption prices for our 9.875% 2025 Senior Secured Notes:
 |  
 | 
 | 
 | 
 | 
 | 
 | 
 
Redemption Period  | 
   | 
Redemption Price1
  | 
   | 
Restricted Amount  | 
 
Prior to August 15, 2020 - using proceeds of a regulatory debt facility  | 
   | 
103.000  | 
%  | 
   | 
Up to 35% of original aggregate principal  | 
 
Prior to October 17, 2022 - using proceeds of equity issuance  | 
   | 
109.875  | 
   | 
   | 
Up to 35% of original aggregate principal  | 
 
Prior to October 17, 20222
  | 
   | 
100.000  | 
   | 
   | 
   | 
 
Beginning on October 17, 2022  | 
   | 
107.406  | 
   | 
   | 
   | 
 
Beginning on April 17, 2023  | 
   | 
104.938  | 
   | 
   | 
   | 
 
Beginning on April 17, 2024  | 
   | 
102.469  | 
   | 
   | 
   | 
 
Beginning on April 17, 2025 and thereafter  | 
   | 
100.000  | 
   | 
   | 
   | 
 
   | 
   | 
   | 
   | 
   | 
   | 
 
1  Plus accrued and unpaid interest, if any, up to, but excluding, the redemption date.
  |  
2  Plus a "make-whole" premium.
  |  
  
 
 
 | 
| 6.375% 2025 Senior Notes [Member] | 
 
 | 
| Debt Instrument, Redemption [Line Items] | 
 
 | 
| Debt Instrument Redemption | 
The following is a summary of redemption prices for our 6.375% 2025 Senior Notes:
 |  
 | 
 | 
 | 
 | 
 | 
 | 
 
Redemption Period  | 
   | 
Redemption Price1
  | 
   | 
Restricted Amount  | 
 
Prior to October 15, 2020 - using proceeds of equity issuance  | 
   | 
106.375  | 
%  | 
   | 
Up to 35% of original aggregate principal  | 
 
Prior to October 15, 20202
  | 
   | 
100.000  | 
   | 
   | 
   | 
 
Beginning on October 15, 2020  | 
   | 
103.188  | 
   | 
   | 
   | 
 
Beginning on October 15, 2021  | 
   | 
101.594  | 
   | 
   | 
   | 
 
Beginning on October 15, 2022 and thereafter  | 
   | 
100.000  | 
   | 
   | 
   | 
 
   | 
   | 
   | 
   | 
   | 
   | 
 
1  Plus accrued and unpaid interest, if any, up to but excluding the redemption date.
  |  
2  Plus a "make-whole" premium.
  |  
  
 
 
 | 
| 7.00% 2027 Senior Notes [Member] | 
 
 | 
| Debt Instrument, Redemption [Line Items] | 
 
 | 
| Debt Instrument Redemption | 
The following is a summary of redemption prices for our 7.00% 2027 Senior Notes:
 |  
 | 
 | 
 | 
 | 
 
Redemption Period  | 
   | 
Redemption Price1
  | 
 
Prior to March 15, 20222
  | 
   | 
100.000  | 
%  | 
 
Beginning on March 15, 2022  | 
   | 
103.500  | 
   | 
 
Beginning on March 15, 2023  | 
   | 
102.333  | 
   | 
 
Beginning on March 15, 2024  | 
   | 
101.167  | 
   | 
 
Beginning on March 15, 2025 and thereafter  | 
   | 
100.000  | 
   | 
 
   | 
   | 
   | 
   | 
 
1  Plus accrued and unpaid interest, if any, up to but excluding the redemption date.
  |  
2  Plus a "make-whole" premium.
  |  
  
 
 
 | 
| 7.50% 2023 AK Senior Notes [Member] | 
 
 | 
| Debt Instrument, Redemption [Line Items] | 
 
 | 
| Debt Instrument Redemption | 
 The following is a summary of redemption prices for the 7.50% 2023 AK Senior Notes: 
 |  
 | 
 | 
 | 
 | 
 
