Cleveland-Cliffs (CLF) 10-Q 27 Apr 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	Apr. 24, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	CLIFFS NATURAL RESOURCES INC.
Entity Central Index Key	764,065
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		296,401,897
Trading Symbol	clf

Statements Of Condensed Consoli

Statements Of Condensed Consolidated Financial Position - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
CURRENT ASSETS
Cash and cash equivalents	$ 295.3	$ 323.4
Accounts receivable, net	61.1	128.7
Inventories	250.8	178.4
Supplies and other inventories	80.4	91.4
Loans to and accounts receivable from the Canadian Entities	49	48.6
Other current assets	76.6	54.1
TOTAL CURRENT ASSETS	813.2	824.6
PROPERTY, PLANT AND EQUIPMENT, NET	995	984.4
OTHER ASSETS
OTHER NON-CURRENT ASSETS	117.5	114.9
TOTAL ASSETS	1,925.7	1,923.9
CURRENT LIABILITIES
Accounts payable	91.1	107.6
Accrued expenses	102.9	123.3
Interest Payable, Current	19.7	40.2
Other current liabilities	95.6	120
TOTAL CURRENT LIABILITIES	309.3	391.1
PENSION AND POSTEMPLOYMENT BENEFIT LIABILITIES	279.1	280.5
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	198.2	193.9
LONG-TERM DEBT	1,642.9	2,175.1
OTHER LIABILITIES	199.2	213.8
TOTAL LIABILITIES	2,628.7	3,254.4
COMMITMENTS AND CONTINGENCIES (SEE NOTE 18)
CLIFFS SHAREHOLDERS' DEFICIT
Common Shares - par value $0.125 per share, Authorized - 400,000,000 shares (2016 - 400,000,000 shares); Issued - 301,886,794 shares (2016 - 238,636,794 shares); Outstanding - 296,398,149 shares (2016 - 233,074,091 shares)	37.7	29.8
Capital in excess of par value of shares	4,000.1	3,347
Retained deficit	(4,602.4)	(4,574.3)
Cost of 5,488,645 common shares in treasury (2016 - 5,562,703 shares)	(241.2)	(245.5)
Accumulated other comprehensive loss	(24.3)	(21.3)
TOTAL CLIFFS SHAREHOLDERS' DEFICIT	(830.1)	(1,464.3)
NONCONTROLLING INTEREST	127.1	133.8
TOTAL DEFICIT	(703)	(1,330.5)
TOTAL LIABILITIES AND DEFICIT	$ 1,925.7	$ 1,923.9

Statements Of Condensed Consol3

Statements Of Condensed Consolidated Financial Position (Parenthetical) - $ / shares	Mar. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Preferred stock, par value	$ 0	$ 0
Common Stock, Par or Stated Value Per Share	$ 0.125	$ 0.125
Common shares, authorized (in shares)	400,000,000	400,000,000
Common shares, issued (in shares)	301,886,794	238,636,794
Common shares, outstanding	296,398,149	233,074,091
Common shares in treasury	5,488,645	5,562,703
Preferred Class A [Member]
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	3,000,000	3,000,000
Cumulative Mandatory Convertible	7.00%	7.00%
Preferred Stock, Liquidation Preference Per Share	$ 1,000	$ 1,000
Preferred Shares, Issued and Outstanding, Shares	0	0
Preferred Class B [Member]
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	4,000,000	4,000,000

Statements Of Condensed Consol4

Statements Of Condensed Consolidated Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
REVENUES FROM PRODUCT SALES AND SERVICES
Product	$ 412.8	$ 275.6
Freight and venture partners' cost reimbursements	48.8	29.9
TOTAL REVENUES	461.6	305.5
COST OF GOODS SOLD AND OPERATING EXPENSES	(365.9)	(274.6)
SALES MARGIN	95.7	30.9
OTHER OPERATING INCOME (EXPENSE)
Selling, general and administrative expenses	(25.7)	(28.2)
Miscellaneous - net	11.9	(3)
Other operating expense	(13.8)	(31.2)
OPERATING INCOME (EXPENSE)	81.9	(0.3)
OTHER INCOME (EXPENSE)
Interest expense, net	(42.8)	(56.8)
Gain (loss) on extinguishment/restructuring of debt	(71.9)	178.8
Other non-operating income	0.7	0.1
TOTAL OTHER INCOME (EXPENSE)	(114)	122.1
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	(32.1)	121.8
INCOME TAX BENEFIT (EXPENSE)	1.8	(7.5)
INCOME (LOSS) FROM CONTINUING OPERATIONS	(30.3)	114.3
INCOME FROM DISCONTINUED OPERATIONS, NET OF TAX	0.5	2.5
NET INCOME (LOSS)	(29.8)	116.8
LOSS (INCOME) ATTRIBUTABLE TO NONCONTROLLING INTEREST	1.7	(8.8)
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$ (28.1)	$ 108
EARNINGS (LOSS) PER COMMON SHARE ATTRIBUTABLE TO CLIFFS SHAREHOLDERS - BASIC
Continuing operations (in dollars per share)	$ (0.11)	$ 0.61
Discontinued operations (in dollars per share)	0	0.01
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Basic (in dollars per share)	(0.11)	0.62
EARNINGS (LOSS) PER COMMON SHARE ATTRIBUTABLE TO CLIFFS SHAREHOLDERS - DILUTED
Continuing operations (in dollars per share)	(0.11)	0.61
Discontinued operations (in dollars per share)	0	0.01
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted (in dollars per share)	$ (0.11)	$ 0.62
AVERAGE NUMBER OF SHARES (IN THOUSANDS)
Basic	265.2	171.7
Diluted	265.2	172

Statements Of Condensed Consol5

Statements Of Condensed Consolidated Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$ (28.1)	$ 108
OTHER COMPREHENSIVE INCOME (LOSS)
Changes in pension and other post-retirement benefits, net of tax	4.7	5.4
Unrealized net gain (loss) on foreign currency translation	(12.7)	4.4
Unrealized net loss on derivative financial instruments, net of tax	0	(3.5)
OTHER COMPREHENSIVE INCOME (LOSS)	(8)	6.3
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	(5)	0.6
Other comprehensive income (loss)	$ (31.1)	$ 113.7

Statements Of Condensed Consol6

Statements Of Condensed Consolidated Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
OPERATING ACTIVITIES
NET INCOME (LOSS)	$ (29.8)	$ 116.8
Adjustments to reconcile net income (loss) to net cash used by operating activities:
Depreciation, depletion and amortization	23.2	35.2
(Gain) loss on extinguishment/restructuring of debt	71.9	(178.8)
Other	(16.9)	14.7
Changes in operating assets and liabilities:
Receivables and other assets	86.5	38.5
Inventories	(70)	(66.1)
Payables, accrued expenses and other liabilities	(90)	(86.8)
Net cash used by operating activities	(25.1)	(126.5)
INVESTING ACTIVITIES
Purchase of property, plant and equipment	(27.9)	(10.4)
Other investing activities	0.5	5.5
Net cash used by investing activities	(27.4)	(4.9)
FINANCING ACTIVITIES
Proceeds from issuance of senior notes	500	0
Debt issuance costs	(8.5)	(5.2)
Net proceeds from issuance of common shares	661.3	0
Repurchase of debt	(1,115.5)	0
Distributions of partnership equity	(8.7)	(11.1)
Repayment of equipment loans	0	(72.9)
Other financing activities	(5.6)	(4.2)
Net cash provided (used) by financing activities	23	(93.4)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	1.4	(0.5)
DECREASE IN CASH AND CASH EQUIVALENTS	(28.1)	(225.3)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	323.4	285.2
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 295.3	$ 59.9

BASIS OF PRESENTATION AND SIGNI

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	NOTE 1 - BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES 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) and cash flows 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 months ended March 31, 2017 are not necessarily indicative of results to be expected for the year ending December 31, 2017 or any other future period. 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, 2016 . We report our results from continuing operations in two reportable segments: U.S. Iron Ore and Asia Pacific Iron Ore. Basis of Consolidation The unaudited condensed consolidated financial statements include our accounts and the accounts of our wholly-owned and majority-owned subsidiaries, including the following operations as of March 31, 2017 : Name Location Ownership Interest Operation Status of Operations Northshore Minnesota 100.0% Iron Ore Active United Taconite Minnesota 100.0% Iron Ore Active Tilden Michigan 85.0% Iron Ore Active Empire Michigan 79.0% Iron Ore Indefinitely Idled Koolyanobbing Western Australia 100.0% Iron Ore Active Intercompany transactions and balances are eliminated upon consolidation. Equity Method Investments Our 23% ownership interest in Hibbing is recorded as an equity method investment. As of March 31, 2017 and December 31, 2016 , our investment in Hibbing was $6.2 million and $8.7 million , respectively, classified as Other liabilities in the Statements of Unaudited Condensed Consolidated Financial Position . Foreign Currency Our financial statements are prepared with the U.S. dollar as the reporting currency. The functional currency of our Australian subsidiaries is the Australian dollar. The functional currency of all other international subsidiaries is the U.S. dollar. The financial statements of international subsidiaries are translated into U.S. dollars using the exchange rate at each balance sheet date for assets and liabilities and a weighted average exchange rate for each period for revenues, expenses, gains and losses. Where the local currency is the functional currency, translation adjustments are recorded as Accumulated other comprehensive loss . Income taxes generally are not provided for foreign currency translation adjustments. To the extent that monetary assets and liabilities, inclusive of short-term and certain long-term intercompany loans, are recorded in a currency other than the functional currency, these amounts are remeasured each reporting period, with the resulting gain or loss being recorded in the Statements of Unaudited Condensed Consolidated Operations . Transaction gains and losses resulting from remeasurement of short-term intercompany loans are included in Miscellaneous - net in the Statements of Unaudited Condensed Consolidated Operations . The following represents the transaction gains and losses resulting from remeasurement for the three months ended March 31, 2017 and 2016: (In Millions) Three Months Ended 2017 2016 Remeasurement of intercompany loans $ 15.1 $ 0.4 Remeasurement of cash and cash equivalents (1.2 ) 0.8 Other remeasurement (0.3 ) (2.4 ) Net impact of transaction gains and (losses) resulting from remeasurement 13.6 (1.2 ) Significant Accounting Policies A detailed description of our significant accounting policies can be found in the audited financial statements for the fiscal year ended December 31, 2016 included in our Annual Report on Form 10-K 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 Not Effective In March 2017, the FASB issued ASU No. 2017-07, Compensation - Retirement Benefits (Topic 715). The new standard requires the service cost component of pension and other postretirement benefit expenses to be included in the same line item as other compensation costs arising from services rendered by employees, with the other components of net benefit cost as defined by paragraphs 715-30-35-4 and 715-60-35-9 to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations. The guidance is effective for fiscal years beginning after December 15, 2017, and early adoption is permitted. The adoption of ASU 2017-07 will impact Statements of Unaudited Condensed Consolidated Operations by changing our classification of the components of pension cost; however, it will not impact our Net income (loss) .

SEGMENT REPORTING

SEGMENT REPORTING	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
SEGMENT REPORTING	NOTE 2 - SEGMENT REPORTING Our continuing operations are organized and managed according to geographic location: U.S. Iron Ore and Asia Pacific Iron Ore. Our U.S. Iron Ore 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. The Asia Pacific Iron Ore segment is located in Western Australia and provides iron ore to the seaborne market for Asian steel producers. There were no intersegment revenues in the first three months of 2017 or 2016. We have historically evaluated segment performance based on sales margin, defined as revenues less cost of goods sold and operating expenses identifiable to each segment. Additionally, we evaluate segment performance based on EBITDA, defined as net income (loss) before interest, income taxes, depreciation, depletion and amortization, and Adjusted EBITDA, defined as EBITDA excluding certain items such as extinguishment/restructuring of debt, foreign currency exchange remeasurement, impacts of discontinued operations, severance and contractor termination costs and intersegment corporate allocations of SG&A costs. These measures allow management and investors to focus on our ability to service our debt as well as illustrate how the business and each operating segment are performing. Additionally, EBITDA and Adjusted EBITDA assist management and investors in their analysis and forecasting as these measures approximate the cash flows associated with operational earnings. The following tables present a summary of our reportable segments for the three months ended March 31, 2017 and 2016 , including a reconciliation of segment sales margin to Income (Loss) from Continuing Operations Before Income Taxes and a reconciliation of Net Income (Loss) to EBITDA and Adjusted EBITDA: (In Millions) Three Months Ended 2017 2016 Revenues from product sales and services: U.S. Iron Ore $ 286.2 62 % $ 185.5 61 % Asia Pacific Iron Ore 175.4 38 % 120.0 39 % Total revenues from product sales and services $ 461.6 100 % $ 305.5 100 % Sales margin: U.S. Iron Ore $ 48.4 $ 13.2 Asia Pacific Iron Ore 47.3 17.7 Sales margin 95.7 30.9 Other operating expense (13.8 ) (31.2 ) Other income (expense) (114.0 ) 122.1 Income (loss) from continuing operations before income taxes $ (32.1 ) $ 121.8 (In Millions) Three Months Ended 2017 2016 Net Income (Loss) $ (29.8 ) $ 116.8 Less: Interest expense, net (42.8 ) (56.8 ) Income tax benefit (expense) 1.8 (7.6 ) Depreciation, depletion and amortization (23.2 ) (35.2 ) EBITDA $ 34.4 $ 216.4 Less: Gain (loss) on extinguishment/restructuring of debt (71.9 ) 178.8 Foreign exchange remeasurement 13.6 (1.2 ) Impact of discontinued operations 0.5 2.6 Severance and contractor termination costs — (0.1 ) Adjusted EBITDA $ 92.2 $ 36.3 EBITDA: U.S. Iron Ore $ 57.9 $ 41.4 Asia Pacific Iron Ore 51.4 22.3 Other (74.9 ) 152.7 Total EBITDA $ 34.4 $ 216.4 Adjusted EBITDA: U.S. Iron Ore $ 64.1 $ 46.1 Asia Pacific Iron Ore 53.8 23.0 Other (25.7 ) (32.8 ) Total Adjusted EBITDA $ 92.2 $ 36.3 (In Millions) Three Months Ended 2017 2016 Depreciation, depletion and amortization: U.S. Iron Ore $ 16.4 $ 26.9 Asia Pacific Iron Ore 4.7 6.8 Other 2.1 1.5 Total depreciation, depletion and amortization $ 23.2 $ 35.2 Capital additions: U.S. Iron Ore $ 27.1 $ 4.5 Asia Pacific Iron Ore 0.2 — Other — 2.3 Total capital additions 1 $ 27.3 $ 6.8 1 Includes cash paid for capital additions of $27.9 million and $10.4 million and a decrease in non-cash accruals of $0.6 million and $3.6 million for the three months ended March 31, 2017 and 2016, respectively. A summary of assets by segment is as follows: (In Millions) March 31, December 31, Assets: U.S. Iron Ore $ 1,440.6 $ 1,372.5 Asia Pacific Iron Ore 168.4 155.1 Total segment assets 1,609.0 1,527.6 Corporate 316.7 396.3 Total assets $ 1,925.7 $ 1,923.9

INVENTORIES

INVENTORIES	3 Months Ended
	Mar. 31, 2017
Inventory Disclosure [Abstract]
Inventories	NOTE 3 - INVENTORIES The following table presents the detail of our Inventories in the Statements of Unaudited Condensed Consolidated Financial Position as of March 31, 2017 and December 31, 2016 : (In Millions) March 31, 2017 December 31, 2016 Segment Finished Goods Work-in Process Total Inventory Finished Goods Work-in Process Total Inventory U.S. Iron Ore $ 194.6 $ 26.3 $ 220.9 $ 124.4 $ 12.6 $ 137.0 Asia Pacific Iron Ore 14.6 15.3 29.9 23.6 17.8 41.4 Total $ 209.2 $ 41.6 $ 250.8 $ 148.0 $ 30.4 $ 178.4

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	3 Months Ended
	Mar. 31, 2017
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	NOTE 4 - PROPERTY, PLANT AND EQUIPMENT The following table indicates the value of each of the major classes of our consolidated depreciable assets as of March 31, 2017 and December 31, 2016 : (In Millions) March 31, December 31, Land rights and mineral rights $ 500.7 $ 500.5 Office and information technology 65.8 65.1 Buildings 68.4 67.9 Mining equipment 595.8 592.2 Processing equipment 558.9 552.0 Electric power facilities 49.6 49.4 Land improvements 23.7 23.5 Asset retirement obligation 19.8 19.8 Other 28.4 28.1 Construction in-progress 69.8 42.8 1,980.9 1,941.3 Allowance for depreciation and depletion (985.9 ) (956.9 ) $ 995.0 $ 984.4 We recorded depreciation and depletion expense of $22.6 million and $33.8 million in the Statements of Unaudited Condensed Consolidated Operations for the three months ended March 31, 2017 and March 31, 2016 , respectively.

