Cleveland-Cliffs (CLF) 10-Q 27 Jul 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Jul. 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	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		296,506,003
Trading Symbol	clf

Statements Of Condensed Consoli

Statements Of Condensed Consolidated Financial Position - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
CURRENT ASSETS
Cash and cash equivalents	$ 321.5	$ 323.4
Accounts receivable, net	76.7	128.7
Inventories	287.6	178.4
Supplies and other inventories	83.6	91.4
Loans to and accounts receivable from the Canadian Entities	50.1	48.6
Other current assets	88.8	54.1
TOTAL CURRENT ASSETS	908.3	824.6
PROPERTY, PLANT AND EQUIPMENT, NET	999.1	984.4
OTHER ASSETS
OTHER NON-CURRENT ASSETS	122.7	114.9
TOTAL ASSETS	2,030.1	1,923.9
CURRENT LIABILITIES
Accounts payable	111.7	107.6
Accrued expenses	112.8	123.3
Interest Payable, Current	30.7	40.2
Contingent claims	50	0
Other current liabilities	108.1	120
TOTAL CURRENT LIABILITIES	413.3	391.1
PENSION AND POSTEMPLOYMENT BENEFIT LIABILITIES	276.1	280.5
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	201.9	193.9
LONG-TERM DEBT	1,611.8	2,175.1
OTHER LIABILITIES	193.7	213.8
TOTAL LIABILITIES	2,696.8	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	3,999.7	3,347
Retained deficit	(4,570.6)	(4,574.3)
Cost of 5,390,473 common shares in treasury (2016 - 5,562,703 shares)	(236.5)	(245.5)
Accumulated other comprehensive loss	(19.4)	(21.3)
TOTAL CLIFFS SHAREHOLDERS' DEFICIT	(789.1)	(1,464.3)
NONCONTROLLING INTEREST	122.4	133.8
TOTAL DEFICIT	(666.7)	(1,330.5)
TOTAL LIABILITIES AND DEFICIT	$ 2,030.1	$ 1,923.9

Statements Of Condensed Consol3

Statements Of Condensed Consolidated Financial Position (Parenthetical) - $ / shares	Jun. 30, 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)	600,000,000	400,000,000
Common shares, issued (in shares)	301,886,794	238,636,794
Common shares, outstanding	296,496,321	233,074,091
Common shares in treasury	5,390,473	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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
REVENUES FROM PRODUCT SALES AND SERVICES
Product	$ 512	$ 452.8	$ 924.8	$ 728.4
Freight and venture partners' cost reimbursements	57.3	43.4	106.1	73.3
TOTAL REVENUES	569.3	496.2	1,030.9	801.7
COST OF GOODS SOLD AND OPERATING EXPENSES	(424.2)	(404.7)	(790.1)	(679.3)
SALES MARGIN	145.1	91.5	240.8	122.4
OTHER OPERATING INCOME (EXPENSE)
Selling, general and administrative expenses	(27.5)	(22.5)	(53.2)	(50.7)
Miscellaneous - net	(3)	5.7	8.9	2.7
Other operating expense	(30.5)	(16.8)	(44.3)	(48)
OPERATING INCOME	114.6	74.7	196.5	74.4
OTHER INCOME (EXPENSE)
Interest expense, net	(31.4)	(50.7)	(74.2)	(107.5)
Gain (loss) on extinguishment/restructuring of debt	(4.9)	3.6	(76.8)	182.4
Other non-operating income	0.8	0.2	1.5	0.3
TOTAL OTHER INCOME (EXPENSE)	(35.5)	(46.9)	(149.5)	75.2
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	79.1	27.8	47	149.6
INCOME TAX BENEFIT (EXPENSE)	(2.6)	2.1	(0.8)	(5.4)
INCOME FROM CONTINUING OPERATIONS	76.5	29.9	46.2	144.2
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAX	(46.4)	(0.4)	(45.9)	2.1
NET INCOME	30.1	29.5	0.3	146.3
LOSS (INCOME) ATTRIBUTABLE TO NONCONTROLLING INTEREST	1.7	(16.7)	3.4	(25.5)
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$ 31.8	$ 12.8	$ 3.7	$ 120.8
EARNINGS (LOSS) PER COMMON SHARE ATTRIBUTABLE TO CLIFFS SHAREHOLDERS - BASIC
Continuing operations (in dollars per share)	$ 0.26	$ 0.07	$ 0.18	$ 0.67
Discontinued operations (in dollars per share)	(0.16)	0	(0.16)	0.01
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Basic (in dollars per share)	0.10	0.07	0.02	0.68
EARNINGS (LOSS) PER COMMON SHARE ATTRIBUTABLE TO CLIFFS SHAREHOLDERS - DILUTED
Continuing operations (in dollars per share)	0.26	0.07	0.17	0.67
Discontinued operations (in dollars per share)	(0.15)	0	(0.16)	0.01
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted (in dollars per share)	$ 0.11	$ 0.07	$ 0.01	$ 0.68
AVERAGE NUMBER OF SHARES (IN THOUSANDS)
Basic	296.1	182.3	280.6	177
Diluted	300.7	184.6	285.2	178.3

