CLEVELAND-CLIFFS INC., 10-Q filed on 10/23/2020
Quarterly Report
v3.20.2
Document and Entity Information - shares
 9 Months Ended
Sep. 30, 2020
Oct. 22, 2020
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2020  
Document Transition Report false  
Entity File Number 1-8944  
Entity Registrant Name CLEVELAND-CLIFFS INC.  
Entity Incorporation, State or Country Code OH  
Entity Tax Identification Number 34-1464672  
Entity Address, Address Line One 200 Public Square,  
Entity Address, City or Town Cleveland,  
Entity Address, State or Province OH  
Entity Address, Postal Zip Code 44114-2315  
City Area Code 216  
Local Phone Number 694-5700  
Title of 12(b) Security Common shares, par value $0.125 per share  
Trading Symbol CLF  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   399,241,687
Entity Central Index Key 0000764065  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2020  
Document Fiscal Period Focus Q3  
Amendment Flag false  
v3.20.2
Statements Of Unaudited Condensed Consolidated Financial Position - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Current assets:    
Cash and cash equivalents $ 56.0 $ 352.6
Accounts receivable, net 653.7 94.0
Inventories 1,795.1 317.4
Income tax receivable, current 9.0 58.6
Other current assets 115.0 75.3
Total current assets 2,628.8 897.9
Non-current assets:    
Property, plant and equipment, net 4,550.7 1,929.0
Goodwill 144.0 2.1
Intangible assets, net 190.1 48.1
Income tax receivable, non-current 0.0 62.7
Deferred income taxes 519.5 459.5
Right-of-use asset, operating lease 207.7 11.7
Other non-current assets 240.1 92.8
TOTAL ASSETS 8,480.9 3,503.8
Current liabilities:    
Accounts payable 710.7 193.2
Accrued liabilities 279.4 126.3
Other current liabilities 224.0 89.9
Total current liabilities 1,214.1 409.4
Non-current liabilities:    
Long-term debt 4,309.8 2,113.8
Operating lease liability, non-current 174.1 10.5
Intangible liabilities, net 65.9 0.0
Pension and OPEB liabilities 1,130.6 311.5
Asset retirement obligations 182.0 163.2
Other non-current liabilities 280.7 137.5
TOTAL LIABILITIES 7,357.2 3,145.9
Commitments and contingencies (See Note 18)
SHAREHOLDERS' EQUITY    
Common shares - par value $0.125 per share, Authorized - 600,000,000 shares (2019 - 600,000,000 shares); Issued - 428,645,866 shares (2019 - 301,886,794 shares); Outstanding - 399,229,917 shares (2019 - 270,084,005 shares) 53.6 37.7
Capital in excess of par value of shares 4,446.3 3,872.1
Retained deficit (3,052.5) (2,842.4)
Cost of 29,415,949 common shares in treasury (2019 - 31,802,789 shares) (354.8) (390.7)
Accumulated other comprehensive loss (282.0) (318.8)
Total Cliffs shareholders' equity 810.6 357.9
Noncontrolling interest 313.1 0.0
TOTAL EQUITY 1,123.7 357.9
TOTAL LIABILITIES AND EQUITY $ 8,480.9 $ 3,503.8
v3.20.2
Statements Of Condensed Consolidated Financial Position (Parenthetical) - $ / shares
Sep. 30, 2020
Dec. 31, 2019
Statement of Financial Position [Abstract]    
Common shares, par value $ 0.125  
Common shares, authorized (in shares) 600,000,000 600,000,000
Common shares, issued (in shares) 428,645,866 301,886,794
Common shares, outstanding (in shares) 399,229,917 270,084,005
Common shares in treasury (in shares) 29,415,949 31,802,789
v3.20.2
Statements Of Unaudited Condensed Consolidated Operations - USD ($)
shares in Thousands, $ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Income Statement [Abstract]        
Revenues $ 1,646.0 $ 555.6 $ 3,063.2 $ 1,455.8
Realization of deferred revenue 0.0 0.0 34.6 0.0
Operating costs:        
Cost of goods sold (1,525.4) (400.7) (3,088.9) (1,007.0)
Selling, general and administrative expenses (59.6) (25.5) (149.2) (82.2)
Acquisition-related costs (7.5) 0.0 (68.4) 0.0
Miscellaneous – net (15.5) (7.8) (40.5) (19.0)
Total operating costs (1,608.0) (434.0) (3,347.0) (1,108.2)
Operating income (loss) 38.0 121.6 (249.2) 347.6
Other income (expense):        
Interest expense, net (68.2) (25.3) (167.9) (76.5)
Gain (loss) on extinguishment of debt 0.0 0.0 132.6 (18.2)
Other non-operating income 10.0 0.3 31.2 1.3
Total other expense (58.2) (25.0) (4.1) (93.4)
Income (loss) from continuing operations before income taxes (20.2) 96.6 (253.3) 254.2
Income tax benefit (expense) 22.4 (4.8) 98.5 (23.1)
Income (loss) from continuing operations 2.2 91.8 (154.8) 231.1
Loss from discontinued operations, net of tax (0.3) (0.9) 0.0 (1.5)
Net income (loss) 1.9 90.9 (154.8) 229.6
Income attributable to noncontrolling interest (11.9) 0.0 (31.2) 0.0
Net income (loss) attributable to Cliffs shareholders $ (10.0) $ 90.9 $ (186.0) $ 229.6
Earnings (loss) per common share attributable to Cliffs shareholders - basic        
Continuing operations (in dollars per share) $ (0.02) $ 0.34 $ (0.51) $ 0.83
Discontinued operations (in dollars per share) 0 0 0 (0.01)
Earnings (Loss) per Common Share - Basic (in dollars per share) (0.02) 0.34 (0.51) 0.82
Earnings (loss) per common share attributable to Cliffs shareholders - diluted        
Continuing operations (in dollars per share) (0.02) 0.33 (0.51) 0.80
Discontinued operations (in dollars per share) 0 0 0 0
Earnings (Loss) per Common Share - Diluted (in dollars per share) $ (0.02) $ 0.33 $ (0.51) $ 0.80
Average number of shares (in thousands)        
Basic 399,399 269,960 365,245 278,418
Diluted 399,399 276,578 365,245 287,755
v3.20.2
Statements Of Unaudited Condensed Consolidated Comprehensive Income - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Statement of Comprehensive Income [Abstract]        
Net income (loss) $ 1.9 $ 90.9 $ (154.8) $ 229.6
Other comprehensive income:        
Changes in pension and OPEB, net of tax 6.6 5.8 18.2 17.3
Changes in foreign currency translation 1.6 0.0 1.4 0.0
Changes in derivative financial instruments, net of tax 15.7 0.4 17.2 1.0
Total other comprehensive income 23.9 6.2 36.8 18.3
Comprehensive income (loss) 25.8 97.1 (118.0) 247.9
Comprehensive income attributable to noncontrolling interests (11.9) 0.0 (31.2) 0.0
Comprehensive income (loss) attributable to Cliffs shareholders $ 13.9 $ 97.1 $ (149.2) $ 247.9
v3.20.2
Statements Of Unaudited Condensed Consolidated Cash Flows - USD ($)
$ in Millions
 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
OPERATING ACTIVITIES    
Net income (loss) $ (154.8) $ 229.6
Adjustments to reconcile net income (loss) to net cash provided (used) by operating activities:    
Depreciation, depletion and amortization 183.9 63.1
Amortization of inventory step-up 74.0 0.0
Deferred income taxes (89.9) 22.7
Loss (gain) on extinguishment of debt (132.6) 18.2
Loss (gain) on derivatives (19.1) 48.4
Other (13.0) 49.4
Changes in operating assets and liabilities, net of business combination:    
Receivables and other assets 259.8 174.1
Inventories (4.2) (147.0)
Payables, accrued expenses and other liabilities (157.3) (70.4)
Net cash provided (used) by operating activities (53.2) 388.1
INVESTING ACTIVITIES    
Purchase of property, plant and equipment (378.9) (460.7)
Acquisition of AK Steel, net of cash acquired (869.3) 0.0
Other investing activities 8.0 11.2
Net cash used by investing activities (1,240.2) (449.5)
FINANCING ACTIVITIES    
Repurchase of common shares 0.0 (252.9)
Proceeds from issuance of debt 1,762.9 720.9
Debt issuance costs (57.5) (6.8)
Repurchase of debt (999.5) (729.3)
Borrowings under credit facilities 800.0 0.0
Repayments under credit facilities (400.0) 0.0
Dividends paid (40.8) (45.1)
Other financing activities (23.3) (53.7)
Net cash provided (used) by financing activities 994.2 (366.9)
Decrease in cash and cash equivalents, including cash classified within other current assets related to discontinued operations (299.2) (428.3)
Less: decrease in cash and cash equivalents from discontinued operations, classified within other current assets (2.6) (4.4)
Net decrease in cash and cash equivalents (296.6) (423.9)
Cash and cash equivalents at beginning of period 352.6 823.2
Cash and cash equivalents at end of period 56.0 399.3
SunCoke Middletown [Member]    
FINANCING ACTIVITIES    
SunCoke Middletown distributions to noncontrolling interest owners $ (47.6) $ 0.0
v3.20.2
Statements of Unaudited Condensed Consolidated Changes in Equity Statement - USD ($)
$ in Millions
Total
Common Stock [Member]
Additional Paid-in Capital [Member]
Retained Earnings [Member]
Treasury Stock [Member]
AOCI Attributable to Parent [Member]
Noncontrolling Interest [Member]
Balance, beginning of period (in shares) at Dec. 31, 2018   292,600,000          
Balance, beginning of period at Dec. 31, 2018 $ 424.2 $ 37.7 $ 3,916.7 $ (3,060.2) $ (186.1) $ (283.9)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Comprehensive Income (Loss), Net of Tax, Attributable to Parent (13.7)     (22.1)   8.4  
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture   1,700,000          
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture (10.0)   (56.5)   46.5    
Stock Repurchased During Period, Shares   (11,500,000)          
Common Share Repurchases, Value (124.3)       (124.3)    
Dividends, Common Stock (14.5)     (14.5)      
Balance, end of period (in shares) at Mar. 31, 2019   282,800,000          
Balance, end of period at Mar. 31, 2019 $ 261.7 $ 37.7 3,860.2 (3,096.8) (263.9) (275.5)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Common Stock, Dividends, Per Share, Declared $ 0.05            
Balance, beginning of period (in shares) at Dec. 31, 2018   292,600,000          
Balance, beginning of period at Dec. 31, 2018 $ 424.2 $ 37.7 3,916.7 (3,060.2) (186.1) (283.9)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Comprehensive Income (Loss), Net of Tax, Attributable to Parent $ 247.9            
Stock Repurchased During Period, Shares (24,400,000)            
Balance, end of period (in shares) at Sep. 30, 2019   270,100,000          
Balance, end of period at Sep. 30, 2019 $ 359.9 $ 37.7 3,867.7 (2,889.0) (390.9) (265.6)  
Balance, beginning of period (in shares) at Mar. 31, 2019   282,800,000          
Balance, beginning of period at Mar. 31, 2019 261.7 $ 37.7 3,860.2 (3,096.8) (263.9) (275.5)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Comprehensive Income (Loss), Net of Tax, Attributable to Parent 164.5     160.8   3.7  
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture   100,000          
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture 4.6   3.4   1.2    
Stock Repurchased During Period, Shares   (12,900,000)          
Common Share Repurchases, Value (128.6)       (128.6)    
Dividends, Common Stock (16.6)     (16.6)      
Balance, end of period (in shares) at Jun. 30, 2019   270,000,000.0          
Balance, end of period at Jun. 30, 2019 $ 285.6 $ 37.7 3,863.6 (2,952.6) (391.3) (271.8)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Common Stock, Dividends, Per Share, Declared $ 0.06            
Comprehensive Income (Loss), Net of Tax, Attributable to Parent $ 97.1     90.9   6.2  
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture   100,000          
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture 4.5   4.1   0.4    
Dividends, Common Stock (27.3)     (27.3)      
Balance, end of period (in shares) at Sep. 30, 2019   270,100,000          
Balance, end of period at Sep. 30, 2019 $ 359.9 $ 37.7 3,867.7 (2,889.0) (390.9) (265.6)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Common Stock, Dividends, Per Share, Declared $ 0.10            
Balance, beginning of period (in shares) at Dec. 31, 2019 270,084,005 270,100,000          
Balance, beginning of period at Dec. 31, 2019 $ 357.9 $ 37.7 3,872.1 (2,842.4) (390.7) (318.8) $ 0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Comprehensive Income (Loss), Net of Tax, Attributable to Parent (46.9)     (52.1)   1.7 3.5
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture   1,700,000          
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture 2.1   (23.6)   25.7    
Stock Issued During Period, Shares, Acquisitions   126,800,000          
Stock Issued During Period, Value, Acquisitions 947.4 $ 15.9 601.7        
Noncontrolling Interest, Increase from Business Combination             329.8
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders (5.5)           (5.5)
Dividends, Common Stock (24.0)     (24.0)      
Balance, end of period (in shares) at Mar. 31, 2020   398,600,000          
Balance, end of period at Mar. 31, 2020 $ 1,231.0 $ 53.6 4,450.2 (2,918.5) (365.0) (317.1) 327.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Common Stock, Dividends, Per Share, Declared $ 0.06            
Balance, beginning of period (in shares) at Dec. 31, 2019 270,084,005 270,100,000          
Balance, beginning of period at Dec. 31, 2019 $ 357.9 $ 37.7 3,872.1 (2,842.4) (390.7) (318.8) 0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Comprehensive Income (Loss), Net of Tax, Attributable to Parent $ (118.0)            
Balance, end of period (in shares) at Sep. 30, 2020 399,229,917 399,200,000          
Balance, end of period at Sep. 30, 2020 $ 1,123.7 $ 53.6 4,446.3 (3,052.5) (354.8) (282.0) 313.1
Balance, beginning of period (in shares) at Mar. 31, 2020   398,600,000          
Balance, beginning of period at Mar. 31, 2020 1,231.0 $ 53.6 4,450.2 (2,918.5) (365.0) (317.1) 327.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Comprehensive Income (Loss), Net of Tax, Attributable to Parent (96.9)     (123.9)   11.2 15.8
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture   600,000          
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture 2.5   (6.6)   9.1    
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders (18.3)           (18.3)
Dividends, Common Stock (0.1)     (0.1)      
Balance, end of period (in shares) at Jun. 30, 2020   399,200,000          
Balance, end of period at Jun. 30, 2020 1,118.2 $ 53.6 4,443.6 (3,042.5) (355.9) (305.9) 325.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Comprehensive Income (Loss), Net of Tax, Attributable to Parent 25.8     (10.0)   23.9 11.9
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture   0          
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture 3.8   2.7   1.1    
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders $ (24.1)           (24.1)
Balance, end of period (in shares) at Sep. 30, 2020 399,229,917 399,200,000          
Balance, end of period at Sep. 30, 2020 $ 1,123.7 $ 53.6 $ 4,446.3 $ (3,052.5) $ (354.8) $ (282.0) $ 313.1
v3.20.2
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Notes)
 9 Months Ended
Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Basis of Presentation and Significant Accounting Policies [Text Block]
Business, Consolidation and Presentation
    The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with SEC rules and regulations and, in the opinion of management, include all adjustments (consisting of normal recurring adjustments) necessary to present fairly the financial position, results of operations, comprehensive income (loss), cash flows and changes in equity for the periods presented. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Management bases its estimates on various assumptions and historical experience, which are believed to be reasonable; however, due to the inherent nature of estimates, actual results may differ significantly due to changed conditions or assumptions. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of results to be expected for the year ending December 31, 2020 or any other future period. Due to the acquisition of AK Steel, certain balances have become material and are no longer being condensed in our Statements of Unaudited Condensed Consolidated Financial Position, such as balances for Right-of-use asset, operating lease and Operating lease liability, non-current. As a result, certain prior period amounts have been reclassified to conform with the current year presentation. These unaudited condensed consolidated financial statements should be read in conjunction with the financial statements and notes included in our Annual Report on Form 10-K for the year ended December 31, 2019 and in our Quarterly Reports on Form 10-Q for the quarterly periods ended March 31, 2020 and June 30, 2020.
    Proposed acquisition of substantially all of the operations of ArcelorMittal USA
On September 28, 2020, we entered into a Transaction Agreement with ArcelorMittal S.A., pursuant to which Cliffs will acquire substantially all of the operations of ArcelorMittal USA for an aggregate purchase price of approximately $1.4 billion, consisting of (i) $505 million in cash, (ii) 78,186,671 of our common shares, par value $0.125 per share, and (iii) 583,273 shares of a new series of our Serial Preferred Stock, Class B, without par value, to be designated as the “Series B Participating Redeemable Preferred Stock” at closing. The cash portion of the purchase price is subject to customary working capital and purchase price adjustments.
We expect to complete the Transaction in the fourth quarter of 2020. Completion of the Transaction is subject to various customary closing conditions, including the receipt of required regulatory approvals in identified jurisdictions, including the expiration or termination of the waiting period under the Hart-Scott-Rodino Act, and it is possible that factors outside of our control could result in the Transaction being completed at a later time or not at all. The Transaction Agreement also contains certain termination rights that may be exercised by either us or ArcelorMittal S.A. We plan to complete the Transaction as soon as reasonably practicable following the satisfaction or waiver of all applicable conditions.
Acquisition of AK Steel
    On March 13, 2020, we consummated the Merger, pursuant to which, upon the terms and subject to the conditions set forth in the Merger Agreement, Merger Sub was merged with and into AK Steel, with AK Steel surviving the Merger as a wholly owned subsidiary of Cliffs. Refer to NOTE 3 - ACQUISITION OF AK STEEL for further information.
    AK Steel is a leading North American producer of flat-rolled carbon, stainless and electrical steel products, primarily for the automotive, infrastructure and manufacturing markets. The acquisition of AK Steel has transformed us into a vertically integrated producer of value-added iron ore and steel products.
    COVID-19
    In response to the COVID-19 pandemic, we made various operational changes to adjust to the demand for our products. Although steel and iron ore production have been considered “essential” by the states in which we operate, certain of our facilities and construction activities were temporarily idled during the second quarter of 2020.  Most of these temporarily idled facilities were restarted during the second quarter, and the remaining operations were restarted during the third quarter.
    Basis of Consolidation
    The unaudited condensed consolidated financial statements consolidate our accounts and the accounts of our wholly owned subsidiaries, all subsidiaries in which we have a controlling interest and two variable interest entities for which we are the primary beneficiary. All intercompany transactions and balances are eliminated upon consolidation.
    Reportable Segments
    The acquisition of AK Steel has transformed us into a vertically integrated producer of value-added iron ore and steel products and we are organized according to our differentiated products in two reportable segments - the Steel and Manufacturing segment and the Mining and Pelletizing segment. Our new Steel and Manufacturing segment includes the assets acquired through the acquisition of AK Steel and our previously reported Metallics segment, and our Mining and Pelletizing segment includes our three active operating mines and our indefinitely idled mine.
    Investments in Affiliates
    We have investments in several businesses accounted for using the equity method of accounting. We review an investment for impairment when circumstances indicate that a loss in value below its carrying amount is other than temporary. Investees and equity ownership percentages are presented below:
InvesteeSegment Reported WithinEquity Ownership Percentage
Combined Metals of Chicago, LLCSteel and Manufacturing40.0%
Hibbing Taconite CompanyMining and Pelletizing23.0%
Spartan Steel Coating, LLCSteel and Manufacturing48.0%
    We recorded a basis difference for Spartan Steel of $32.5 million as part of our acquisition of AK Steel.  The basis difference relates to the excess of the fair value over the investee's carrying amount of property, plant and equipment and will be amortized over the remaining useful lives of the underlying assets.
Significant Accounting Policies
    A detailed description of our significant accounting policies can be found in the audited financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC, which were updated and can be found in the unaudited condensed consolidated financial statements included in our Quarterly Reports on Form 10-Q for the quarterly periods ended March 31, 2020 and June 30, 2020 filed with the SEC. There have been no material changes in our significant accounting policies and estimates from those disclosed therein.
Recent Accounting Pronouncements
    Issued and Adopted
    On March 2, 2020, the SEC issued a final rule that amended the disclosure requirements related to certain registered securities under SEC Regulation S-X, Rule 3-10, which required separate financial statements for subsidiary issuers and guarantors of registered debt securities unless certain exceptions are met. The final rule replaces the previous requirement under Rule 3-10 to provide condensed consolidating financial information in the registrant’s financial statements with a requirement to provide alternative financial disclosures (which include summarized financial information of the parent and any issuers and guarantors, as well as other qualitative disclosures) in either the registrant’s Management's Discussion and Analysis of Financial Condition and Results of Operations or its financial statements, in addition to other simplifications. The final rule is effective for filings on or after January 4, 2021, and early adoption is permitted. We elected to early adopt this disclosure update for the period ended March 31, 2020. As a result, we have excluded the footnote disclosures required under the previous Rule 3-10, and applied the final rule by including the summarized financial information and qualitative disclosures in Part I - Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operations of this Quarterly Report on Form 10-Q and Exhibit 22.1, hereto.
Issued and Not EffectiveIn August 2020, the Financial Accounting Standards Board issued Accounting Standards Update No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40). This update requires certain convertible instruments to be accounted for as a single liability measured at its amortized cost. Additionally, the update requires the use of the "if-converted" method, removing the treasury stock method, when calculating diluted shares. The two methods of adoption are the full and modified retrospective approaches. We expect to utilize the modified retrospective approach. Using this approach, the guidance shall be applied to transactions outstanding as of the beginning of the fiscal year in which the amendment is adopted. The final rule is effective for fiscal years beginning after December 15, 2021. Early adoption is permitted for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. We are continuing to evaluate the impact of this update to our financials and would expect to adopt at the required adoption date of January 1, 2022.
v3.20.2
SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION (Notes)
 9 Months Ended
Sep. 30, 2020
Disclosure Text Block [Abstract]  
Supplementary Financial Statement Information
Revenues
    The following table represents our consolidated Revenues (excluding intercompany revenues) by market:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Steel and Manufacturing:
Automotive$920.0 $— $1,404.0 $— 
Infrastructure and manufacturing198.8 — 446.2 — 
Distributors and converters142.9 — 344.1 — 
Total Steel and Manufacturing1,261.7 — 2,194.3 — 
Mining and Pelletizing:
Steel producers1
384.3 555.6 903.5 1,455.8 
Total revenues$1,646.0 $555.6 $3,097.8 $1,455.8 
1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
    The following table represents our consolidated Revenues (excluding intercompany revenues) by product line:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Steel and Manufacturing:
Carbon steel$821.2 $— $1,391.6 $— 
Stainless and electrical steel303.2 — 585.1 — 
Tubular products, components and other137.3 — 217.6 — 
Total Steel and Manufacturing1,261.7 — 2,194.3 — 
Mining and Pelletizing:
Iron ore1
357.1 515.0 838.1 1,357.8 
Freight27.2 40.6 65.4 98.0 
Total Mining and Pelletizing384.3 555.6 903.5 1,455.8 
Total revenues$1,646.0 $555.6 $3,097.8 $1,455.8 
1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
    We sell to customers located primarily in the United States and to foreign customers, primarily in Canada, Mexico and Western Europe. Net revenues to customers located outside the United States were $265.0 million and $487.7 million for the three and nine months ended September 30, 2020, respectively, and $138.9 million and $318.3 million for the three and nine months ended September 30, 2019, respectively.