DEBT AND CREDIT FACILITIES

DEBT AND CREDIT FACILITIES	3 Months Ended
	Mar. 31, 2017
Debt Disclosure [Abstract]
DEBT AND CREDIT FACILITIES	NOTE 5 - DEBT AND CREDIT FACILITIES The following represents a summary of our long-term debt as of March 31, 2017 and December 31, 2016 : ($ in Millions) March 31, 2017 Debt Instrument Annual Effective Interest Rate Total Principal Amount Debt Issuance Costs Unamortized Discounts Total Debt Secured Notes $540 Million 8.25% 2020 First Lien Notes 9.97% $ 540.0 $ (7.4 ) $ (24.0 ) $ 508.6 Unsecured Notes $400 Million 5.90% 2020 Senior Notes 5.98% 88.9 (0.2 ) (0.2 ) 88.5 $500 Million 4.80% 2020 Senior Notes 4.83% 122.4 (0.3 ) (0.1 ) 122.0 $700 Million 4.875% 2021 Senior Notes 4.89% 138.4 (0.4 ) (0.1 ) 137.9 $500 Million 5.75% 2025 Senior Notes 5.75% 500.0 (8.3 ) — 491.7 $800 Million 6.25% 2040 Senior Notes 6.34% 298.4 (2.5 ) (3.4 ) 292.5 ABL Facility N/A 550.0 N/A N/A — Fair Value Adjustment to Interest Rate Hedge 1.7 Long-term debt $ 1,642.9 ($ in Millions) December 31, 2016 Debt Instrument Annual Effective Interest Rate Total Principal Amount Debt Issuance Costs Undiscounted Interest/(Unamortized Discounts) Total Debt Secured Notes $540 Million 8.25% 2020 First Lien Notes 9.97% $ 540.0 $ (8.0 ) $ (25.7 ) $ 506.3 $218.5 Million 8.00% 2020 1.5 Lien Notes N/A 218.5 — 65.7 284.2 $544.2 Million 7.75% 2020 Second Lien Notes 15.55% 430.1 (5.8 ) (85.2 ) 339.1 Unsecured Notes $400 Million 5.90% 2020 Senior Notes 5.98% 225.6 (0.6 ) (0.5 ) 224.5 $500 Million 4.80% 2020 Senior Notes 4.83% 236.8 (0.7 ) (0.2 ) 235.9 $700 Million 4.875% 2021 Senior Notes 4.89% 309.4 (1.0 ) (0.2 ) 308.2 $800 Million 6.25% 2040 Senior Notes 6.34% 298.4 (2.5 ) (3.4 ) 292.5 ABL Facility N/A 550.0 N/A N/A — Fair Value Adjustment to Interest Rate Hedge 1.9 Total debt $ 2,192.6 Less current portion 17.5 Long-term debt $ 2,175.1 $500 million 5.75% 2025 Senior Notes - 2017 Offering On February 27, 2017, we entered into an indenture among the Company, the guarantors party thereto and U.S. Bank National Association, as trustee, relating to the issuance of $500 million aggregate principal amount of 5.75% Senior Notes due 2025 (the "5.75% Senior Notes"). The 5.75% Senior Notes were issued on February 27, 2017 in a private transaction exempt from the registration requirements of the Securities Act. The 5.75% Senior Notes bear interest at a rate of 5.75% per annum, which is payable semi-annually in arrears on March 1 and September 1 of each year, commencing on September 1, 2017. The 5.75% Senior Notes mature on March 1, 2025. The 5.75% Senior Notes are general unsecured senior obligations and rank equally in right of payment with all of our existing and future senior unsecured indebtedness and rank senior in right of payment to all of our existing and future subordinated indebtedness. The 5.75% Senior Notes are effectively subordinated to our existing or future secured indebtedness to the extent of the value of the assets securing such indebtedness. The 5.75% Senior Notes are guaranteed on a senior unsecured basis by our material direct and indirect wholly-owned domestic subsidiaries and, therefore, are structurally senior to any of our existing and future indebtedness that is not guaranteed by such guarantors and are structurally subordinated to all existing and future indebtedness and other liabilities of our subsidiaries that do not guarantee the 5.75% Senior Notes. The terms of the 5.75% Senior Notes are governed by an indenture, which contains customary covenants that, among other things, limit our and our subsidiaries' ability to create liens on property that secure indebtedness, enter into sale and leaseback transactions and merge, consolidate or amalgamate with another company. Upon the occurrence of a “change of control triggering event,” as defined in the indenture, we are required to offer to repurchase the 5.75% Senior Notes at 101% of the aggregate principal amount thereof, plus any accrued and unpaid interest, if any, to, but excluding, the repurchase date. We may redeem the 5.75% Senior Notes, in whole or in part, on or after March 1, 2020, at the redemption prices set forth in the indenture, plus accrued and unpaid interest, if any, to, but not including, the date of redemption, and prior to March 1, 2020, at a redemption price equal to 100% of the principal amount thereof plus a “make-whole” premium set forth in the indenture, plus accrued and unpaid interest, if any, to, but not including, the date of redemption. We may also redeem up to 35% of the aggregate principal amount of the 5.75% Senior Notes on or prior to March 1, 2020 at a redemption price equal to 105.75% of the principal amount thereof, plus accrued and unpaid interest, if any, to, but not including, the date of redemption with the net cash proceeds of one or more equity offerings. The 5.75% Senior Notes indenture contains customary events of default, including failure to make required payments, failure to comply with certain agreements or covenants, failure to pay or acceleration of certain other indebtedness, certain events of bankruptcy and insolvency, and failure to pay certain judgments. An event of default under the indenture will allow either the trustee or the holders of at least 25% in aggregate principal amount of the then-outstanding notes issued under the indenture to accelerate, or in certain cases, will automatically cause the acceleration of, the amounts due under the 5.75% Senior Notes. Debt issuance costs incurred of $8.5 million related to the offering of the 5.75% Senior Notes included in the Long-term debt in the Statements of Unaudited Condensed Consolidated Financial Position as of March 31, 2017 . Debt Extinguishment The following is a summary of the debt extinguished during the three months ended March 31, 2017 : ($ In Millions) Debt Extinguished Gain (Loss) on Extinguishment 1 Secured Notes $218.5 Million 8.00% 2020 1.5 Lien Notes $ 218.5 $ 45.1 $544.2 Million 7.75% 2020 Second Lien Notes 430.1 (104.5 ) Unsecured Notes $400 Million 5.90% 2020 Senior Notes 136.8 (7.8 ) $500 Million 4.80% 2020 Senior Notes 114.4 (1.9 ) $700 Million 4.875% 2021 Senior Notes 171.0 (2.8 ) $ 1,070.8 $ (71.9 ) 1 Includes write-off of undiscounted interest, unamortized discounts and debt issuance costs. In addition, we paid premiums of $44.7 million related to the redemption of our notes. Debt Maturities The following represents a summary of our maturities of debt instruments, excluding borrowings on the ABL Facility, based on the principal amounts outstanding at March 31, 2017 : (In Millions) Maturities of Debt 2017 (April 1 - December 31) $ — 2018 — 2019 — 2020 751.3 2021 138.4 2022 — 2023 and thereafter 798.4 Total maturities of debt $ 1,688.1 ABL Facility As of March 31, 2017 and December 31, 2016 , no loans were drawn under the ABL Facility and we had total availability of $256.3 million and $333.0 million , respectively, as a result of borrowing base limitations. As of March 31, 2017 and December 31, 2016 , the principal amount of letter of credit obligations totaled $95.5 million and $106.0 million , respectively, to support business obligations primarily related to workers compensation and environmental obligations, thereby further reducing available borrowing capacity on our ABL Facility to $160.8 million and $227.0 million , respectively.

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	NOTE 6 - FAIR VALUE MEASUREMENTS The following represents the assets and liabilities of the Company measured at fair value at March 31, 2017 and December 31, 2016 : (In Millions) March 31, 2017 Description 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 $ 90.0 $ 45.0 $ — $ 135.0 Derivative assets — — 59.4 59.4 Loans to and accounts receivable from the Canadian Entities — — 49.0 49.0 Total $ 90.0 $ 45.0 $ 108.4 $ 243.4 Liabilities: Derivative liabilities $ — $ — $ 9.1 $ 9.1 Contingent liabilities — — 37.5 37.5 Total $ — $ — $ 46.6 $ 46.6 (In Millions) December 31, 2016 Description 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 $ 177.0 $ — $ — $ 177.0 Derivative assets — 1.5 31.6 33.1 Loans to and accounts receivable from the Canadian Entities — — 48.6 48.6 Total $ 177.0 $ 1.5 $ 80.2 $ 258.7 Liabilities: Derivative liabilities $ — $ — $ 0.5 $ 0.5 Contingent liabilities — — 37.2 37.2 Total $ — $ — $ 37.7 $ 37.7 Financial assets classified in Level 1 as of March 31, 2017 and December 31, 2016 include money market funds of $90.0 million and $177.0 million , respectively. The valuation of these instruments is based upon unadjusted quoted prices for identical assets in active markets. 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 included $45.0 million of commercial paper and $1.5 million of commodity hedge contracts at March 31, 2017 and December 31, 2016 , respectively. The Level 3 assets include amounts receivable from the Canadian Entities and derivative assets which consist of a freestanding derivative instrument related to certain supply agreements with one of our U.S Iron Ore customers and certain provisional pricing arrangements with our U.S. Iron Ore and Asia Pacific Iron Ore customers. Prior to the deconsolidations, various Cliffs wholly-owned entities made loans to the Canadian Entities for the purpose of funding their operations and had accounts receivable generated in the ordinary course of business. The loans, corresponding interest and the accounts receivable were considered intercompany transactions and were eliminated from our consolidated financial statements. Since the deconsolidations, the loans, associated interest and accounts receivable are considered related party transactions and have been recognized in our consolidated financial statements at their estimated fair value of $49.0 million and $48.6 million in the Statements of Unaudited Condensed Consolidated Financial Position at March 31, 2017 and December 31, 2016 , respectively, and are classified as Level 3 assets. The supply agreements included in our Level 3 assets include provisions for supplemental revenue or refunds based on the customer’s annual steel pricing at the time the product is consumed in the customer’s blast furnaces. We account for this provision as a derivative instrument at the time of sale and adjust this provision to fair value as an adjustment to Product revenues each reporting period until the product is consumed and the amounts are settled. The fair value of the instrument is determined using a market approach based on an estimate of the annual realized price of hot-rolled coil steel at the steelmaker’s facilities and takes into consideration current market conditions and nonperformance risk. We had assets of $35.9 million and $21.3 million at March 31, 2017 and December 31, 2016 , respectively, related to supply agreements. The provisional pricing arrangements included in our Level 3 assets 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 at the date of sale and the estimated final revenue rate is characterized as a derivative and is required to be accounted for separately once the revenue has been recognized. The derivative instrument is adjusted to fair value through Product revenues each reporting period based upon current market data and forward-looking estimates provided by management until the final revenue rate is determined. We had assets of $23.5 million and $10.3 million at March 31, 2017 and December 31, 2016 , respectively, related to provisional pricing arrangements. Level 3 liabilities include guarantees backstopped by standby letters of credit for certain environmental obligations of the Canadian Entities. We have liabilities of $37.5 million and $37.2 million in our consolidated results, classified as Other liabilities in the Statements of Unaudited Condensed Consolidated Financial Position as of March 31, 2017 and December 31, 2016 , respectively. In addition, we have liabilities of $9.1 million and $0.5 million related to provisional pricing arrangements at March 31, 2017 and December 31, 2016 , respectively. The following table illustrates information about quantitative inputs and assumptions for the assets and liabilities categorized in Level 3 of the fair value hierarchy: Qualitative/Quantitative Information About Level 3 Fair Value Measurements (In Millions) Fair Value at March 31, 2017 Balance Sheet Location Valuation Technique Unobservable Input Range or Point Estimate per dry metric ton (Weighted Average) Provisional pricing arrangements $ 23.5 Other current assets Market Approach Management's Estimate of Platts 62% Price $79 Hot-Rolled Coil Steel Estimate $651 Provisional pricing arrangements $ 9.1 Other current liabilities Market Approach Management's Estimate of Platts 62% Price $79 Customer supply agreement $ 35.9 Other current assets Market Approach Hot-Rolled Coil Steel Estimate $520 - $630 ($575) Loans to and accounts receivable from the Canadian Entities $ 49.0 Loans to and accounts receivable from the Canadian Entities * * N/A Contingent liabilities $ 37.5 Other liabilities * * N/A * To assess the fair value and recoverability of the amounts receivable from the Canadian Entities, we estimated the fair value of the underlying net assets of the Canadian Entities available for distribution to their creditors in relation to the estimated creditor claims and the priority of those claims. The recorded expenses include an accrual for the estimated probable loss related to claims that may be asserted against us. We are not able to estimate reasonably a range of possible losses in excess of the accrual because there are significant factual and legal issues to be resolved. Our estimates involve significant judgment. Our estimates are based on currently available information, an assessment of the validity of certain claims and estimated payments by the Canadian Entities. The significant unobservable inputs used in the fair value measurement of our provisional pricing arrangements are management’s estimates of Platts 62% Price based upon current market data, index pricing, and the annual average steel pricing benchmark for hot-rolled coil, each of which include forward-looking estimates determined by management. Significant increases or decreases in these inputs would result in a significantly higher or lower fair value measurement, respectively. The significant unobservable input used in the fair value measurement of our customer supply agreement is the customer's future hot-rolled coil steel price that is estimated based on current market data, analysts' projections, projections provided by the customer and forward-looking estimates determined by management. Significant increases or decreases in this input would result in a significantly higher or lower fair value measurement, respectively. We recognize any transfers between levels as of the beginning of the reporting period, including both transfers into and out of levels. There were no transfers between Level 1 and Level 2 of the fair value hierarchy during the three months ended March 31, 2017 and 2016 . 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) for the three months ended March 31, 2017 and 2016 . (In Millions) Level 3 Assets Three Months Ended 2017 2016 Beginning balance $ 80.2 $ 80.7 Total gains (losses) Included in earnings 42.5 8.2 Settlements (14.3 ) (10.0 ) Transfers into Level 3 — — Transfers out of Level 3 — — Ending balance - March 31 $ 108.4 $ 78.9 Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date $ 33.2 $ 3.6 (In Millions) Level 3 Liabilities Three Months Ended 2017 2016 Beginning balance $ (37.7 ) $ (135.8 ) Total gains (losses) Included in earnings (8.9 ) (7.9 ) Settlements — 75.7 Transfers into Level 3 — — Transfers out of Level 3 — — Ending balance - March 31 $ (46.6 ) $ (68.0 ) Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date $ (9.1 ) $ (0.8 ) Gains and losses from derivative assets and liabilities, contingent liabilities and accounts receivables from the Canadian Entities are included in earnings and are reported in Product revenues , Miscellaneous - net , and Income from Discontinued Operations, net of tax , respectively, for the three months ended March 31, 2017 and 2016 . The carrying amount for certain financial instruments (e.g., Accounts receivable, net , Accounts payable and Accrued expenses ) approximates fair value and, therefore, has been excluded from the table below. A summary of the carrying amount and fair value of other financial instruments at March 31, 2017 and December 31, 2016 were as follows: (In Millions) March 31, 2017 December 31, 2016 Classification Carrying Value Fair Value Carrying Value Fair Value Long-term debt: Secured Notes First Senior Lien Notes —$540 million Level 1 $ 508.6 $ 583.9 $ 506.3 $ 595.0 1.5 Senior Lien Notes —$218.5 million Level 2 — — 284.2 229.5 Second Senior Lien Notes —$544.2 million Level 1 — — 339.1 439.7 Unsecured Notes Senior Notes—$500 million Level 1 491.7 486.3 — — Senior Notes—$400 million Level 1 88.5 88.4 224.5 219.6 Senior Notes—$1.3 billion Level 1 414.5 358.9 528.4 455.8 Senior Notes—$700 million Level 1 137.9 134.3 308.2 283.1 ABL Facility Level 2 — — — — Fair value adjustment to interest rate hedge Level 2 1.7 1.7 1.9 1.9 Total long-term debt $ 1,642.9 $ 1,653.5 $ 2,192.6 $ 2,224.6 The fair value of long-term debt was determined using quoted market prices based upon current borrowing rates.