Redemption Period  | 
   | 
Redemption Price1
  | 
 
Prior to July 15, 2020  | 
   | 
103.750  | 
%  | 
 
Beginning on July 15, 2020  | 
   | 
101.875  | 
   | 
 
Beginning on July 15, 2021 and thereafter  | 
   | 
100.000  | 
   | 
 
   | 
   | 
   | 
   | 
 
1  Plus accrued and unpaid interest, if any, up to but excluding the redemption date.
  |  
  
 
 
 | 
| 6.375% 2025 AK Senior Notes [Member] | 
 
 | 
| Debt Instrument, Redemption [Line Items] | 
 
 | 
| Debt Instrument Redemption | 
 The following is a summary of redemption prices for the 6.375% 2025 AK Senior Notes: 
 |  
 | 
 | 
 | 
 | 
 
Redemption Period  | 
   | 
Redemption Price1
  | 
 
Prior to October 15, 20202
  | 
   | 
100.000  | 
%  | 
 
Beginning on October 15, 2020  | 
   | 
103.188  | 
   | 
 
Beginning on October 15, 2021  | 
   | 
101.594  | 
   | 
 
Beginning on October 15, 2022 and thereafter  | 
   | 
100.000  | 
   | 
 
   | 
   | 
   | 
   | 
 
1  Plus accrued and unpaid interest, if any, up to but excluding the redemption date.
  |  
2  Plus a "make-whole" premium.
  |  
  
 
 
 | 
| 6.75% 2026 Senior Secured Notes [Member] | 
 
 | 
| Debt Instrument, Redemption [Line Items] | 
 
 | 
| Debt Instrument Redemption | 
The following is a summary of redemption prices for our 6.75% 2026 Senior Secured Notes:
 |  
 | 
 | 
 | 
 | 
 | 
 | 
 
Redemption Period  | 
   | 
Redemption Price1
  | 
   | 
Restricted Amount  | 
 
Prior to March 15, 2022 - using proceeds of equity issuance  | 
   | 
106.750  | 
%  | 
   | 
Up to 35% of original aggregate principal  | 
 
Prior to March 15, 20222
  | 
   | 
100.000  | 
   | 
   | 
   | 
 
Beginning on March 15, 2022  | 
   | 
105.063  | 
   | 
   | 
   | 
 
Beginning on March 15, 2023  | 
   | 
103.375  | 
   | 
   | 
   | 
 
Beginning on March 15, 2024  | 
   | 
101.688  | 
   | 
   | 
   | 
 
Beginning on March 15, 2025 and thereafter  | 
   | 
100.000  | 
   | 
   | 
   | 
 
   | 
   | 
   | 
   | 
   | 
   | 
 
1  Plus accrued and unpaid interest, if any, up to, but excluding, the redemption date.
  |  
2  Plus a "make-whole" premium.
  |  
  
 
 
 | 
| 7.00% 2027 AK Senior Notes [Member] | 
 
 | 
| Debt Instrument, Redemption [Line Items] | 
 
 | 
| Debt Instrument Redemption | 
 The following is a summary of redemption prices for the 7.00% 2027 AK Senior Notes: 
 |  
 | 
 | 
 | 
 | 
 
Redemption Period  | 
   | 
Redemption Price1
  | 
 
Prior to March 15, 20222
  | 
   | 
100.000  | 
%  | 
 
Beginning on March 15, 2022  | 
   | 
103.500  | 
   | 
 
Beginning on March 15, 2023  | 
   | 
102.333  | 
   | 
 
Beginning on March 15, 2024  | 
   | 
101.167  | 
   | 
 
Beginning on March 15, 2025 and thereafter  | 
   | 
100.000  | 
   | 
 
   | 
   | 
   | 
   | 
 
1  Plus accrued and unpaid interest, if any, up to but excluding the redemption date.
  |  
2  Plus a "make-whole" premium.
  |  
  
 
 
 |