Statements Of Condensed Consol5

Statements Of Condensed Consolidated Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$ 31.8	$ 12.8	$ 3.7	$ 120.8
OTHER COMPREHENSIVE INCOME (LOSS)
Changes in pension and other post-retirement benefits, net of tax	6.7	6.5	11.4	11.9
Unrealized net gain (loss) on foreign currency translation	(1.4)	(2.7)	(14.1)	1.7
Unrealized net gain (loss) on derivative financial instruments, net of tax	0	0.2	0	(3.3)
OTHER COMPREHENSIVE INCOME (LOSS)	5.3	4	(2.7)	10.3
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	0.4	0.7	(4.6)	1.3
Other comprehensive income (loss)	$ 36.7	$ 16.1	$ 5.6	$ 129.8

Statements Of Condensed Consol6

Statements Of Condensed Consolidated Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
OPERATING ACTIVITIES
NET INCOME	$ 0.3	$ 146.3
Adjustments to reconcile net income to net cash provided (used) by operating activities:
Depreciation, depletion and amortization	44.8	62.1
(Gain) loss on extinguishment/restructuring of debt	76.8	(182.4)
(Gain) loss on deconsolidation, net of cash deconsolidated	48.6	(4.1)
Other	(8.3)	5.2
Changes in operating assets and liabilities:
Receivables and other assets	68.3	103.6
Inventories	(106.6)	(52.2)
Payables, accrued expenses and other liabilities	(56.1)	(97.8)
Net cash provided (used) by operating activities	67.8	(19.3)
INVESTING ACTIVITIES
Purchase of property, plant and equipment	(49.4)	(20.2)
Other investing activities	1.1	5.9
Net cash used by investing activities	(48.3)	(14.3)
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	(1,154)	0
Distributions of partnership equity	(8.7)	(28.1)
Repayment of equipment loans	0	(95.6)
Borrowings under credit facilities	0	105
Repayment under credit facilities	0	(105)
Other financing activities	(13.9)	(13.6)
Net cash used by financing activities	(23.8)	(142.5)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	2.4	(0.9)
DECREASE IN CASH AND CASH EQUIVALENTS	(1.9)	(177)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	323.4	285.2
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 321.5	$ 108.2