PENSIONS AND OTHER POSTRETIREME

PENSIONS AND OTHER POSTRETIREMENT BENEFITS	3 Months Ended
	Mar. 31, 2017
Postemployment Benefits [Abstract]
PENSIONS AND OTHER POSTRETIREMENT BENEFITS	NOTE 7 - 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 in the United States as part of a total compensation and benefits program. We do not have employee retirement benefit obligations at our Asia Pacific Iron Ore operations. The defined benefit pension plans largely 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. The following are the components of defined benefit pension and OPEB costs and credits for the three months ended March 31, 2017 and 2016 : Defined Benefit Pension Costs (In Millions) Three Months Ended 2017 2016 Service cost $ 4.8 $ 4.5 Interest cost 7.5 7.5 Expected return on plan assets (13.5 ) (13.7 ) Amortization: Prior service costs 0.6 0.5 Net actuarial loss 5.3 5.3 Net periodic benefit cost to continuing operations $ 4.7 $ 4.1 Other Postretirement Benefits Credit (In Millions) Three Months Ended 2017 2016 Service cost $ 0.5 $ 0.4 Interest cost 2.1 2.3 Expected return on plan assets (4.4 ) (4.3 ) Amortization: Prior service credits (0.7 ) (0.9 ) Net actuarial loss 1.2 1.4 Net periodic benefit credit to continuing operations $ (1.3 ) $ (1.1 ) We made no pension contributions for the three months ended March 31, 2017 compared to pension contributions of $0.3 million for the three months ended March 31, 2016 . OPEB contributions 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 were required or made for the three months ended March 31, 2017 and March 31, 2016 .

STOCK COMPENSATION PLANS

STOCK COMPENSATION PLANS	3 Months Ended
	Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Compensation Plans	NOTE 8 - STOCK COMPENSATION PLANS Employees’ Plans During the first quarter of 2017, the Compensation and Organization Committee of the Board of Directors approved grants under the 2015 Equity Plan to certain officers and employees for the 2017 to 2019 performance period. Shares granted under the awards consisted of 0.6 million restricted share units and 0.6 million performance shares. The restricted share units are subject to continued employment, are retention based, will vest December 31, 2019, and are payable in common shares at a time determined by the Committee at its discretion. The performance shares are subject to continued employment, and each performance share, if earned, entitles the holder to receive common shares or cash within a range between a threshold and maximum number of our common shares, with the actual number of common shares earned dependent upon whether the Company achieves certain objectives and performance goals as established by the Compensation and Organization Committee. The performance share grants vest over a period of three years and are intended to be paid out in common shares. The performance awards granted have a performance condition that is measured on the basis of relative TSR for the period of January 1, 2017 to December 31, 2019 and measured against the constituents of the S&P Metals and Mining ETF Index at the beginning of the relevant performance period. The final payouts will vary from zero to 200% of the original grant. Determination of Fair Value The fair value of each performance share grant is estimated on the date of grant using a Monte Carlo simulation to forecast relative TSR performance. A correlation matrix of historic and projected stock prices was developed for both the Company and our predetermined peer group of mining and metals companies. The fair value assumes that performance goals will be achieved. The expected term of the grant represents the time from the grant date to the end of the service period for each of the three plan-year agreements. We estimate the volatility of our common shares and that of the peer group of mining and metals companies using daily price intervals for all companies. The risk-free interest rate is the rate at the grant date on zero-coupon government bonds with a term commensurate with the remaining life of the performance period. The following assumptions were utilized to estimate the fair value for the first quarter of 2017 performance share grants: Grant Date Grant Date Market Price Average Expected Term (Years) Expected Volatility Risk-Free Interest Rate Dividend Yield Fair Value Fair Value (Percent of Grant Date Market Price) February 21, 2017 $ 11.67 2.86 92.1% 1.51% —% $ 19.69 168.72%

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 9 - INCOME TAXES Our 2017 estimated annual effective tax rate before discrete items is approximately 5.4% . The annual effective tax rate differs from the U.S. statutory rate of 35% primarily due to the reversal of valuation allowance from operations in the current year and deductions for percentage depletion in excess of cost depletion related to U.S. operations. The 2016 estimated annual effective tax rate before discrete items at March 31, 2016 was 6.8% .

LEASE OBLIGATIONS

LEASE OBLIGATIONS	3 Months Ended
	Mar. 31, 2017
Leases [Abstract]
LEASE OBLIGATIONS	NOTE 10 - LEASE OBLIGATIONS We lease certain mining, production and other equipment under operating and capital leases. The capital leases are for varying lengths, generally at market interest rates and contain purchase and/or renewal options at the end of the terms. Our operating lease expense was $1.7 million for the three months ended March 31, 2017 compared with $2.4 million for the three months ended March 31, 2016 . Future minimum payments under capital leases and non-cancellable operating leases at March 31, 2017 are as follows: (In Millions) Capital Leases Operating Leases 2017 (April 1 - December 31) $ 17.2 $ 5.3 2018 18.8 5.8 2019 10.4 3.0 2020 9.4 2.9 2021 8.7 3.0 2022 and thereafter 1.4 — Total minimum lease payments $ 65.9 $ 20.0 Amounts representing interest 11.8 Present value of net minimum lease payments 1 $ 54.1 1 The total is comprised of $18.0 million and $36.1 million classified as Other current liabilities and Other liabilities , respectively, in the Statements of Unaudited Condensed Consolidated Financial Position at March 31, 2017.

ENVIRONMENTAL AND MINE CLOSURE

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	3 Months Ended
	Mar. 31, 2017
Environmental Remediation Obligations [Abstract]
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	NOTE 11 - ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS We had environmental and mine closure liabilities of $211.0 million and $206.8 million at March 31, 2017 and December 31, 2016 , respectively. The following is a summary of the obligations as of March 31, 2017 and December 31, 2016 : (In Millions) March 31, December 31, Environmental $ 2.8 $ 2.8 Mine closure U.S. Iron Ore 1 190.9 187.8 Asia Pacific Iron Ore 17.3 16.2 Total mine closure 208.2 204.0 Total environmental and mine closure obligations 211.0 206.8 Less current portion 12.8 12.9 Long-term environmental and mine closure obligations $ 198.2 $ 193.9 1 U.S. Iron Ore includes our active operating mines, our indefinitely idled Empire mine and a closed mine formerly operating as LTVSMC. Mine Closure The accrued closure obligation for our active mining operations provides for contractual and legal obligations associated with the eventual closure of the mining operations. The accretion of the liability and amortization of the related asset is recognized over the estimated mine lives for each location. The following represents a roll forward of our asset retirement obligation liability for the three months ended March 31, 2017 and for the year ended December 31, 2016 : (In Millions) March 31, December 31, 2016 Asset retirement obligation at beginning of period $ 204.0 $ 230.4 Accretion expense 3.6 14.0 Remediation payments (0.3 ) (2.2 ) Exchange rate changes 0.9 (0.2 ) Revision in estimated cash flows — (38.0 ) Asset retirement obligation at end of period $ 208.2 $ 204.0 For the year ended December 31, 2016 , the revisions in estimated cash flows recorded during the year related primarily to revisions in the timing of the estimated cash flows related to two of our U.S. mines. The Empire mine asset retirement obligation was reduced $29.6 million as a result of the further refinement of the timing of cash flows and a downward revision of estimated asset retirement costs related to technology associated with required storm water management systems expected to be implemented. Additionally, during 2016, a new economic reserve estimate was completed for United Taconite, increasing salable product reserves by 115 million long tons and consequently significantly increasing the life-of-mine plan, resulting in a $9.2 million decrease in the asset retirement obligation.

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES	3 Months Ended
	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES	NOTE 12 - GOODWILL AND OTHER INTANGIBLE ASSETS Goodwill The carrying amount of goodwill as of March 31, 2017 and December 31, 2016 was $2.0 million and related to our U.S. Iron Ore operating segment. Other Intangible Assets The following table is a summary of intangible assets as of March 31, 2017 and December 31, 2016 : (In Millions) March 31, 2017 December 31, 2016 Classification Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Definite-lived intangible assets: Permits Other non-current assets $ 78.7 $ (25.1 ) $ 53.6 $ 78.4 $ (24.6 ) $ 53.8 Total intangible assets $ 78.7 $ (25.1 ) $ 53.6 $ 78.4 $ (24.6 ) $ 53.8 Amortization expense relating to intangible assets was $0.6 million for the three months ended March 31, 2017 and is recognized in Cost of goods sold and operating expenses in the Statements of Unaudited Condensed Consolidated Operations . Amortization expense relating to intangible assets was $1.4 million for the comparable period in 2016 . Amortization expense of other intangible assets is expected to continue to be immaterial going forward.

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	NOTE 13 - 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 as of March 31, 2017 and December 31, 2016 : (In Millions) Derivative Assets Derivative Liabilities March 31, 2017 December 31, 2016 March 31, 2017 December 31, 2016 Derivative Instrument Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Customer supply agreement Other current assets 35.9 Other current assets 21.3 — — Provisional pricing arrangements Other current assets 23.5 Other current assets 10.3 Other current liabilities 9.1 Other current liabilities 0.5 Commodity contracts — Other current assets 1.5 — — Total derivatives not designated as hedging instruments under ASC 815 $ 59.4 $ 33.1 $ 9.1 $ 0.5 Derivatives Not Designated as Hedging Instruments Customer Supply Agreements Most of our U.S. Iron Ore long-term supply agreements are comprised of a base price with annual price adjustment factors. The base price is the primary component of the purchase price for each contract. The indexed price adjustment factors are integral to the iron ore supply contracts and vary based on the agreement, but typically include adjustments based upon changes in the Platts 62% Price, along with pellet premiums, published Platts international indexed freight rates and changes in specified Producer Price Indices, including those for industrial commodities, fuel and steel. 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. In most cases, these adjustment factors have not been finalized at the time our product is sold. In these cases, we historically have estimated the adjustment factors at each reporting period based upon the best third-party information available. The estimates are then adjusted to actual when the information has been finalized. The price adjustment factors have been evaluated to determine if they contain embedded derivatives. The price adjustment factors share the same economic characteristics and risks as the host contract and are integral to the host contract as inflation adjustments; accordingly, they have not been separately valued as derivative instruments. A certain supply agreement with one U.S. Iron Ore customer provides for supplemental revenue or refunds to the customer based on the customer’s average annual steel pricing at the time the product is consumed in the customer’s blast furnace. The supplemental pricing is characterized as a freestanding derivative and is required to be accounted for separately once the product is shipped. The derivative instrument, which is finalized based on a future price, is adjusted to fair value as a revenue adjustment each reporting period until the pellets are consumed and the amounts are settled. We recognized a $17.8 million net gain in Product revenues in the Statements of Unaudited Condensed Consolidated Operations for the three months ended March 31, 2017 related to the supplemental payments. This compares with a net loss in Product revenues of $0.1 million for the comparable period in 2016 . Other current assets , representing the fair value of the pricing factors, were $35.9 million and $21.3 million in the March 31, 2017 and December 31, 2016 Statements of Unaudited Condensed Consolidated Financial Position , respectively. Provisional Pricing Arrangements Certain of our U.S. Iron Ore and Asia Pacific Iron Ore customer supply agreements 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 period in time in the future, per the terms of the supply agreements. U.S. Iron Ore sales revenue is primarily recognized when cash is received. For U.S. Iron Ore sales, the difference between the provisionally agreed-upon price and the estimated final revenue rate is characterized as a freestanding derivative and must be accounted for separately once the provisional revenue has been recognized. Asia Pacific Iron Ore sales revenue is recorded initially at the provisionally agreed-upon price with the pricing provision embedded in the receivable. The pricing provision is an embedded derivative that must be bifurcated and accounted for separately from the receivable. Subsequently, the derivative instruments for both U.S. Iron Ore and Asia Pacific Iron Ore are adjusted to fair value through Product revenues each reporting period based upon current market data and forward-looking estimates provided by management until the final revenue rate is determined. At March 31, 2017 and December 31, 2016 , we recorded $23.5 million and $10.3 million , respectively, as Other current assets in the Statements of Unaudited Condensed Consolidated Financial Position related to our estimate of the final revenue rate with our U.S. Iron Ore and Asia Pacific Iron Ore customers. At March 31, 2017 and December 31, 2016 , we recorded $9.1 million and $0.5 million , respectively, as Other current liabilities in the Statements of Unaudited Condensed Consolidated Financial Position related to our estimate of the final revenue rate with our U.S. Iron Ore and Asia Pacific Iron Ore customers. These amounts represent the difference between the provisional price agreed upon with our customers based on the supply agreement terms and our estimate of the final revenue rate based on the price calculations established in the supply agreements. As a result, we recognized a net increase of $15.7 million and a net decrease of $1.5 million in Product revenues in the Statements of Unaudited Condensed Consolidated Operations for the three months ended March 31, 2017 and 2016 . The following summarizes the effect of our derivatives that are not designated as hedging instruments in the Statements of Unaudited Condensed Consolidated Operations for the three months ended March 31, 2017 and 2016 : (In Millions) Derivatives Not Designated as Hedging Instruments Location of Gain (Loss) Recognized in Amount of Gain (Loss) Recognized in Income on Derivative Three Months Ended 2017 2016 Customer supply agreement Product revenues 17.8 (0.1 ) Provisional pricing arrangements Product revenues 15.7 (1.5 ) Commodity contracts Cost of goods sold and operating expenses (1.3 ) — Total $ 32.2 $ (1.6 ) Refer to NOTE 6 - FAIR VALUE MEASUREMENTS for additional information.

CAPITAL STOCK

CAPITAL STOCK	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
CAPITAL STOCK	NOTE 14 - CAPITAL STOCK Common Share Public Offering On February 9, 2017, we issued 63.25 million common shares in an underwritten public offering. We received net proceeds of $661.3 million at a public offering price of $10.75 per common share. The net proceeds from the issuance of our common shares and our 5.75% Senior Notes were used to redeem in full all of our outstanding 8.00% 1.5 Lien Notes due 2020 and 7.75% Second Lien Notes due 2020. The aggregate principal amount outstanding of debt redeemed was $648.6 million . Additionally, through tender offers, we purchased $422.2 million in principal debt, excluding unamortized discounts and deferred charges, of our 5.90% Senior Notes due 2020, our 4.80% Senior Notes due 2020 and our 4.875% Senior Notes due 2021.