Allowance for Credit Losses
    The following is a roll forward of our allowance for credit losses associated with Accounts receivable, net:
(In Millions)
20202019
Allowance for credit losses as of January 1$— $— 
Increase in allowance5.2 — 
Allowance for credit losses as of September 30$5.2 $— 
Inventories
    The following table presents the detail of our Inventories in the Statements of Unaudited Condensed Consolidated Financial Position:
(In Millions)
September 30,
2020		December 31,
2019
Product inventories
Finished and semi-finished goods$940.5 $114.1 
Work-in-process78.2 68.7 
Raw materials382.3 9.4 
Total product inventories1,401.0 192.2 
Manufacturing supplies and critical spares394.1 125.2 
Inventories$1,795.1 $317.4 
Deferred Revenue
    The table below summarizes our deferred revenue balances:
(In Millions)
Deferred Revenue (Current)Deferred Revenue (Long-Term)
2020201920202019
Opening balance as of January 1$22.1 $21.0 $25.7 $38.5 
Net decrease(19.8)(2.7)(25.7)(8.5)
Closing balance as of September 30$2.3 $18.3 $— $30.0 
    Prior to the Merger, our iron ore pellet sales agreement with Severstal, subsequently assumed by AK Steel, required supplemental payments to be paid by the customer during the period 2009 through 2013. Installment amounts received under this arrangement in excess of sales were classified as deferred revenue in the Statements of Consolidated Financial Position upon receipt of payment and the revenue was recognized over the term of the supply agreement, which had extended until 2022, in equal annual installments. As a result of the termination of that iron ore pellet sales agreement, we realized $34.6 million of deferred revenue, which was recognized within Realization of deferred revenue in the Statements of Unaudited Condensed Consolidated Operations, during the nine months ended September 30, 2020.
    We have certain other sales agreements that require customers to pay in advance. Payments received pursuant to these agreements prior to revenue being recognized are recorded as deferred revenue in Other current liabilities.
Accrued Liabilities
    The following table presents the detail of our Accrued liabilities in the Statements of Unaudited Condensed Consolidated Financial Position:
(In Millions)
September 30,
2020		December 31, 2019
Accrued employment costs$146.6 $61.7 
Accrued interest81.8 29.0 
Accrued dividends1.0 17.8 
Other50.0 17.8 
Accrued liabilities$279.4 $126.3 
Cash Flow Information
    A reconciliation of capital additions to cash paid for capital expenditures is as follows:
(In Millions)
Nine Months Ended
September 30,
20202019
Capital additions$333.0 $505.6 
Less:
Non-cash accruals(88.4)26.1 
Right-of-use assets - finance leases42.5 29.3 
Grants— (10.5)
Cash paid for capital expenditures including deposits$378.9 $460.7 
    Cash payments (receipts) for income taxes and interest are as follows:
(In Millions)
Nine Months Ended
September 30,
20202019
Taxes paid on income$3.2 $0.1 
Income tax refunds(119.3)(117.9)
Interest paid on debt obligations net of capitalized interest1
106.0 71.9 
1 Capitalized interest was $38.0 million and $16.9 million for the nine months ended September 30, 2020 and 2019, respectively.
    Non-Cash Investing and Financing Activities
(In Millions)
Nine Months Ended
September 30,
20202019
Fair value of common shares issued for consideration for business combination$617.6 $— 
Fair value of equity awards assumed from AK Steel acquisition3.9 — 
v3.20.2
ACQUISITION OF AK STEEL (Notes)
 9 Months Ended
Sep. 30, 2020
Business Combinations [Abstract]  
Business Combination Disclosure [Text Block]
Overview
    On March 13, 2020, pursuant to the Merger Agreement, we completed the acquisition of AK Steel, in which we were the acquirer. As a result of the Merger, each share of AK Steel common stock issued and outstanding
immediately prior to the effective time of the Merger (other than excluded shares) was converted into the right to receive 0.400 Cliffs common shares and, if applicable, cash in lieu of any fractional Cliffs common shares.
    The acquisition combined Cliffs, North America’s largest producer of iron ore pellets, with AK Steel, a leading producer of innovative flat-rolled carbon, stainless and electrical steel products, to create a vertically integrated producer of value-added iron ore and steel products. The combination is expected to create significant opportunities to generate additional value from market trends across the entire steel value chain and enable more consistent, predictable performance through normal market cycles. Together, Cliffs and AK Steel have a presence across the entire manufacturing process, from mining to pelletizing to the development and production of finished high value steel products, including Next Generation Advanced High Strength Steels for automotive and other markets. We expect the combination will generate additional cost synergies, which we have identified and already set into motion savings of approximately $150 million, primarily from consolidating corporate functions, reducing duplicative overhead costs, and procurement and energy cost savings, as well as operational and supply chain efficiencies. The combined company is well positioned to provide high-value iron ore and steel solutions to customers primarily across North America.
    Total net revenues for AK Steel for the most recent pre-acquisition year ended December 31, 2019 were $6,359.4 million. Following the acquisition, the operating results of AK Steel are included in our unaudited condensed consolidated financial statements and are reported as part of our Steel and Manufacturing segment. For the three months ended September 30, 2020, AK Steel generated Revenues of $1,261.7 million and a loss of $30.4 million included within Net income (loss) attributable to Cliffs shareholders, which included $14.6 million and $2.4 million related to amortization of the fair value inventory step-up and severance costs, respectively. For the period subsequent to the acquisition (March 13, 2020 through September 30, 2020), AK Steel generated Revenues of $2,194.3 million and a loss of $292.0 million included within Net income (loss) attributable to Cliffs shareholders, which included $74.0 million and $35.1 million related to amortization of the fair value inventory step-up and severance costs, respectively.
    Additionally, we incurred acquisition-related costs in connection with the acquisition of AK Steel, excluding severance costs, of $0.6 million and $25.6 million for the three and nine months ended September 30, 2020, respectively, which were recorded in Acquisition-related costs on the Statements of Unaudited Condensed Consolidated Operations.
    Refer to NOTE 7 - DEBT AND CREDIT FACILITIES for information regarding debt transactions executed in connection with the Merger.
    The Merger was accounted for under the acquisition method of accounting for business combinations. The acquisition date fair value of the consideration transferred totaled $1.5 billion. The following tables summarize the consideration paid for AK Steel and the estimated fair values of the assets acquired and liabilities assumed at the acquisition date.
    The fair value of the total purchase consideration was determined as follows:
(In Millions)
Fair value of Cliffs common shares issued for AK Steel outstanding common stock$617.6 
Fair value of replacement equity awards3.9 
Fair value of AK Steel debt913.6 
Total purchase consideration$1,535.1 
    The fair value of Cliffs common shares issued for outstanding shares of AK Steel common stock and with respect to Cliffs common shares underlying converted AK Steel equity awards that vested upon completion of the Merger is calculated as follows:
(In Millions, Except Per Share Amounts)
Number of shares of AK Steel common stock issued and outstanding316.9 
Exchange ratio0.400 
Number of Cliffs common shares issued to AK Steel stockholders126.8 
Price per share of Cliffs common shares$4.87 
Fair value of Cliffs common shares issued for AK Steel outstanding common stock$617.6 
    The fair value of AK Steel's debt included in the consideration is calculated as follows:
(In Millions)
Credit Facility$590.0 
7.50% Senior Secured Notes due July 2023323.6 
Fair value of debt included in consideration$913.6 
Valuation Assumption and Preliminary Purchase Price Allocation
    We estimated fair values at March 13, 2020 for the preliminary allocation of consideration to the net tangible and intangible assets acquired and liabilities assumed. During the measurement period, we will continue to obtain information to assist in finalizing the fair value of assets acquired and liabilities assumed, which may differ materially from these preliminary estimates. If we determine any measurement period adjustments are material, we will apply those adjustments, including any related impacts to net income, in the reporting period in which the adjustments are determined. We are in the process of conducting a valuation of the assets acquired and liabilities assumed related to the acquisition, most notably, inventories, including manufacturing supplies and critical spares, personal and real property, leases, investments, deferred taxes, asset retirement obligations, pension and OPEB liabilities and intangible assets and liabilities, and the final allocation will be made when completed, including the result of any identified goodwill. Accordingly, the provisional measurements noted below are preliminary and subject to modification in the future.
    The preliminary purchase price allocation to assets acquired and liabilities assumed in the Merger was:
(In Millions)
Initial Allocation of ConsiderationMeasurement Period AdjustmentsUpdated Preliminary Allocation
Cash and cash equivalents$37.7 $2.0 $39.7 
Accounts receivable666.0 (3.1)662.9 
Inventories1,562.8 (39.8)1,523.0 
Other current assets67.5 (15.4)52.1 
Property, plant and equipment2,184.4 (20.1)2,164.3 
Intangible assets163.0 (15.0)148.0 
Right of use asset, operating leases225.9 (16.3)209.6 
Other non-current assets85.9 26.2 112.1 
Accounts payable(636.3)(6.1)(642.4)
Accrued liabilities(222.5)0.1 (222.4)
Other current liabilities(181.8)6.6 (175.2)
Long-term debt(1,179.4)— (1,179.4)
Deferred income taxes(19.7)(0.2)(19.9)
Operating lease liability, non-current(188.1)12.7 (175.4)
Intangible liabilities(140.0)69.5 (70.5)
Pension and OPEB liabilities(873.0)2.1 (870.9)
Asset retirement obligations(13.9)(2.0)(15.9)
Other non-current liabilities(144.2)(2.3)(146.5)
Net identifiable assets acquired1,394.3 (1.1)1,393.2 
Goodwill141.2 0.7 141.9 
Total net assets acquired$1,535.5 $(0.4)$1,535.1 
    During the second and third quarter of 2020, we made certain measurement period adjustments to the acquired assets and liabilities assumed due to clarification of information utilized to determine fair value during the measurement period. The Inventories measurement period adjustments of $39.8 million resulted in a favorable impact of $0.2 million and $8.0 million, respectively, to Cost of goods sold for the three and nine months ended September 30, 2020.
    The goodwill resulting from the acquisition of AK Steel was assigned to Precision Partners, our downstream tooling and stamping operations, and AK Tube, our tubing operations, that are reporting units included in the Steel and Manufacturing segment. Goodwill is calculated as the excess of the purchase price over the net identifiable assets recognized and primarily represents the growth opportunities in lightweighting solutions to automotive customers, as well as any synergistic benefits to be realized from the acquisition of AK Steel. None of the goodwill is expected be deductible for income tax purposes.
    The preliminary purchase price allocated to identifiable intangible assets and liabilities acquired was:
(In Millions)Weighted Average Life (In Years)
Intangible assets:
Customer relationships$77.0 18
Developed technology60.0 17
Trade names and trademarks11.0 10
Total identifiable intangible assets$148.0 17
Intangible liabilities:
Above-market supply contracts$(70.5)12
    The above-market supply contracts relate to the long-term coke and energy supply agreements with SunCoke Energy, which includes SunCoke Middletown, a consolidated VIE. Refer to NOTE 16 - VARIABLE INTEREST ENTITIES for further information.
Pro Forma Results
    The following table provides unaudited pro forma financial information, prepared in accordance with Topic 805, for the three and nine months ended September 30, 2020 and 2019, as if AK Steel had been acquired as of January 1, 2019:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Revenues$1,646.0 $1,937.6 $4,265.1 $5,958.7 
Net income (loss) attributable to Cliffs shareholders(6.0)84.2 (123.9)213.3 
    The unaudited pro forma financial information has been calculated after applying our accounting policies and adjusting the historical results with pro forma adjustments, net of tax, that assume the acquisition occurred on January 1, 2019. Significant pro forma adjustments include the following:
1.The elimination of intercompany revenues between Cliffs and AK Steel of $135.6 million and $394.8 million for the three and nine months ended September 30, 2020, respectively, and $153.5 million and $410.8 million for the three and nine months ended September 30, 2019, respectively.
2.The 2020 pro forma net loss was adjusted to exclude $14.6 million and $74.0 million of non-recurring inventory acquisition accounting adjustments incurred during the three and nine months ended September 30, 2020, respectively. The 2019 pro forma net income was adjusted to include $74.0 million of non-recurring inventory acquisition accounting adjustments for the nine months ended September 30, 2019.
3.The elimination of nonrecurring transaction costs incurred by Cliffs and AK Steel in connection with the Merger of $0.7 million and $29.1 million for the three and nine months ended September 30, 2020, respectively.
4.Total other pro forma adjustments included expense of $10.0 million for the three and nine months ended September 30, 2020, primarily due to increased interest expense, offset by reduced amortization expense, depreciation expense and pension and OPEB expense. Total other pro forma adjustments for the three and nine months ended September 30, 2019 included expense of $1.1 million and $7.0 million, respectively, primarily due to reduced interest and amortization expense, offset by additional depreciation expense and pension and OPEB expense.
5.The income tax impact of pro forma transaction adjustments that affect Net income (loss) attributable to Cliffs shareholders at a statutory rate of 24.3% resulted in an income tax benefit of $5.6 million and $2.1 million for the three and nine months ended September 30, 2020, respectively, and an income tax benefit of $2.1 million and $4.5 million for the three and nine months ended September 30, 2019, respectively.
    The unaudited pro forma financial information does not reflect the potential realization of synergies or cost savings, nor does it reflect other costs relating to the integration of the two companies. This unaudited pro forma financial information should not be considered indicative of the results that would have actually occurred if the acquisition had been consummated on January 1, 2019, nor are they indicative of future results.
v3.20.2
SEGMENT REPORTING (Notes)
 9 Months Ended
Sep. 30, 2020
Segment Reporting [Abstract]  
Segment Reporting Disclosure Our Company is a vertically integrated producer of value-added iron ore and steel products. Our operations are organized and managed in two operating segments according to our upstream and downstream operations. Our Steel and Manufacturing segment is a leading producer of flat-rolled carbon, stainless and electrical steel products, primarily for the automotive, infrastructure and manufacturing, and distributors and converters markets. Our Steel and Manufacturing segment includes subsidiaries that provide customer solutions with carbon and stainless steel tubing products, advanced-engineered solutions, tool design and build, hot- and cold-stamped steel components, and complex assemblies. Construction of our HBI production plant in Toledo, Ohio, included as part of our Steel and Manufacturing segment, is expected to be completed with production beginning in the fourth quarter of 2020. Our Mining and Pelletizing segment is a major supplier of iron ore pellets to the North American steel industry from our mines and pellet plants located in Michigan and Minnesota. All intercompany transactions were eliminated in consolidation.
    We evaluate performance on a segment basis, as well as a consolidated basis, based on Adjusted EBITDA, which is a non-GAAP measure. This measure is used by management, investors, lenders and other external users of our financial statements to assess our operating performance and to compare operating performance to other companies in the steel and iron ore industries. In addition, management believes Adjusted EBITDA is a useful measure to assess the earnings power of the business without the impact of capital structure and can be used to assess our ability to service debt and fund future capital expenditures in the business.
    Our results by segment are as follows:
(In Millions, Except Sales Tons)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Sales volume (in thousands):
Steel and Manufacturing (net tons)1,117 — 1,935— 
Mining and Pelletizing sales (long tons)4,907 5,750 11,80013,527
Less: Intercompany sales (long tons)(1,204)(346)(3,028)(384)
Mining and Pelletizing consolidated sales (long tons)3,703 5,404 8,772 13,143 
Revenues:
Steel and Manufacturing net sales to external customers$1,261.7 $— $2,194.3 $— 
Mining and Pelletizing net sales1
520.3 590.6 1,238.7 1,494.8 
Less: Intercompany sales(136.0)(35.0)(335.2)(39.0)
Mining and Pelletizing net sales to external customers384.3 555.6 903.5 1,455.8 
Total revenues$1,646.0 $555.6 $3,097.8 $1,455.8 
Adjusted EBITDA:
Steel and Manufacturing$33.3 $(2.1)$(81.8)$(4.0)
Mining and Pelletizing145.3 182.7 309.5 510.7 
Corporate and eliminations(52.3)(36.5)(160.7)(93.0)
Total Adjusted EBITDA$126.3 $144.1 $67.0 $413.7 
1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
    The following table provides a reconciliation of our consolidated Net income (loss) to total Adjusted EBITDA:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Net income (loss)$1.9 $90.9 $(154.8)$229.6 
Less:
Interest expense, net(68.2)(25.4)(167.9)(76.8)
Income tax benefit (expense)22.4 (4.8)98.5 (23.1)
Depreciation, depletion and amortization(72.4)(22.2)(183.9)(63.1)
Total EBITDA$120.1 $143.3 $98.5 $392.6 
Less:
EBITDA of noncontrolling interests1
$16.2 $— $41.3 $— 
Gain (loss) on extinguishment of debt— — 132.6 (18.2)
Severance costs(2.4)— (38.3)(1.7)
Acquisition-related costs excluding severance costs(5.1)— (30.1)— 
Amortization of inventory step-up(14.6)— (74.0)— 
Impact of discontinued operations(0.3)(0.8)— (1.2)
Total Adjusted EBITDA$126.3 $144.1 $67.0 $413.7 
1 EBITDA of noncontrolling interests includes $11.9 million and $31.2 million for income and $4.3 million and $10.1 million for depreciation, depletion and amortization for the three and nine months ended September 30, 2020, respectively.
    The following summarizes our assets by segment:
(In Millions)
September 30,
2020		December 31,
2019
Assets:
Steel and Manufacturing$6,345.7 $913.6 
Mining and Pelletizing1,643.3 1,643.1 
Total segment assets7,989.0 2,556.7 
Corporate and Other (including discontinued operations)491.9 947.1 
Total assets$8,480.9 $3,503.8 
    The following table summarizes our capital additions by segment:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Capital additions1:
Steel and Manufacturing$88.0 $160.5 $266.8 $398.0 
Mining and Pelletizing13.3 22.1 64.9 104.5 
Corporate and Other1.0 2.1 1.3 3.1 
Total capital additions$102.3 $184.7 $333.0 $505.6 
1 Refer to NOTE 2 - SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION for additional information.
v3.20.2
PROPERTY, PLANT AND EQUIPMENT (Notes)
 9 Months Ended
Sep. 30, 2020
Property, Plant and Equipment [Abstract]  
PROPERTY, PLANT AND EQUIPMENT The following table indicates the carrying value of each of the major classes of our depreciable assets:
(In Millions)
September 30,
2020		December 31,
2019
Land, land improvements and mineral rights$653.2 $582.2 
Buildings454.4 157.8 
Steel and Manufacturing equipment2,128.0 42.0 
Mining and Pelletizing equipment1,455.2 1,413.6 
Other121.3 101.5 
Construction-in-progress1,145.9 730.3 
Total property, plant and equipment1
5,958.0 3,027.4 
Allowance for depreciation and depletion(1,407.3)(1,098.4)
Property, plant and equipment, net$4,550.7 $1,929.0 
1 Includes right-of-use assets related to finance leases of $97.1 million and $49.0 million as of September 30, 2020 and December 31, 2019, respectively.
    We recorded capitalized interest into property, plant and equipment of $14.7 million and $38.0 million during the three and nine months ended September 30, 2020, respectively, and $7.0 million and $16.9 million for the three and nine months ended September 30, 2019, respectively.
    We recorded depreciation and depletion expense of $71.8 million and $182.5 million for the three and nine months ended September 30, 2020, respectively, and $22.0 million and $62.5 million for the three and nine months ended September 30, 2019, respectively.
v3.20.2
GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES (Notes)
 9 Months Ended
Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]  
Goodwill and Intangible Assets Disclosure [Text Block]
Goodwill
    The increase in the balance of Goodwill as of September 30, 2020, compared to December 31, 2019, is due to the preliminary assignment of $141.9 million to Goodwill in 2020 based on the preliminary purchase price allocation for the acquisition of AK Steel. The carrying amount of goodwill related to our Mining and Pelletizing segment was $2.1 million as of both September 30, 2020 and December 31, 2019.
Intangible Assets and Liabilities    
The following is a summary of our intangible assets and liabilities:
(In Millions)
Classification1
Gross AmountAccumulated AmortizationNet Amount
As of September 30, 2020
Intangible assets:
Customer relationshipsIntangible assets, net$77.0 $(2.6)$74.4 
Developed technologyIntangible assets, net60.0 (2.1)57.9 
Trade names and trademarksIntangible assets, net11.0 (0.7)10.3 
Mining permitsIntangible assets, net72.2 (24.7)47.5 
Total intangible assets$220.2 $(30.1)$190.1 
Intangible liabilities:
Above-market supply contractsIntangible liabilities, net$(70.5)$4.6 $(65.9)
As of December 31, 2019
Intangible assets:
Mining permitsIntangible assets, net$72.2 $(24.1)$48.1 
1 Amortization of intangible liabilities related to above-market supply contracts and intangible assets related to mining permits is recognized in Cost of goods sold. Amortization of all other intangible assets is recognized in Selling, general and administrative expenses.
    Amortization expense related to intangible assets was $2.5 million and $6.0 million for the three and nine months ended September 30, 2020, respectively, and $0.2 million and $0.6 million for the three and nine months ended September 30, 2019, respectively.
    Estimated future amortization expense related to intangible assets at September 30, 2020 is as follows:
(In Millions)
Years ending December 31,
2020 (remaining period of the year)$2.5 
202110.0 
202210.0 
202310.0 
202410.0 
202510.0 
    Income from amortization related to the intangible liabilities was $1.9 million and $4.6 million for the three and nine months ended September 30, 2020, respectively.