BASIS OF PRESENTATION AND SIGNI

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 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 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 and six months ended June 30, 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 June 30, 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 June 30, 2017 and December 31, 2016 , our investment in Hibbing was $6.5 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 our Australian 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. 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, including short-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 and six months ended June 30, 2017 and 2016: (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Remeasurement of short-term intercompany loans $ 1.5 $ (0.1 ) $ 16.6 $ 0.2 Remeasurement of cash and cash equivalents (0.5 ) 0.5 (1.7 ) 1.5 Other remeasurement (1.0 ) (0.2 ) (1.3 ) (2.6 ) Net impact of transaction gains and (losses) resulting from remeasurement — 0.2 13.6 (0.9 ) 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): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. 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 No. 2017-07 will impact Statements of Unaudited Condensed Consolidated Operations by changing our classification of the components of pension and OPEB costs; however, it will not impact our Net Income . In February 2016, the FASB issued ASU No. 2016-02, Leases. The new standard requires lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases with the exception of short-term leases. For lessees, leases will continue to be classified as either operating or finance leases in the income statement. The effective date of the new standard for public companies is for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. Early adoption is permitted. The new standard must be adopted using a modified retrospective transition and requires application of the new guidance at the beginning of the earliest comparative period presented. We are currently evaluating the effect the updated standard will have on our consolidated financial statements and related disclosures. Based on our analysis to date, we anticipate the largest impact will be the balance sheet recognition of operating leases. In May 2014, the FASB issued ASU No. 2014-09, Revenues from Contracts with Customers. The new revenue guidance broadly replaces the revenue guidance provided throughout the Codification. The core principle of the revenue guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve that core principle, an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract and (5) recognize revenue when (or as) the entity satisfies a performance obligation. Reporting entities must prepare new disclosures providing qualitative and quantitative information on the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. New disclosures also include qualitative and quantitative information on significant judgments, changes in judgments, and contract acquisition assets. At issuance, ASU No. 2014-09 was effective starting in 2017 for calendar-year public entities, and interim periods within that year. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers: Deferral of the Effective Date, which defers the adoption of ASU No. 2014-09 to annual reporting periods beginning after December 15, 2017, including interim reporting periods within that reporting period. Earlier application is permitted. As of June 30, 2017, we have completed the initial evaluation of the new standard and the related review and assessment of a representative sample of existing contracts with our customers. We determined, on a preliminary basis, that the timing and pattern of revenue recognition for our U.S. Iron Ore contracts will likely change; however, the total amount of revenue recognized during the year should remain substantially the same as under current GAAP. We do not anticipate any significant changes in the timing and pattern of revenue recognition for our Asia Pacific Iron Ore contracts. We anticipate utilizing the modified retrospective transition method. Based on our analysis to date, we anticipate the primary impact of the adoption on our consolidated financial statements will be the additional required disclosures around revenue recognition in the notes to the consolidated financial statements.