SHAREHOLDERS' EQUITY

SHAREHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
SHAREHOLDERS' EQUITY	NOTE 15 - SHAREHOLDERS' DEFICIT The following table reflects the changes in shareholders' deficit attributable to both Cliffs and the noncontrolling interests primarily related to Tilden and Empire of which Cliffs owns 85% and 79% , respectively, for the three months ended March 31, 2017 and March 31, 2016 : (In Millions) Cliffs Noncontrolling Interest (Deficit) Total Equity (Deficit) December 31, 2016 $ (1,464.3 ) $ 133.8 $ (1,330.5 ) Comprehensive loss Net loss (28.1 ) (1.7 ) (29.8 ) Other comprehensive loss (3.0 ) (5.0 ) (8.0 ) Total comprehensive loss (31.1 ) (6.7 ) (37.8 ) Issuance of common shares 661.3 — 661.3 Stock and other incentive plans 4.0 — 4.0 March 31, 2017 $ (830.1 ) $ 127.1 $ (703.0 ) (In Millions) Cliffs Noncontrolling Total Equity (Deficit) December 31, 2015 $ (1,981.4 ) $ 169.8 $ (1,811.6 ) Comprehensive income Net income 108.0 8.8 116.8 Other comprehensive income 5.7 0.6 6.3 Total comprehensive income 113.7 9.4 123.1 Issuance of common shares 5.4 — 5.4 Stock and other incentive plans 2.9 — 2.9 Distributions of partnership equity — (17.0 ) (17.0 ) Undistributed losses to noncontrolling interest — 0.5 0.5 March 31, 2016 $ (1,859.4 ) $ 162.7 $ (1,696.7 ) The following table reflects the changes in Accumulated other comprehensive income (loss) related to Cliffs shareholders’ deficit for March 31, 2017 and March 31, 2016 : (In Millions) Changes in Pension and Other Post-Retirement Benefits, net of tax Unrealized Net Gain (Loss) on Foreign Currency Translation Accumulated Other Comprehensive Income (Loss) December 31, 2016 $ (260.6 ) $ 239.3 $ (21.3 ) Other comprehensive income (loss) before reclassifications 3.3 (12.7 ) (9.4 ) Net loss reclassified from accumulated other comprehensive income (loss) 6.4 — 6.4 March 31, 2017 $ (250.9 ) $ 226.6 $ (24.3 ) (In Millions) Changes in Pension and Other Post-Retirement Benefits, net of tax Unrealized Net Gain (Loss) on Securities, net of tax Unrealized Net Gain (Loss) on Foreign Currency Translation Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax Accumulated Other Comprehensive Income (Loss) December 31, 2015 $ (241.4 ) $ 0.1 $ 220.7 $ 2.6 $ (18.0 ) Other comprehensive income (loss) before reclassifications (1.5 ) (0.1 ) 4.4 (3.4 ) (0.6 ) Net loss (gain) reclassified from accumulated other comprehensive income (loss) 6.3 — — — 6.3 March 31, 2016 $ (236.6 ) $ — $ 225.1 $ (0.8 ) $ (12.3 ) The following table reflects the details about Accumulated other comprehensive income (loss) components related to Cliffs shareholders’ deficit for the three months ended March 31, 2017 : (In Millions) Details about Accumulated Other Comprehensive Income (Loss) Components Amount of (Gain)/Loss Reclassified into Income Affected Line Item in the Statement of Unaudited Condensed Consolidated Operations Three Months Ended 2017 2016 Amortization of pension and postretirement benefit liability: Prior service credits 1 $ (0.1 ) $ (0.4 ) Net actuarial loss 1 6.5 6.7 Total before taxes 6.4 6.3 — — Income tax benefit (expense) Total reclassifications for the period, net of tax $ 6.4 $ 6.3 1 These accumulated other comprehensive income components are included in the computation of net periodic benefit cost (credit). See NOTE 7 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.

RELATED PARTIES

RELATED PARTIES	3 Months Ended
	Mar. 31, 2017
Related Party Transactions [Abstract]
RELATED PARTIES	NOTE 16 - RELATED PARTIES Two of our four operating U.S. iron ore mines and our indefinitely-idled Empire mine are co-owned joint ventures with companies that are integrated steel producers or their subsidiaries. We are the manager of each of the mines we co-own and rely on our joint venture partners to make their required capital contributions and to pay for their share of the iron ore pellets that we produce. One of the joint venture partners is also our customer. The following is a summary of the mine ownership of these iron ore mines at March 31, 2017 : Mine Cliffs Natural Resources ArcelorMittal U.S. Steel Corporation Empire 79.0 % 21.0 % — Tilden 85.0 % — 15.0 % Hibbing 23.0 % 62.3 % 14.7 % ArcelorMittal has a unilateral right to put its interest in the Empire mine to us but has not exercised this right to date. Furthermore, as part of a 2014 extension agreement between us and ArcelorMittal, which amended certain terms of the Empire partnership agreement, certain minimum distributions of the partners’ equity amounts were required to be made on a quarterly basis beginning in the first quarter of 2015 and continued through January 2017. The partnership dissolved on December 31, 2016, and the partners are in discussion regarding distribution of the remaining assets and/or equity interest, if any, in the partnership. We paid $8.7 million in January 2017 related to 2016 distributions. During the three months ended March 31, 2016 , we recorded distributions of $17.0 million under this agreement and paid distributions of $11.1 million related to 2015 distributions. Product revenues from related parties were as follows: (In Millions) Three Months Ended 2017 2016 Product revenues from related parties $ 118.5 $ 103.4 Total product revenues 412.8 275.6 Related party product revenue as a percent of total product revenue 28.7 % 37.5 % Amounts due from related parties recorded in Accounts receivable, net were $9.1 million and $46.9 million at March 31, 2017 and December 31, 2016 , respectively. Amounts including a customer supply agreement and provisional pricing arrangements recorded in Other current assets were $53.8 million and $26.8 million at March 31, 2017 and December 31, 2016 , respectively. Additionally, at December 31, 2016 we had $8.7 million recorded in Other current liabilities , including provisional pricing arrangements and liabilities to related parties. A supply agreement with one of our customers includes provisions for supplemental revenue or refunds based on the customer’s annual steel pricing for the year the product is consumed in the customer’s blast furnace. The supplemental pricing is characterized as a freestanding derivative. Refer to NOTE 13 - DERIVATIVE INSTRUMENTS for further information.

EARNINGS PER SHARE

EARNINGS PER SHARE	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
EARNINGS PER SHARE	NOTE 17 - EARNINGS PER SHARE The following table summarizes the computation of basic and diluted earnings (loss) per share: (In Millions, Except Per Share Amounts) Three Months Ended 2017 2016 Income (Loss) from Continuing Operations $ (30.3 ) $ 114.3 Loss (Income) from Continuing Operations Attributable to Noncontrolling Interest 1.7 (8.8 ) Net Income (Loss) from Continuing Operations Attributable to Cliffs Shareholders $ (28.6 ) $ 105.5 Income from Discontinued Operations, net of tax 0.5 2.5 Net Income (Loss) Attributable to Cliffs Shareholders $ (28.1 ) $ 108.0 Weighted Average Number of Shares: Basic 265.2 171.7 Employee Stock Plans — 0.3 Diluted 265.2 172.0 Earnings (Loss) per Common Share Attributable to Continuing operations $ (0.11 ) $ 0.61 Discontinued operations — 0.01 $ (0.11 ) $ 0.62 Earnings (Loss) per Common Share Attributable to Continuing operations $ (0.11 ) $ 0.61 Discontinued operations — 0.01 $ (0.11 ) $ 0.62 The diluted earnings per share calculation excludes 4.6 million of equity plan awards that were anti-dilutive for the three months ended March 31, 2017.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	NOTE 18 - COMMITMENTS AND CONTINGENCIES Contingencies We are currently the subject of, or party to, various claims and legal proceedings incidental to our operations. If management believes that a loss arising from these matters is probable and can reasonably be estimated, we record the amount of the loss or the minimum estimated liability when the loss is estimated using a range, and no point within the range is more probable than another. As additional information becomes available, any potential liability related to these matters is assessed and the estimates are revised, if necessary. Based on currently available information, management believes that the ultimate outcome of these matters, individually and in the aggregate, will not have a material effect on our financial position, results of operations or cash flows. However, 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 impact on the financial position and results of operations for the period in which the ruling occurs or future periods. However, we do not believe that any pending claims or legal proceedings will result in a material liability in relation to our consolidated financial statements. Currently, we have recorded a liability in the Statements of Unaudited Condensed Consolidated Financial Position related to the following legal matter: Michigan Electricity Matters. On February 19, 2015, in connection with various proceedings before FERC with respect to certain cost allocations for continued operation of the Presque Isle Power Plant in Marquette, Michigan, FERC issued an order directing MISO to submit a revised methodology for allocating SSR costs that identified the load serving entities that require the operation of SSR units at the power plant for reliability purposes. On September 17, 2015, FERC issued an order conditionally approving MISO’s revised allocation methodology. On September 22, 2016, FERC denied requests for rehearing of the February 19 order, rejecting arguments that FERC did not have the authority to order refunds in a cost allocation case and to impose retroactive surcharges to effectuate such refunds. FERC, however, suspended any refunds and surcharges pending its review of a July 25, 2016 ALJ initial decision on the appropriate amount of SSR compensation. Should FERC award SSR costs based on retroactive surcharges and the amount of SSR compensation not be adjusted, our current estimate of the potential liability to the Empire and Tilden mines is $13.6 million , based on MISO's June 14, 2016 refund report (as revised in MISO's July 20, 2016 errata refund report) for the Escanaba, White Pine and Presque Isle SSRs. We, however, continue to vigorously challenge both the amount of the SSR compensation and the imposition of any SSR costs before FERC and the U.S. Court of Appeals for the D.C. Circuit. As of March 31, 2017 , this potential liability of $13.6 million is included in our Statements of Unaudited Condensed Consolidated Financial Position as part of Accrued expenses . On November 8, 2016, Tilden and Empire, along with various Michigan-aligned parties, filed petitions for review of FERC’s order regarding allocation and non-cost SSR issues with the U.S. Court of Appeals for the D.C. Circuit. On January 27, 2017, Tilden, Empire and other appellants filed a motion to terminate further abeyance of briefing so that cost allocation issues could be heard earlier at the Court of Appeals than revenue requirement issues still pending at FERC, which motion was granted on April 4, 2017. We will continue to vigorously challenge both the amount of the SSR compensation and the imposition of any SSR costs before FERC and the U.S. Court of Appeals for the D.C. Circuit. CCAA Proceedings In January 2015, the Bloom Lake Group commenced CCAA proceedings. Effective January 27, 2015, following the CCAA filing of the Bloom Lake Group, we deconsolidated the Bloom Lake Group and certain other wholly-owned subsidiaries comprising substantially all of our Canadian operations. Additionally, on May 20, 2015, the Wabush Group commenced CCAA proceedings which resulted in the deconsolidation of the remaining Wabush Group entities that were not previously deconsolidated. As a result of this action, the CCAA protections granted to the Bloom Lake Group were extended to include the Wabush Group to facilitate the reorganization or divestiture of each of their businesses and operations. Prior to the deconsolidations, various Cliffs wholly-owned entities made loans to the Canadian Entities for the purpose of funding their operations and had accounts receivable generated in the ordinary course of business. The loans, corresponding interest and the accounts receivable were considered intercompany transactions and eliminated from our consolidated financial statements. Since the deconsolidations, the loans, associated interest and accounts receivable are considered related party transactions and have been recognized in our consolidated financial statements at their estimated fair value of $49.0 million and $48.6 million classified as Loans to and accounts receivable from the Canadian Entities in the Statements of Unaudited Condensed Consolidated Financial Position at March 31, 2017 and December 31, 2016 , respectively. We have liabilities of $37.5 million and $37.2 million including guarantees for certain environmental obligations of the Canadian Entities in our consolidated results, classified as Other liabilities in the Statements of Unaudited Condensed Consolidated Financial Position as of March 31, 2017 and December 31, 2016 , respectively. As of March 31, 2017 , the majority of assets available to the estate have been liquidated. The CCAA proceedings are still ongoing and the Monitor is evaluating all claims into the estate including our related party claims. Currently, there is uncertainty as to the amount of the distribution that will be made to the creditors of the estate, including, if any, to Cliffs, and whether Cliffs could be held liable for claims that may be asserted by or on behalf of the Bloom Lake Group or the Wabush Group or by their respective representatives against non-debtor affiliates of the Bloom Lake Group and the Wabush Group. After payment of sale expenses and taxes and repayment of the DIP financing, the net proceeds from the liquidation of assets and certain other divestitures by the Canadian Entities are currently being held by the Monitor, on behalf of the Canadian Entities, to fund the costs of the CCAA proceedings and for eventual distribution to creditors of the Canadian Entities pending further order of the Montreal Court.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2017
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	NOTE 19 - SUBSEQUENT EVENTS On March 24, 2017, we issued an irrevocable notice of redemption with respect to the $35.6 million aggregate principal amount of our outstanding 8.25% First Lien Notes due 2020. On April 24, 2017, $35.6 million aggregate principal amount of the 8.25% First Lien Notes due 2020 was redeemed with the remaining net proceeds from our first quarter common share offering resulting in a $5.0 million loss on extinguishment of debt related to the paid premiums and write off of unamortized discounts and debt issuance costs.

BASIS OF PRESENTATION AND SIG26

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis Of Consolidation	Basis of Consolidation The unaudited condensed consolidated financial statements include our accounts and the accounts of our wholly-owned and majority-owned subsidiaries, including the following operations as of March 31, 2017 : Name Location Ownership Interest Operation Status of Operations Northshore Minnesota 100.0% Iron Ore Active United Taconite Minnesota 100.0% Iron Ore Active Tilden Michigan 85.0% Iron Ore Active Empire Michigan 79.0% Iron Ore Indefinitely Idled Koolyanobbing Western Australia 100.0% Iron Ore Active Intercompany transactions and balances are eliminated upon consolidation.
Equity Method Investments	Equity Method Investments Our 23% ownership interest in Hibbing is recorded as an equity method investment. As of March 31, 2017 and December 31, 2016 , our investment in Hibbing was $6.2 million and $8.7 million , respectively, classified as Other liabilities in the Statements of Unaudited Condensed Consolidated Financial Position .
Foreign Currency	Foreign Currency Our financial statements are prepared with the U.S. dollar as the reporting currency. The functional currency of our Australian subsidiaries is the Australian dollar. The functional currency of all other international subsidiaries is the U.S. dollar. The financial statements of international subsidiaries are translated into U.S. dollars using the exchange rate at each balance sheet date for assets and liabilities and a weighted average exchange rate for each period for revenues, expenses, gains and losses. Where the local currency is the functional currency, translation adjustments are recorded as Accumulated other comprehensive loss . Income taxes generally are not provided for foreign currency translation adjustments. To the extent that monetary assets and liabilities, inclusive of short-term and certain long-term intercompany loans, are recorded in a currency other than the functional currency, these amounts are remeasured each reporting period, with the resulting gain or loss being recorded in the Statements of Unaudited Condensed Consolidated Operations . Transaction gains and losses resulting from remeasurement of short-term intercompany loans are included in Miscellaneous - net in the Statements of Unaudited Condensed Consolidated Operations . The following represents the transaction gains and losses resulting from remeasurement for the three months ended March 31, 2017 and 2016: (In Millions) Three Months Ended 2017 2016 Remeasurement of intercompany loans $ 15.1 $ 0.4 Remeasurement of cash and cash equivalents (1.2 ) 0.8 Other remeasurement (0.3 ) (2.4 ) Net impact of transaction gains and (losses) resulting from remeasurement 13.6 (1.2 )
Significant Accounting Policies	Significant Accounting Policies A detailed description of our significant accounting policies can be found in the audited financial statements for the fiscal year ended December 31, 2016 included in our Annual Report on Form 10-K filed with the SEC. There have been no material changes in our significant accounting policies and estimates from those disclosed therein.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Issued and Not Effective In March 2017, the FASB issued ASU No. 2017-07, Compensation - Retirement Benefits (Topic 715). The new standard requires the service cost component of pension and other postretirement benefit expenses to be included in the same line item as other compensation costs arising from services rendered by employees, with the other components of net benefit cost as defined by paragraphs 715-30-35-4 and 715-60-35-9 to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations. The guidance is effective for fiscal years beginning after December 15, 2017, and early adoption is permitted. The adoption of ASU 2017-07 will impact Statements of Unaudited Condensed Consolidated Operations by changing our classification of the components of pension cost; however, it will not impact our Net income (loss) .