    Estimated future amortization income related to the intangible liabilities at September 30, 2020 is as follows:
(In Millions)
Years ending December 31,
2020 (remaining period of the year)$2.0 
20217.8 
20227.8 
20237.8 
20247.8 
20257.8 
v3.20.2
DEBT AND CREDIT FACILITIES (Notes)
 9 Months Ended
Sep. 30, 2020
Debt Disclosure [Abstract]  
DEBT AND CREDIT FACILITIES The following represents a summary of our long-term debt:
(In Millions)
September 30, 2020
Debt Instrument
Issuer1
Annual Effective
Interest Rate
Total Principal AmountDebt Issuance CostsUnamortized Premiums (Discounts)Total Debt
Senior Secured Notes:
4.875% 2024 Senior Secured NotesCliffs5.00%$394.5 $(3.7)$(1.5)$389.3 
9.875% 2025 Senior Secured NotesCliffs10.57%955.2 (8.1)(25.8)921.3 
6.75% 2026 Senior Secured NotesCliffs6.99%845.0 (21.4)(9.0)814.6 
Senior Unsecured Notes:
7.625% 2021 AK Senior NotesAK Steel7.33%33.5 — 0.1 33.6 
7.50% 2023 AK Senior NotesAK Steel6.17%12.8 — 0.5 13.3 
6.375% 2025 Senior NotesCliffs8.11%64.3 (0.2)(4.6)59.5 
6.375% 2025 AK Senior NotesAK Steel8.11%38.4 — (2.7)35.7 
1.50% 2025 Convertible Senior NotesCliffs6.26%296.3 (3.7)(53.0)239.6 
5.75% 2025 Senior NotesCliffs6.01%396.2 (2.6)(4.1)389.5 
7.00% 2027 Senior NotesCliffs9.24%88.0 (0.3)(9.6)78.1 
7.00% 2027 AK Senior NotesAK Steel9.24%56.3 — (6.0)50.3 
5.875% 2027 Senior NotesCliffs6.49%555.5 (4.3)(18.6)532.6 
6.25% 2040 Senior NotesCliffs6.34%262.7 (1.8)(2.8)258.1 
IRBs due 2024 to 2028AK SteelVarious92.0 — 2.3 94.3 
ABL Facility
Cliffs2
2.77%2,000.0 — — 400.0 
Total long-term debt$4,309.8 
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 AmountDebt Issuance CostsUnamortized DiscountsTotal Debt
Senior Secured Notes:
4.875% 2024 Senior NotesCliffs5.00%$400.0 $(4.6)$(1.8)$393.6 
Senior Unsecured Notes:
1.50% 2025 Convertible Senior NotesCliffs6.26%316.3 (4.6)(65.0)246.7 
5.75% 2025 Senior NotesCliffs6.01%473.3 (3.6)(5.5)464.2 
5.875% 2027 Senior NotesCliffs6.49%750.0 (6.3)(27.3)716.4 
6.25% 2040 Senior NotesCliffs6.34%298.4 (2.2)(3.3)292.9 
Former ABL Facility
Cliffs2
N/A450.0 N/AN/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.
Debt Extinguishments - 2020
    On April 24, 2020, we used the net proceeds from the offering of the additional 9.875% 2025 Senior Secured Notes to repurchase $736.4 million aggregate principal amount of our outstanding senior notes of various series, which resulted in debt reduction of $181.2 million. During the second quarter of 2020, we also repurchased an additional $11.2 million aggregate principal amount of our outstanding senior notes of various series with cash on hand. On June 1, 2020, we redeemed $7.3 million aggregate principal amount of our outstanding 2020 IRBs.
    On March 13, 2020, in connection with the Merger, we purchased $364.2 million aggregate principal amount of 7.625% 2021 AK Senior Notes and $310.7 million aggregate principal amount of 7.50% 2023 AK Senior Notes upon early settlement of tender offers made by Cliffs. The net proceeds from the offering of 6.75% 2026 Senior Secured Notes, along with a portion of the ABL Facility borrowings, were used to fund such purchases. As the 7.625% 2021 AK Senior Notes and 7.50% 2023 AK Senior Notes were recorded at fair value just prior to being purchased, there was no gain or loss on extinguishment. Additionally, in connection with the final settlement of the tender offers, on March 27, 2020, we purchased $8.5 million aggregate principal amount of the 7.625% 2021 AK Senior Notes and $56.5 million aggregate principal amount of the 7.50% 2023 AK Senior Notes with cash on hand.
    The following is a summary of the debt extinguished and the respective gain on extinguishment:
(In Millions)
Nine Months Ended
September 30, 2020
Debt InstrumentDebt ExtinguishedGain on Extinguishment
7.625% 2021 AK Senior Notes$372.7 $0.4 
7.50% 2023 AK Senior Notes367.2 2.8 
4.875% 2024 Senior Secured Notes5.5 0.5 
6.375% 2025 Senior Notes167.5 21.3 
1.50% 2025 Convertible Senior Notes20.0 1.3 
5.75% 2025 Senior Notes77.1 16.3 
7.00% 2027 Senior Notes247.3 28.4 
5.875% 2027 Senior Notes194.5 48.7 
6.25% 2040 Senior Notes35.7 12.9 
$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)
Nine Months Ended
September 30, 2019
Debt InstrumentDebt Extinguished(Loss) on Extinguishment
4.875% 2021 Senior Notes$124.0 $(5.3)
5.75% 2025 Senior Notes600.0 (12.9)
$724.0 $(18.2)
ABL Facility
    As of September 30, 2020, we were in compliance with the ABL Facility liquidity requirements and, therefore, the springing financial covenant requiring a minimum fixed charge coverage ratio of 1.0 to 1.0 was not applicable.
    The following represents a summary of our borrowing capacity under the ABL Facility:
(In Millions)
September 30,
2020
Available borrowing base on ABL Facility1
$1,715.2 
Borrowings(400.0)
Letter of credit obligations2
(192.2)
Borrowing capacity available$1,123.0 
1 As of September 30, 2020, the ABL Facility has a maximum borrowing base of $2.0 billion. The available borrowing base is determined by applying customary advance rates to eligible accounts receivable, inventory and certain mobile equipment.
2 We issued standby letters of credit with certain financial institutions in order to support business obligations including, but not limited to, workers' compensation, employee severance, IRBs and environmental obligations.
Debt Maturities
    The following represents a summary of our maturities of debt instruments based on the principal amounts outstanding at September 30, 2020:
(In Millions)
Maturities of Debt
2020 (remaining period of year)$— 
202133.5 
2022— 
202312.8 
2024456.5 
Thereafter3,987.9 
Total maturities of debt$4,490.7 
v3.20.2
FAIR VALUE MEASUREMENTS (Notes)
 9 Months Ended
Sep. 30, 2020
Fair Value Disclosures [Abstract]  
FAIR VALUE MEASUREMENTS The following represents the assets and liabilities measured at fair value:
(In Millions)
September 30, 2020
Quoted Prices in Active
Markets for Identical Assets/Liabilities
(Level 1)
Significant Other Observable Inputs
(Level 2)
Significant Unobservable Inputs
(Level 3)
Total
Assets:
Other current assets:
Commodity contracts$— $15.8 $— $15.8 
Customer supply agreement — — 34.5 34.5 
Provisional pricing arrangement— — 26.9 26.9 
Other non-current assets:
Commodity contracts— 1.8 — 1.8 
     Total$— $17.6 $61.4 $79.0 
Liabilities:
Other current liabilities:
Commodity contracts$— $(8.7)$— $(8.7)
Provisional pricing arrangement— — (0.3)(0.3)
Foreign exchange contracts— (0.6)— (0.6)
Other non-current liabilities:
Foreign exchange contracts— (0.1)— (0.1)
     Total$— $(9.4)$(0.3)$(9.7)
(In Millions)
December 31, 2019
Quoted Prices in Active
Markets for Identical Assets/Liabilities
(Level 1)
Significant Other Observable Inputs
(Level 2)
Significant Unobservable Inputs
(Level 3)
Total
Assets:
Cash equivalents - Commercial paper$— $187.6 $— $187.6 
Other current assets:
Customer supply agreement — — 44.5 44.5 
Provisional pricing arrangement— — 1.3 1.3 
Total$— $187.6 $45.8 $233.4 
Liabilities:
Other current liabilities:
Commodity contracts $— $(3.2)$— $(3.2)
Provisional pricing arrangement— — (1.1)(1.1)
Total$— $(3.2)$(1.1)$(4.3)
The valuation of financial assets and liabilities classified in Level 2 is determined using a market approach based upon quoted prices for similar assets and liabilities in active markets, or other inputs that are observable. Level 2 assets include commercial paper and commodity hedge contracts. Our commodity hedge contracts primarily include those related to natural gas, electricity and zinc, and our foreign exchange contracts include Canadian dollars.
    The Level 3 assets consist of a freestanding derivative instrument related to a certain supply agreement and derivative assets related to certain provisional pricing arrangements with our customers. The Level 3 liabilities consist of derivative liabilities related to certain provisional pricing arrangements with our customers.
    The supply agreement included in our Level 3 assets contains provisions for supplemental revenue or refunds based on the hot-rolled coil steel price in the year the iron ore product is consumed in the customer’s blast furnaces. We account for these provisions as a derivative instrument at the time of sale and adjust the derivative instrument to fair value through Revenues each reporting period until the product is consumed and the amounts are settled.
    The provisional pricing arrangements included in our Level 3 assets/liabilities specify provisional price calculations, where the pricing mechanisms generally are based on market pricing, with the final revenue rate to be based on market inputs at a specified point in time in the future, per the terms of the supply agreements. The difference between the estimated final revenue rate at the date of sale and the estimated final revenue rate at the measurement date is characterized as a derivative and is required to be accounted for separately once control has transferred upon delivery. The derivative instruments are adjusted to fair value through Revenues each reporting period based upon current market data and forward-looking estimates provided by management until the final revenue rates are determined.
    The following table illustrates information about quantitative inputs and assumptions for the derivative assets and derivative liabilities categorized in Level 3 of the fair value hierarchy:
Qualitative/Quantitative Information About Level 3 Fair Value Measurements
Fair Value at September 30, 2020
(In Millions)		Balance Sheet
Location		Valuation TechniqueUnobservable InputRange or Point Estimate (Weighted Average)
Customer supply agreement$34.5 Other current assetsMarket ApproachManagement's estimate of hot-rolled coil steel price per net ton
$542 - $634
$(548)
Provisional pricing arrangements$26.9 Other current assetsMarket ApproachManagement's
estimate of Platts 62% Price per dry metric ton
$104 - $123
($105)
Atlantic Basin Pellet Premium$30
Provisional pricing arrangements$(0.3)Other current liabilitiesMarket ApproachManagement's
estimate of Platts 62% Price per dry metric ton		$104
PPI Estimates110
    The following tables represent a reconciliation of the changes in fair value of financial instruments measured at fair value on a recurring basis using significant unobservable inputs (Level 3):
(In Millions)
Level 3 Assets
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Beginning balance$35.3 $118.1 $45.8 $91.4 
Total gains (losses) included in earnings29.5 (6.5)43.3 83.1 
Settlements(3.4)(38.8)(27.7)(101.7)
Ending balance$61.4 $72.8 $61.4 $72.8 
Total gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) on assets still held at the reporting date$27.8 $(6.5)$40.4 $81.8 
(In Millions)
Level 3 Liabilities
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Beginning balance$— $— $(1.1)$— 
Total losses included in earnings(0.3)(34.4)(0.9)(39.7)
Settlements— 4.2 1.7 9.5 
Ending balance$(0.3)$(30.2)$(0.3)$(30.2)
Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date$(0.3)$(30.2)$(0.3)$(30.2)
    The carrying values of certain financial instruments (e.g., Accounts receivable, net, Accounts payable and Other current liabilities) approximate fair value and, therefore, have been excluded from the table below. A summary of the carrying value and fair value of other financial instruments were as follows:
(In Millions)
September 30, 2020December 31, 2019
Classification
Carrying
Value
Fair Value
Carrying
Value
Fair Value
Long-term debt:
Senior NotesLevel 1$3,815.5 $3,975.2 $2,113.8 $2,237.0 
IRBs due 2024 to 2028Level 194.3 90.2 — — 
ABL Facility - outstanding balanceLevel 2400.0 400.0 — — 
Total long-term debt$4,309.8 $4,465.4 $2,113.8 $2,237.0 
    The fair value of long-term debt was determined using quoted market prices.
v3.20.2
PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Notes)
 9 Months Ended
Sep. 30, 2020
Postemployment Benefits [Abstract]  
PENSIONS AND OTHER POSTRETIREMENT BENEFITS We offer defined benefit pension plans, defined contribution pension plans and OPEB plans, primarily consisting of retiree healthcare benefits, to most employees as part of a total compensation and benefits program. The defined benefit pension plans are noncontributory and benefits generally are based on a minimum formula or employees’ years of service and average earnings for a defined period prior to retirement.    As a result of the acquisition of AK Steel, we assumed the obligations under AK Steel's defined benefit pension plans and OPEB plans. Noncontributory pension and various healthcare and life insurance benefits are provided to a significant portion of our employees and retirees. AK Steel also contributes to multiemployer pension plans according to collective bargaining agreements that cover certain union-represented employees and defined contribution pension plans. The AK Steel pension and OPEB plans were remeasured as of March 13, 2020.
    The following are the components of defined benefit pension and OPEB costs (credits):
Defined Benefit Pension Costs (Credits)
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Service cost$5.4 $4.6 $16.0 $12.9 
Interest cost19.6 8.9 42.7 26.2 
Expected return on plan assets(36.7)(13.7)(91.9)(41.0)
Amortization:
Prior service costs0.2 0.3 0.7 0.9 
Net actuarial loss7.3 5.9 20.6 17.7 
Net periodic benefit cost (credit)$(4.2)$6.0 $(11.9)$16.7 
OPEB Costs (Credits)
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Service cost$1.4 $0.5 $3.3 $1.3 
Interest cost4.4 2.3 10.9 7.0 
Expected return on plan assets(4.5)(4.2)(13.6)(12.6)
Amortization:
Prior service credits(0.5)(0.5)(1.5)(1.5)
Net actuarial loss0.8 1.3 2.2 3.8 
Net periodic benefit cost (credit)$1.6 $(0.6)$1.3 $(2.0)
    As a result of the CARES Act enacted on March 27, 2020, we have deferred pension contributions starting in the second quarter of 2020. Based on prior funding requirements, we made defined benefit pension contributions of $0.9 million and $4.9 million for the three and nine months ended September 30, 2020, respectively, compared to defined benefit pension contributions of $5.6 million and $12.3 million for the three and nine months ended September 30, 2019, respectively. OPEB contributions for our voluntary employee benefit association trust plans are typically made on an annual basis in the first quarter of each year, but due to plan funding requirements being met, no OPEB contributions for our voluntary employee benefit association trust plans were required or made for the three and nine months ended September 30, 2020 and 2019.
v3.20.2
INCOME TAXES (Notes)
 9 Months Ended
Sep. 30, 2020
Income Tax Disclosure [Abstract]  
Income Taxes Our 2020 estimated annual effective tax rate before discrete items as of September 30, 2020 is 35.5%. The estimated annual effective tax rate differs from the U.S. statutory rate of 21.0% primarily due to the deduction for percentage depletion in excess of cost depletion related to our Mining and Pelletizing segment operations, as well as non-deductible transaction costs, executive officers' compensation, global intangible low-taxed income and income of noncontrolling interests for which no tax is recognized. The 2019 estimated annual effective tax rate before discrete items as of September 30, 2019 was 9.6%. The increase in the estimated annual effective tax rate before discrete items is driven by the change in the mix of income, as well as transaction costs and other acquisition-related charges that were incurred only in 2020.    For the three and nine months ended September 30, 2020, we recorded discrete items that resulted in an income tax benefit of $5.0 million and $8.6 million, respectively. The discrete adjustments are primarily related to the release of uncertain tax positions due to favorable resolution of an international audit issue. The discrete adjustments also include interest on uncertain tax positions and the refunds received during the year of amounts sequestered by the Internal Revenue Service on previously filed AMT credit refund claims. For the three and nine months ended September 30, 2019, we recorded discrete items that resulted in an income tax benefit of $0.5 million and $1.3 million, respectively.
v3.20.2
ASSET RETIREMENT OBLIGATIONS (Notes)
 9 Months Ended
Sep. 30, 2020
Asset Retirement Obligation [Abstract]  
ASSET RETIREMENT OBLIGATIONS The following is a summary of our asset retirement obligations:
(In Millions)
September 30,
2020		December 31,
2019
Asset retirement obligations1
$186.4 $165.3 
Less current portion4.4 2.1 
Long-term asset retirement obligations$182.0 $163.2 
1 Includes $33.7 million and $22.0 million related to our active operations as of September 30, 2020 and December 31, 2019, respectively.
    The accrued closure obligation is predominantly related to our indefinitely idled and closed iron ore mining operations and provides for contractual and legal obligations associated with the eventual closure of those operations. Additionally, we have included in our asset retirement obligation $16.7 million for our integrated steel facilities and other operations acquired in the Merger. The closure date for each of our active mine sites was determined based on the exhaustion date of the remaining iron ore reserves and the amortization of the related asset and accretion of the liability is recognized over the estimated mine lives. The closure date and expected timing of the capital requirements to meet our obligations for our indefinitely idled or closed mines is determined based on the unique circumstances of each property. For indefinitely idled or closed mines, the accretion of the liability is recognized over the anticipated timing of remediation. As the majority of our asset retirement obligations at our steelmaking operations have indeterminate settlement dates, asset retirement obligations have been recorded at present values using estimated ranges of the economic lives of the underlying assets.
    The following is a roll forward of our asset retirement obligation liability:
(In Millions)
20202019
Asset retirement obligation as of January 1$165.3 $172.4 
Increase from AK Steel acquisition16.7 — 
Accretion expense7.8 7.6 
Remediation payments(3.4)(0.5)
Asset retirement obligation as of September 30$186.4 $179.5 
v3.20.2
DERIVATIVE INSTRUMENTS (Notes)
 9 Months Ended
Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
DERIVATIVE INSTRUMENTS The following table presents the fair value of our derivative instruments and the classification of each in the Statements of Unaudited Condensed Consolidated Financial Position:
Derivatives designated as hedging instruments under Topic 815:Derivatives not designated as hedging instruments under Topic 815:
Derivative Asset (Liability)September 30,
2020		December 31,
2019		September 30,
2020		December 31,
2019
Other current assets:
Customer supply agreement$— $— $34.5 $44.5 
Provisional pricing arrangements— — 26.9 1.3 
Commodity contracts7.9 — 7.9 — 
Other non-current assets:
Commodity contracts1.8 — — — 
Other current liabilities:
Provisional pricing arrangements— — (0.3)(1.1)
Commodity contracts(1.8)(3.2)(6.9)— 
Foreign exchange contracts(0.6)— — — 
Other non-current liabilities:
Foreign exchange contracts(0.1)— — — 
Derivatives Designated as Hedging Instruments - Cash Flow Hedges
    Exchange rate fluctuations affect a portion of revenues and operating costs that are denominated in foreign currencies, and we use forward currency and currency option contracts to reduce our exposure to certain of these currency price fluctuations. Contracts to purchase Canadian dollars are designated as cash flow hedges for accounting purposes, and we record the gains and losses for the derivatives and premiums paid for option contracts in Accumulated other comprehensive loss until we reclassify them into Cost of goods sold when we recognize the associated underlying operating costs.
    We are exposed to fluctuations in market prices of raw materials and energy sources. We may use cash-settled commodity swaps and options to hedge the market risk associated with the purchase of certain of our raw materials and energy requirements. Our hedging strategy is to reduce the effect on earnings from the price volatility of these various commodity exposures, including timing differences between when we incur raw material commodity costs and when we receive sales surcharges from our customers based on those raw materials. Independent of any hedging activities, price changes in any of these commodity markets could negatively affect operating costs.
    The following table presents the notional amount of our outstanding hedge contracts:
(In Millions)
September 30, 2020December 31, 2019
Unit of MeasureMaturity DatesNotional Amount Notional Amount
Commodity contracts:
Natural gasMMBtuOctober 2020 - December 202129.7 20.1 
DieselGallons—— 0.8 
ZincPoundsOctober 2020 - December 202110.9 — 
ElectricityMegawatt hoursOctober 2020 - December 20210.8 — 
Foreign exchange contracts:
Canadian dollarsCADOctober 2020 - December 2021C$38.8 C$— 
    Estimated gains before tax expected to be reclassified into Cost of goods sold within the next 12 months for our existing derivatives that qualify as cash flow hedges are presented below:
(In Millions)
Hedge:Estimated Gains
Natural gas$10.8 
Zinc2.3 
Electricity1.1 
Canadian dollars0.2 
Derivatives Not Designated as Hedging Instruments
    Customer Supply Agreement
    A supply agreement with one customer provides for supplemental revenue or refunds to the customer based on the hot-rolled coil steel price at the time the iron ore product is consumed in the customer’s blast furnaces. The supplemental pricing is characterized as a freestanding derivative instrument and is required to be accounted for separately once control transfers to the customer. The derivative instrument, which is finalized based on a future price, is adjusted to fair value through Revenues each reporting period based upon current market data and forward-looking estimates provided by management until the pellets are consumed and the amounts are settled.
    Provisional Pricing Arrangements
    Certain of our supply agreements specify provisional price calculations, where the pricing mechanisms generally are based on market pricing, with the final revenue rate based on certain market inputs at a specified period in time in the future, per the terms of the supply agreements. Market inputs are tied to indexed price adjustment factors that are integral to the iron ore supply contracts and vary based on the agreement. The pricing mechanisms typically include adjustments based upon changes in the Platts 62% Price, Atlantic Basin Pellet Premium, Platts international indexed freight rates and changes in specified PPI. The pricing adjustments generally operate in the same manner, with each factor typically comprising a portion of the price adjustment, although the weighting of each factor varies based upon the specific terms of each agreement. The price adjustment factors have been evaluated to determine if they qualify as embedded derivatives. The price adjustment factors share the same economic characteristics and risks as the host sales contract and are integral to the host sales contract as inflation adjustments; accordingly, they have not been separately valued as derivative instruments.
    Revenue is recognized generally upon delivery to our customers. Revenue is measured at the point that control transfers and represents the amount of consideration we expect to receive in exchange for transferring goods. Changes in the expected revenue rate from the date that control transfers through final settlement of contract terms is recorded in accordance with Topic 815 and is characterized as a derivative instrument and accounted for separately.  Subsequently, the derivative instruments are adjusted to fair value through Revenues each reporting period based upon current market data and forward-looking estimates provided by management until the final revenue rate is determined.
    The following summarizes the effect of our derivatives that are not designated as hedging instruments in the Statements of Unaudited Condensed Consolidated Operations:
(In Millions)
Derivatives Not Designated as Hedging InstrumentsLocation of Gain (Loss) Recognized in Income on DerivativesThree Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Customer supply agreementsRevenues$8.8 $7.6 $14.4 $82.2 
Provisional pricing arrangementsRevenues20.4 (48.5)28.0 (38.8)
Commodity contractsCost of goods sold3.9 — (0.8)— 
Total$33.1 $(40.9)$41.6 $43.4 
    Refer to NOTE 8 - FAIR VALUE MEASUREMENTS for additional information.
v3.20.2
SHAREHOLDERS' EQUITY (Notes)
 9 Months Ended
Sep. 30, 2020
Stockholders' Equity Note [Abstract]  
SHAREHOLDERS' EQUITY
Acquisition of AK Steel
    As more fully described in NOTE 3 - ACQUISITION OF AK STEEL, we acquired AK Steel on March 13, 2020. At the effective time of the Merger, each share of AK Steel common stock issued and outstanding prior to the effective time of the Merger was converted into, and became exchangeable for, 0.400 Cliffs common shares, par value $0.125 per share. We issued a total of 126.8 million Cliffs common shares in connection with the Merger at a fair value of $617.6 million. Following the closing of the Merger, AK Steel's common stock was de-listed from the New York Stock Exchange.
Dividends
    The below table summarizes our recent dividend activity:    
Declaration DateRecord DatePayment Date
Dividend Declared per Common Share1
2/18/20204/3/20204/15/2020$0.06 
12/2/20191/3/20201/15/20200.06 
9/3/201910/4/201910/15/20190.10 
5/31/20197/5/20197/15/20190.06 
2/19/20194/5/20194/15/20190.05 
10/18/20181/4/20191/15/20190.05 
1 The dividend declared on September 3, 2019 included a special cash dividend of $0.04 per common share.
    Subsequent to the dividend paid on April 15, 2020, our Board temporarily suspended future dividends as a result of the COVID-19 pandemic in order to preserve cash during this time of economic uncertainty.