SEGMENT REPORTING

SEGMENT REPORTING	6 Months Ended
	Jun. 30, 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 six months of 2017 or 2016. We evaluate 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 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 and six months ended June 30, 2017 and 2016 , including a reconciliation of segment sales margin to Income from Continuing Operations Before Income Taxes and a reconciliation of Net Income to EBITDA and Adjusted EBITDA: (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Revenues from product sales and services: U.S. Iron Ore $ 471.3 83 % $ 361.7 73 % $ 757.5 73 % $ 547.2 68 % Asia Pacific Iron Ore 98.0 17 % 134.5 27 % 273.4 27 % 254.5 32 % Total revenues from product sales and services $ 569.3 100 % $ 496.2 100 % $ 1,030.9 100 % $ 801.7 100 % Sales margin: U.S. Iron Ore $ 144.2 $ 70.0 $ 192.6 $ 83.2 Asia Pacific Iron Ore 0.9 21.5 48.2 39.2 Sales margin 145.1 91.5 240.8 122.4 Other operating expense (30.5 ) (16.8 ) (44.3 ) (48.0 ) Other income (expense) (35.5 ) (46.9 ) (149.5 ) 75.2 Income from continuing operations before income taxes $ 79.1 $ 27.8 $ 47.0 $ 149.6 (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Net Income $ 30.1 $ 29.5 $ 0.3 $ 146.3 Less: Interest expense, net (31.4 ) (50.7 ) (74.2 ) (107.5 ) Income tax benefit (expense) (2.6 ) 2.1 (0.8 ) (5.4 ) Depreciation, depletion and amortization (21.6 ) (26.9 ) (44.8 ) (62.1 ) EBITDA $ 85.7 $ 105.0 $ 120.1 $ 321.3 Less: Gain (loss) on extinguishment/restructuring of debt (4.9 ) 3.6 (76.8 ) 182.4 Foreign exchange remeasurement — 0.2 13.6 (0.9 ) Impact of discontinued operations (46.4 ) (0.4 ) (45.9 ) 2.1 Severance and contractor termination costs — — — (0.1 ) Adjusted EBITDA $ 137.0 $ 101.6 $ 229.2 $ 137.8 EBITDA: U.S. Iron Ore $ 155.0 $ 94.1 $ 212.9 $ 135.5 Asia Pacific Iron Ore 1.2 26.1 52.6 48.4 Other (70.5 ) (15.2 ) (145.4 ) 137.4 Total EBITDA $ 85.7 $ 105.0 $ 120.1 $ 321.3 Adjusted EBITDA: U.S. Iron Ore $ 161.5 $ 97.2 $ 225.6 $ 143.3 Asia Pacific Iron Ore 3.0 26.5 56.8 49.5 Other (27.5 ) (22.1 ) (53.2 ) (55.0 ) Total Adjusted EBITDA $ 137.0 $ 101.6 $ 229.2 $ 137.8 (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Depreciation, depletion and amortization: U.S. Iron Ore $ 16.7 $ 19.4 $ 33.1 $ 46.3 Asia Pacific Iron Ore 3.3 6.1 8.0 12.9 Other 1.6 1.4 3.7 2.9 Total depreciation, depletion and amortization $ 21.6 $ 26.9 $ 44.8 $ 62.1 Capital additions: U.S. Iron Ore $ 24.6 $ 9.2 $ 51.7 $ 13.7 Asia Pacific Iron Ore 0.6 — 0.8 — Other — 2.1 — 4.4 Total capital additions 1 $ 25.2 $ 11.3 $ 52.5 $ 18.1 1 Includes cash paid for capital additions of $49.4 million and $20.2 million and an increase in non-cash accruals of $3.1 million and a decrease in non-cash accruals of $2.1 million for the six months ended June 30, 2017 and 2016, respectively. A summary of assets by segment is as follows: (In Millions) June 30, December 31, Assets: U.S. Iron Ore $ 1,525.9 $ 1,372.5 Asia Pacific Iron Ore 157.7 155.1 Total segment assets 1,683.6 1,527.6 Corporate 346.5 396.3 Total assets $ 2,030.1 $ 1,923.9

INVENTORIES

INVENTORIES	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : (In Millions) June 30, 2017 December 31, 2016 Segment Finished Goods Work-in Process Total Inventory Finished Goods Work-in Process Total Inventory U.S. Iron Ore $ 238.3 $ 14.3 $ 252.6 $ 124.4 $ 12.6 $ 137.0 Asia Pacific Iron Ore 22.7 12.3 35.0 23.6 17.8 41.4 Total $ 261.0 $ 26.6 $ 287.6 $ 148.0 $ 30.4 $ 178.4

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : (In Millions) June 30, December 31, Land rights and mineral rights $ 500.7 $ 500.5 Office and information technology 66.0 65.1 Buildings 71.8 67.9 Mining equipment 600.1 592.2 Processing equipment 621.5 552.0 Electric power facilities 54.0 49.4 Land improvements 23.8 23.5 Asset retirement obligation 19.7 19.8 Other 28.7 28.1 Construction in-progress 19.8 42.8 2,006.1 1,941.3 Allowance for depreciation and depletion (1,007.0 ) (956.9 ) $ 999.1 $ 984.4 We recorded depreciation and depletion expense of $21.2 million and $43.8 million in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2017 , respectively. This compares with depreciation and depletion expense of $25.7 million and $59.5 million for the three and six months ended June 30, 2016 , respectively.