BASIS OF PRESENTATION AND SIG27

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Tables)	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule Of Subsidiaries	The unaudited condensed consolidated financial statements include our accounts and the accounts of our wholly-owned and majority-owned subsidiaries, including the following operations as of March 31, 2017 : Name Location Ownership Interest Operation Status of Operations Northshore Minnesota 100.0% Iron Ore Active United Taconite Minnesota 100.0% Iron Ore Active Tilden Michigan 85.0% Iron Ore Active Empire Michigan 79.0% Iron Ore Indefinitely Idled Koolyanobbing Western Australia 100.0% Iron Ore Active
Foreign Currency Transaction [Table Text Block]	The following represents the transaction gains and losses resulting from remeasurement for the three months ended March 31, 2017 and 2016: (In Millions) Three Months Ended 2017 2016 Remeasurement of intercompany loans $ 15.1 $ 0.4 Remeasurement of cash and cash equivalents (1.2 ) 0.8 Other remeasurement (0.3 ) (2.4 ) Net impact of transaction gains and (losses) resulting from remeasurement 13.6 (1.2 )

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Schedule Of Segment Reporting Information, By Segment	The following tables present a summary of our reportable segments for the three months ended March 31, 2017 and 2016 , including a reconciliation of segment sales margin to Income (Loss) from Continuing Operations Before Income Taxes and a reconciliation of Net Income (Loss) to EBITDA and Adjusted EBITDA: (In Millions) Three Months Ended 2017 2016 Revenues from product sales and services: U.S. Iron Ore $ 286.2 62 % $ 185.5 61 % Asia Pacific Iron Ore 175.4 38 % 120.0 39 % Total revenues from product sales and services $ 461.6 100 % $ 305.5 100 % Sales margin: U.S. Iron Ore $ 48.4 $ 13.2 Asia Pacific Iron Ore 47.3 17.7 Sales margin 95.7 30.9 Other operating expense (13.8 ) (31.2 ) Other income (expense) (114.0 ) 122.1 Income (loss) from continuing operations before income taxes $ (32.1 ) $ 121.8 (In Millions) Three Months Ended 2017 2016 Net Income (Loss) $ (29.8 ) $ 116.8 Less: Interest expense, net (42.8 ) (56.8 ) Income tax benefit (expense) 1.8 (7.6 ) Depreciation, depletion and amortization (23.2 ) (35.2 ) EBITDA $ 34.4 $ 216.4 Less: Gain (loss) on extinguishment/restructuring of debt (71.9 ) 178.8 Foreign exchange remeasurement 13.6 (1.2 ) Impact of discontinued operations 0.5 2.6 Severance and contractor termination costs — (0.1 ) Adjusted EBITDA $ 92.2 $ 36.3 EBITDA: U.S. Iron Ore $ 57.9 $ 41.4 Asia Pacific Iron Ore 51.4 22.3 Other (74.9 ) 152.7 Total EBITDA $ 34.4 $ 216.4 Adjusted EBITDA: U.S. Iron Ore $ 64.1 $ 46.1 Asia Pacific Iron Ore 53.8 23.0 Other (25.7 ) (32.8 ) Total Adjusted EBITDA $ 92.2 $ 36.3 (In Millions) Three Months Ended 2017 2016 Depreciation, depletion and amortization: U.S. Iron Ore $ 16.4 $ 26.9 Asia Pacific Iron Ore 4.7 6.8 Other 2.1 1.5 Total depreciation, depletion and amortization $ 23.2 $ 35.2 Capital additions: U.S. Iron Ore $ 27.1 $ 4.5 Asia Pacific Iron Ore 0.2 — Other — 2.3 Total capital additions 1 $ 27.3 $ 6.8 1 Includes cash paid for capital additions of $27.9 million and $10.4 million and a decrease in non-cash accruals of $0.6 million and $3.6 million for the three months ended March 31, 2017 and 2016, respectively.
Summary of Assets by Segment	A summary of assets by segment is as follows: (In Millions) March 31, December 31, Assets: U.S. Iron Ore $ 1,440.6 $ 1,372.5 Asia Pacific Iron Ore 168.4 155.1 Total segment assets 1,609.0 1,527.6 Corporate 316.7 396.3 Total assets $ 1,925.7 $ 1,923.9

INVENTORIES (Tables)

INVENTORIES (Tables)	3 Months Ended
	Mar. 31, 2017
Inventory Disclosure [Abstract]
Schedule Of Inventories	The following table presents the detail of our Inventories in the Statements of Unaudited Condensed Consolidated Financial Position as of March 31, 2017 and December 31, 2016 : (In Millions) March 31, 2017 December 31, 2016 Segment Finished Goods Work-in Process Total Inventory Finished Goods Work-in Process Total Inventory U.S. Iron Ore $ 194.6 $ 26.3 $ 220.9 $ 124.4 $ 12.6 $ 137.0 Asia Pacific Iron Ore 14.6 15.3 29.9 23.6 17.8 41.4 Total $ 209.2 $ 41.6 $ 250.8 $ 148.0 $ 30.4 $ 178.4

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	3 Months Ended
	Mar. 31, 2017
Property, Plant and Equipment [Abstract]
Value Of Each Of The Major Classes Of Consolidated Depreciable Assets	The following table indicates the value of each of the major classes of our consolidated depreciable assets as of March 31, 2017 and December 31, 2016 : (In Millions) March 31, December 31, Land rights and mineral rights $ 500.7 $ 500.5 Office and information technology 65.8 65.1 Buildings 68.4 67.9 Mining equipment 595.8 592.2 Processing equipment 558.9 552.0 Electric power facilities 49.6 49.4 Land improvements 23.7 23.5 Asset retirement obligation 19.8 19.8 Other 28.4 28.1 Construction in-progress 69.8 42.8 1,980.9 1,941.3 Allowance for depreciation and depletion (985.9 ) (956.9 ) $ 995.0 $ 984.4

DEBT AND CREDIT FACILITIES (Tab

DEBT AND CREDIT FACILITIES (Tables)	3 Months Ended
	Mar. 31, 2017
Debt Disclosure [Abstract]
Schedule Of Long-Term Debt	The following represents a summary of our long-term debt as of March 31, 2017 and December 31, 2016 : ($ in Millions) March 31, 2017 Debt Instrument Annual Effective Interest Rate Total Principal Amount Debt Issuance Costs Unamortized Discounts Total Debt Secured Notes $540 Million 8.25% 2020 First Lien Notes 9.97% $ 540.0 $ (7.4 ) $ (24.0 ) $ 508.6 Unsecured Notes $400 Million 5.90% 2020 Senior Notes 5.98% 88.9 (0.2 ) (0.2 ) 88.5 $500 Million 4.80% 2020 Senior Notes 4.83% 122.4 (0.3 ) (0.1 ) 122.0 $700 Million 4.875% 2021 Senior Notes 4.89% 138.4 (0.4 ) (0.1 ) 137.9 $500 Million 5.75% 2025 Senior Notes 5.75% 500.0 (8.3 ) — 491.7 $800 Million 6.25% 2040 Senior Notes 6.34% 298.4 (2.5 ) (3.4 ) 292.5 ABL Facility N/A 550.0 N/A N/A — Fair Value Adjustment to Interest Rate Hedge 1.7 Long-term debt $ 1,642.9 ($ in Millions) December 31, 2016 Debt Instrument Annual Effective Interest Rate Total Principal Amount Debt Issuance Costs Undiscounted Interest/(Unamortized Discounts) Total Debt Secured Notes $540 Million 8.25% 2020 First Lien Notes 9.97% $ 540.0 $ (8.0 ) $ (25.7 ) $ 506.3 $218.5 Million 8.00% 2020 1.5 Lien Notes N/A 218.5 — 65.7 284.2 $544.2 Million 7.75% 2020 Second Lien Notes 15.55% 430.1 (5.8 ) (85.2 ) 339.1 Unsecured Notes $400 Million 5.90% 2020 Senior Notes 5.98% 225.6 (0.6 ) (0.5 ) 224.5 $500 Million 4.80% 2020 Senior Notes 4.83% 236.8 (0.7 ) (0.2 ) 235.9 $700 Million 4.875% 2021 Senior Notes 4.89% 309.4 (1.0 ) (0.2 ) 308.2 $800 Million 6.25% 2040 Senior Notes 6.34% 298.4 (2.5 ) (3.4 ) 292.5 ABL Facility N/A 550.0 N/A N/A — Fair Value Adjustment to Interest Rate Hedge 1.9 Total debt $ 2,192.6 Less current portion 17.5 Long-term debt $ 2,175.1
Schedule of Extinguishment of Debt [Table Text Block]	The following is a summary of the debt extinguished during the three months ended March 31, 2017 : ($ In Millions) Debt Extinguished Gain (Loss) on Extinguishment 1 Secured Notes $218.5 Million 8.00% 2020 1.5 Lien Notes $ 218.5 $ 45.1 $544.2 Million 7.75% 2020 Second Lien Notes 430.1 (104.5 ) Unsecured Notes $400 Million 5.90% 2020 Senior Notes 136.8 (7.8 ) $500 Million 4.80% 2020 Senior Notes 114.4 (1.9 ) $700 Million 4.875% 2021 Senior Notes 171.0 (2.8 ) $ 1,070.8 $ (71.9 ) 1 Includes write-off of undiscounted interest, unamortized discounts and debt issuance costs. In addition, we paid premiums of $44.7 million related to the redemption of our notes.
Schedule of Maturities of Long-term Debt	Debt Maturities The following represents a summary of our maturities of debt instruments, excluding borrowings on the ABL Facility, based on the principal amounts outstanding at March 31, 2017 : (In Millions) Maturities of Debt 2017 (April 1 - December 31) $ — 2018 — 2019 — 2020 751.3 2021 138.4 2022 — 2023 and thereafter 798.4 Total maturities of debt $ 1,688.1

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value, by Balance Sheet Grouping [Table Text Block]	The following represents the assets and liabilities of the Company measured at fair value at March 31, 2017 and December 31, 2016 : (In Millions) March 31, 2017 Description 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 $ 90.0 $ 45.0 $ — $ 135.0 Derivative assets — — 59.4 59.4 Loans to and accounts receivable from the Canadian Entities — — 49.0 49.0 Total $ 90.0 $ 45.0 $ 108.4 $ 243.4 Liabilities: Derivative liabilities $ — $ — $ 9.1 $ 9.1 Contingent liabilities — — 37.5 37.5 Total $ — $ — $ 46.6 $ 46.6 (In Millions) December 31, 2016 Description 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 $ 177.0 $ — $ — $ 177.0 Derivative assets — 1.5 31.6 33.1 Loans to and accounts receivable from the Canadian Entities — — 48.6 48.6 Total $ 177.0 $ 1.5 $ 80.2 $ 258.7 Liabilities: Derivative liabilities $ — $ — $ 0.5 $ 0.5 Contingent liabilities — — 37.2 37.2 Total $ — $ — $ 37.7 $ 37.7
Fair Value, Recurring and Nonrecurring, Valuation Techniques	The following table illustrates information about quantitative inputs and assumptions for the assets and liabilities categorized in Level 3 of the fair value hierarchy: Qualitative/Quantitative Information About Level 3 Fair Value Measurements (In Millions) Fair Value at March 31, 2017 Balance Sheet Location Valuation Technique Unobservable Input Range or Point Estimate per dry metric ton (Weighted Average) Provisional pricing arrangements $ 23.5 Other current assets Market Approach Management's Estimate of Platts 62% Price $79 Hot-Rolled Coil Steel Estimate $651 Provisional pricing arrangements $ 9.1 Other current liabilities Market Approach Management's Estimate of Platts 62% Price $79 Customer supply agreement $ 35.9 Other current assets Market Approach Hot-Rolled Coil Steel Estimate $520 - $630 ($575) Loans to and accounts receivable from the Canadian Entities $ 49.0 Loans to and accounts receivable from the Canadian Entities * * N/A Contingent liabilities $ 37.5 Other liabilities * * N/A * To assess the fair value and recoverability of the amounts receivable from the Canadian Entities, we estimated the fair value of the underlying net assets of the Canadian Entities available for distribution to their creditors in relation to the estimated creditor claims and the priority of those claims. The recorded expenses include an accrual for the estimated probable loss related to claims that may be asserted against us. We are not able to estimate reasonably a range of possible losses in excess of the accrual because there are significant factual and legal issues to be resolved. Our estimates involve significant judgment. Our estimates are based on currently available information, an assessment of the validity of certain claims and estimated payments by the Canadian Entities.
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation	(In Millions) Level 3 Assets Three Months Ended 2017 2016 Beginning balance $ 80.2 $ 80.7 Total gains (losses) Included in earnings 42.5 8.2 Settlements (14.3 ) (10.0 ) Transfers into Level 3 — — Transfers out of Level 3 — — Ending balance - March 31 $ 108.4 $ 78.9 Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date $ 33.2 $ 3.6
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	(In Millions) Level 3 Liabilities Three Months Ended 2017 2016 Beginning balance $ (37.7 ) $ (135.8 ) Total gains (losses) Included in earnings (8.9 ) (7.9 ) Settlements — 75.7 Transfers into Level 3 — — Transfers out of Level 3 — — Ending balance - March 31 $ (46.6 ) $ (68.0 ) Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date $ (9.1 ) $ (0.8 )
Schedule Of Carrying Value And Fair Value Of Financial Instruments	A summary of the carrying amount and fair value of other financial instruments at March 31, 2017 and December 31, 2016 were as follows: (In Millions) March 31, 2017 December 31, 2016 Classification Carrying Value Fair Value Carrying Value Fair Value Long-term debt: Secured Notes First Senior Lien Notes —$540 million Level 1 $ 508.6 $ 583.9 $ 506.3 $ 595.0 1.5 Senior Lien Notes —$218.5 million Level 2 — — 284.2 229.5 Second Senior Lien Notes —$544.2 million Level 1 — — 339.1 439.7 Unsecured Notes Senior Notes—$500 million Level 1 491.7 486.3 — — Senior Notes—$400 million Level 1 88.5 88.4 224.5 219.6 Senior Notes—$1.3 billion Level 1 414.5 358.9 528.4 455.8 Senior Notes—$700 million Level 1 137.9 134.3 308.2 283.1 ABL Facility Level 2 — — — — Fair value adjustment to interest rate hedge Level 2 1.7 1.7 1.9 1.9 Total long-term debt $ 1,642.9 $ 1,653.5 $ 2,192.6 $ 2,224.6

PENSIONS AND OTHER POSTRETIRE33

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Tables)	3 Months Ended
	Mar. 31, 2017
Postemployment Benefits [Abstract]
Schedule of Net Benefit Costs	The following are the components of defined benefit pension and OPEB costs and credits for the three months ended March 31, 2017 and 2016 : Defined Benefit Pension Costs (In Millions) Three Months Ended 2017 2016 Service cost $ 4.8 $ 4.5 Interest cost 7.5 7.5 Expected return on plan assets (13.5 ) (13.7 ) Amortization: Prior service costs 0.6 0.5 Net actuarial loss 5.3 5.3 Net periodic benefit cost to continuing operations $ 4.7 $ 4.1 Other Postretirement Benefits Credit (In Millions) Three Months Ended 2017 2016 Service cost $ 0.5 $ 0.4 Interest cost 2.1 2.3 Expected return on plan assets (4.4 ) (4.3 ) Amortization: Prior service credits (0.7 ) (0.9 ) Net actuarial loss 1.2 1.4 Net periodic benefit credit to continuing operations $ (1.3 ) $ (1.1 )

STOCK COMPENSATION PLANS STOCK

STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Tables)	3 Months Ended
	Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]	The following assumptions were utilized to estimate the fair value for the first quarter of 2017 performance share grants: Grant Date Grant Date Market Price Average Expected Term (Years) Expected Volatility Risk-Free Interest Rate Dividend Yield Fair Value Fair Value (Percent of Grant Date Market Price) February 21, 2017 $ 11.67 2.86 92.1% 1.51% —% $ 19.69 168.72%

LEASE OBLIGATIONS (Tables)

LEASE OBLIGATIONS (Tables)	3 Months Ended
	Mar. 31, 2017
Leases [Abstract]
Schedule Of Future Minimum Lease Payments For Capital Leases And Operating Leases	Future minimum payments under capital leases and non-cancellable operating leases at March 31, 2017 are as follows: (In Millions) Capital Leases Operating Leases 2017 (April 1 - December 31) $ 17.2 $ 5.3 2018 18.8 5.8 2019 10.4 3.0 2020 9.4 2.9 2021 8.7 3.0 2022 and thereafter 1.4 — Total minimum lease payments $ 65.9 $ 20.0 Amounts representing interest 11.8 Present value of net minimum lease payments 1 $ 54.1 1 The total is comprised of $18.0 million and $36.1 million classified as Other current liabilities and Other liabilities , respectively, in the Statements of Unaudited Condensed Consolidated Financial Position at March 31, 2017.