Preferred Stock
    We have 3,000,000 shares of Serial Preferred Stock, Class A, without par value, authorized and 4,000,000 shares of Serial Preferred Stock, Class B, without par value, authorized; no preferred shares are issued or outstanding. Pursuant to the terms of the Transaction Agreement, we agreed to issue ArcelorMittal S.A. 583,273 shares of a new series of our Serial Preferred Stock, Class B, without par value, to be designated as the "Series B Participating Redeemable Preferred Stock" at closing of the pending Transaction.
Share Repurchase Program
    In November 2018, our Board authorized a program to repurchase outstanding common shares in the open market or in privately negotiated transactions, up to a maximum of $200 million, excluding commissions and fees. In April 2019, our Board increased the common share repurchase authorization by an additional $100 million, excluding commissions and fees. During the nine months ended September 30, 2019, we repurchased 24.4 million common shares at a cost of $252.9 million in the aggregate, including commissions and fees. The share repurchase program was effective until December 31, 2019.
v3.20.2
ACCUMULATED OTHER COMPREHENSIVE LOSS (Notes)
 9 Months Ended
Sep. 30, 2020
Equity [Abstract]  
Comprehensive Income (Loss) Note [Text Block] The following tables reflect the changes in Accumulated other comprehensive loss related to shareholders’ equity:
(In Millions)
Postretirement Benefit Liability,
net of tax
Foreign Currency TranslationDerivative Financial Instruments, net of taxAccumulated Other Comprehensive Loss
December 31, 2019$(315.7)$— $(3.1)$(318.8)
Other comprehensive loss before reclassifications— (0.9)(5.2)(6.1)
Net loss reclassified from accumulated other comprehensive loss5.6 — 2.2 7.8 
March 31, 2020$(310.1)$(0.9)$(6.1)$(317.1)
Other comprehensive income before reclassifications0.4 0.7 1.4 2.5 
Net loss reclassified from accumulated other comprehensive loss5.6 — 3.1 8.7 
June 30, 2020$(304.1)$(0.2)$(1.6)$(305.9)
Other comprehensive income before reclassifications0.4 1.6 12.2 14.2 
Net loss reclassified from accumulated other comprehensive loss6.2 — 3.5 9.7 
September 30, 2020$(297.5)$1.4 $14.1 $(282.0)
(In Millions)
Postretirement Benefit Liability, net of tax
Derivative Financial Instruments,
net of tax
Accumulated Other Comprehensive Loss
December 31, 2018$(281.1)$(2.8)$(283.9)
Other comprehensive income before reclassifications0.2 2.5 2.7 
Net loss reclassified from accumulated other comprehensive loss5.5 0.2 5.7 
March 31, 2019$(275.4)$(0.1)$(275.5)
Other comprehensive income (loss) before reclassifications0.3 (2.3)(2.0)
Net loss reclassified from accumulated other comprehensive loss5.5 0.2 5.7 
June 30, 2019$(269.6)$(2.2)$(271.8)
Other comprehensive income (loss) before reclassifications0.3 (0.5)(0.2)
Net loss reclassified from accumulated other comprehensive loss5.5 0.9 6.4 
September 30, 2019$(263.8)$(1.8)$(265.6)
    The following table reflects the details about Accumulated other comprehensive loss components related to shareholders’ equity:
(In Millions)
Details about Accumulated Other Comprehensive Loss ComponentsAmount of (Gain)/Loss Reclassified into Income, Net of TaxAffected Line Item in the Statement of Unaudited Condensed Consolidated Operations
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Amortization of pension and OPEB liability:
Prior service credits$(0.3)$(0.2)$(0.8)$(0.6)Other non-operating income
Net actuarial loss8.1 7.2 22.8 21.5 Other non-operating income
7.8 7.0 22.0 20.9 Total before taxes
(1.6)(1.5)(4.6)(4.4)Income tax benefit (expense)
$6.2 $5.5 $17.4 $16.5 Net of taxes
Unrealized loss on derivative financial instruments:
Commodity contracts$4.5 $1.2 $11.2 $1.7 Cost of goods sold
(1.0)(0.3)(2.4)(0.4)Income tax benefit (expense)
$3.5 $0.9 $8.8 $1.3 Net of taxes
Total reclassifications for the period, net of tax$9.7 $6.4 $26.2 $17.8 
v3.20.2
RELATED PARTIES (Notes)
 9 Months Ended
Sep. 30, 2020
Related Party Transactions [Abstract]  
RELATED PARTIES We have certain co-owned joint ventures with companies from the steel and mining industries, including integrated steel companies, their subsidiaries and other downstream users of steel and iron ore products. In addition, we have certain long-term contracts, and from time to time, enter into other sales agreements with these parties, and as a result, generate Revenues from related parties.
    Hibbing is a co-owned joint venture with companies that are integrated steel producers or their subsidiaries. The following is a summary of the mine ownership of the co-owned iron ore mine at September 30, 2020:
MineCleveland-Cliffs Inc.ArcelorMittal USAU.S. Steel
Hibbing23.0%62.3%14.7%
    The tables below summarize our material related party transactions:
    Revenues from related parties were as follows:
(Dollars In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Revenue from related parties$294.9 $293.5 $587.5 $792.8 
Revenues1
$1,646.0 $555.6 $3,097.8 $1,455.8 
Related party revenues as a percent of Revenues1
17.9 %52.8 %19.0 %54.5 %
Purchases from related parties$8.2 $— $20.4 $— 
1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
    The following table presents the classification of related party assets and liabilities in the Statements of Unaudited Condensed Consolidated Financial Position:
(In Millions)
Balance Sheet LocationSeptember 30,
2020		December 31,
2019
Accounts receivable, net$91.6 $31.1 
Other current assets58.5 44.5 
Accounts payable(1.2)— 
Other current liabilities(1.7)(2.0)
Other current assets
    A supply agreement with one customer provides for supplemental revenue or refunds to the customer based on the hot-rolled coil steel price at the time the product is consumed in the customer’s blast furnaces. The supplemental pricing is characterized as a freestanding derivative. Additionally, the customer also has certain provisional pricing arrangements where the difference between the estimated final revenue rate at the date of sale and the estimated final revenue rate at the measurement date is characterized as a derivative and is required to be accounted for separately once control has transferred upon delivery. Refer to NOTE 12 - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES for further information.
v3.20.2
VARIABLE INTEREST ENTITIES (Notes)
 9 Months Ended
Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Variable Interest Entity Disclosure [Text Block]
SunCoke Middletown
    We purchase all the coke and electrical power generated from SunCoke Middletown’s plant under long-term supply agreements. SunCoke Middletown is a VIE because we have committed to purchase all the expected production from the facility through 2032 and we are the primary beneficiary. Therefore, we consolidate SunCoke Middletown’s financial results with our financial results, even though we have no ownership interest in SunCoke Middletown. SunCoke Middletown had income before income taxes of $11.8 million and $31.3 million for the three and nine months ended September 30, 2020, respectively, that was included in our consolidated income before income taxes.
    The assets of the consolidated VIE can only be used to settle the obligations of the consolidated VIE and not obligations of the Company. The creditors of SunCoke Middletown do not have recourse to the assets or general credit of the Company to satisfy liabilities of the VIE. The consolidated balance sheet as of September 30, 2020 includes the following amounts for SunCoke Middletown:
(In Millions)
September 30,
2020
Cash and cash equivalents$0.3 
Inventories22.5 
Property, plant and equipment, net305.4 
Accounts payable(10.0)
Other assets (liabilities), net(5.6)
Noncontrolling interests(312.6)
v3.20.2
EARNINGS PER SHARE (Notes)
 9 Months Ended
Sep. 30, 2020
Earnings Per Share [Abstract]  
EARNINGS PER SHARE The following table summarizes the computation of basic and diluted earnings per share:
(In Millions, Except Per Share Amounts)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Income (loss) from continuing operations $2.2 $91.8 $(154.8)$231.1 
Income from continuing operations attributable to noncontrolling interest(11.9)— (31.2)— 
Net income (loss) from continuing operations attributable to Cliffs shareholders(9.7)91.8 (186.0)231.1 
Loss from discontinued operations, net of tax(0.3)(0.9)— (1.5)
Net income (loss) attributable to Cliffs shareholders$(10.0)$90.9 $(186.0)$229.6 
Weighted average number of shares:
Basic399.4 270.0 365.2 278.4 
Convertible senior notes— 3.7 — 5.8 
Employee stock plans— 2.9 — 3.6 
Diluted399.4 276.6 365.2 287.8 
Earnings (loss) per common share attributable to Cliffs shareholders - basic:
Continuing operations$(0.02)$0.34 $(0.51)$0.83 
Discontinued operations— — — (0.01)
$(0.02)$0.34 $(0.51)$0.82 
Earnings (loss) per common share attributable to Cliffs shareholders - diluted:
Continuing operations$(0.02)$0.33 $(0.51)$0.80 
Discontinued operations— — — — 
$(0.02)$0.33 $(0.51)$0.80 
    The following table summarizes the shares that have been excluded from the diluted earnings per share calculation as they were anti-dilutive:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Shares related to employee stock plans1.8 — 1.6 — 
    There was no dilution during the three and nine months ended September 30, 2020 related to the common share equivalents for the convertible senior notes as our common shares average price did not rise above the conversion price.
v3.20.2
COMMITMENTS AND CONTINGENCIES (Notes)
 9 Months Ended
Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]  
COMMITMENTS AND CONTINGENCIES
Purchase Commitments
    HBI production plant
    In 2017, we began to incur capital commitments related to the construction of our HBI production plant in Toledo, Ohio; however, due to the COVID-19 pandemic, we temporarily halted construction in March 2020. In June 2020, we resumed construction and now expect to complete the project and begin production in the fourth quarter of 2020. In total, to complete the project, we expect to spend approximately $1 billion on the HBI production plant, excluding capitalized interest, of which $940.2 million was paid as of September 30, 2020. As of September 30, 2020, we have contracts and purchase orders in place for $97.8 million.
Contingencies
    We are currently the subject of, or party to, various claims and legal proceedings incidental to our operations. These claims and legal proceedings are subject to inherent uncertainties and unfavorable rulings could occur. An unfavorable ruling could include monetary damages, additional funding requirements or an injunction. If an unfavorable ruling were to occur, there exists the possibility of a material effect on the financial position and results of operations for the period in which the ruling occurs or future periods. However, based on currently available information we do not believe that any pending claims or legal proceedings will result in a material effect in relation to our consolidated financial statements.
    Environmental Contingencies
    Although we believe our operating practices have been consistent with prevailing industry standards, hazardous materials may have been released at operating sites or third-party sites in the past, including operating sites that we no longer own. If we reasonably can, we estimate potential remediation expenditures for those sites where future remediation efforts are probable based on identified conditions, regulatory requirements or contractual obligations arising from the sale of a business or facility. For sites involving government required investigations, we typically make an estimate of potential remediation expenditures only after the investigation is complete and when we better understand the nature and scope of the remediation. In general, the material factors in these estimates include the costs associated with investigations, delineations, risk assessments, remedial work, governmental response and oversight, site monitoring, and preparation of reports to the appropriate environmental agencies.
    The following is a summary of our environmental obligations:
(In Millions)
September 30,
2020		December 31,
2019
Environmental obligations$40.9 $2.0 
Less current portion6.4 0.3 
Long-term environmental obligations$34.5 $1.7 
    We cannot predict the ultimate costs for each site with certainty because of the evolving nature of the investigation and remediation process. Rather, to estimate the probable costs, we must make certain assumptions. The most significant of these assumptions is for the nature and scope of the work that will be necessary to investigate and remediate a particular site and the cost of that work. Other significant assumptions include the cleanup technology that will be used, whether and to what extent any other parties will participate in paying the investigation and remediation costs, reimbursement of past response costs and future oversight costs by governmental agencies, and the reaction of the governing environmental agencies to the proposed work plans. Costs for future investigation and remediation are not discounted to their present value, unless the amount and timing of the cash disbursements are readily known. To the extent that we have been able to reasonably estimate future liabilities, we do not believe that there is a reasonable possibility that we will incur a loss or losses that exceed the amounts we accrued for the environmental matters discussed below that would, either individually or in the aggregate, have a material adverse effect on our consolidated financial condition, results of operations or cash flows. However, since we recognize amounts in the consolidated financial statements in accordance with GAAP that exclude potential losses that are not probable or that may not be currently estimable, the ultimate costs of these environmental matters may be higher than the liabilities we currently have recorded in our consolidated financial statements.
    Except as we expressly note below, we do not currently anticipate any material effect on our consolidated financial position, results of operations or cash flows as a result of compliance with current environmental regulations. Moreover, because all domestic steel and iron ore producers operate under the same federal environmental regulations, we do not believe that we are more disadvantaged than our domestic competitors by our need to comply with these regulations. Some foreign competitors may benefit from less stringent environmental requirements in the countries where they produce, resulting in lower compliance costs for them and providing those foreign competitors with a cost advantage on their products.
    According to RCRA, which governs the treatment, handling and disposal of hazardous waste, the EPA and authorized state environmental agencies may conduct inspections of RCRA-regulated facilities to identify areas where there have been releases of hazardous waste or hazardous constituents into the environment and may order the facilities to take corrective action to remediate such releases. Environmental regulators may inspect our major iron ore and steelmaking facilities. While we cannot predict the future actions of these regulators, it is possible that they may identify conditions in future inspections of these facilities which they believe require corrective action.
    Under authority from CERCLA, the EPA and state environmental authorities have conducted site investigations at certain of our facilities and other third-party facilities, portions of which previously may have been used for disposal of materials that are currently regulated. The results of these investigations are still pending, and we could be directed to spend funds for remedial activities at the former disposal areas. Because of the uncertain status of these investigations, however, we cannot reliably predict whether or when such spending might be required or its magnitude.
    On April 29, 2002, AK Steel entered a mutually agreed-upon administrative order on consent with the EPA pursuant to Section 122 of CERCLA to perform a Remedial Investigation/Feasibility Study (“RI/FS”) of the Hamilton Plant site located in New Miami, Ohio. The plant ceased operations in 1990 and all of its former structures have been demolished. AK Steel submitted the investigation portion of the RI/FS and completed supplemental studies. We currently have accrued $0.7 million for the remaining cost of the RI/FS. Until the RI/FS is complete, we cannot reliably estimate the additional costs, if any, we may incur for potentially required remediation of the site or when we may incur them.
    On September 26, 2012, the EPA issued an order under Section 3013 of RCRA requiring a plan to be developed for investigation of four areas at the Ashland Works coke plant. The Ashland Works coke plant ceased operations in 2011 and all of its former structures have been demolished and removed. In 1981, AK Steel acquired the plant from Honeywell International Corporation (as successor to Allied Corporation), who had managed the coking operations there for approximately 60 years. In connection with the sale of the coke plant, Honeywell agreed to indemnify AK Steel against certain claims and obligations that could arise from the investigation, and we intend to pursue such indemnification from Honeywell, if necessary. We cannot reliably estimate how long it will take to complete the site investigation. On March 10, 2016, the EPA invited AK Steel to participate in settlement discussions regarding an enforcement action. Settlement discussions between the parties are ongoing, though whether the parties will reach agreement and any such agreement’s terms are uncertain. We currently have accrued $1.4 million for the projected cost of the investigation and known remediation. Until the site investigation is complete, we cannot reliably estimate the costs, if any, we may incur for potential additional required remediation of the site or when we may incur them.
    On May 12, 2014, the Michigan Department of Environment, Great Lakes, and Energy (“EGLE”) (previously the Michigan Department of Environmental Quality) issued to Dearborn Works an Air Permit to Install No. 182-05C (the “PTI”) to increase the emission limits for the blast furnace and other emission sources. The PTI was issued as a correction to a prior permit to install that did not include certain information during the prior permitting process. On July 10, 2014, the South Dearborn Environmental Improvement Association (“SDEIA”), Detroiters Working for Environmental Justice, Original United Citizens of Southwest Detroit and the Sierra Club filed a Claim of Appeal of the PTI in the State of Michigan, Wayne County Circuit Court, Case No. 14-008887-AA. The appellants and EGLE required the intervention of Severstal Dearborn, LLC (later merged into AK Steel Corporation) in this action as an additional appellee. The appellants allege multiple deficiencies with the PTI and the permitting process. On July 2, 2019, the Circuit Court dismissed the PTI appeal and ruled that EGLE appropriately issued the permit modification. The appellants have appealed that decision. Until the appeal is resolved, we cannot determine what the ultimate permit limits will be. Until the permit limits are determined and final, we cannot reliably estimate the costs we may incur, if any, or when we may incur them.
    On August 21, 2014, the SDEIA filed a Complaint under the Michigan Environmental Protection Act (“MEPA”) in the State of Michigan, Wayne County Circuit Court, Case No. 14-010875-CE. The plaintiffs allege that the air emissions from Dearborn Works are impacting the air, water and other natural resources, as well as the public trust in
such resources. The plaintiffs are requesting, among other requested relief, that the court assess and determine the sufficiency of the PTI’s limitations. On October 15, 2014, the court ordered a stay of the proceedings until a final order is issued in Wayne County Circuit Court Case No. 14-008887-AA (discussed above). When the proceedings resume, we intend to vigorously contest these claims. Until the claims in this complaint are resolved, we cannot reliably estimate the costs we may incur, if any, or when we may incur them.
    On November 18, 2019, November 26, 2019, and March 16, 2020, EGLE issued Notices of Violations (“NOVs”) with respect to the basic oxygen furnace electrostatic precipitator at Dearborn Works alleging violations of manganese, lead and opacity limits. We are investigating these claims and will work with EGLE to attempt to resolve them. We intend to vigorously contest any claims which cannot be resolved through a settlement. Until a settlement is reached with EGLE or the claims of the NOVs are otherwise resolved, we cannot reliably estimate the costs, if any, associated with any potentially required work.
    In addition to the foregoing matters, we are or may be involved in proceedings with various regulatory authorities that may require us to pay fines, comply with more rigorous standards or other requirements or incur capital and operating expenses for environmental compliance. We believe that the ultimate disposition of the proceedings will not have, individually or in the aggregate, a material adverse effect on our consolidated financial condition, results of operations or cash flows.
    Other Contingencies
    In addition to the matters discussed above, there are various pending and potential claims against us and our subsidiaries involving product liability, commercial, employee benefits, and other matters arising in the ordinary course of business. Because of the considerable uncertainties which exist for any claim, it is difficult to reliably or accurately estimate what the amount of a loss would be if a claimant prevails. If material assumptions or factual understandings we rely on to evaluate exposure for these contingencies prove to be inaccurate or otherwise change, we may be required to record a liability for an adverse outcome. If, however, we have reasonably evaluated potential future liabilities for all of these contingencies, including those described more specifically above, it is our opinion, unless we otherwise noted, that the ultimate liability from these contingencies, individually and in the aggregate, should not have a material adverse effect on our consolidated financial position, results of operations or cash flows.
v3.20.2
SUBSEQUENT EVENTS (Notes)
 9 Months Ended
Sep. 30, 2020
Subsequent Events [Abstract]  
SUBSEQUENT EVENTS We have evaluated subsequent events through the date of financial statement issuance.
v3.20.2
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)
 9 Months Ended
Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Basis of Accounting
Business, Consolidation and Presentation
    The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with SEC rules and regulations and, in the opinion of management, include all adjustments (consisting of normal recurring adjustments) necessary to present fairly the financial position, results of operations, comprehensive income (loss), cash flows and changes in equity for the periods presented. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Management bases its estimates on various assumptions and historical experience, which are believed to be reasonable; however, due to the inherent nature of estimates, actual results may differ significantly due to changed conditions or assumptions. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of results to be expected for the year ending December 31, 2020 or any other future period. Due to the acquisition of AK Steel, certain balances have become material and are no longer being condensed in our Statements of Unaudited Condensed Consolidated Financial Position, such as balances for Right-of-use asset, operating lease and Operating lease liability, non-current. As a result, certain prior period amounts have been reclassified to conform with the current year presentation. These unaudited condensed consolidated financial statements should be read in conjunction with the financial statements and notes included in our Annual Report on Form 10-K for the year ended December 31, 2019 and in our Quarterly Reports on Form 10-Q for the quarterly periods ended March 31, 2020 and June 30, 2020.
Basis of Consolidation Basis of Consolidation
    The unaudited condensed consolidated financial statements consolidate our accounts and the accounts of our wholly owned subsidiaries, all subsidiaries in which we have a controlling interest and two variable interest entities for which we are the primary beneficiary. All intercompany transactions and balances are eliminated upon consolidation.
    Reportable Segments
    The acquisition of AK Steel has transformed us into a vertically integrated producer of value-added iron ore and steel products and we are organized according to our differentiated products in two reportable segments - the Steel and Manufacturing segment and the Mining and Pelletizing segment. Our new Steel and Manufacturing segment includes the assets acquired through the acquisition of AK Steel and our previously reported Metallics segment, and our Mining and Pelletizing segment includes our three active operating mines and our indefinitely idled mine.
Equity Method Investments Investments in Affiliates
    We have investments in several businesses accounted for using the equity method of accounting. We review an investment for impairment when circumstances indicate that a loss in value below its carrying amount is other than temporary. Investees and equity ownership percentages are presented below:
InvesteeSegment Reported WithinEquity Ownership Percentage
Combined Metals of Chicago, LLCSteel and Manufacturing40.0%
Hibbing Taconite CompanyMining and Pelletizing23.0%
Spartan Steel Coating, LLCSteel and Manufacturing48.0%
New Accounting Pronouncements
Recent Accounting Pronouncements
    Issued and Adopted
    On March 2, 2020, the SEC issued a final rule that amended the disclosure requirements related to certain registered securities under SEC Regulation S-X, Rule 3-10, which required separate financial statements for subsidiary issuers and guarantors of registered debt securities unless certain exceptions are met. The final rule replaces the previous requirement under Rule 3-10 to provide condensed consolidating financial information in the registrant’s financial statements with a requirement to provide alternative financial disclosures (which include summarized financial information of the parent and any issuers and guarantors, as well as other qualitative disclosures) in either the registrant’s Management's Discussion and Analysis of Financial Condition and Results of Operations or its financial statements, in addition to other simplifications. The final rule is effective for filings on or after January 4, 2021, and early adoption is permitted. We elected to early adopt this disclosure update for the period ended March 31, 2020. As a result, we have excluded the footnote disclosures required under the previous Rule 3-10, and applied the final rule by including the summarized financial information and qualitative disclosures in Part I - Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operations of this Quarterly Report on Form 10-Q and Exhibit 22.1, hereto.