DEBT AND CREDIT FACILITIES

DEBT AND CREDIT FACILITIES	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : (In Millions) June 30, 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% $ 504.4 $ (6.3 ) $ (20.7 ) $ 477.4 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 (8.1 ) — 491.9 $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 1.6 Long-term debt $ 1,611.8 (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 of $8.5 million were incurred related to the offering of the 5.75% Senior Notes, $8.1 million of which is included in Long-term debt in the Statements of Unaudited Condensed Consolidated Financial Position as of June 30, 2017 . Debt Extinguishment The following is a summary of the debt extinguished during the six months ended June 30, 2017 and the respective gain (loss) on extinguishment for the three and six months ended June 30, 2017 : (In Millions) Gain (Loss) on Extinguishment 1 Debt Extinguished Three Months Ended Six Months Ended Secured Notes $540 Million 8.25% 2020 First Lien Notes $ 35.6 $ (4.9 ) $ (4.9 ) $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 ) $ 1,106.4 $ (4.9 ) $ (76.8 ) 1 Includes write-off of undiscounted interest, unamortized discounts and debt issuance costs. In addition, this includes premiums paid of $2.9 million and $47.6 million related to the redemption of our notes for the three and six months ended June 30, 2017, respectively. Debt Maturities The following represents a summary of our maturities of debt instruments, excluding borrowings under the ABL Facility, based on the principal amounts outstanding at June 30, 2017 : (In Millions) Maturities of Debt 2017 (July 1 - December 31) $ — 2018 — 2019 — 2020 715.7 2021 138.4 2022 — 2023 and thereafter 798.4 Total maturities of debt $ 1,652.5 ABL Facility As of June 30, 2017 and December 31, 2016 , no loans were drawn under the ABL Facility and we had total availability of $296.6 million and $333.0 million , respectively, as a result of borrowing base limitations. As of June 30, 2017 and December 31, 2016 , the principal amount of letter of credit obligations totaled $82.5 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 $214.1 million and $227.0 million , respectively.