ENVIRONMENTAL AND MINE CLOSUR36

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Tables)	3 Months Ended
	Mar. 31, 2017
Environmental Remediation Obligations [Abstract]
Summary Of Mine Closure Obligations	The following is a summary of the obligations as of March 31, 2017 and December 31, 2016 : (In Millions) March 31, December 31, Environmental $ 2.8 $ 2.8 Mine closure U.S. Iron Ore 1 190.9 187.8 Asia Pacific Iron Ore 17.3 16.2 Total mine closure 208.2 204.0 Total environmental and mine closure obligations 211.0 206.8 Less current portion 12.8 12.9 Long-term environmental and mine closure obligations $ 198.2 $ 193.9 1 U.S. Iron Ore includes our active operating mines, our indefinitely idled Empire mine and a closed mine formerly operating as LTVSMC.
Asset Retirement Obligation Disclosure	The following represents a roll forward of our asset retirement obligation liability for the three months ended March 31, 2017 and for the year ended December 31, 2016 : (In Millions) March 31, December 31, 2016 Asset retirement obligation at beginning of period $ 204.0 $ 230.4 Accretion expense 3.6 14.0 Remediation payments (0.3 ) (2.2 ) Exchange rate changes 0.9 (0.2 ) Revision in estimated cash flows — (38.0 ) Asset retirement obligation at end of period $ 208.2 $ 204.0

GOODWILL AND OTHER INTANGIBLE37

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Tables)	3 Months Ended
	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule Of Finite-Lived Intangible Assets By Major Class	The following table is a summary of intangible assets as of March 31, 2017 and December 31, 2016 : (In Millions) March 31, 2017 December 31, 2016 Classification Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Definite-lived intangible assets: Permits Other non-current assets $ 78.7 $ (25.1 ) $ 53.6 $ 78.4 $ (24.6 ) $ 53.8 Total intangible assets $ 78.7 $ (25.1 ) $ 53.6 $ 78.4 $ (24.6 ) $ 53.8

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	3 Months Ended
	Mar. 31, 2017
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 as of March 31, 2017 and December 31, 2016 : (In Millions) Derivative Assets Derivative Liabilities March 31, 2017 December 31, 2016 March 31, 2017 December 31, 2016 Derivative Instrument Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Customer supply agreement Other current assets 35.9 Other current assets 21.3 — — Provisional pricing arrangements Other current assets 23.5 Other current assets 10.3 Other current liabilities 9.1 Other current liabilities 0.5 Commodity contracts — Other current assets 1.5 — — Total derivatives not designated as hedging instruments under ASC 815 $ 59.4 $ 33.1 $ 9.1 $ 0.5
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 for the three months ended March 31, 2017 and 2016 : (In Millions) Derivatives Not Designated as Hedging Instruments Location of Gain (Loss) Recognized in Amount of Gain (Loss) Recognized in Income on Derivative Three Months Ended 2017 2016 Customer supply agreement Product revenues 17.8 (0.1 ) Provisional pricing arrangements Product revenues 15.7 (1.5 ) Commodity contracts Cost of goods sold and operating expenses (1.3 ) — Total $ 32.2 $ (1.6 )

SHAREHOLDERS' EQUITY Shareholde

SHAREHOLDERS' EQUITY Shareholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Schedule of Stockholders Equity	The following table reflects the changes in shareholders' deficit attributable to both Cliffs and the noncontrolling interests primarily related to Tilden and Empire of which Cliffs owns 85% and 79% , respectively, for the three months ended March 31, 2017 and March 31, 2016 : (In Millions) Cliffs Noncontrolling Interest (Deficit) Total Equity (Deficit) December 31, 2016 $ (1,464.3 ) $ 133.8 $ (1,330.5 ) Comprehensive loss Net loss (28.1 ) (1.7 ) (29.8 ) Other comprehensive loss (3.0 ) (5.0 ) (8.0 ) Total comprehensive loss (31.1 ) (6.7 ) (37.8 ) Issuance of common shares 661.3 — 661.3 Stock and other incentive plans 4.0 — 4.0 March 31, 2017 $ (830.1 ) $ 127.1 $ (703.0 ) (In Millions) Cliffs Noncontrolling Total Equity (Deficit) December 31, 2015 $ (1,981.4 ) $ 169.8 $ (1,811.6 ) Comprehensive income Net income 108.0 8.8 116.8 Other comprehensive income 5.7 0.6 6.3 Total comprehensive income 113.7 9.4 123.1 Issuance of common shares 5.4 — 5.4 Stock and other incentive plans 2.9 — 2.9 Distributions of partnership equity — (17.0 ) (17.0 ) Undistributed losses to noncontrolling interest — 0.5 0.5 March 31, 2016 $ (1,859.4 ) $ 162.7 $ (1,696.7 )
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table reflects the changes in Accumulated other comprehensive income (loss) related to Cliffs shareholders’ deficit for March 31, 2017 and March 31, 2016 : (In Millions) Changes in Pension and Other Post-Retirement Benefits, net of tax Unrealized Net Gain (Loss) on Foreign Currency Translation Accumulated Other Comprehensive Income (Loss) December 31, 2016 $ (260.6 ) $ 239.3 $ (21.3 ) Other comprehensive income (loss) before reclassifications 3.3 (12.7 ) (9.4 ) Net loss reclassified from accumulated other comprehensive income (loss) 6.4 — 6.4 March 31, 2017 $ (250.9 ) $ 226.6 $ (24.3 ) (In Millions) Changes in Pension and Other Post-Retirement Benefits, net of tax Unrealized Net Gain (Loss) on Securities, net of tax Unrealized Net Gain (Loss) on Foreign Currency Translation Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax Accumulated Other Comprehensive Income (Loss) December 31, 2015 $ (241.4 ) $ 0.1 $ 220.7 $ 2.6 $ (18.0 ) Other comprehensive income (loss) before reclassifications (1.5 ) (0.1 ) 4.4 (3.4 ) (0.6 ) Net loss (gain) reclassified from accumulated other comprehensive income (loss) 6.3 — — — 6.3 March 31, 2016 $ (236.6 ) $ — $ 225.1 $ (0.8 ) $ (12.3 )
Details of Accumulated Other Comprehensive Income (Loss) Components	The following table reflects the details about Accumulated other comprehensive income (loss) components related to Cliffs shareholders’ deficit for the three months ended March 31, 2017 : (In Millions) Details about Accumulated Other Comprehensive Income (Loss) Components Amount of (Gain)/Loss Reclassified into Income Affected Line Item in the Statement of Unaudited Condensed Consolidated Operations Three Months Ended 2017 2016 Amortization of pension and postretirement benefit liability: Prior service credits 1 $ (0.1 ) $ (0.4 ) Net actuarial loss 1 6.5 6.7 Total before taxes 6.4 6.3 — — Income tax benefit (expense) Total reclassifications for the period, net of tax $ 6.4 $ 6.3 1 These accumulated other comprehensive income components are included in the computation of net periodic benefit cost (credit). See NOTE 7 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.

RELATED PARTIES (Tables)

RELATED PARTIES (Tables)	3 Months Ended
	Mar. 31, 2017
Related Party Transactions [Abstract]
Summary Of Other Ownership Interests	The following is a summary of the mine ownership of these iron ore mines at March 31, 2017 : Mine Cliffs Natural Resources ArcelorMittal U.S. Steel Corporation Empire 79.0 % 21.0 % — Tilden 85.0 % — 15.0 % Hibbing 23.0 % 62.3 % 14.7 %
Summary Of Related Party Transactions Table Disclosure	Product revenues from related parties were as follows: (In Millions) Three Months Ended 2017 2016 Product revenues from related parties $ 118.5 $ 103.4 Total product revenues 412.8 275.6 Related party product revenue as a percent of total product revenue 28.7 % 37.5 %

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share Computation	The following table summarizes the computation of basic and diluted earnings (loss) per share: (In Millions, Except Per Share Amounts) Three Months Ended 2017 2016 Income (Loss) from Continuing Operations $ (30.3 ) $ 114.3 Loss (Income) from Continuing Operations Attributable to Noncontrolling Interest 1.7 (8.8 ) Net Income (Loss) from Continuing Operations Attributable to Cliffs Shareholders $ (28.6 ) $ 105.5 Income from Discontinued Operations, net of tax 0.5 2.5 Net Income (Loss) Attributable to Cliffs Shareholders $ (28.1 ) $ 108.0 Weighted Average Number of Shares: Basic 265.2 171.7 Employee Stock Plans — 0.3 Diluted 265.2 172.0 Earnings (Loss) per Common Share Attributable to Continuing operations $ (0.11 ) $ 0.61 Discontinued operations — 0.01 $ (0.11 ) $ 0.62 Earnings (Loss) per Common Share Attributable to Continuing operations $ (0.11 ) $ 0.61 Discontinued operations — 0.01 $ (0.11 ) $ 0.62

BASIS OF PRESENTATION AND SIG42

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) - Hibbing [Member] - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Other Noncurrent Assets [Member]
Related Party Transaction [Line Items]
Ownership interest, equity method investment	23.00%
Other Noncurrent Liabilities [Member]
Related Party Transaction [Line Items]
Equity Method Investments	$ 6.2	$ 8.7

BASIS OF PRESENTATION AND SIG43

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)	3 Months Ended
	Mar. 31, 2017
Northshore [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Minnesota
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Segment Reporting Information, Description of Products and Services	Iron Ore
United Taconite [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Minnesota
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Segment Reporting Information, Description of Products and Services	Iron Ore
Tilden [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Michigan
Noncontrolling Interest, Ownership Percentage by Parent	85.00%
Segment Reporting Information, Description of Products and Services	Iron Ore
Empire [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Michigan
Noncontrolling Interest, Ownership Percentage by Parent	79.00%
Segment Reporting Information, Description of Products and Services	Iron Ore
Koolyanobbing [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Western Australia
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Segment Reporting Information, Description of Products and Services	Iron Ore

BASIS OF PRESENTATION AND SIG44

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Foreign Currency Translation) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Foreign Currency Transaction Gain (Loss), before Tax	$ (0.3)	$ (2.4)
Transaction Gains and Losses Resulting from Remeasurement [Member]
Foreign Currency Transaction Gain (Loss), before Tax	13.6	(1.2)
Cash and Cash Equivalents [Member]
Foreign Currency Transaction Gain (Loss), before Tax	(1.2)	0.8
Short-term intercompany loan [Member]
Foreign Currency Transaction Gain (Loss), before Tax	$ 15.1	$ 0.4

SEGMENT REPORTING (Schedule Of

SEGMENT REPORTING (Schedule Of Segment Reporting Information, By Segment) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	100.00%	100.00%
Revenues from product sales and services	$ 461.6	$ 305.5
Sales margin	95.7	30.9
Other operating expense	(13.8)	(31.2)
Other income (expense)	(114)	122.1
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	(32.1)	121.8
Net Income (Loss)	(29.8)	116.8
Interest expense, net	(42.8)	(56.8)
Income tax benefit (expense)	1.8	(7.6)
Depreciation, depletion and amortization	23.2	35.2
EBITDA	34.4	216.4
Gain (loss) on extinguishment/restructuring of debt	(71.9)	178.8
Adjusted EBITDA	92.2	36.3
Property, Plant and Equipment, Additions	27.3	6.8
Payments To Acquire Property Plant And Equipment Net	27.9	10.4
Capital Expenditures Incurred but Not yet Paid	$ (0.6)	$ (3.6)
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	62.00%	61.00%
Revenues from product sales and services	$ 286.2	$ 185.5
Sales margin	48.4	13.2
Depreciation, depletion and amortization	16.4	26.9
EBITDA	57.9	41.4
Adjusted EBITDA	64.1	46.1
Property, Plant and Equipment, Additions	$ 27.1	$ 4.5
Asia Pacific Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	38.00%	39.00%
Revenues from product sales and services	$ 175.4	$ 120
Sales margin	47.3	17.7
Depreciation, depletion and amortization	4.7	6.8
EBITDA	51.4	22.3
Adjusted EBITDA	53.8	23
Property, Plant and Equipment, Additions	0.2	0
All Other Segments [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization	2.1	1.5
EBITDA	(74.9)	152.7
Adjusted EBITDA	(25.7)	(32.8)
Property, Plant and Equipment, Additions	0	2.3
EBITDA Calculation [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization	23.2	35.2
Adjusted EBITDA Calculation [Member]
Segment Reporting Information [Line Items]
Impact of discontinued operations	0.5	2.6
Severance and contractor termination costs	0	(0.1)
Foreign exchange remeasurement	$ 13.6	$ (1.2)

SEGMENT REPORTING Segment Repor

SEGMENT REPORTING Segment Reporting (Summary of Assets by Segment) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Assets	$ 1,925.7	$ 1,923.9
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Assets	1,440.6	1,372.5
Asia Pacific Iron Ore [Member]
Segment Reporting Information [Line Items]
Assets	168.4	155.1
Total Segment Assets [Member]
Segment Reporting Information [Line Items]
Assets	1,609	1,527.6
Corporate [Member]
Segment Reporting Information [Line Items]
Assets	$ 316.7	$ 396.3

INVENTORIES (Schedule Of Invent

INVENTORIES (Schedule Of Inventories) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Inventory, Net [Abstract]
Finished Goods	$ 209.2	$ 148
Work-in Process	41.6	30.4
Total Inventory	250.8	178.4
U.S. Iron Ore [Member]
Inventory, Net [Abstract]
Finished Goods	194.6	124.4
Work-in Process	26.3	12.6
Total Inventory	220.9	137
Asia Pacific Iron Ore [Member]
Inventory, Net [Abstract]
Finished Goods	14.6	23.6
Work-in Process	15.3	17.8
Total Inventory	$ 29.9	$ 41.4

PROPERTY, PLANT AND EQUIPMENT48

PROPERTY, PLANT AND EQUIPMENT (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Property, Plant and Equipment [Abstract]
Depreciation and depletion	$ 22.6	$ 33.8