Issued and Not EffectiveIn August 2020, the Financial Accounting Standards Board issued Accounting Standards Update No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40). This update requires certain convertible instruments to be accounted for as a single liability measured at its amortized cost. Additionally, the update requires the use of the "if-converted" method, removing the treasury stock method, when calculating diluted shares. The two methods of adoption are the full and modified retrospective approaches. We expect to utilize the modified retrospective approach. Using this approach, the guidance shall be applied to transactions outstanding as of the beginning of the fiscal year in which the amendment is adopted. The final rule is effective for fiscal years beginning after December 15, 2021. Early adoption is permitted for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. We are continuing to evaluate the impact of this update to our financials and would expect to adopt at the required adoption date of January 1, 2022.
v3.20.2
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Tables)
 9 Months Ended
Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Equity Method Investments Investees and equity ownership percentages are presented below:
InvesteeSegment Reported WithinEquity Ownership Percentage
Combined Metals of Chicago, LLCSteel and Manufacturing40.0%
Hibbing Taconite CompanyMining and Pelletizing23.0%
Spartan Steel Coating, LLCSteel and Manufacturing48.0%
v3.20.2
SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION (Tables)
 9 Months Ended
Sep. 30, 2020
Disclosure Text Block [Abstract]  
Revenues from Product Sales and Services [Table Text Block] The following table represents our consolidated Revenues (excluding intercompany revenues) by market:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Steel and Manufacturing:
Automotive$920.0 $— $1,404.0 $— 
Infrastructure and manufacturing198.8 — 446.2 — 
Distributors and converters142.9 — 344.1 — 
Total Steel and Manufacturing1,261.7 — 2,194.3 — 
Mining and Pelletizing:
Steel producers1
384.3 555.6 903.5 1,455.8 
Total revenues$1,646.0 $555.6 $3,097.8 $1,455.8 
1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
    The following table represents our consolidated Revenues (excluding intercompany revenues) by product line:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Steel and Manufacturing:
Carbon steel$821.2 $— $1,391.6 $— 
Stainless and electrical steel303.2 — 585.1 — 
Tubular products, components and other137.3 — 217.6 — 
Total Steel and Manufacturing1,261.7 — 2,194.3 — 
Mining and Pelletizing:
Iron ore1
357.1 515.0 838.1 1,357.8 
Freight27.2 40.6 65.4 98.0 
Total Mining and Pelletizing384.3 555.6 903.5 1,455.8 
Total revenues$1,646.0 $555.6 $3,097.8 $1,455.8 
1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] The following is a roll forward of our allowance for credit losses associated with Accounts receivable, net:
(In Millions)
20202019
Allowance for credit losses as of January 1$— $— 
Increase in allowance5.2 — 
Allowance for credit losses as of September 30$5.2 $— 
Schedule of Inventory, Current [Table Text Block] The following table presents the detail of our Inventories in the Statements of Unaudited Condensed Consolidated Financial Position:
(In Millions)
September 30,
2020		December 31,
2019
Product inventories
Finished and semi-finished goods$940.5 $114.1 
Work-in-process78.2 68.7 
Raw materials382.3 9.4 
Total product inventories1,401.0 192.2 
Manufacturing supplies and critical spares394.1 125.2 
Inventories$1,795.1 $317.4 
Contract with Customer, Asset and Liability [Table Text Block] The table below summarizes our deferred revenue balances:
(In Millions)
Deferred Revenue (Current)Deferred Revenue (Long-Term)
2020201920202019
Opening balance as of January 1$22.1 $21.0 $25.7 $38.5 
Net decrease(19.8)(2.7)(25.7)(8.5)
Closing balance as of September 30$2.3 $18.3 $— $30.0 
Schedule of Accrued Liabilities [Table Text Block] The following table presents the detail of our Accrued liabilities in the Statements of Unaudited Condensed Consolidated Financial Position:
(In Millions)
September 30,
2020		December 31, 2019
Accrued employment costs$146.6 $61.7 
Accrued interest81.8 29.0 
Accrued dividends1.0 17.8 
Other50.0 17.8 
Accrued liabilities$279.4 $126.3 
Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] A reconciliation of capital additions to cash paid for capital expenditures is as follows:
(In Millions)
Nine Months Ended
September 30,
20202019
Capital additions$333.0 $505.6 
Less:
Non-cash accruals(88.4)26.1 
Right-of-use assets - finance leases42.5 29.3 
Grants— (10.5)
Cash paid for capital expenditures including deposits$378.9 $460.7 
    Cash payments (receipts) for income taxes and interest are as follows:
(In Millions)
Nine Months Ended
September 30,
20202019
Taxes paid on income$3.2 $0.1 
Income tax refunds(119.3)(117.9)
Interest paid on debt obligations net of capitalized interest1
106.0 71.9 
1 Capitalized interest was $38.0 million and $16.9 million for the nine months ended September 30, 2020 and 2019, respectively.
    Non-Cash Investing and Financing Activities
(In Millions)
Nine Months Ended
September 30,
20202019
Fair value of common shares issued for consideration for business combination$617.6 $— 
Fair value of equity awards assumed from AK Steel acquisition3.9 — 
v3.20.2
ACQUISITION OF AK STEEL (Tables)
 9 Months Ended
Sep. 30, 2020
Business Combinations [Abstract]  
Schedule of Business Acquisitions by Acquisition, by Acquisition [Table Text Block] The fair value of the total purchase consideration was determined as follows:
(In Millions)
Fair value of Cliffs common shares issued for AK Steel outstanding common stock$617.6 
Fair value of replacement equity awards3.9 
Fair value of AK Steel debt913.6 
Total purchase consideration$1,535.1 
The fair value of AK Steel's debt included in the consideration is calculated as follows:
(In Millions)
Credit Facility$590.0 
7.50% Senior Secured Notes due July 2023323.6 
Fair value of debt included in consideration$913.6 
Schedule of Business Acquisitions by Acquisition, Equity Interest Issued or Issuable [Table Text Block] The fair value of the total purchase consideration was determined as follows:
(In Millions)
Fair value of Cliffs common shares issued for AK Steel outstanding common stock$617.6 
Fair value of replacement equity awards3.9 
Fair value of AK Steel debt913.6 
Total purchase consideration$1,535.1 
    The fair value of Cliffs common shares issued for outstanding shares of AK Steel common stock and with respect to Cliffs common shares underlying converted AK Steel equity awards that vested upon completion of the Merger is calculated as follows:
(In Millions, Except Per Share Amounts)
Number of shares of AK Steel common stock issued and outstanding316.9 
Exchange ratio0.400 
Number of Cliffs common shares issued to AK Steel stockholders126.8 
Price per share of Cliffs common shares$4.87 
Fair value of Cliffs common shares issued for AK Steel outstanding common stock$617.6 
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] The preliminary purchase price allocation to assets acquired and liabilities assumed in the Merger was:
(In Millions)
Initial Allocation of ConsiderationMeasurement Period AdjustmentsUpdated Preliminary Allocation
Cash and cash equivalents$37.7 $2.0 $39.7 
Accounts receivable666.0 (3.1)662.9 
Inventories1,562.8 (39.8)1,523.0 
Other current assets67.5 (15.4)52.1 
Property, plant and equipment2,184.4 (20.1)2,164.3 
Intangible assets163.0 (15.0)148.0 
Right of use asset, operating leases225.9 (16.3)209.6 
Other non-current assets85.9 26.2 112.1 
Accounts payable(636.3)(6.1)(642.4)
Accrued liabilities(222.5)0.1 (222.4)
Other current liabilities(181.8)6.6 (175.2)
Long-term debt(1,179.4)— (1,179.4)
Deferred income taxes(19.7)(0.2)(19.9)
Operating lease liability, non-current(188.1)12.7 (175.4)
Intangible liabilities(140.0)69.5 (70.5)
Pension and OPEB liabilities(873.0)2.1 (870.9)
Asset retirement obligations(13.9)(2.0)(15.9)
Other non-current liabilities(144.2)(2.3)(146.5)
Net identifiable assets acquired1,394.3 (1.1)1,393.2 
Goodwill141.2 0.7 141.9 
Total net assets acquired$1,535.5 $(0.4)$1,535.1 
Finite-Lived and Indefinite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block] The preliminary purchase price allocated to identifiable intangible assets and liabilities acquired was:
(In Millions)Weighted Average Life (In Years)
Intangible assets:
Customer relationships$77.0 18
Developed technology60.0 17
Trade names and trademarks11.0 10
Total identifiable intangible assets$148.0 17
Intangible liabilities:
Above-market supply contracts$(70.5)12
Business Acquisition, Pro Forma Information [Table Text Block] The following table provides unaudited pro forma financial information, prepared in accordance with Topic 805, for the three and nine months ended September 30, 2020 and 2019, as if AK Steel had been acquired as of January 1, 2019:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Revenues$1,646.0 $1,937.6 $4,265.1 $5,958.7 
Net income (loss) attributable to Cliffs shareholders(6.0)84.2 (123.9)213.3 
v3.20.2
SEGMENT REPORTING (Tables)
 9 Months Ended
Sep. 30, 2020
Segment Reporting [Abstract]  
Schedule Of Segment Reporting Information, By Segment Our results by segment are as follows:
(In Millions, Except Sales Tons)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Sales volume (in thousands):
Steel and Manufacturing (net tons)1,117 — 1,935— 
Mining and Pelletizing sales (long tons)4,907 5,750 11,80013,527
Less: Intercompany sales (long tons)(1,204)(346)(3,028)(384)
Mining and Pelletizing consolidated sales (long tons)3,703 5,404 8,772 13,143 
Revenues:
Steel and Manufacturing net sales to external customers$1,261.7 $— $2,194.3 $— 
Mining and Pelletizing net sales1
520.3 590.6 1,238.7 1,494.8 
Less: Intercompany sales(136.0)(35.0)(335.2)(39.0)
Mining and Pelletizing net sales to external customers384.3 555.6 903.5 1,455.8 
Total revenues$1,646.0 $555.6 $3,097.8 $1,455.8 
Adjusted EBITDA:
Steel and Manufacturing$33.3 $(2.1)$(81.8)$(4.0)
Mining and Pelletizing145.3 182.7 309.5 510.7 
Corporate and eliminations(52.3)(36.5)(160.7)(93.0)
Total Adjusted EBITDA$126.3 $144.1 $67.0 $413.7 
1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
    The following table provides a reconciliation of our consolidated Net income (loss) to total Adjusted EBITDA:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Net income (loss)$1.9 $90.9 $(154.8)$229.6 
Less:
Interest expense, net(68.2)(25.4)(167.9)(76.8)
Income tax benefit (expense)22.4 (4.8)98.5 (23.1)
Depreciation, depletion and amortization(72.4)(22.2)(183.9)(63.1)
Total EBITDA$120.1 $143.3 $98.5 $392.6 
Less:
EBITDA of noncontrolling interests1
$16.2 $— $41.3 $— 
Gain (loss) on extinguishment of debt— — 132.6 (18.2)
Severance costs(2.4)— (38.3)(1.7)
Acquisition-related costs excluding severance costs(5.1)— (30.1)— 
Amortization of inventory step-up(14.6)— (74.0)— 
Impact of discontinued operations(0.3)(0.8)— (1.2)
Total Adjusted EBITDA$126.3 $144.1 $67.0 $413.7 
1 EBITDA of noncontrolling interests includes $11.9 million and $31.2 million for income and $4.3 million and $10.1 million for depreciation, depletion and amortization for the three and nine months ended September 30, 2020, respectively.
The following table summarizes our capital additions by segment:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Capital additions1:
Steel and Manufacturing$88.0 $160.5 $266.8 $398.0 
Mining and Pelletizing13.3 22.1 64.9 104.5 
Corporate and Other1.0 2.1 1.3 3.1 
Total capital additions$102.3 $184.7 $333.0 $505.6 
1 Refer to NOTE 2 - SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION for additional information.
Reconciliation of Assets from Segment to Consolidated The following summarizes our assets by segment:
(In Millions)
September 30,
2020		December 31,
2019
Assets:
Steel and Manufacturing$6,345.7 $913.6 
Mining and Pelletizing1,643.3 1,643.1 
Total segment assets7,989.0 2,556.7 
Corporate and Other (including discontinued operations)491.9 947.1 
Total assets$8,480.9 $3,503.8 
v3.20.2
PROPERTY, PLANT AND EQUIPMENT (Tables)
 9 Months Ended
Sep. 30, 2020
Property, Plant and Equipment [Abstract]  
Value Of Each Of The Major Classes Of Consolidated Depreciable Assets The following table indicates the carrying value of each of the major classes of our depreciable assets:
(In Millions)
September 30,
2020		December 31,
2019
Land, land improvements and mineral rights$653.2 $582.2 
Buildings454.4 157.8 
Steel and Manufacturing equipment2,128.0 42.0 
Mining and Pelletizing equipment1,455.2 1,413.6 
Other121.3 101.5 
Construction-in-progress1,145.9 730.3 
Total property, plant and equipment1
5,958.0 3,027.4 
Allowance for depreciation and depletion(1,407.3)(1,098.4)
Property, plant and equipment, net$4,550.7 $1,929.0 
1 Includes right-of-use assets related to finance leases of $97.1 million and $49.0 million as of September 30, 2020 and December 31, 2019, respectively.
v3.20.2
GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES (Tables)
 9 Months Ended
Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]  
Schedule of Intangible Assets and Goodwill [Table Text Block]
The following is a summary of our intangible assets and liabilities:
(In Millions)
Classification1
Gross AmountAccumulated AmortizationNet Amount
As of September 30, 2020
Intangible assets:
Customer relationshipsIntangible assets, net$77.0 $(2.6)$74.4 
Developed technologyIntangible assets, net60.0 (2.1)57.9 
Trade names and trademarksIntangible assets, net11.0 (0.7)10.3 
Mining permitsIntangible assets, net72.2 (24.7)47.5 
Total intangible assets$220.2 $(30.1)$190.1 
Intangible liabilities:
Above-market supply contractsIntangible liabilities, net$(70.5)$4.6 $(65.9)
As of December 31, 2019
Intangible assets:
Mining permitsIntangible assets, net$72.2 $(24.1)$48.1 
1 Amortization of intangible liabilities related to above-market supply contracts and intangible assets related to mining permits is recognized in Cost of goods sold. Amortization of all other intangible assets is recognized in Selling, general and administrative expenses.
Finite-lived Intangible Assets Amortization Expense [Table Text Block] Estimated future amortization expense related to intangible assets at September 30, 2020 is as follows:
(In Millions)
Years ending December 31,
2020 (remaining period of the year)$2.5 
202110.0 
202210.0 
202310.0 
202410.0 
202510.0 
Schedule of Finite-Lived Intangible Liabilities, Future Amortization Credit [Table Text Block] Estimated future amortization income related to the intangible liabilities at September 30, 2020 is as follows:
(In Millions)
Years ending December 31,
2020 (remaining period of the year)$2.0 
20217.8 
20227.8 
20237.8 
20247.8 
20257.8 
v3.20.2
DEBT AND CREDIT FACILITIES (Tables)
 9 Months Ended
Sep. 30, 2020
Debt Disclosure [Abstract]  
Schedule Of Long-Term Debt The following represents a summary of our long-term debt:
(In Millions)
September 30, 2020
Debt Instrument
Issuer1
Annual Effective
Interest Rate
Total Principal AmountDebt Issuance CostsUnamortized Premiums (Discounts)Total Debt
Senior Secured Notes:
4.875% 2024 Senior Secured NotesCliffs5.00%$394.5 $(3.7)$(1.5)$389.3 
9.875% 2025 Senior Secured NotesCliffs10.57%955.2 (8.1)(25.8)921.3 
6.75% 2026 Senior Secured NotesCliffs6.99%845.0 (21.4)(9.0)814.6 
Senior Unsecured Notes:
7.625% 2021 AK Senior NotesAK Steel7.33%33.5 — 0.1 33.6 
7.50% 2023 AK Senior NotesAK Steel6.17%12.8 — 0.5 13.3 
6.375% 2025 Senior NotesCliffs8.11%64.3 (0.2)(4.6)59.5 
6.375% 2025 AK Senior NotesAK Steel8.11%38.4 — (2.7)35.7 
1.50% 2025 Convertible Senior NotesCliffs6.26%296.3 (3.7)(53.0)239.6 
5.75% 2025 Senior NotesCliffs6.01%396.2 (2.6)(4.1)389.5 
7.00% 2027 Senior NotesCliffs9.24%88.0 (0.3)(9.6)78.1 
7.00% 2027 AK Senior NotesAK Steel9.24%56.3 — (6.0)50.3 
5.875% 2027 Senior NotesCliffs6.49%555.5 (4.3)(18.6)532.6 
6.25% 2040 Senior NotesCliffs6.34%262.7 (1.8)(2.8)258.1 
IRBs due 2024 to 2028AK SteelVarious92.0 — 2.3 94.3 
ABL Facility
Cliffs2
2.77%2,000.0 — — 400.0 
Total long-term debt$4,309.8 
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 AmountDebt Issuance CostsUnamortized DiscountsTotal Debt
Senior Secured Notes:
4.875% 2024 Senior NotesCliffs5.00%$400.0 $(4.6)$(1.8)$393.6 
Senior Unsecured Notes:
1.50% 2025 Convertible Senior NotesCliffs6.26%316.3 (4.6)(65.0)246.7 
5.75% 2025 Senior NotesCliffs6.01%473.3 (3.6)(5.5)464.2 
5.875% 2027 Senior NotesCliffs6.49%750.0 (6.3)(27.3)716.4 
6.25% 2040 Senior NotesCliffs6.34%298.4 (2.2)(3.3)292.9 
Former ABL Facility
Cliffs2
N/A450.0 N/AN/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)
Nine Months Ended
September 30, 2020
Debt InstrumentDebt ExtinguishedGain on Extinguishment
7.625% 2021 AK Senior Notes$372.7 $0.4 
7.50% 2023 AK Senior Notes367.2 2.8 
4.875% 2024 Senior Secured Notes5.5 0.5 
6.375% 2025 Senior Notes167.5 21.3 
1.50% 2025 Convertible Senior Notes20.0 1.3 
5.75% 2025 Senior Notes77.1 16.3 
7.00% 2027 Senior Notes247.3 28.4 
5.875% 2027 Senior Notes194.5 48.7 
6.25% 2040 Senior Notes35.7 12.9 
$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)
Nine Months Ended
September 30, 2019
Debt InstrumentDebt Extinguished(Loss) on Extinguishment
4.875% 2021 Senior Notes$124.0 $(5.3)
5.75% 2025 Senior Notes600.0 (12.9)
$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)
September 30,
2020
Available borrowing base on ABL Facility1
$1,715.2 
Borrowings(400.0)
Letter of credit obligations2
(192.2)
Borrowing capacity available$1,123.0 
1 As of September 30, 2020, the ABL Facility has a maximum borrowing base of $2.0 billion. The available borrowing base is determined by applying customary advance rates to eligible accounts receivable, inventory and certain mobile equipment.
2 We issued standby letters of credit with certain financial institutions in order to support business obligations including, but not limited to, workers' compensation, employee severance, IRBs and environmental obligations.
Schedule of Maturities of Long-term Debt The following represents a summary of our maturities of debt instruments based on the principal amounts outstanding at September 30, 2020:
(In Millions)
Maturities of Debt
2020 (remaining period of year)$— 
202133.5 
2022— 
202312.8 
2024456.5 
Thereafter3,987.9 
Total maturities of debt$4,490.7 
v3.20.2
FAIR VALUE MEASUREMENTS (Tables)
 9 Months Ended
Sep. 30, 2020
Fair Value Disclosures [Abstract]  
Fair Value, by Balance Sheet Grouping The following represents the assets and liabilities measured at fair value:
(In Millions)
September 30, 2020
Quoted Prices in Active
Markets for Identical Assets/Liabilities
(Level 1)
Significant Other Observable Inputs
(Level 2)
Significant Unobservable Inputs
(Level 3)
Total
Assets:
Other current assets:
Commodity contracts$— $15.8 $— $15.8 
Customer supply agreement — — 34.5 34.5 
Provisional pricing arrangement— — 26.9 26.9 
Other non-current assets:
Commodity contracts— 1.8 — 1.8 
     Total$— $17.6 $61.4 $79.0 
Liabilities:
Other current liabilities:
Commodity contracts$— $(8.7)$— $(8.7)
Provisional pricing arrangement— — (0.3)(0.3)
Foreign exchange contracts— (0.6)— (0.6)
Other non-current liabilities:
Foreign exchange contracts— (0.1)— (0.1)
     Total$— $(9.4)$(0.3)$(9.7)
(In Millions)
December 31, 2019
Quoted Prices in Active
Markets for Identical Assets/Liabilities
(Level 1)
Significant Other Observable Inputs
(Level 2)
Significant Unobservable Inputs
(Level 3)
Total
Assets:
Cash equivalents - Commercial paper$— $187.6 $— $187.6 
Other current assets:
Customer supply agreement — — 44.5 44.5 
Provisional pricing arrangement— — 1.3 1.3 
Total$— $187.6 $45.8 $233.4 
Liabilities:
Other current liabilities:
Commodity contracts $— $(3.2)$— $(3.2)
Provisional pricing arrangement— — (1.1)(1.1)
Total$— $(3.2)$(1.1)$(4.3)
Fair Value, Recurring and Nonrecurring, Valuation Techniques The following table illustrates information about quantitative inputs and assumptions for the derivative assets and derivative liabilities categorized in Level 3 of the fair value hierarchy:
Qualitative/Quantitative Information About Level 3 Fair Value Measurements
Fair Value at September 30, 2020
(In Millions)		Balance Sheet
Location		Valuation TechniqueUnobservable InputRange or Point Estimate (Weighted Average)
Customer supply agreement$34.5 Other current assetsMarket ApproachManagement's estimate of hot-rolled coil steel price per net ton
$542 - $634
$(548)
Provisional pricing arrangements$26.9 Other current assetsMarket ApproachManagement's
estimate of Platts 62% Price per dry metric ton
$104 - $123
($105)
Atlantic Basin Pellet Premium$30
Provisional pricing arrangements$(0.3)Other current liabilitiesMarket ApproachManagement's
estimate of Platts 62% Price per dry metric ton		$104
PPI Estimates110
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation The following tables represent a reconciliation of the changes in fair value of financial instruments measured at fair value on a recurring basis using significant unobservable inputs (Level 3):
(In Millions)
Level 3 Assets
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Beginning balance$35.3 $118.1 $45.8 $91.4 
Total gains (losses) included in earnings29.5 (6.5)43.3 83.1 
Settlements(3.4)(38.8)(27.7)(101.7)
Ending balance$61.4 $72.8 $61.4 $72.8 
Total gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) on assets still held at the reporting date$27.8 $(6.5)$40.4 $81.8 
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
(In Millions)
Level 3 Liabilities
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Beginning balance$— $— $(1.1)$— 
Total losses included in earnings(0.3)(34.4)(0.9)(39.7)
Settlements— 4.2 1.7 9.5 
Ending balance$(0.3)$(30.2)$(0.3)$(30.2)
Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date$(0.3)$(30.2)$(0.3)$(30.2)
Schedule Of Carrying Value And Fair Value Of Financial Instruments A summary of the carrying value and fair value of other financial instruments were as follows:
(In Millions)
September 30, 2020December 31, 2019
Classification
Carrying
Value
Fair Value
Carrying
Value
Fair Value
Long-term debt:
Senior NotesLevel 1$3,815.5 $3,975.2 $2,113.8 $2,237.0 
IRBs due 2024 to 2028Level 194.3 90.2 — — 
ABL Facility - outstanding balanceLevel 2400.0 400.0 — — 
Total long-term debt$4,309.8 $4,465.4 $2,113.8 $2,237.0 
v3.20.2
PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Tables)
 9 Months Ended
Sep. 30, 2020
Postemployment Benefits [Abstract]  
Schedule of Net Benefit Costs The following are the components of defined benefit pension and OPEB costs (credits):
Defined Benefit Pension Costs (Credits)
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Service cost$5.4 $4.6 $16.0 $12.9 
Interest cost19.6 8.9 42.7 26.2 
Expected return on plan assets(36.7)(13.7)(91.9)(41.0)
Amortization:
Prior service costs0.2 0.3 0.7 0.9 
Net actuarial loss7.3 5.9 20.6 17.7 
Net periodic benefit cost (credit)$(4.2)$6.0 $(11.9)$16.7 
OPEB Costs (Credits)
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Service cost$1.4 $0.5 $3.3 $1.3 
Interest cost4.4 2.3 10.9 7.0 
Expected return on plan assets(4.5)(4.2)(13.6)(12.6)
Amortization:
Prior service credits(0.5)(0.5)(1.5)(1.5)
Net actuarial loss0.8 1.3 2.2 3.8 
Net periodic benefit cost (credit)$1.6 $(0.6)$1.3 $(2.0)
v3.20.2
ASSET RETIREMENT OBLIGATIONS (Tables)
 9 Months Ended
Sep. 30, 2020
Asset Retirement Obligation [Abstract]  
Summary Of Asset Retirement Obligations The following is a summary of our asset retirement obligations:
(In Millions)
September 30,
2020		December 31,
2019
Asset retirement obligations1
$186.4 $165.3 
Less current portion4.4 2.1 
Long-term asset retirement obligations$182.0 $163.2 
1 Includes $33.7 million and $22.0 million related to our active operations as of September 30, 2020 and December 31, 2019, respectively.