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : (In Millions) June 30, 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 $ 40.0 $ 120.0 $ — $ 160.0 Derivative assets — — 72.5 72.5 Total $ 40.0 $ 120.0 $ 72.5 $ 232.5 Liabilities: Derivative liabilities $ — $ — $ 20.8 $ 20.8 Total $ — $ — $ 20.8 $ 20.8 (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 Total $ 177.0 $ 1.5 $ 31.6 $ 210.1 Liabilities: Derivative liabilities $ — $ — $ 0.5 $ 0.5 Total $ — $ — $ 0.5 $ 0.5 Financial assets classified in Level 1 as of June 30, 2017 and December 31, 2016 include money market funds of $40.0 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 $120.0 million of commercial paper and $1.5 million of commodity hedge contracts at June 30, 2017 and December 31, 2016 , respectively. The Level 3 assets include derivative assets that 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. The supply agreements included in our Level 3 assets/liabilities include provisions for supplemental revenue or refunds based on the customer’s annual steel pricing or the average annual daily market price for hot-rolled coil steel at the time the product is consumed in the customer’s blast furnaces. We account for these provisions as derivative instruments at the time of sale and adjust these provisions 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 instruments are determined using a market approach with one supply agreement based on an estimate of the annual realized price of hot-rolled coil steel at the steelmaker’s facilities and the other supply agreement based on the estimate of the average annual daily market price for hot-rolled coil steel. Both estimates take into consideration current market conditions and nonperformance risk. We had assets of $66.4 million and $21.3 million at June 30, 2017 and December 31, 2016 , respectively, related to supply agreements. The provisional pricing arrangements included in our Level 3 assets/liabilities specify provisional price calculations, where the pricing mechanisms generally are based on market pricing, with the final revenue rate to be based on market inputs at a specified point in time in the future, per the terms of the supply agreements. The difference between the estimated final revenue at the date of sale and the estimated final revenue rate at the measurement date is characterized as a derivative and is required to be accounted for separately once 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 $6.1 million and $10.3 million at June 30, 2017 and December 31, 2016 , respectively, related to provisional pricing arrangements. In addition, we have liabilities of $20.8 million and $0.5 million related to provisional pricing arrangements at June 30, 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 June 30, 2017 Balance Sheet Location Valuation Technique Unobservable Input Range or Point Estimate (Weighted Average) Provisional pricing arrangements $ 6.1 Other current assets Market Approach Management's Estimate of Platts 62% Price per dry metric ton $60 - $75 Market Hot-Rolled Coil Steel Estimate $580 - $660 Provisional pricing arrangements $ 20.8 Other current liabilities Market Approach Management's Estimate of Platts 62% Price per dry metric ton $60 - $75 Customer supply agreements $ 66.4 Other current assets Market Approach Customer Hot-Rolled Steel Estimate $541 - $630 Market Hot-Rolled Coil Steel Estimate $580 - $660 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 average annual daily steel market price for hot-rolled coil steel, 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 inputs used in the fair value measurement of our customer supply agreements are the customer's future hot-rolled coil steel price that is estimated based on projections provided by the customer, analysts' projections and estimates determined by management, and the average annual daily market price for hot-rolled coil steel, 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. 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 and no transfers into or out of Level 3 of the fair value hierarchy during the three and six months ended June 30, 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 and six months ended June 30, 2017 and 2016 . (In Millions) Level 3 Assets Three Months Ended Six Months Ended 2017 2016 2017 2016 Beginning balance $ 59.4 $ 9.0 $ 31.6 $ 7.8 Total gains (losses) Included in earnings 53.3 34.5 95.4 45.7 Settlements (40.2 ) (17.7 ) (54.5 ) (27.7 ) Ending balance - June 30 $ 72.5 $ 25.8 $ 72.5 $ 25.8 Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date $ 20.1 $ 21.6 $ 53.3 $ 21.9 (In Millions) Level 3 Liabilities Three Months Ended Six Months Ended 2017 2016 2017 2016 Beginning balance $ (9.1 ) $ (6.2 ) $ (0.5 ) $ (3.4 ) Total gains (losses) Included in earnings (36.8 ) (2.8 ) (45.5 ) (8.4 ) Settlements 25.1 6.4 25.2 9.2 Ending balance - June 30 $ (20.8 ) $ (2.6 ) $ (20.8 ) $ (2.6 ) Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date $ (11.7 ) $ (0.7 ) $ (20.8 ) $ (2.6 ) Gains and losses from derivative assets and liabilities are included in earnings and are reported in Product revenues for the three and six months ended June 30, 2017 and 2016 . The carrying amount of 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 June 30, 2017 and December 31, 2016 were as follows: (In Millions) June 30, 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 $ 477.4 $ 550.0 $ 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 1 491.9 473.8 — — Senior Notes—$400 million Level 1 88.5 86.0 224.5 219.6 Senior Notes—$1.3 billion Level 1 414.5 339.7 528.4 455.8 Senior Notes—$700 million Level 1 137.9 131.6 308.2 283.1 ABL Facility Level 2 — — — — Fair value adjustment to interest rate hedge Level 2 1.6 1.6 1.9 1.9 Total long-term debt $ 1,611.8 $ 1,582.7 $ 2,192.6 $ 2,224.6 The fair value of long-term debt was determined using quoted market prices based upon current borrowing rates. Items Measured at Fair Value on a Non-Recurring Basis The following tables present information about the financial assets and liabilities that were measured on a fair value basis at June 30, 2017 and December 31, 2016 for the Canadian Entities. The tables also indicate the fair value hierarchy of the valuation techniques used to determine such fair value. (In Millions) June 30, 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 Total Gains Assets: Loans to and accounts receivables from the Canadian Entities $ — $ — $ 50.1 $ 50.1 $ 1.5 Liabilities: Guarantees $ — $ — $ 38.5 $ 38.5 $ 1.3 (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 Total Gains (Losses) Assets: Loans to and accounts receivables from the Canadian Entities $ — $ — $ 48.6 $ 48.6 $ (17.5 ) Liabilities: Guarantees $ — $ — $ 37.2 $ 37.2 $ 0.4 We determined the fair value and recoverability of our Canadian investments by comparing the estimated fair value of the remaining underlying assets of the Canadian Entities to remaining estimated liabilities. We recorded the guarantees at book value, which best approximated fair value. 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. Our estimates involve significant judgment and are based on currently available information, an assessment of the validity of certain claims and estimated payments made by the Canadian Entities. Our ultimate recovery is subject to the final liquidation value of the Canadian Entities. Further, the final liquidation value and ultimate recovery of the creditors of the Canadian Entities, including, if any, to Cliffs and various subsidiaries, may impact our estimates of liability exposure described previously.