PROPERTY, PLANT AND EQUIPMENT49

PROPERTY, PLANT AND EQUIPMENT (Value Of Each Of The Major Classes Of Consolidated Depreciable Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,980.9	$ 1,941.3
Allowance for depreciation and depletion	(985.9)	(956.9)
Property, plant and equipment, net	995	984.4
Land Rights And Mineral Rights [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	500.7	500.5
Office And Information Technology [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	65.8	65.1
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	68.4	67.9
Mining Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	595.8	592.2
Processing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	558.9	552
Electric Power Facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	49.6	49.4
Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	23.7	23.5
Asset Retirement Obligation [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	19.8	19.8
Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	28.4	28.1
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 69.8	$ 42.8

DEBT AND CREDIT FACILITIES (Nar

DEBT AND CREDIT FACILITIES (Narrative) (Details)	3 Months Ended
	Mar. 31, 2017USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)
Line of Credit Facility [Line Items]
Payments of Debt Issuance Costs	$ 8,500,000	$ 5,200,000
Gain (loss) on extinguishment/restructuring of debt	(71,900,000)	$ 178,800,000
Debt redemption premiums paid	44,700,000
$500 Million 5.75% 2025 Senior Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Par Value	$ 500,000,000
Debt Instrument, Interest Rate, Effective Percentage	5.75%
Note Redemption Price, Percent of Principal Amount to be Redeemed	100.00%
Amount in aggregate that can be redeemed on or prior to March 1, 2020	0.3500
Repurchase price if triggering event occurs	1.01
Redemption Price of 35 percent or less of Outstanding	1.0575
In the Event of Default Amount that will Accelerate	0.25
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility, amount outstanding	$ 0		$ 0
Line of Credit Facility, Maximum Borrowing Capacity	256,300,000		333,000,000
Debt Instrument, Par Value	550,000,000		550,000,000
Credit facility remaining capacity	160,800,000		227,000,000
Letters of credit outstanding	$ 95,500,000		$ 106,000,000

DEBT AND CREDIT FACILITIES (Sch

DEBT AND CREDIT FACILITIES (Schedule Of Long-Term Debt) (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term Debt		$ 2,192,600,000
Long-term Debt, Current Maturities		17,500,000
Long-term Debt, Excluding Current Maturities	$ 1,642,900,000	$ 2,175,100,000
$540 Million 8.25% 2020 Lien Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	9.97%	9.97%
Debt Instrument, Par Value	$ 540,000,000	$ 540,000,000
Unamortized Debt Issuance Expense	(7,400,000)	(8,000,000)
Debt Instrument, Unamortized Discount	(24,000,000)	(25,700,000)
Long-term Debt	$ 508,600,000	506,300,000
$218.5 Million 8.00% 2020 Lien Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Par Value		218,500,000
Unamortized Debt Issuance Expense		0
Debt Instrument, Unamortized Discount		65,700,000
Long-term Debt		$ 284,200,000
$544 Million 7.75% 2020 Lien Notes[Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage		15.55%
Debt Instrument, Par Value		$ 430,100,000
Unamortized Debt Issuance Expense		(5,800,000)
Debt Instrument, Unamortized Discount		(85,200,000)
Long-term Debt		$ 339,100,000
$400 Million 5.90% 2020 Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	5.98%	5.98%
Debt Instrument, Par Value	$ 88,900,000	$ 225,600,000
Unamortized Debt Issuance Expense	(200,000)	(600,000)
Debt Instrument, Unamortized Discount	(200,000)	(500,000)
Long-term Debt	$ 88,500,000	$ 224,500,000
$500 million 4.80% 2020 Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	4.83%	4.83%
Debt Instrument, Par Value	$ 122,400,000	$ 236,800,000
Unamortized Debt Issuance Expense	(300,000)	(700,000)
Debt Instrument, Unamortized Discount	(100,000)	(200,000)
Long-term Debt	$ 122,000,000	$ 235,900,000
$700 Million 4.875% 2021 Senior Note [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	4.89%	4.89%
Debt Instrument, Par Value	$ 138,400,000	$ 309,400,000
Unamortized Debt Issuance Expense	(400,000)	(1,000,000)
Debt Instrument, Unamortized Discount	(100,000)	(200,000)
Long-term Debt	$ 137,900,000	$ 308,200,000
$500 Million 5.75% 2025 Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	5.75%
Debt Instrument, Par Value	$ 500,000,000
Unamortized Debt Issuance Expense	(8,300,000)
Debt Instrument, Unamortized Discount	0
Long-term Debt	$ 491,700,000
$800 Million 6.25% 2040 Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	6.34%	6.34%
Debt Instrument, Par Value	$ 298,400,000	$ 298,400,000
Unamortized Debt Issuance Expense	(2,500,000)	(2,500,000)
Debt Instrument, Unamortized Discount	(3,400,000)	(3,400,000)
Long-term Debt	292,500,000	292,500,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Par Value	550,000,000	550,000,000
Credit facility, amount outstanding	0	0
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Fair Value Adjustment to Interest Rate Hedge	$ 1,700,000	$ 1,900,000

DEBT AND CREDIT FACILITIES DEBT

DEBT AND CREDIT FACILITIES DEBT AND CREDIT FACILITIES (Debt Restructuring) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount	$ 1,070.8
Gain (loss) on extinguishment/restructuring of debt	(71.9)	$ 178.8
$218.5 Million 8.00% 2020 Lien Notes [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount	218.5
Gain (loss) on extinguishment/restructuring of debt	45.1
$544 Million 7.75% 2020 Lien Notes[Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount	430.1
Gain (loss) on extinguishment/restructuring of debt	(104.5)
$400 Million 5.90% 2020 Senior Notes [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount	136.8
Gain (loss) on extinguishment/restructuring of debt	(7.8)
Five Hundred Million Four Point Eight Zero Percent Senior Note [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount	114.4
Gain (loss) on extinguishment/restructuring of debt	(1.9)
$700 Million 4.875% 2021 Senior Note [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount	171
Gain (loss) on extinguishment/restructuring of debt	$ (2.8)

DEBT AND CREDIT FACILITIES DE53

DEBT AND CREDIT FACILITIES DEBT AND CREDIT FACILITIES (Schedule of Debt Maturities) (Details) $ in Millions	Mar. 31, 2017USD ($)
Debt Disclosure [Abstract]
2017 (April 1 - December 31)	$ 0
Debt Maturities 2018	0
Debt Maturities 2019	0
Debt Maturities 2020	751.3
Debt Maturities 2021	138.4
Debt Maturities 2022	0
2023 and thereafter	798.4
Total maturities of debt	$ 1,688.1

FAIR VALUE MEASUREMENTS (Narrat

FAIR VALUE MEASUREMENTS (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets And Liabilities Components [Line Items]
Loans to and accounts receivable from the Canadian Entities	$ 49	$ 48.6
Cash equivalents	$ 135	177
Management Estimate of 62% Fe	62.00%
Contingent Liabilities recognized in Consolidated Financials	$ 37.5	37.2
Derivative Asset	59.4	33.1
Derivative Liability	9.1	0.5
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Loans to and accounts receivable from the Canadian Entities	0	0
Cash equivalents	90	177
Contingent Liabilities recognized in Consolidated Financials	0	0
Derivative Asset	0	0
Derivative Liability	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Loans to and accounts receivable from the Canadian Entities	0	0
Cash equivalents	45	0
Contingent Liabilities recognized in Consolidated Financials	0	0
Derivative Asset	0	1.5
Derivative Liability	0	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Loans to and accounts receivable from the Canadian Entities	49	48.6
Cash equivalents	0	0
Contingent Liabilities recognized in Consolidated Financials	37.5	37.2
Derivative Asset	59.4	31.6
Derivative Liability	9.1	0.5
Not Designated as Hedging Instrument [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Derivative asset, fair value	59.4	33.1
Other Current Assets [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Derivative asset, fair value	35.9	21.3
Other Current Assets [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Derivative asset, fair value	$ 23.5	$ 10.3

FAIR VALUE MEASUREMENTS FAIR VA

FAIR VALUE MEASUREMENTS FAIR VALUE MEASUREMENTS (Fair Value of Assets and Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	$ 135	$ 177
Derivative Asset	59.4	33.1
Loans to and accounts receivable from the Canadian Entities	49	48.6
Total Asset	243.4	258.7
Derivative Liability	9.1	0.5
Contingent Liabilities recognized in Consolidated Financials	37.5	37.2
Total Liability	46.6	37.7
Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	90	177
Derivative Asset	0	0
Loans to and accounts receivable from the Canadian Entities	0	0
Total Asset	90	177
Derivative Liability	0	0
Contingent Liabilities recognized in Consolidated Financials	0	0
Total Liability	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	45	0
Derivative Asset	0	1.5
Loans to and accounts receivable from the Canadian Entities	0	0
Total Asset	45	1.5
Derivative Liability	0	0
Contingent Liabilities recognized in Consolidated Financials	0	0
Total Liability	0	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	0	0
Derivative Asset	59.4	31.6
Loans to and accounts receivable from the Canadian Entities	49	48.6
Total Asset	108.4	80.2
Derivative Liability	9.1	0.5
Contingent Liabilities recognized in Consolidated Financials	37.5	37.2
Total Liability	$ 46.6	$ 37.7

FAIR VALUE MEASUREMENTS (Schedu

FAIR VALUE MEASUREMENTS (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans to and accounts receivable from the Canadian Entities	$ 49,000,000	$ 48,600,000
Management Estimate of 62% Fe	62.00%
Contingent Liabilities recognized in Consolidated Financials	$ 37,500,000	37,200,000
Not Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, fair value	59,400,000	33,100,000
Derivative liability, fair value	9,100,000	500,000
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans to and accounts receivable from the Canadian Entities	49,000,000	48,600,000
Contingent Liabilities recognized in Consolidated Financials	$ 37,500,000	37,200,000
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Managements Estimate Of 62% Fee [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Management Estimate of 62% Fe	62.00%
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member] | Managements Estimate Of 62% Fee [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	$ 79
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member] | Hot-Rolled Steel Estimate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	651
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Hot-Rolled Steel Estimate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	575
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Hot-Rolled Steel Estimate [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	520
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Hot-Rolled Steel Estimate [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	630
Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, fair value	23,500,000	10,300,000
Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, fair value	35,900,000	21,300,000
Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Commodity Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, fair value	0	1,500,000
Other Current Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, fair value	9,100,000	500,000
Other Current Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Commodity Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, fair value	$ 0	$ 0

FAIR VALUE MEASUREMENTS (Fair V

FAIR VALUE MEASUREMENTS (Fair Value, Assets and Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance - January 1	$ 80.2	$ 80.7
Total gains (losses)
Included in earnings	42.5	8.2
Settlements	(14.3)	(10)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance - March 31	108.4	78.9
Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date	33.2	3.6
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance - January 1	(37.7)	(135.8)
Total gains (losses)
Included in earnings	(8.9)	(7.9)
Settlements	0	75.7
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance - March 31	(46.6)	(68)
Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date	$ (9.1)	$ (0.8)

FAIR VALUE MEASUREMENTS (Carryi

FAIR VALUE MEASUREMENTS (Carrying Value And Fair Value Of Financial Instruments Disclosure) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Interest Rate Swap [Member]
Long-term debt:
Fair Value Adjustment to Interest Rate Hedge	$ 1.7	$ 1.9
Carrying Value [Member] | Fair Value, Inputs, Level 2 [Member]
Long-term debt:
Total long-term debt, fair value	1,642.9	2,192.6
Carrying Value [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Long-term debt:
Fair Value Adjustment to Interest Rate Hedge	1.7	1.9
Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]
Long-term debt:
Total long-term debt, fair value	1,653.5	2,224.6
Fair Value [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Long-term debt:
Fair Value Adjustment to Interest Rate Hedge	1.7	1.9
Senior Notes [Member] | $540 Million 8.25% 2020 Lien Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Original Face Value	540	540
Senior Notes [Member] | $218.5 Million 8.00% 2020 Lien Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Original Face Value	218.5	218.5
Senior Notes [Member] | $544 Million 7.75% 2020 Lien Notes[Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Original Face Value	544.2	544.2
Senior Notes [Member] | $400 Million 5.90% 2020 Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Original Face Value	400	400
Senior Notes [Member] | Senior Notes One Point Three Billion [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Original Face Value	1,300	1,300
Senior Notes [Member] | $700 Million 4.875% 2021 Senior Note [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Original Face Value	700	700
Senior Notes [Member] | $500 Million 5.75% 2025 Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Original Face Value	500	0
Senior Notes [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 1 [Member] | $540 Million 8.25% 2020 Lien Notes [Member]
Long-term debt:
Total long-term debt, fair value	508.6	506.3
Senior Notes [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 1 [Member] | $544 Million 7.75% 2020 Lien Notes[Member]
Long-term debt:
Total long-term debt, fair value	0	339.1
Senior Notes [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 1 [Member] | $400 Million 5.90% 2020 Senior Notes [Member]
Long-term debt:
Total long-term debt, fair value	88.5	224.5
Senior Notes [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 1 [Member] | Senior Notes One Point Three Billion [Member]
Long-term debt:
Total long-term debt, fair value	414.5	528.4
Senior Notes [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 1 [Member] | $700 Million 4.875% 2021 Senior Note [Member]
Long-term debt:
Total long-term debt, fair value	137.9	308.2
Senior Notes [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 1 [Member] | $500 Million 5.75% 2025 Senior Notes [Member]
Long-term debt:
Total long-term debt, fair value	491.7	0
Senior Notes [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 2 [Member] | $218.5 Million 8.00% 2020 Lien Notes [Member]
Long-term debt:
Total long-term debt, fair value	0	284.2
Senior Notes [Member] | Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] | $540 Million 8.25% 2020 Lien Notes [Member]
Long-term debt:
Total long-term debt, fair value	583.9	595
Senior Notes [Member] | Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] | $544 Million 7.75% 2020 Lien Notes[Member]
Long-term debt:
Total long-term debt, fair value	0	439.7
Senior Notes [Member] | Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] | $400 Million 5.90% 2020 Senior Notes [Member]
Long-term debt:
Total long-term debt, fair value	88.4	219.6
Senior Notes [Member] | Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] | Senior Notes One Point Three Billion [Member]
Long-term debt:
Total long-term debt, fair value	358.9	455.8
Senior Notes [Member] | Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] | $700 Million 4.875% 2021 Senior Note [Member]
Long-term debt:
Total long-term debt, fair value	134.3	283.1
Senior Notes [Member] | Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] | $500 Million 5.75% 2025 Senior Notes [Member]
Long-term debt:
Total long-term debt, fair value	486.3	0
Senior Notes [Member] | Fair Value [Member] | Fair Value, Inputs, Level 2 [Member] | $218.5 Million 8.00% 2020 Lien Notes [Member]
Long-term debt:
Total long-term debt, fair value	0	229.5
Line of Credit [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 2 [Member] | Revolving Credit Facility [Member]
Long-term debt:
Total long-term debt, fair value	0	0
Line of Credit [Member] | Fair Value [Member] | Fair Value, Inputs, Level 2 [Member] | Revolving Credit Facility [Member]
Long-term debt:
Total long-term debt, fair value	$ 0	$ 0

PENSIONS AND OTHER POSTRETIRE59

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension Plans, Defined Benefit [Member]
Definted Benefit Plan Disclosure [Line Items]
Pension Contributions	$ 0	$ 0.3
Other Postretirement Benefit Plans, Defined Benefit [Member]
Definted Benefit Plan Disclosure [Line Items]
OPEB Contributions	$ 0	$ 0

PENSIONS AND OTHER POSTRETIRE60

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Estimated Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 4.8	$ 4.5
Interest cost	7.5	7.5
Expected return on plan assets	(13.5)	(13.7)
Prior service credits	0.6	0.5
Net actuarial loss	5.3	5.3
Net periodic benefit credit to continuing operations	4.7	4.1
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.5	0.4
Interest cost	2.1	2.3
Expected return on plan assets	(4.4)	(4.3)
Prior service credits	(0.7)	(0.9)
Net actuarial loss	1.2	1.4
Net periodic benefit credit to continuing operations	$ (1.3)	$ (1.1)