Schedule of Change in Asset Retirement Obligation The following is a roll forward of our asset retirement obligation liability:
(In Millions)
20202019
Asset retirement obligation as of January 1$165.3 $172.4 
Increase from AK Steel acquisition16.7 — 
Accretion expense7.8 7.6 
Remediation payments(3.4)(0.5)
Asset retirement obligation as of September 30$186.4 $179.5 
v3.20.2
DERIVATIVE INSTRUMENTS (Tables)
 9 Months Ended
Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value The following table presents the fair value of our derivative instruments and the classification of each in the Statements of Unaudited Condensed Consolidated Financial Position:
Derivatives designated as hedging instruments under Topic 815:Derivatives not designated as hedging instruments under Topic 815:
Derivative Asset (Liability)September 30,
2020		December 31,
2019		September 30,
2020		December 31,
2019
Other current assets:
Customer supply agreement$— $— $34.5 $44.5 
Provisional pricing arrangements— — 26.9 1.3 
Commodity contracts7.9 — 7.9 — 
Other non-current assets:
Commodity contracts1.8 — — — 
Other current liabilities:
Provisional pricing arrangements— — (0.3)(1.1)
Commodity contracts(1.8)(3.2)(6.9)— 
Foreign exchange contracts(0.6)— — — 
Other non-current liabilities:
Foreign exchange contracts(0.1)— — — 
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] The following table presents the notional amount of our outstanding hedge contracts:
(In Millions)
September 30, 2020December 31, 2019
Unit of MeasureMaturity DatesNotional Amount Notional Amount
Commodity contracts:
Natural gasMMBtuOctober 2020 - December 202129.7 20.1 
DieselGallons—— 0.8 
ZincPoundsOctober 2020 - December 202110.9 — 
ElectricityMegawatt hoursOctober 2020 - December 20210.8 — 
Foreign exchange contracts:
Canadian dollarsCADOctober 2020 - December 2021C$38.8 C$— 
Derivative Instruments, Gain (Loss) [Table Text Block] Estimated gains before tax expected to be reclassified into Cost of goods sold within the next 12 months for our existing derivatives that qualify as cash flow hedges are presented below:
(In Millions)
Hedge:Estimated Gains
Natural gas$10.8 
Zinc2.3 
Electricity1.1 
Canadian dollars0.2 
Schedule Of Derivatives Not Designated As Hedging Instruments Statements Of Financial Performance Location Table The following summarizes the effect of our derivatives that are not designated as hedging instruments in the Statements of Unaudited Condensed Consolidated Operations:
(In Millions)
Derivatives Not Designated as Hedging InstrumentsLocation of Gain (Loss) Recognized in Income on DerivativesThree Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Customer supply agreementsRevenues$8.8 $7.6 $14.4 $82.2 
Provisional pricing arrangementsRevenues20.4 (48.5)28.0 (38.8)
Commodity contractsCost of goods sold3.9 — (0.8)— 
Total$33.1 $(40.9)$41.6 $43.4 
v3.20.2
SHAREHOLDERS' EQUITY - Dividends Declared (Tables)
 9 Months Ended
Sep. 30, 2020
Stockholders' Equity Note [Abstract]  
Dividends Declared [Table Text Block] The below table summarizes our recent dividend activity:    
Declaration DateRecord DatePayment Date
Dividend Declared per Common Share1
2/18/20204/3/20204/15/2020$0.06 
12/2/20191/3/20201/15/20200.06 
9/3/201910/4/201910/15/20190.10 
5/31/20197/5/20197/15/20190.06 
2/19/20194/5/20194/15/20190.05 
10/18/20181/4/20191/15/20190.05 
1 The dividend declared on September 3, 2019 included a special cash dividend of $0.04 per common share.
v3.20.2
ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)
 9 Months Ended
Sep. 30, 2020
Equity [Abstract]  
Schedule of Accumulated Other Comprehensive Income (Loss) The following tables reflect the changes in Accumulated other comprehensive loss related to shareholders’ equity:
(In Millions)
Postretirement Benefit Liability,
net of tax
Foreign Currency TranslationDerivative Financial Instruments, net of taxAccumulated Other Comprehensive Loss
December 31, 2019$(315.7)$— $(3.1)$(318.8)
Other comprehensive loss before reclassifications— (0.9)(5.2)(6.1)
Net loss reclassified from accumulated other comprehensive loss5.6 — 2.2 7.8 
March 31, 2020$(310.1)$(0.9)$(6.1)$(317.1)
Other comprehensive income before reclassifications0.4 0.7 1.4 2.5 
Net loss reclassified from accumulated other comprehensive loss5.6 — 3.1 8.7 
June 30, 2020$(304.1)$(0.2)$(1.6)$(305.9)
Other comprehensive income before reclassifications0.4 1.6 12.2 14.2 
Net loss reclassified from accumulated other comprehensive loss6.2 — 3.5 9.7 
September 30, 2020$(297.5)$1.4 $14.1 $(282.0)
(In Millions)
Postretirement Benefit Liability, net of tax
Derivative Financial Instruments,
net of tax
Accumulated Other Comprehensive Loss
December 31, 2018$(281.1)$(2.8)$(283.9)
Other comprehensive income before reclassifications0.2 2.5 2.7 
Net loss reclassified from accumulated other comprehensive loss5.5 0.2 5.7 
March 31, 2019$(275.4)$(0.1)$(275.5)
Other comprehensive income (loss) before reclassifications0.3 (2.3)(2.0)
Net loss reclassified from accumulated other comprehensive loss5.5 0.2 5.7 
June 30, 2019$(269.6)$(2.2)$(271.8)
Other comprehensive income (loss) before reclassifications0.3 (0.5)(0.2)
Net loss reclassified from accumulated other comprehensive loss5.5 0.9 6.4 
September 30, 2019$(263.8)$(1.8)$(265.6)
Details of Accumulated Other Comprehensive Income (Loss) Components The following table reflects the details about Accumulated other comprehensive loss components related to shareholders’ equity:
(In Millions)
Details about Accumulated Other Comprehensive Loss ComponentsAmount of (Gain)/Loss Reclassified into Income, Net of TaxAffected Line Item in the Statement of Unaudited Condensed Consolidated Operations
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Amortization of pension and OPEB liability:
Prior service credits$(0.3)$(0.2)$(0.8)$(0.6)Other non-operating income
Net actuarial loss8.1 7.2 22.8 21.5 Other non-operating income
7.8 7.0 22.0 20.9 Total before taxes
(1.6)(1.5)(4.6)(4.4)Income tax benefit (expense)
$6.2 $5.5 $17.4 $16.5 Net of taxes
Unrealized loss on derivative financial instruments:
Commodity contracts$4.5 $1.2 $11.2 $1.7 Cost of goods sold
(1.0)(0.3)(2.4)(0.4)Income tax benefit (expense)
$3.5 $0.9 $8.8 $1.3 Net of taxes
Total reclassifications for the period, net of tax$9.7 $6.4 $26.2 $17.8 
v3.20.2
RELATED PARTIES (Tables)
 9 Months Ended
Sep. 30, 2020
Schedule of Equity Method Investments [Line Items]  
Equity Method Investments Investees and equity ownership percentages are presented below:
InvesteeSegment Reported WithinEquity Ownership Percentage
Combined Metals of Chicago, LLCSteel and Manufacturing40.0%
Hibbing Taconite CompanyMining and Pelletizing23.0%
Spartan Steel Coating, LLCSteel and Manufacturing48.0%
Summary Of Related Party Transactions Table Disclosure The tables below summarize our material related party transactions:
    Revenues from related parties were as follows:
(Dollars In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Revenue from related parties$294.9 $293.5 $587.5 $792.8 
Revenues1
$1,646.0 $555.6 $3,097.8 $1,455.8 
Related party revenues as a percent of Revenues1
17.9 %52.8 %19.0 %54.5 %
Purchases from related parties$8.2 $— $20.4 $— 
1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
    The following table presents the classification of related party assets and liabilities in the Statements of Unaudited Condensed Consolidated Financial Position:
(In Millions)
Balance Sheet LocationSeptember 30,
2020		December 31,
2019
Accounts receivable, net$91.6 $31.1 
Other current assets58.5 44.5 
Accounts payable(1.2)— 
Other current liabilities(1.7)(2.0)
Hibbing Taconite Company [Member]  
Schedule of Equity Method Investments [Line Items]  
Equity Method Investments Hibbing is a co-owned joint venture with companies that are integrated steel producers or their subsidiaries. The following is a summary of the mine ownership of the co-owned iron ore mine at September 30, 2020:
MineCleveland-Cliffs Inc.ArcelorMittal USAU.S. Steel
Hibbing23.0%62.3%14.7%
v3.20.2
VARIABLE INTEREST ENTITIES (Tables)
 9 Months Ended
Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Schedule of Variable Interest Entities [Table Text Block] The consolidated balance sheet as of September 30, 2020 includes the following amounts for SunCoke Middletown:
(In Millions)
September 30,
2020
Cash and cash equivalents$0.3 
Inventories22.5 
Property, plant and equipment, net305.4 
Accounts payable(10.0)
Other assets (liabilities), net(5.6)
Noncontrolling interests(312.6)
v3.20.2
EARNINGS PER SHARE (Tables)
 9 Months Ended
Sep. 30, 2020
Earnings Per Share [Abstract]  
Earnings Per Share Computation The following table summarizes the computation of basic and diluted earnings per share:
(In Millions, Except Per Share Amounts)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Income (loss) from continuing operations $2.2 $91.8 $(154.8)$231.1 
Income from continuing operations attributable to noncontrolling interest(11.9)— (31.2)— 
Net income (loss) from continuing operations attributable to Cliffs shareholders(9.7)91.8 (186.0)231.1 
Loss from discontinued operations, net of tax(0.3)(0.9)— (1.5)
Net income (loss) attributable to Cliffs shareholders$(10.0)$90.9 $(186.0)$229.6 
Weighted average number of shares:
Basic399.4 270.0 365.2 278.4 
Convertible senior notes— 3.7 — 5.8 
Employee stock plans— 2.9 — 3.6 
Diluted399.4 276.6 365.2 287.8 
Earnings (loss) per common share attributable to Cliffs shareholders - basic:
Continuing operations$(0.02)$0.34 $(0.51)$0.83 
Discontinued operations— — — (0.01)
$(0.02)$0.34 $(0.51)$0.82 
Earnings (loss) per common share attributable to Cliffs shareholders - diluted:
Continuing operations$(0.02)$0.33 $(0.51)$0.80 
Discontinued operations— — — — 
$(0.02)$0.33 $(0.51)$0.80 
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] The following table summarizes the shares that have been excluded from the diluted earnings per share calculation as they were anti-dilutive:
(In Millions)
Three Months Ended
September 30,		Nine Months Ended
September 30,
2020201920202019
Shares related to employee stock plans1.8 — 1.6 — 
v3.20.2
COMMITMENTS AND CONTINGENCIES (Tables)
 9 Months Ended
Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]  
Schedule of Environmental Obligations The following is a summary of our environmental obligations:
(In Millions)
September 30,
2020		December 31,
2019
Environmental obligations$40.9 $2.0 
Less current portion6.4 0.3 
Long-term environmental obligations$34.5 $1.7 
v3.20.2
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended
Dec. 31, 2020
Sep. 30, 2020
Business Acquisition [Line Items]    
Common shares, par value   $ 0.125
Forecast [Member] | ArcelorMittal USA [Member]    
Business Acquisition [Line Items]    
Business Combination, Consideration Transferred $ 1,400  
Payments to Acquire Businesses, Gross $ 505  
Forecast [Member] | ArcelorMittal USA [Member] | Common Stock [Member]    
Business Acquisition [Line Items]    
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares 78,186,671  
Forecast [Member] | ArcelorMittal USA [Member] | Series B Participating Redeemable Preferred Stock [Member]    
Business Acquisition [Line Items]    
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares 583,273  
v3.20.2
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Equity Method Investments (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Mar. 13, 2020
Combined Metals of Chicago, LLC [Member]    
Schedule of Equity Method Investments [Line Items]    
Equity Method Investment, Ownership Percentage 40.00%  
Hibbing Taconite Company [Member]    
Schedule of Equity Method Investments [Line Items]    
Equity Method Investment, Ownership Percentage 23.00%  
Spartan Steel Coating, LLC [Member]    
Schedule of Equity Method Investments [Line Items]    
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity   $ 32.5
Equity Method Investment, Ownership Percentage 48.00%  
v3.20.2
SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION - Revenues (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Disaggregation of Revenue [Line Items]        
Revenues $ 1,646.0 $ 555.6 $ 3,097.8 [1] $ 1,455.8
Realization of deferred revenue 0.0 0.0 34.6 0.0
Steel and Manufacturing [Member]        
Disaggregation of Revenue [Line Items]        
Revenues 1,261.7 0.0 2,194.3 0.0
Steel and Manufacturing [Member] | Carbon Steel [Member]        
Disaggregation of Revenue [Line Items]        
Revenues 821.2 0.0 1,391.6 0.0
Steel and Manufacturing [Member] | Stainless and Electrical Steel [Member]        
Disaggregation of Revenue [Line Items]        
Revenues 303.2 0.0 585.1 0.0
Steel and Manufacturing [Member] | Other Product Lines [Member]        
Disaggregation of Revenue [Line Items]        
Revenues 137.3 0.0 217.6 0.0
Mining and Pelletizing [Member]        
Disaggregation of Revenue [Line Items]        
Revenues 384.3 555.6 903.5 1,455.8
Mining and Pelletizing [Member] | Iron Ore [Member]        
Disaggregation of Revenue [Line Items]        
Revenues [1] 357.1 515.0 838.1 1,357.8
Mining and Pelletizing [Member] | Freight [Member]        
Disaggregation of Revenue [Line Items]        
Revenues 27.2 40.6 65.4 98.0
Automotive [Member] | Steel and Manufacturing [Member]        
Disaggregation of Revenue [Line Items]        
Revenues 920.0 0.0 1,404.0 0.0
Infrastructure and Manufacturing [Member] | Steel and Manufacturing [Member]        
Disaggregation of Revenue [Line Items]        
Revenues 198.8 0.0 446.2 0.0
Distributors and Converters [Member] | Steel and Manufacturing [Member]        
Disaggregation of Revenue [Line Items]        
Revenues 142.9 0.0 344.1 0.0
Steel Producers [Member] | Mining and Pelletizing [Member]        
Disaggregation of Revenue [Line Items]        
Revenues [1] 384.3 555.6 903.5 1,455.8
Non-US [Member]        
Disaggregation of Revenue [Line Items]        
Revenues $ 265.0 $ 138.9 $ 487.7 $ 318.3
[1] 1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
v3.20.2
SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION - Allowance for Credit Losses (Details) - USD ($)
$ in Millions
 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]    
Allowance for credit losses as of beginning of period $ 0.0 $ 0.0
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease) 5.2 0.0
Allowance for credit losses as of end of period $ 5.2 $ 0.0
v3.20.2
SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION - Inventories (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Inventory Disclosure [Abstract]    
Finished and semi-finished goods inventories $ 940.5 $ 114.1
Work-in-process 78.2 68.7
Raw materials 382.3 9.4
Total product inventories 1,401.0 192.2
Manufacturing supplies and critical spares 394.1 125.2
Inventories $ 1,795.1 $ 317.4
v3.20.2
SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION - Deferred Revenue (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]        
Realization of deferred revenue $ 0.0 $ 0.0 $ 34.6 $ 0.0
Other Current Liabilities [Member]        
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]        
Opening balance as of January 1     22.1 21.0
Net decrease     (19.8) (2.7)
Closing balance as of September 30 2.3 18.3 2.3 18.3
Other Noncurrent Liabilities [Member]        
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]        
Opening balance as of January 1     25.7 38.5
Net decrease     (25.7) (8.5)
Closing balance as of September 30 $ 0.0 $ 30.0 $ 0.0 $ 30.0
v3.20.2
SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION - Accrued Liabilities (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Disclosure Text Block [Abstract]    
Accrued employment costs $ 146.6 $ 61.7
Accrued interest 81.8 29.0
Accrued dividends 1.0 17.8
Other 50.0 17.8
Accrued liabilities $ 279.4 $ 126.3
v3.20.2
SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION - Cash Flow Information (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Supplemental Cash Flow Information [Abstract]        
Property, Plant and Equipment, Additions $ 102.3 $ 184.7 $ 333.0 $ 505.6
Non-cash accruals     (88.4) 26.1
Right-of-use assets - finance leases     42.5 29.3
Grants     0.0 (10.5)
Cash paid for capital expenditures including deposits     378.9 460.7
Taxes paid on income     3.2 0.1
Income tax refunds     (119.3) (117.9)
Interest paid on debt obligations net of capitalized interest [1]     106.0 71.9
Interest Costs Capitalized $ 14.7 $ 7.0 $ 38.0 $ 16.9
[1] 1 Capitalized interest was $38.0 million and $16.9 million for the nine months ended September 30, 2020 and 2019, respectively.