PENSIONS AND OTHER POSTRETIREME

PENSIONS AND OTHER POSTRETIREMENT BENEFITS	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 2017 and 2016 : Defined Benefit Pension Costs (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Service cost $ 4.7 $ 4.5 $ 9.5 $ 9.0 Interest cost 7.5 7.5 15.0 14.9 Expected return on plan assets (13.6 ) (13.7 ) (27.1 ) (27.4 ) Amortization: Prior service costs 0.7 0.5 1.3 1.1 Net actuarial loss 5.3 5.3 10.6 10.5 Net periodic benefit cost $ 4.6 $ 4.1 $ 9.3 $ 8.1 Other Postretirement Benefits Credit (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Service cost $ 0.5 $ 0.4 $ 1.0 $ 0.9 Interest cost 2.2 2.3 4.3 4.5 Expected return on plan assets (4.5 ) (4.3 ) (8.9 ) (8.5 ) Amortization: Prior service credits (0.8 ) (0.9 ) (1.5 ) (1.8 ) Net actuarial loss 1.3 1.4 2.5 2.8 Net periodic benefit credit $ (1.3 ) $ (1.1 ) $ (2.6 ) $ (2.1 ) We made pension contributions of $2.3 million for the three and six months ended June 30, 2017 . We made no contributions for the three months ended June 30, 2016 and $0.3 million for the six months ended June 30, 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 and six months ended June 30, 2017 and June 30, 2016 .

STOCK COMPENSATION PLANS

STOCK COMPENSATION PLANS	6 Months Ended
	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Compensation Plans	NOTE 8 - STOCK COMPENSATION PLANS Employees’ Plans On June 26, 2017, the Compensation and Organization Committee of the Board of Directors approved a grant under the A&R 2015 Equity Plan to the Chief Executive Officer for the performance period commencing June 1, 2017 and ending December 31, 2019. Shares granted under the awards consisted of 0.5 million restricted share units and 0.2 million performance shares. On February 21, 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. Restricted share units granted during 2017 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 Compensation and Organization Committee at its discretion. Performance shares are subject to continued employment, and each performance share, if earned, entitles the holder to receive common shares 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 the performance period. 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 the period of June 1, 2017 to December 31, 2019, for the February 21, 2017 and the June 26, 2017 grants, respectively, and measured against the constituents of the S&P Metals and Mining ETF Index and the SPDR S&P Metals and Mining ETF Index, respectively, at the beginning of the relevant performance period. The final payout 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 plan 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 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% June 26, 2017 $ 6.64 2.51 92.8% 1.45% —% $ 10.74 161.75%

INCOME TAXES

INCOME TAXES	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 9 - INCOME TAXES Our 2017 estimated annual effective tax rate before discrete items is approximately 1.3% . 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 June 30, 2016 was 3.1% .