STOCK COMPENSATION PLANS (Narra

STOCK COMPENSATION PLANS (Narrative) (Details) - 2015 Equity Plan [Member] shares in Millions	3 Months Ended
	Mar. 31, 2017shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of restricted shares granted	0.6
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of restricted shares granted	0.6
2017 to 2019 Performance Period [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Goods And Nonemployee Services Transaction Valuation Method Payout Rate	0.00%
2017 to 2019 Performance Period [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Goods And Nonemployee Services Transaction Valuation Method Payout Rate	200.00%

STOCK COMPENSATION PLANS STOC62

STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Assumptions Utilized to Estimate Fair Value for Performance Share Grants) (Details)	3 Months Ended
	Mar. 31, 2017$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Date Market Price	$ 11.67
Average Expected Term	2 years 10 months 9 days
Expected Volatility	92.10%
Risk-Free Interest Rate	1.51%
Dividend Yield	0.00%
Fair Value	$ 19.69
Fair Value (Percent of Grant Date Market Price)	168.72%

INCOME TAXES (Narrative) (Detai

INCOME TAXES (Narrative) (Details)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Percent	5.40%	6.80%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%

LEASE OBLIGATIONS (Narrative) (

LEASE OBLIGATIONS (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Leases [Abstract]
Operating lease expense	$ 1.7	$ 2.4

LEASE OBLIGATIONS (Future Minim

LEASE OBLIGATIONS (Future Minimum Lease Payments) (Details) $ in Millions	Mar. 31, 2017USD ($)
Capital Leases
2017 (April 1 - December 31)	$ 17.2
2,018	18.8
2,019	10.4
2,020	9.4
2,021	8.7
2022 and thereafter	1.4
Total minimum lease payments	65.9
Amounts representing interest	11.8
Present value of net minimum lease payments	54.1
Operating Leases
2017 (April 1 - December 31)	5.3
2,018	5.8
2,019	3
2,020	2.9
2,021	3
2022 and thereafter	0
Total minimum lease payments	20
Other Current Liabilities [Member]
Capital Leases
Present value of net minimum lease payments	18
Other Liabilities [Member]
Capital Leases
Present value of net minimum lease payments	$ 36.1

ENVIRONMENTAL AND MINE CLOSUR66

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)T	Mar. 31, 2017USD ($)
Accrual for Environmental Loss Contingencies, Period Increase (Decrease)	$ 9.2
Reserve increase (decrease), tons | T	115,000,000
Selenium [Domain]
Accrual for Environmental Loss Contingencies, Period Increase (Decrease)	$ (29.6)
Eastern Canadian Iron Ore [Member] | Owned Or Operating Facilities [Member]
Mine Reclamation and Closing Liability, current and noncurrent	$ 206.8	$ 211

ENVIRONMENTAL AND MINE CLOSUR67

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Summary Of Mine Closure Obligations) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Environmental	$ 2.8	$ 2.8
Environmental Loss Contingency And Mine Reclamation And Closing Liability Current	12.8	12.9
Environmental Loss Contingency And Mine Reclamation And Closing Liability Noncurrent	198.2	193.9
U.S. Iron Ore [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	190.9	187.8
Asia Pacific Iron Ore [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	17.3	16.2
North American Coal [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	208.2	204
Eastern Canadian Iron Ore [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	$ 211	$ 206.8

ENVIRONMENTAL AND MINE CLOSUR68

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Asset Retirement Obligation Disclosure) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Asset Retirement Obligation [Roll Forward]
Asset retirement obligation at beginning of period	$ 204	$ 230.4
Accretion expense	3.6	14
Asset Retirement Obligation, Liabilities Settled	(0.3)	(2.2)
Exchange rate changes	0.9	(0.2)
Revision in estimated cash flows		(38)
Asset retirement obligation at end of period	$ 208.2	$ 204

GOODWILL AND OTHER INTANGIBLE69

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Cost of Sales [Member]
Goodwill [Line Items]
Amortization expense relating to intangible assets	$ 0.6	$ 1.4
U.S. Iron Ore [Member]
Goodwill [Line Items]
Goodwill	$ 2		$ 2

GOODWILL AND OTHER INTANGIBLE70

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Schedule Of Finite-Lived Intangible Assets By Major Class) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	$ 78.7	$ 78.4
Definite lived intangible assets - Accumulated Amortization	(25.1)	(24.6)
Definite lived intangible assets - Net Carrying Amount	53.6	53.8
Permits [Member] | Other Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	78.7	78.4
Definite lived intangible assets - Accumulated Amortization	(25.1)	(24.6)
Definite lived intangible assets - Net Carrying Amount	$ 53.6	$ 53.8

DERIVATIVE INSTRUMENTS (Narrati

DERIVATIVE INSTRUMENTS (Narrative) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Customer Supply Agreement [Member] | Product Revenues [Member]
Derivative [Line Items]
Amount of gain/(loss) recognized in income on derivative	$ 17.8	$ 0.1
Customer Supply Agreement [Member] | Derivative Financial Instruments, Assets [Member]
Derivative [Line Items]
Derivative assets	35.9		$ 21.3
Provisional Pricing Arrangements [Member] | U S Iron Ore And Asia Pacific Iron Ore [Member] | Product Revenues [Member]
Derivative [Line Items]
Amount of gain/(loss) recognized in income on derivative	15.7	$ (1.5)
Provisional Pricing Arrangements [Member] | U S Iron Ore And Asia Pacific Iron Ore [Member] | Derivative Financial Instruments, Assets [Member]
Derivative [Line Items]
Derivative assets	23.5		10.3
Provisional Pricing Arrangements [Member] | U S Iron Ore And Asia Pacific Iron Ore [Member] | Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Derivative liabilities	$ 9.1		$ 0.5

DERIVATIVE INSTRUMENTS (Schedul

DERIVATIVE INSTRUMENTS (Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	$ 59.4	$ 33.1
Derivative liability, fair value	9.1	0.5
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Customer Supply Agreement [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	35.9	21.3
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Customer Supply Agreement [Member] | Derivative Financial Instruments, Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	0	0
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Provisional Pricing Arrangements [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	23.5	10.3
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	9.1	0.5
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Commodity Contract [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	0	1.5
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	$ 0	$ 0

DERIVATIVE INSTRUMENTS (Sched73

DERIVATIVE INSTRUMENTS (Schedule Of Derivatives Not Designated As Hedging Instruments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 32.2	$ (1.6)
Commodity Contract [Member] | Other Nonoperating Income (Expense) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(1.3)	0
Customer Supply Agreements [Member] | Product Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	17.8	(0.1)
Provisional Pricing Arrangements [Member] | Product Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 15.7	$ (1.5)

CAPITAL STOCK (Details)

CAPITAL STOCK (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Feb. 09, 2017
Class of Stock [Line Items]
Common Stock, Shares, Issued	63,250
Net proceeds from issuance of common shares	$ 661.3	$ 0
Shares Issued, Price Per Share			$ 10.75
Extinguishment of Debt, Amount	1,070.8
Secured Debt [Member]
Class of Stock [Line Items]
Extinguishment of Debt, Amount	648.6
Unsecured Debt [Member]
Class of Stock [Line Items]
Extinguishment of Debt, Amount	$ 422.2

SHAREHOLDERS' EQUITY Narrative

SHAREHOLDERS' EQUITY Narrative (Details)	Mar. 31, 2017
Empire [Member]
Noncontrolling Interest, Ownership Percentage by Parent	79.00%
Tilden [Member]
Noncontrolling Interest, Ownership Percentage by Parent	85.00%

SHAREHOLDERS' EQUITY Schedule o

SHAREHOLDERS' EQUITY Schedule of Shareholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Stockholders' Equity Attributable to Parent	$ (830.1)		$ (1,464.3)
Stockholders' Equity Attributable to Noncontrolling Interest	127.1		133.8
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(703)	$ (1,696.7)	(1,330.5)	$ (1,811.6)
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	(28.1)	108
INCOME (LOSS) ATTRIBUTABLE TO NONCONTROLLING INTEREST	(1.7)	8.8
Net Income (Loss)	(29.8)	116.8
Other comprehensive income (loss)	(31.1)	113.7
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	(5)	0.6
Other Comprehensive Income (Loss), Net of Tax	(8)	6.3
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	(37.8)	123.1
Stock and Other Incentive Plans	4	2.9
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		(17)
Undistributed Gains To Noncontrolling Interest		0.5
Cliffs Shareholders Equity [Member]
Stockholders' Equity Attributable to Parent	(830.1)	(1,859.4)	(1,464.3)	(1,981.4)
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	(28.1)	108
Other comprehensive income (loss)	(3)	5.7
TOTAL COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	(31.1)	113.7
Stock and Other Incentive Plans	4	2.9
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		0
Undistributed Gains To Noncontrolling Interest		0
Noncontrolling Interest [Member]
Stockholders' Equity Attributable to Noncontrolling Interest	127.1	162.7	$ 133.8	$ 169.8
INCOME (LOSS) ATTRIBUTABLE TO NONCONTROLLING INTEREST	(1.7)	8.8
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	(5)	0.6
OTHER COMPREHENSIVE LOSS (INCOME) ATTRIBUTABLE TO THE NONCONTROLLING INTEREST	(6.7)	9.4
Stock and Other Incentive Plans	0	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders		(17)
Undistributed Gains To Noncontrolling Interest		(0.5)
Common Stock [Member]
Stock Issued During Period, Value, New Issues	661.3	5.4
Common Stock [Member] | Cliffs Shareholders Equity [Member]
Stock Issued During Period, Value, New Issues	661.3	5.4
Common Stock [Member] | Noncontrolling Interest [Member]
Stock Issued During Period, Value, New Issues	$ 0	$ 0

SHAREHOLDERS' EQUITY Accumulate

SHAREHOLDERS' EQUITY Accumulate Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ (1,330.5)	$ (1,811.6)
Ending Balance	(703)	(1,696.7)
Changes in Pension and Other Post-Retirement Benefits, net of tax [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(260.6)	(241.4)
Other comprehensive income (loss) before reclassifications	3.3	(1.5)
Net loss reclassified from accumulated other comprehensive income (loss)	6.4	6.3
Ending Balance	(250.9)	(236.6)
Unrealized Net Gain (Loss) on Securities, net of tax [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		0.1
Other comprehensive income (loss) before reclassifications		(0.1)
Net loss reclassified from accumulated other comprehensive income (loss)		0
Ending Balance		0
Unrealized Net Gain (Loss) on Foreign Currency Translation [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	239.3	220.7
Other comprehensive income (loss) before reclassifications	(12.7)	4.4
Net loss reclassified from accumulated other comprehensive income (loss)	0	0
Ending Balance	226.6	225.1
Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		2.6
Other comprehensive income (loss) before reclassifications		(3.4)
Net loss reclassified from accumulated other comprehensive income (loss)		0
Ending Balance		(0.8)
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(21.3)	(18)
Other comprehensive income (loss) before reclassifications	(9.4)	(0.6)
Net loss reclassified from accumulated other comprehensive income (loss)	6.4	6.3
Ending Balance	$ (24.3)	$ (12.3)

SHAREHOLDERS' EQUITY Details of

SHAREHOLDERS' EQUITY Details of Accumulated Other Comprehensive Income (Loss) Components (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 6.4	$ 6.3
Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	6.4	6.3
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Prior service credits	(0.1)	(0.4)
Defined Benefit Plan, Amortization of Gains (Losses)	6.5	6.7
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	6.4	6.3
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax	$ 0	$ 0

RELATED PARTIES (Narrative) (De

RELATED PARTIES (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)Facility	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)
Segment Reporting Information [Line Items]
Due to Related Parties, Current			$ 8.7
Trade Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Due from Related Parties, Current	$ 9.1		46.9
Other Current Assets [Member]
Segment Reporting Information [Line Items]
Due from Related Parties, Current	$ 53.8		$ 26.8
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Number of mines (in number of facilities) | Facility	4
Joint Venture Partners [Member] | U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Number of mines (in number of facilities) | Facility	2
Empire [Member] | Arcelor Mittal [Member]
Segment Reporting Information [Line Items]
Subsequent Paid Distributions of Partners' Equity Amounts	$ 8.7	$ 11.1
Recorded Distributions of Partners' Equity Amounts		$ 17

RELATED PARTIES (Summary Of Oth

RELATED PARTIES (Summary Of Other Ownership Interests) (Details)	Mar. 31, 2017
Hibbing [Member] | Arcelor Mittal [Member]
Related Party Transaction [Line Items]
Ownership interest, equity method investment	62.30%
Hibbing [Member] | U. S. Steel Canada [Member]
Related Party Transaction [Line Items]
Ownership interest, equity method investment	14.70%
Empire [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent	79.00%
Empire [Member] | Arcelor Mittal [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	21.00%
Empire [Member] | U. S. Steel Canada [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	0.00%
Tilden [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent	85.00%
Tilden [Member] | Arcelor Mittal [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	0.00%
Tilden [Member] | U. S. Steel Canada [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	15.00%
Other Noncurrent Assets [Member] | Hibbing [Member]
Related Party Transaction [Line Items]
Ownership interest, equity method investment	23.00%

RELATED PARTIES (Summary Of Rel

RELATED PARTIES (Summary Of Related Party Transactions Table Disclosure) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Related Party Transactions [Abstract]
Product revenues from related parties	$ 118.5	$ 103.4
Product	$ 412.8	$ 275.6
Related party product revenue as a percent of total product revenue	28.70%	37.50%

EARNINGS PER SHARE EARNINGS PER

EARNINGS PER SHARE EARNINGS PER SHARE (Narrative) (Details) shares in Millions	3 Months Ended
	Mar. 31, 2017shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements	4.6

EARNINGS PER SHARE (Earnings Pe

EARNINGS PER SHARE (Earnings Per Share Computation) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Income (Loss) from Continuing Operations	$ (30.3)	$ 114.3
Loss (Income) from Continuing Operations Attributable to Noncontrolling Interest	1.7	(8.8)
Net Income (Loss) from Continuing Operations Attributable to Cliffs Shareholders	(28.6)	105.5
Income from Discontinued Operations, net of tax	0.5	2.5
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$ (28.1)	$ 108
Weighted Average Number of Shares:
Basic	265.2	171.7
Employee Stock Plans	0	0.3
Diluted	265.2	172
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Basic:
Continuing operations (in dollars per share)	$ (0.11)	$ 0.61
Discontinued operations (in dollars per share)	0	0.01
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Basic (in dollars per share)	(0.11)	0.62
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted:
Continuing operations (in dollars per share)	(0.11)	0.61
Discontinued operations (in dollars per share)	0	0.01
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted (in dollars per share)	$ (0.11)	$ 0.62

COMMITMENTS AND CONTINGENCIES N

COMMITMENTS AND CONTINGENCIES Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Loans to and accounts receivable from the Canadian Entities	$ 49	$ 48.6
Contingent Liabilities recognized in Consolidated Financials	37.5	37.2
Michigan Electricity Matters [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual	13.6
Fair Value, Inputs, Level 3 [Member]
Loss Contingencies [Line Items]
Loans to and accounts receivable from the Canadian Entities	49	48.6
Contingent Liabilities recognized in Consolidated Financials	$ 37.5	$ 37.2

SUBSEQUENT EVENTS SUBSEQUENT EV

SUBSEQUENT EVENTS SUBSEQUENT EVENTS (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Mar. 31, 2016	Apr. 24, 2017
Subsequent Event [Line Items]
Gain (loss) on extinguishment/restructuring of debt		$ (71.9)	$ 178.8
Equity Claw Redemption [Domain]
Subsequent Event [Line Items]
Gain (loss) on extinguishment/restructuring of debt	$ 5
Debt Instrument, Repurchase Amount				$ 35.6