v3.20.2
SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION - Non-Cash Investing and Financing Activities (Details) - USD ($)
$ in Millions
 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Common Stock [Member]    
Other Significant Noncash Transactions [Line Items]    
Other Significant Noncash Transaction, Value of Consideration Given $ 617.6 $ 0.0
Share-based Payment Arrangement [Member]    
Other Significant Noncash Transactions [Line Items]    
Other Significant Noncash Transaction, Value of Consideration Given $ 3.9 $ 0.0
v3.20.2
ACQUISITION OF AK STEEL - Overview (Details)
$ in Millions
 3 Months Ended 7 Months Ended 9 Months Ended 12 Months Ended
Mar. 13, 2020
USD ($)
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Sep. 30, 2020
USD ($)
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Dec. 31, 2019
USD ($)
Oct. 01, 2020
USD ($)
Business Acquisition [Line Items]                
Revenues   $ 1,646.0 $ 555.6   $ 3,097.8 [1] $ 1,455.8    
Net income (loss)   (10.0) 90.9   (186.0) 229.6    
Amortization of inventory step-up         74.0 0.0    
Acquisition-related costs   7.5 $ 0.0   68.4 $ 0.0    
AK Steel Holding Corporation [Member]                
Business Acquisition [Line Items]                
Business Acquisition, Shares Exchange Ratio 0.400              
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period             $ 6,359.4  
Revenues   1,261.7   $ 2,194.3        
Net income (loss)   (30.4)   (292.0)        
Amortization of inventory step-up   14.6   74.0        
Severance costs   2.4   $ 35.1        
Acquisition-related costs   $ 0.6     $ 25.6      
Business Combination, Consideration Transferred $ 1,535.1              
Forecast [Member] | AK Steel Holding Corporation [Member]                
Business Acquisition [Line Items]                
Cost synergies               $ 150.0
[1] 1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
v3.20.2
ACQUISITION OF AK STEEL - Consideration (Details)
$ / shares in Units, $ in Millions
Mar. 13, 2020
USD ($)
$ / shares
shares
Sep. 30, 2020
shares
Jun. 30, 2020
shares
Mar. 31, 2020
shares
Dec. 31, 2019
shares
Sep. 30, 2019
shares
Jun. 30, 2019
shares
Mar. 31, 2019
shares
Dec. 31, 2018
shares
Business Acquisition [Line Items]                  
Fair value of Cliffs common shares issued for AK Steel outstanding common stock $ 617.6                
Common shares, outstanding (in shares) | shares   399,229,917     270,084,005        
AK Steel Holding Corporation [Member]                  
Business Acquisition [Line Items]                  
Fair value of Cliffs common shares issued for AK Steel outstanding common stock 617.6                
Fair value of debt included in consideration 913.6                
Business Combination, Consideration Transferred $ 1,535.1                
Common shares, outstanding (in shares) | shares 316,900,000                
Business Acquisition, Shares Exchange Ratio 0.400                
Shares of Cliffs common shares issued to AK Steel stockholders | shares 126,800,000                
Price per share of Cliffs common shares | $ / shares $ 4.87                
Credit Facility | AK Steel Holding Corporation [Member]                  
Business Acquisition [Line Items]                  
Fair value of debt included in consideration $ 590.0                
7.50% 2023 AK Senior Notes [Member] | AK Steel Holding Corporation [Member]                  
Business Acquisition [Line Items]                  
Fair value of debt included in consideration 323.6                
Share-based Payment Arrangement [Member] | AK Steel Holding Corporation [Member]                  
Business Acquisition [Line Items]                  
Fair value of Cliffs common shares issued for AK Steel outstanding common stock 3.9                
Common Stock [Member]                  
Business Acquisition [Line Items]                  
Common shares, outstanding (in shares) | shares   399,200,000 399,200,000 398,600,000 270,100,000 270,100,000 270,000,000.0 282,800,000 292,600,000
Common Stock [Member] | AK Steel Holding Corporation [Member]                  
Business Acquisition [Line Items]                  
Fair value of Cliffs common shares issued for AK Steel outstanding common stock $ 617.6                
v3.20.2
ACQUISITION OF AK STEEL - Assets and Liabilities Assumed (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2020
Sep. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Business Acquisition [Line Items]          
Goodwill $ 144.0 $ 144.0 $ 144.0   $ 2.1
AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Cash and cash equivalents 39.7 39.7 39.7 $ 37.7  
Accounts receivable 662.9 662.9 662.9 666.0  
Inventories 1,523.0 1,523.0 1,523.0 1,562.8  
Other current assets 52.1 52.1 52.1 67.5  
Property, plant and equipment 2,164.3 2,164.3 2,164.3 2,184.4  
Intangible assets 148.0 148.0 148.0 163.0  
Right of use asset, operating leases 209.6 209.6 209.6 225.9  
Other non-current assets 112.1 112.1 112.1 85.9  
Accounts payable (642.4) (642.4) (642.4) (636.3)  
Accrued liabilities (222.4) (222.4) (222.4) (222.5)  
Other current liabilities (175.2) (175.2) (175.2) (181.8)  
Long-term debt (1,179.4) (1,179.4) (1,179.4) (1,179.4)  
Deferred income taxes (19.9) (19.9) (19.9) (19.7)  
Operating lease liability, non-current (175.4) (175.4) (175.4) (188.1)  
Intangible liabilities (70.5) (70.5) (70.5) (140.0)  
Pension and OPEB liabilities (870.9) (870.9) (870.9) (873.0)  
Asset retirement obligations (15.9) (15.9) (15.9) (13.9)  
Other non-current liabilities (146.5) (146.5) (146.5) (144.2)  
Net identifiable assets acquired 1,393.2 1,393.2 1,393.2 1,394.3  
Goodwill 141.9 141.9 141.9 141.2  
Total net assets acquired 1,535.1 1,535.1 1,535.1 $ 1,535.5  
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Net Identifiable Assets   (1.1)      
Goodwill, Purchase Accounting Adjustments   0.7      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Consideration Transferred   (0.4)      
Cash and Cash Equivalents [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets   2.0      
Accounts Receivable [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets   (3.1)      
Inventories [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory   (39.8)      
Other Current Assets [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets   (15.4)      
Property, Plant and Equipment [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment   (20.1)      
Finite-Lived Intangible Assets [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles   (15.0)      
Right-of-use asset, operating lease [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets   (16.3)      
Other Noncurrent Assets [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets   26.2      
Accounts Payable [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities   (6.1)      
Accrued Liabilities [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities   0.1      
Other Current Liabilities [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities   6.6      
Long-term Debt [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities   0.0      
Deferred income taxes [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities   (0.2)      
Operating lease liability, non-current [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities   12.7      
Intangible liabilities [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles   69.5      
Pension and OPEB liabilities [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities   2.1      
Asset Retirement Obligation [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities   (2.0)      
Other Noncurrent Liabilities [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities   $ (2.3)      
Cost of Sales [Member] | AK Steel Holding Corporation [Member]          
Business Acquisition [Line Items]          
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments Related to Previous Period $ 0.2   $ 8.0    
v3.20.2
ACQUISITION OF AK STEEL - Intangible Assets and Liabilities (Details) - AK Steel Holding Corporation [Member]
$ in Millions
 9 Months Ended
Sep. 30, 2020
USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]  
Finite-lived Intangible Assets Acquired $ 148.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life (in years) 17 years
Intangible Liability Assumed $ (70.5)
Assumed Finite-lived Intangible Liabilities, Weighted Average Useful Life (in years) 12 years
Customer Relationships [Member]  
Acquired Finite-Lived Intangible Assets [Line Items]  
Finite-lived Intangible Assets Acquired $ 77.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life (in years) 18 years
Technology-Based Intangible Assets [Member]  
Acquired Finite-Lived Intangible Assets [Line Items]  
Finite-lived Intangible Assets Acquired $ 60.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life (in years) 17 years
Trademarks and Trade Names [Member]  
Acquired Finite-Lived Intangible Assets [Line Items]  
Finite-lived Intangible Assets Acquired $ 11.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life (in years) 10 years
v3.20.2
ACQUISITION OF AK STEEL - Pro Forma Information (Details) - AK Steel Holding Corporation [Member] - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]        
Business Acquisition, Pro Forma Revenue $ 1,646.0 $ 1,937.6 $ 4,265.1 $ 5,958.7
Business Acquisition, Pro Forma Net Income (Loss) (6.0) 84.2 $ (123.9) 213.3
Business Acquisition, Pro Forma Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent     24.30%  
Business Acquisition, Pro Forma Income Tax Expense (Benefit) (5.6) (2.1) $ (2.1) (4.5)
Fair Value Adjustment to Inventory [Member]        
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]        
Business Acquisition, Pro Forma Net Income (Loss) 14.6   74.0 74.0
Acquisition-related Costs [Member]        
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]        
Business Acquisition, Pro Forma Net Income (Loss) 0.7   29.1  
Other Adjustments [Member]        
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]        
Business Acquisition, Pro Forma Net Income (Loss) (10.0) (1.1) (10.0) (7.0)
Intersegment Eliminations [Member]        
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]        
Business Acquisition, Pro Forma Revenue $ 135.6 $ 153.5 $ 394.8 $ 410.8
v3.20.2
SEGMENT REPORTING - Results by Segment (Details)
T in Thousands, $ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
USD ($)
T
Sep. 30, 2019
USD ($)
T
Sep. 30, 2020
USD ($)
unit
T
Sep. 30, 2019
USD ($)
T
Segment Reporting Information [Line Items]        
Number of Reporting Units | unit     2  
Revenues $ 1,646.0 $ 555.6 $ 3,097.8 [1] $ 1,455.8
Adjusted EBITDA 126.3 144.1 67.0 413.7
Realization of deferred revenue $ 0.0 $ 0.0 $ 34.6 $ 0.0
Steel and Manufacturing [Member]        
Segment Reporting Information [Line Items]        
Sales Volume (Net Tons) | T 1,117 0 1,935 0
Revenues $ 1,261.7 $ 0.0 $ 2,194.3 $ 0.0
Adjusted EBITDA $ 33.3 $ (2.1) $ (81.8) $ (4.0)
Mining and Pelletizing [Member]        
Segment Reporting Information [Line Items]        
Sales Volume (Long Tons) | T 3,703 5,404 8,772 13,143
Revenues $ 384.3 $ 555.6 $ 903.5 $ 1,455.8
Adjusted EBITDA 145.3 182.7 309.5 510.7
Corporate and Other [Member]        
Segment Reporting Information [Line Items]        
Adjusted EBITDA $ (52.3) $ (36.5) $ (160.7) $ (93.0)
Operating Segments [Member] | Mining and Pelletizing [Member]        
Segment Reporting Information [Line Items]        
Sales Volume (Long Tons) | T 4,907 5,750 11,800 13,527
Revenues [1] $ 520.3 $ 590.6 $ 1,238.7 $ 1,494.8
Intersegment Eliminations [Member] | Mining and Pelletizing [Member]        
Segment Reporting Information [Line Items]        
Sales Volume (Long Tons) | T (1,204) (346) (3,028) (384)
Revenues $ (136.0) $ (35.0) $ (335.2) $ (39.0)
[1] 1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
v3.20.2
SEGMENT REPORTING - Net Income (Loss) to Total Adjusted EBITDA (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Segment Reporting Information [Line Items]        
Net income (loss) $ 1.9 $ 90.9 $ (154.8) $ 229.6
Interest expense, net (68.2) (25.3) (167.9) (76.5)
Income tax benefit (expense) 22.4 (4.8) 98.5 (23.1)
Depreciation, depletion and amortization     (183.9) (63.1)
EBITDA 120.1 143.3 98.5 392.6
Gain (loss) on extinguishment of debt 0.0 0.0 132.6 (18.2)
Acquisition-related costs excluding severance costs (7.5) 0.0 (68.4) 0.0
Amortization of Inventory Step-up     (74.0) 0.0
Impact of discontinued operations (0.3) (0.9) 0.0 (1.5)
Adjusted EBITDA 126.3 144.1 67.0 413.7
Net Income (Loss) Attributable to Noncontrolling Interest 11.9 0.0 31.2 0.0
Depreciation, Depletion and Amortization Attributable to Noncontrolling Interests 4.3   10.1  
EBITDA Calculation [Member]        
Segment Reporting Information [Line Items]        
Interest expense, net (68.2) (25.4) (167.9) (76.8)
Income tax benefit (expense) 22.4 (4.8) 98.5 (23.1)
Depreciation, depletion and amortization (72.4) (22.2) (183.9) (63.1)
Adjusted EBITDA Calculation [Member]        
Segment Reporting Information [Line Items]        
EBITDA of Noncontrolling Interests 16.2 [1] 0.0 41.3 [1] 0.0
Gain (loss) on extinguishment of debt 0.0 0.0 132.6 (18.2)
Severance costs (2.4) 0.0 (38.3) (1.7)
Acquisition-related costs excluding severance costs (5.1) 0.0 (30.1) 0.0
Amortization of Inventory Step-up (14.6) 0.0 (74.0) 0.0
Impact of discontinued operations $ (0.3) $ (0.8) $ 0.0 $ (1.2)
[1] 1 EBITDA of noncontrolling interests includes $11.9 million and $31.2 million for income and $4.3 million and $10.1 million for depreciation, depletion and amortization for the three and nine months ended September 30, 2020, respectively.
v3.20.2
SEGMENT REPORTING - Segment Assets (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Segment Reporting Information [Line Items]    
Total assets $ 8,480.9 $ 3,503.8
Corporate and Other [Member]    
Segment Reporting Information [Line Items]    
Total assets 491.9 947.1
Operating Segments [Member]    
Segment Reporting Information [Line Items]    
Total assets 7,989.0 2,556.7
Operating Segments [Member] | Steel and Manufacturing [Member]    
Segment Reporting Information [Line Items]    
Total assets 6,345.7 913.6
Operating Segments [Member] | Mining and Pelletizing [Member]    
Segment Reporting Information [Line Items]    
Total assets $ 1,643.3 $ 1,643.1
v3.20.2
SEGMENT REPORTING - Segment Capital Additions (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Segment Reporting Information [Line Items]        
Property, Plant and Equipment, Additions $ 102.3 $ 184.7 $ 333.0 $ 505.6
Steel and Manufacturing [Member]        
Segment Reporting Information [Line Items]        
Property, Plant and Equipment, Additions 88.0 160.5 266.8 398.0
Mining and Pelletizing [Member]        
Segment Reporting Information [Line Items]        
Property, Plant and Equipment, Additions 13.3 22.1 64.9 104.5
Corporate and Other [Member]        
Segment Reporting Information [Line Items]        
Property, Plant and Equipment, Additions $ 1.0 $ 2.1 $ 1.3 $ 3.1
v3.20.2
PROPERTY, PLANT AND EQUIPMENT (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross $ 5,958.0   $ 5,958.0   $ 3,027.4
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment 1,407.3   1,407.3   1,098.4
Property, plant and equipment, net 4,550.7   4,550.7   1,929.0
Finance Lease, Right-of-Use Asset 97.1   97.1   49.0
Interest Costs Capitalized 14.7 $ 7.0 38.0 $ 16.9  
Depreciation and depletion expense 71.8 $ 22.0 182.5 $ 62.5  
Land, Land Improvements and Mineral Rights [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross 653.2   653.2   582.2
Building [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross 454.4   454.4   157.8
Steel and Manufacturing Equipment [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross 2,128.0   2,128.0   42.0
Mining and Pelletizing Equipment [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross 1,455.2   1,455.2   1,413.6
Other Assets [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross 121.3   121.3   101.5
Construction in Progress [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross $ 1,145.9   $ 1,145.9   $ 730.3
v3.20.2
GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES - Goodwill (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Goodwill [Line Items]    
Goodwill $ 144.0 $ 2.1
Steel and Manufacturing [Member]    
Goodwill [Line Items]    
Goodwill 141.9  
Mining and Pelletizing [Member]    
Goodwill [Line Items]    
Goodwill $ 2.1 $ 2.1
v3.20.2
GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES - Intangible Assets and Liabilities (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]    
Finite-Lived Intangible Assets, Gross $ 220.2  
Finite-Lived Intangible Assets, Accumulated Amortization (30.1)  
Finite-Lived Intangible Assets, Net 190.1  
Finite-Lived Intangible Liabilities, Gross (70.5)  
Finite-Lived Intangible Liabilities, Accumulated Amortization 4.6  
Finite-Lived Intangible Liabilities, Net (65.9)  
Customer Relationships [Member]    
Finite-Lived Intangible Assets [Line Items]    
Finite-Lived Intangible Assets, Gross 77.0  
Finite-Lived Intangible Assets, Accumulated Amortization (2.6)  
Finite-Lived Intangible Assets, Net 74.4  
Technology-Based Intangible Assets [Member]    
Finite-Lived Intangible Assets [Line Items]    
Finite-Lived Intangible Assets, Gross 60.0  
Finite-Lived Intangible Assets, Accumulated Amortization (2.1)  
Finite-Lived Intangible Assets, Net 57.9  
Trademarks and Trade Names [Member]    
Finite-Lived Intangible Assets [Line Items]    
Finite-Lived Intangible Assets, Gross 11.0  
Finite-Lived Intangible Assets, Accumulated Amortization (0.7)  
Finite-Lived Intangible Assets, Net 10.3  
Mining Permits [Member]    
Finite-Lived Intangible Assets [Line Items]    
Finite-Lived Intangible Assets, Gross 72.2 $ 72.2
Finite-Lived Intangible Assets, Accumulated Amortization (24.7) (24.1)
Finite-Lived Intangible Assets, Net $ 47.5 $ 48.1
v3.20.2
GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES - Amortization of Intangible Assets (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]        
Amortization of Intangible Assets $ 2.5 $ 0.2 $ 6.0 $ 0.6
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year 2.5   2.5  
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 10.0   10.0  
Finite-Lived Intangible Assets, Amortization Expense, Year Two 10.0   10.0  
Finite-Lived Intangible Assets, Amortization Expense, Year Three 10.0   10.0  
Finite-Lived Intangible Assets, Amortization Expense, Year Four 10.0   10.0  
Finite-Lived Intangible Assets, Amortization Expense, Year Five $ 10.0   $ 10.0  
v3.20.2
GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES - Amortization of Intangible Liability (Details)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
USD ($)
Sep. 30, 2020
USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]    
Amortization of Intangible Liabilities $ 1.9 $ 4.6
Finite-Lived Intangible Liabilities, Amortization Credit, Remainder of Fiscal Year 2.0 2.0
Finite-Lived Intangible Liabilities, Amortization Credit, Next Twelve Months 7.8 7.8
Finite-Lived Intangible Liabilities, Amortization Credit, Year Two 7.8 7.8
Finite-Lived Intangible Liabilities, Amortization Credit, Year Three 7.8 7.8
Finite-Lived Intangible Liabilities, Amortization Credit, Year Four 7.8 7.8
Finite-Lived Intangible Liabilities, Amortization Credit, Year Five $ 7.8 $ 7.8
v3.20.2
DEBT AND CREDIT FACILITIES - Schedule Of Long-Term Debt (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Debt Instrument [Line Items]    
Long-term Debt, Gross $ 4,490.7  
LONG-TERM DEBT 4,309.8 $ 2,113.8
Credit Facility    
Debt Instrument [Line Items]    
Long-term Line of Credit $ 400.0  
Cleveland-Cliffs Inc. [Member] | 4.875% 2024 Senior Secured Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 5.00% 5.00%
Long-term Debt, Gross $ 394.5 $ 400.0
Unamortized Debt Issuance Expense (3.7) (4.6)
Debt Instrument, Unamortized Discount (1.5) (1.8)
Long-term Debt $ 389.3 $ 393.6
Cleveland-Cliffs Inc. [Member] | 9.875% 2025 Senior Secured Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 10.57%  
Long-term Debt, Gross $ 955.2  
Unamortized Debt Issuance Expense (8.1)  
Debt Instrument, Unamortized Discount (25.8)  
Long-term Debt $ 921.3  
Cleveland-Cliffs Inc. [Member] | 6.75% 2026 Senior Secured Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 6.99%  
Long-term Debt, Gross $ 845.0  
Unamortized Debt Issuance Expense (21.4)  
Debt Instrument, Unamortized Discount (9.0)  
Long-term Debt $ 814.6  
Cleveland-Cliffs Inc. [Member] | 6.375% 2025 Senior Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 8.11%  
Long-term Debt, Gross $ 64.3  
Unamortized Debt Issuance Expense (0.2)  
Debt Instrument, Unamortized Discount (4.6)  
Long-term Debt $ 59.5  
Cleveland-Cliffs Inc. [Member] | 1.50% 2025 Convertible Senior Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 6.26% 6.26%
Long-term Debt, Gross $ 296.3 $ 316.3
Unamortized Debt Issuance Expense (3.7) (4.6)
Debt Instrument, Unamortized Discount (53.0) (65.0)
Long-term Debt $ 239.6 $ 246.7
Cleveland-Cliffs Inc. [Member] | 5.75% 2025 Senior Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 6.01% 6.01%
Long-term Debt, Gross $ 396.2 $ 473.3
Unamortized Debt Issuance Expense (2.6) (3.6)
Debt Instrument, Unamortized Discount (4.1) (5.5)
Long-term Debt $ 389.5 $ 464.2
Cleveland-Cliffs Inc. [Member] | 7.00% 2027 Senior Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 9.24%  
Long-term Debt, Gross $ 88.0  
Unamortized Debt Issuance Expense (0.3)  
Debt Instrument, Unamortized Discount (9.6)  
Long-term Debt $ 78.1  
Cleveland-Cliffs Inc. [Member] | 5.875% 2027 Senior Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 6.49% 6.49%
Long-term Debt, Gross $ 555.5 $ 750.0
Unamortized Debt Issuance Expense (4.3) (6.3)
Debt Instrument, Unamortized Discount (18.6) (27.3)
Long-term Debt $ 532.6 $ 716.4
Cleveland-Cliffs Inc. [Member] | 6.25% 2040 Senior Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 6.34% 6.34%
Long-term Debt, Gross $ 262.7 $ 298.4
Unamortized Debt Issuance Expense (1.8) (2.2)
Debt Instrument, Unamortized Discount (2.8) (3.3)
Long-term Debt $ 258.1 292.9
Cleveland-Cliffs Inc. [Member] | Credit Facility    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 2.77%  
Long-term Debt, Gross $ 2,000.0 450.0
Long-term Line of Credit $ 400.0 $ 0.0
AK Steel Holding Corporation [Member] | 7.625% 2021 Senior Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 7.33%  
Long-term Debt, Gross $ 33.5  
Unamortized Debt Issuance Expense 0.0  
Debt Instrument, Unamortized Premium 0.1  
Long-term Debt $ 33.6  
AK Steel Holding Corporation [Member] | 7.50% 2023 AK Senior Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 6.17%  
Long-term Debt, Gross $ 12.8  
Unamortized Debt Issuance Expense 0.0  
Debt Instrument, Unamortized Premium 0.5  
Long-term Debt $ 13.3  
AK Steel Holding Corporation [Member] | 6.375% 2025 AK Senior Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 8.11%  
Long-term Debt, Gross $ 38.4  
Unamortized Debt Issuance Expense 0.0  
Debt Instrument, Unamortized Discount (2.7)  
Long-term Debt $ 35.7  
AK Steel Holding Corporation [Member] | 7.00% 2027 AK Senior Notes [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage 9.24%  
Long-term Debt, Gross $ 56.3  
Unamortized Debt Issuance Expense 0.0  
Debt Instrument, Unamortized Discount (6.0)  
Long-term Debt 50.3  
AK Steel Holding Corporation [Member] | Industrial Revenue Bonds [Member]    
Debt Instrument [Line Items]    
Long-term Debt, Gross 92.0  
Unamortized Debt Issuance Expense 0.0  
Debt Instrument, Unamortized Premium 2.3  
Long-term Debt $ 94.3  
v3.20.2
DEBT AND CREDIT FACILITIES - Schedule of Extinguishment of Debt (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 01, 2020
Apr. 24, 2020
Mar. 27, 2020
Mar. 13, 2020
Sep. 30, 2020
Jun. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount   $ 736.4           $ 1,487.5 $ 724.0
Reduction of Principal Long-Term Debt   $ 181.2              
Gain (loss) on extinguishment of debt         $ 0.0   $ 0.0 132.6 (18.2)
Senior Notes [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount           $ 11.2      
7.625% 2021 AK Senior Notes [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount     $ 8.5 $ 364.2       372.7  
Gain (loss) on extinguishment of debt               0.4  
7.50% 2023 AK Senior Notes [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount     $ 56.5 $ 310.7       367.2  
Gain (loss) on extinguishment of debt               2.8  
4.875% 2024 Senior Secured Notes [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount               5.5  
Gain (loss) on extinguishment of debt               0.5  
6.375% 2025 Senior Notes [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount               167.5  
Gain (loss) on extinguishment of debt               21.3  
1.50% 2025 Convertible Senior Notes [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount               20.0  
Gain (loss) on extinguishment of debt               1.3  
4.875% 2021 Senior Notes [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount                 124.0
Gain (loss) on extinguishment of debt                 (5.3)
5.75% 2025 Senior Notes [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount               77.1 600.0
Gain (loss) on extinguishment of debt               16.3 $ (12.9)
7.00% 2027 Senior Notes [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount               247.3  
Gain (loss) on extinguishment of debt               28.4  
5.875% 2027 Senior Notes [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount               194.5  
Gain (loss) on extinguishment of debt               48.7  
6.25% 2040 Senior Notes [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount               35.7  
Gain (loss) on extinguishment of debt               $ 12.9  
AK Steel Holding Corporation [Member] | Unsecured Industrial Revenue Bonds [Member]                  
Extinguishment of Debt [Line Items]                  
Extinguishment of Debt, Amount $ 7.3                
v3.20.2
DEBT AND CREDIT FACILITIES - ABL Facility (Details)
$ in Millions
 9 Months Ended
Sep. 30, 2020
USD ($)
Line of Credit Facility [Line Items]  
Line of Credit Facility, Maximum Borrowing Capacity $ 2,000.0
Credit Facility  
Line of Credit Facility [Line Items]  
Available borrowing base on ABL Facility 1,715.2 [1]
Long-term Line of Credit (400.0)
Borrowing capacity available $ 1,123.0
Line of Credit Facility, Covenant Compliance As of September 30, 2020, we were in compliance with the ABL Facility liquidity requirements and, therefore, the springing financial covenant requiring a minimum fixed charge coverage ratio of 1.0 to 1.0 was not applicable.
Letter of Credit [Member]  
Line of Credit Facility [Line Items]  
Long-term Line of Credit $ (192.2) [2]
[1] 1 As of September 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] 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.
v3.20.2
DEBT AND CREDIT FACILITIES - Schedule of Debt Maturities (Details)
$ in Millions
Sep. 30, 2020
USD ($)
Debt Disclosure [Abstract]  
Debt Maturities 2020 $ 0.0
Debt Maturities 2021 33.5
Debt Maturities 2022 0.0
Debt Maturities 2023 12.8
Debt Maturities 2024 456.5
2025 and thereafter 3,987.9
Total maturities of debt $ 4,490.7
v3.20.2
FAIR VALUE MEASUREMENTS - Fair Value of Assets and Liabilities (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Assets, Fair Value Disclosure $ 79.0 $ 233.4
Liabilities, Fair Value Disclosure (9.7) (4.3)
Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Assets, Fair Value Disclosure 0.0 0.0
Liabilities, Fair Value Disclosure 0.0 0.0
Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Assets, Fair Value Disclosure 17.6 187.6
Liabilities, Fair Value Disclosure (9.4) (3.2)
Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Assets, Fair Value Disclosure 61.4 45.8
Liabilities, Fair Value Disclosure (0.3) (1.1)
Cash and Cash Equivalents [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash equivalents   187.6
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash equivalents   0.0
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash equivalents   187.6
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash equivalents   0.0
Commodity Contract [Member] | Other Current Assets [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 15.8  
Commodity Contract [Member] | Other Current Assets [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 0.0  
Commodity Contract [Member] | Other Current Assets [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 15.8  
Commodity Contract [Member] | Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 0.0  
Commodity Contract [Member] | Other Noncurrent Assets [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 1.8  
Commodity Contract [Member] | Other Noncurrent Assets [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 0.0  
Commodity Contract [Member] | Other Noncurrent Assets [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 1.8  
Commodity Contract [Member] | Other Noncurrent Assets [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 0.0  
Commodity Contract [Member] | Other Current Liabilities [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability (8.7) (3.2)
Commodity Contract [Member] | Other Current Liabilities [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability 0.0 0.0
Commodity Contract [Member] | Other Current Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability (8.7) (3.2)
Commodity Contract [Member] | Other Current Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability 0.0 0.0
Customer Supply Agreement [Member] | Other Current Assets [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 34.5 44.5
Customer Supply Agreement [Member] | Other Current Assets [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 0.0 0.0
Customer Supply Agreement [Member] | Other Current Assets [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 0.0 0.0
Customer Supply Agreement [Member] | Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 34.5 44.5
Provisional Pricing Arrangements [Member] | Other Current Assets [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 26.9 1.3
Provisional Pricing Arrangements [Member] | Other Current Assets [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 0.0 0.0
Provisional Pricing Arrangements [Member] | Other Current Assets [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 0.0 0.0
Provisional Pricing Arrangements [Member] | Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Asset 26.9 1.3
Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability (0.3) (1.1)
Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability 0.0 0.0
Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability 0.0 0.0
Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability (0.3) $ (1.1)
Foreign Exchange Contract [Member] | Other Current Liabilities [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability (0.6)  
Foreign Exchange Contract [Member] | Other Current Liabilities [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability 0.0  
Foreign Exchange Contract [Member] | Other Current Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability (0.6)  
Foreign Exchange Contract [Member] | Other Current Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability 0.0  
Foreign Exchange Contract [Member] | Other Noncurrent Liabilities [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability (0.1)  
Foreign Exchange Contract [Member] | Other Noncurrent Liabilities [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability 0.0  
Foreign Exchange Contract [Member] | Other Noncurrent Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability (0.1)  
Foreign Exchange Contract [Member] | Other Noncurrent Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative Liability $ 0.0  
v3.20.2
FAIR VALUE MEASUREMENTS - Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities (Details)
$ in Millions
Sep. 30, 2020
USD ($)
Dec. 31, 2019
USD ($)
Other Current Assets [Member] | Customer Supply Agreement [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset $ 34.5 $ 44.5
Other Current Assets [Member] | Provisional Pricing Arrangements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset 26.9 1.3
Other Current Assets [Member] | Not Designated as Hedging Instrument [Member] | Customer Supply Agreement [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset 34.5 44.5
Other Current Assets [Member] | Not Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset 26.9 1.3
Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Customer Supply Agreement [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset 34.5 44.5
Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Provisional Pricing Arrangements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset $ 26.9 1.3
Other Current Assets [Member] | Customer's Hot-Rolled Steel Estimate [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Customer Supply Agreement [Member] | Minimum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 542  
Other Current Assets [Member] | Customer's Hot-Rolled Steel Estimate [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Customer Supply Agreement [Member] | Maximum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 634  
Other Current Assets [Member] | Customer's Hot-Rolled Steel Estimate [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Customer Supply Agreement [Member] | Weighted Average [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 548  
Other Current Assets [Member] | Platts 62% Price | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member] | Minimum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 104  
Other Current Assets [Member] | Platts 62% Price | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member] | Maximum [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 123  
Other Current Assets [Member] | Platts 62% Price | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member] | Weighted Average [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 105  
Other Current Assets [Member] | Atlantic Basin Pellet Premium [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member] | Weighted Average [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 30  
Other Current Liabilities [Member] | Provisional Pricing Arrangements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Liability $ (0.3) (1.1)
Other Current Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Liability (0.3) (1.1)
Other Current Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Provisional Pricing Arrangements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Liability $ (0.3) $ (1.1)
Other Current Liabilities [Member] | Platts 62% Price | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member] | Weighted Average [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 104  
Other Current Liabilities [Member] | Producer Price Indices | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member] | Weighted Average [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 110  
v3.20.2
FAIR VALUE MEASUREMENTS - Fair Value, Assets and Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning balance $ 35.3 $ 118.1 $ 45.8 $ 91.4
Included in earnings 29.5 (6.5) 43.3 83.1
Settlements (3.4) (38.8) (27.7) (101.7)
Ending balance 61.4 72.8 61.4 72.8
Total gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) on assets still held at the reporting date 27.8 (6.5) 40.4 81.8
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning balance 0.0 0.0 (1.1) 0.0
Included in earnings (0.3) (34.4) (0.9) (39.7)
Settlements 0.0 4.2 1.7 9.5
Ending balance (0.3) (30.2) (0.3) (30.2)
Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date $ (0.3) $ (30.2) $ (0.3) $ (30.2)
v3.20.2
FAIR VALUE MEASUREMENTS - Carrying Value And Fair Value Of Financial Instruments Disclosure (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Carrying Value [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total long-term debt, fair value $ 4,309.8 $ 2,113.8
Fair Value [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total long-term debt, fair value 4,465.4 2,237.0
Senior Notes [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total long-term debt, fair value 3,815.5 2,113.8
Senior Notes [Member] | Fair Value [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total long-term debt, fair value 3,975.2 2,237.0
Industrial Revenue Bonds [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total long-term debt, fair value 94.3 0.0
Industrial Revenue Bonds [Member] | Fair Value [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total long-term debt, fair value 90.2 0.0
Line of Credit [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 2 [Member] | Credit Facility    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total long-term debt, fair value 400.0 0.0
Line of Credit [Member] | Fair Value [Member] | Fair Value, Inputs, Level 2 [Member] | Credit Facility    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total long-term debt, fair value $ 400.0 $ 0.0
v3.20.2
PENSIONS AND OTHER POSTRETIREMENT BENEFITS - Pension and Other Postretirement Benefits (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Pension Plan [Member]        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Service cost $ 5.4 $ 4.6 $ 16.0 $ 12.9
Interest cost 19.6 8.9 42.7 26.2
Expected return on plan assets (36.7) (13.7) (91.9) (41.0)
Prior service cost (credits) 0.2 0.3 0.7 0.9
Net actuarial loss 7.3 5.9 20.6 17.7
Net periodic benefit cost (credit) (4.2) 6.0 (11.9) 16.7
Defined Benefit Pension Contributions 0.9 5.6 4.9 12.3
Other Postretirement Benefit Plans, Defined Benefit [Member]        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Service cost 1.4 0.5 3.3 1.3
Interest cost 4.4 2.3 10.9 7.0
Expected return on plan assets (4.5) (4.2) (13.6) (12.6)
Prior service cost (credits) (0.5) (0.5) (1.5) (1.5)
Net actuarial loss 0.8 1.3 2.2 3.8
Net periodic benefit cost (credit) 1.6 (0.6) $ 1.3 (2.0)
OPEB Contributions $ 0.0 $ 0.0   $ 0.0
v3.20.2
INCOME TAXES - Narrative (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Income Tax Disclosure [Abstract]        
Effective Income Tax Rate Reconciliation, Percent     35.50% 9.60%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent     21.00%  
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount of Expense (Benefit) $ (5.0) $ (0.5) $ (8.6) $ (1.3)
v3.20.2
ASSET RETIREMENT OBLIGATIONS - Summary Of Asset Retirement Obligations (Details) - USD ($)
$ in Millions
 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Dec. 31, 2018
Environmental Exit Cost [Line Items]        
Asset Retirement Obligation $ 186.4 $ 179.5 $ 165.3 $ 172.4
Asset Retirement Obligation, Current 4.4   2.1  
Long-term asset retirement obligations 182.0   163.2  
Increase from AK Steel acquisition 16.7 $ 0.0    
Operating Segments [Member]        
Environmental Exit Cost [Line Items]        
Asset Retirement Obligation $ 33.7   $ 22.0  
v3.20.2
ASSET RETIREMENT OBLIGATIONS - Asset Retirement Obligation Disclosure (Details) - USD ($)
$ in Millions
 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Asset Retirement Obligation [Roll Forward]    
Asset retirement obligation at beginning of period $ 165.3 $ 172.4
Increase from AK Steel acquisition 16.7 0.0
Accretion expense 7.8 7.6
Remediation payments (3.4) (0.5)
Asset retirement obligation at end of period $ 186.4 $ 179.5
v3.20.2
DERIVATIVE INSTRUMENTS - Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Customer Supply Agreement [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset $ 34.5 $ 44.5
Provisional Pricing Arrangements [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 26.9 1.3
Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability (0.3) (1.1)
Commodity Contract [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 15.8  
Commodity Contract [Member] | Other Noncurrent Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 1.8  
Commodity Contract [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability (8.7) (3.2)
Foreign Exchange Contract [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability (0.6)  
Foreign Exchange Contract [Member] | Other Noncurrent Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability (0.1)  
Designated as Hedging Instrument [Member] | Customer Supply Agreement [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 0.0 0.0
Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 0.0 0.0
Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability 0.0 0.0
Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 7.9 0.0
Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 1.8 0.0
Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability (1.8) (3.2)
Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability (0.6) 0.0
Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Other Noncurrent Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability (0.1) 0.0
Not Designated as Hedging Instrument [Member] | Customer Supply Agreement [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 34.5 44.5
Not Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 26.9 1.3
Not Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability (0.3) (1.1)
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 7.9 0.0
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 0.0 0.0
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability (6.9) 0.0
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability 0.0 0.0
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Other Noncurrent Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability $ 0.0 $ 0.0
v3.20.2
DERIVATIVE INSTRUMENTS - Schedule of Notional Amounts of Outstanding Derivatives (Details) - Designated as Hedging Instrument [Member]
lb in Millions, gal in Millions, MWh in Millions, MMBTU in Millions, $ in Millions
 9 Months Ended 12 Months Ended
Sep. 30, 2020
CAD ($)
lb
gal
MMBTU
MWh
Dec. 31, 2019
CAD ($)
MMBTU
lb
gal
MWh
Natural Gas [Member]    
Derivative [Line Items]    
Derivative, Nonmonetary Notional Amount | MMBTU 29.7 20.1
Diesel [Member]    
Derivative [Line Items]    
Derivative, Nonmonetary Notional Amount | gal 0.0 0.8
Zinc [Member]    
Derivative [Line Items]    
Derivative, Nonmonetary Notional Amount | lb 10.9 0.0
Electricity [Member]    
Derivative [Line Items]    
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh 0.8 0.0
Canada, Dollars | Foreign Exchange Contract [Member]    
Derivative [Line Items]    
Derivative, Notional Amount | $ $ 38.8 $ 0.0
v3.20.2
DERIVATIVE INSTRUMENTS - Estimated Losses in Future Periods (Details) - Designated as Hedging Instrument [Member]
$ in Millions
 9 Months Ended
Sep. 30, 2020
USD ($)
Natural Gas [Member]  
Derivative Instruments, Gain (Loss) [Line Items]  
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred $ 10.8
Zinc [Member]  
Derivative Instruments, Gain (Loss) [Line Items]  
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred 2.3
Electricity [Member]  
Derivative Instruments, Gain (Loss) [Line Items]  
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred 1.1
Foreign Exchange Contract [Member]  
Derivative Instruments, Gain (Loss) [Line Items]  
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred $ 0.2
v3.20.2
DERIVATIVE INSTRUMENTS - Schedule Of Derivatives Not Designated As Hedging Instruments (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net $ 33.1 $ (40.9) $ 41.6 $ 43.4
Customer Supply Agreement [Member] | Sales [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net 8.8 7.6 14.4 82.2
Provisional Pricing Arrangements [Member] | Sales [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net 20.4 (48.5) 28.0 (38.8)
Commodity Contract [Member] | Cost of Sales [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net $ 3.9 $ 0.0 $ (0.8) $ 0.0
v3.20.2
SHAREHOLDERS' EQUITY - Narrative (Details) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 9 Months Ended
Mar. 13, 2020
Dec. 31, 2020
Mar. 31, 2020
Jun. 30, 2019
Mar. 31, 2019
Sep. 30, 2020
Sep. 30, 2019
Apr. 24, 2019
Nov. 26, 2018
Class of Stock [Line Items]                  
Common shares, par value           $ 0.125      
Fair value of Cliffs common shares issued for AK Steel outstanding common stock $ 617.6                
Stock Repurchase Program, Authorized Amount               $ 100.0 $ 200.0
Stock Repurchased During Period, Shares             24,400,000    
Payments for Repurchase of common shares           $ 0.0 $ 252.9    
Forecast [Member] | ArcelorMittal USA [Member] | Series B Participating Redeemable Preferred Stock [Member]                  
Class of Stock [Line Items]                  
Shares of Cliffs common shares issued to AK Steel stockholders   583,273              
Preferred Class A [Member]                  
Class of Stock [Line Items]                  
Preferred Stock, Shares Authorized           3,000,000      
Preferred Stock, Shares Outstanding           0      
Preferred Stock, Shares Issued           0      
Preferred Class B [Member]                  
Class of Stock [Line Items]                  
Preferred Stock, Shares Authorized           4,000,000      
Preferred Stock, Shares Outstanding           0      
Preferred Stock, Shares Issued           0      
Common Stock [Member]                  
Class of Stock [Line Items]                  
Stock Issued During Period, Shares, Acquisitions 126,800,000   126,800,000            
Stock Repurchased During Period, Shares       12,900,000 11,500,000        
v3.20.2
SHAREHOLDERS' EQUITY - Dividends Declared (Details) - $ / shares
 3 Months Ended
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dividends, Common Stock [Abstract]            
Common Stock, Dividends, Per Share, Cash Paid $ 0.06 $ 0.06 $ 0.10 [1] $ 0.06 $ 0.05 $ 0.05
Common Stock, Special Dividends Per Share, Cash Paid     $ 0.04      
[1] 1 The dividend declared on September 3, 2019 included a special cash dividend of $0.04 per common share.
v3.20.2
ACCUMULATED OTHER COMPREHENSIVE LOSS - Changes in AOCI (loss) related to shareholders' equity (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Sep. 30, 2020
Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]                
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax, Beginning Balance $ (304.1) $ (310.1) $ (315.7) $ (269.6) $ (275.4) $ (281.1) $ (315.7) $ (281.1)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax, Beginning Balance (0.2) (0.9) 0.0       0.0  
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax, Beginning Balance (1.6) (6.1) (3.1) (2.2) (0.1) (2.8) (3.1) (2.8)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance (305.9) (317.1) (318.8) (271.8) (275.5) (283.9) (318.8) (283.9)
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax, Ending Balance (297.5) (304.1) (310.1) (263.8) (269.6) (275.4) (297.5) (263.8)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax, Ending Balance 1.4 (0.2) (0.9)       1.4  
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax, Ending Balance 14.1 (1.6) (6.1) (1.8) (2.2) (0.1) 14.1 (1.8)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance (282.0) (305.9) (317.1) (265.6) (271.8) (275.5) $ (282.0) $ (265.6)
Changes in Pension and Other Post-Retirement Benefits, net of tax [Member]                
Accumulated Other Comprehensive Income (Loss) [Line Items]                
Other comprehensive income (loss) before reclassifications 0.4 0.4 0.0 0.3 0.3 0.2    
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax 6.2 5.6 5.6 5.5 5.5 5.5    
Unrealized Net Gain (Loss) on Foreign Currency Translation [Member]                
Accumulated Other Comprehensive Income (Loss) [Line Items]                
Other comprehensive income (loss) before reclassifications 1.6 0.7 (0.9)          
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax 0.0 0.0 0.0          
Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax [Member]                
Accumulated Other Comprehensive Income (Loss) [Line Items]                
Other comprehensive income (loss) before reclassifications 12.2 1.4 (5.2) (0.5) (2.3) 2.5    
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax 3.5 3.1 2.2 0.9 0.2 0.2    
Accumulated Other Comprehensive Income (Loss) [Member]                
Accumulated Other Comprehensive Income (Loss) [Line Items]                
Other comprehensive income (loss) before reclassifications 14.2 2.5 (6.1) (0.2) (2.0) 2.7    
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax $ 9.7 $ 8.7 $ 7.8 $ 6.4 $ 5.7 $ 5.7    
v3.20.2
ACCUMULATED OTHER COMPREHENSIVE LOSS - Accumulated Other Comprehensive Income (Loss) Components (Details) - Reclassification out of Accumulated Other Comprehensive Income [Member] - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]        
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax $ (0.3) $ (0.2) $ (0.8) $ (0.6)
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax 8.1 7.2 22.8 21.5
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax 7.8 7.0 22.0 20.9
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax (1.6) (1.5) (4.6) (4.4)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax 6.2 5.5 17.4 16.5
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax 4.5 1.2 11.2 1.7
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax (1.0) (0.3) (2.4) (0.4)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax 3.5 0.9 8.8 1.3
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax $ 9.7 $ 6.4 $ 26.2 $ 17.8
v3.20.2
RELATED PARTIES - Summary Of Ownership Interests (Details) - Hibbing Taconite Company [Member]
Sep. 30, 2020
Related Party Transaction [Line Items]  
Equity Method Investment, Ownership Percentage 23.00%
Arcelor Mittal [Member]  
Related Party Transaction [Line Items]  
Equity Method Investment, Ownership Percentage 62.30%
U. S. Steel [Member]  
Related Party Transaction [Line Items]  
Equity Method Investment, Ownership Percentage 14.70%
v3.20.2
RELATED PARTIES - Summary Of Related Party Transactions Table Disclosure (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Related Party Transaction [Line Items]          
Product revenues from related parties $ 294.9 $ 293.5 $ 587.5 $ 792.8  
Revenues $ 1,646.0 $ 555.6 $ 3,097.8 [1] $ 1,455.8  
Related party product revenue as a percent of total product revenue 17.90% 52.80% 19.00% [1] 54.50%  
Purchases from related parties $ 8.2 $ 0.0 $ 20.4 $ 0.0  
Realization of deferred revenue 0.0 $ 0.0 34.6 $ 0.0  
Trade Accounts Receivable [Member]          
Related Party Transaction [Line Items]          
Due from Related Parties, Current 91.6   91.6   $ 31.1
Other Current Assets [Member]          
Related Party Transaction [Line Items]          
Due from Related Parties, Current 58.5   58.5   44.5
Accounts Payable [Member]          
Related Party Transaction [Line Items]          
Due to Related Parties, Current (1.2)   (1.2)   0.0
Other Current Liabilities [Member]          
Related Party Transaction [Line Items]          
Due to Related Parties, Current $ (1.7)   $ (1.7)   $ (2.0)
[1] 1 Includes Realization of deferred revenue of $34.6 million for the nine months ended September 30, 2020.
v3.20.2
VARIABLE INTEREST ENTITIES (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Variable Interest Entity [Line Items]          
Net Income (Loss) Attributable to Noncontrolling Interest $ 11.9 $ 0.0 $ 31.2 $ 0.0  
Cash and cash equivalents 56.0   56.0   $ 352.6
Inventories 1,795.1   1,795.1   317.4
Property, plant and equipment, net 4,550.7   4,550.7   1,929.0
Accounts payable (710.7)   (710.7)   (193.2)
Noncontrolling interest (313.1)   (313.1)   $ 0.0
SunCoke Middletown [Member] | Variable Interest Entity, Primary Beneficiary [Member]          
Variable Interest Entity [Line Items]          
Net Income (Loss) Attributable to Noncontrolling Interest 11.8   31.3    
Cash and cash equivalents 0.3   0.3    
Inventories 22.5   22.5    
Property, plant and equipment, net 305.4   305.4    
Accounts payable (10.0)   (10.0)    
Other Assets (Liabilities), Net (5.6)   (5.6)    
Noncontrolling interest $ (312.6)   $ (312.6)    
v3.20.2
EARNINGS PER SHARE - Earnings Per Share Computation (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Earnings Per Share [Abstract]        
Income (loss) from continuing operations $ 2.2 $ 91.8 $ (154.8) $ 231.1
Income attributable to noncontrolling interest (11.9) 0.0 (31.2) 0.0
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent (9.7) 91.8 (186.0) 231.1
Loss from discontinued operations, net of tax (0.3) (0.9) 0.0 (1.5)
Net income (loss) attributable to Cliffs shareholders $ (10.0) $ 90.9 $ (186.0) $ 229.6
Weighted average number of shares:        
Basic 399,399 269,960 365,245 278,418
Convertible Senior Notes 0 3,700 0 5,800
Employee stock plans 0 2,900 0 3,600
Diluted 399,399 276,578 365,245 287,755
Earnings (loss) per common share attributable to Cliffs shareholders - basic:        
Continuing operations (in dollars per share) $ (0.02) $ 0.34 $ (0.51) $ 0.83
Discontinued operations (in dollars per share) 0 0 0 (0.01)
Earnings (Loss) per Common Share - Basic (in dollars per share) (0.02) 0.34 (0.51) 0.82
Earnings (loss) per common share attributable to Cliffs shareholders - diluted:        
Continuing operations (in dollars per share) (0.02) 0.33 (0.51) 0.80
Discontinued operations (in dollars per share) 0 0 0 0
Earnings (Loss) per Common Share - Diluted (in dollars per share) $ (0.02) $ 0.33 $ (0.51) $ 0.80
v3.20.2
EARNINGS PER SHARE - Antidilutive Securities (Details) - shares
shares in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Convertible Debt Securities [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount 0.0   0.0  
Share-based Payment Arrangement [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount 1.8 0.0 1.6 0.0
v3.20.2
COMMITMENTS AND CONTINGENCIES - Purchase Commitments (Details)
$ in Millions
 9 Months Ended
Sep. 30, 2020
USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]  
Estimated Project Capital Expenditures $ 1,000.0
Total Project Expenditures, Excluding Capitalized Interest 940.2
Capital Addition Purchase Commitments [Member]  
Unrecorded Unconditional Purchase Obligation [Line Items]  
Capital Additions, Purchase Commitments $ 97.8
v3.20.2
COMMITMENTS AND CONTINGENCIES - Contingencies (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Loss Contingencies [Line Items]    
Environmental obligations $ 40.9 $ 2.0
Less current portion 6.4 0.3
Long-term environmental obligations 34.5 $ 1.7
Hamilton Plant [Member]    
Loss Contingencies [Line Items]    
Environmental obligations 0.7  
Ashland Works Coke Plant [Member]    
Loss Contingencies [Line Items]    
Environmental obligations $ 1.4