LEASE OBLIGATIONS

LEASE OBLIGATIONS	6 Months Ended
	Jun. 30, 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 $1.8 million and $ 3.5 million for the three and six months ended June 30, 2017 , compared with $2.2 million and $ 4.6 million for the comparable periods in 2016 . Future minimum payments under capital leases and non-cancellable operating leases at June 30, 2017 are as follows: (In Millions) Capital Leases Operating Leases 2017 (July 1 - December 31) $ 11.7 $ 3.6 2018 18.9 5.8 2019 10.5 2.9 2020 9.5 2.9 2021 8.8 3.0 2022 and thereafter 0.6 — Total minimum lease payments $ 60.0 $ 18.2 Amounts representing interest 10.0 Present value of net minimum lease payments 1 $ 50.0 1 The total is comprised of $17.4 million and $32.6 million classified as Other current liabilities and Other liabilities , respectively, in the Statements of Unaudited Condensed Consolidated Financial Position at June 30, 2017.

ENVIRONMENTAL AND MINE CLOSURE

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	6 Months Ended
	Jun. 30, 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 $214.1 million and $206.8 million at June 30, 2017 and December 31, 2016 , respectively. The following is a summary of the obligations as of June 30, 2017 and December 31, 2016 : (In Millions) June 30, December 31, Environmental $ 2.8 $ 2.8 Mine closure U.S. Iron Ore 1 193.6 187.8 Asia Pacific Iron Ore 17.7 16.2 Total mine closure 211.3 204.0 Total environmental and mine closure obligations 214.1 206.8 Less current portion 12.2 12.9 Long-term environmental and mine closure obligations $ 201.9 $ 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 six months ended June 30, 2017 and for the year ended December 31, 2016 : (In Millions) June 30, December 31, 2016 Asset retirement obligation at beginning of period $ 204.0 $ 230.4 Accretion expense 7.1 14.0 Remediation payments (0.8 ) (2.2 ) Exchange rate changes 1.0 (0.2 ) Revision in estimated cash flows — (38.0 ) Asset retirement obligation at end of period $ 211.3 $ 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	6 Months Ended
	Jun. 30, 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 June 30, 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 definite-lived intangible assets as of June 30, 2017 and December 31, 2016 : (In Millions) June 30, 2017 December 31, 2016 Classification Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Permits Other non-current assets $ 78.8 $ (25.6 ) $ 53.2 $ 78.4 $ (24.6 ) $ 53.8 Amortization expense relating to intangible assets was $0.4 million and $1.0 million for the three and six months ended June 30, 2017 and is recognized in Cost of goods sold and operating expenses in the Statements of Unaudited Condensed Consolidated Operations . Amortization expense relating to other intangible assets was $1.2 million and $2.6 million for the comparable periods in 2016 . Amortization expense of other intangible assets is expected to continue to be immaterial going forward.

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : (In Millions) Derivative Assets Derivative Liabilities June 30, 2017 December 31, 2016 June 30, 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 agreements Other current assets 66.4 Other current assets 21.3 — — Provisional pricing arrangements Other current assets 6.1 Other current assets 10.3 Other current liabilities 20.8 Other current liabilities 0.5 Commodity contracts — Other current assets 1.5 — — Total derivatives not designated as hedging instruments under ASC 815 $ 72.5 $ 33.1 $ 20.8 $ 0.5 Derivatives Not Designated as Hedging Instruments Customer Supply Agreements Certain supply agreements with one U.S. Iron Ore customer provide for supplemental revenue or refunds to the customer based on the customer’s average annual steel pricing or based on the average annual daily steel market price for hot-rolled coil steel 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 $51.4 million and $ 69.2 million net gain in Product revenues in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2017 , respectively, related to the supplemental payments. This compares with a net gain in Product revenues of $19.5 million and $ 19.9 million for the comparable periods in 2016 . Other current assets , representing the fair value of the supplemental revenue, were $66.4 million and $21.3 million as of June 30, 2017 and December 31, 2016 in the 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. The market inputs are tied to indexed price adjustment factors that are integral to the iron ore supply contracts and vary based on the agreement. The pricing mechanisms typically include adjustments based upon changes in the Platts 62% Price, 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. 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 June 30, 2017 , we recorded $6.1 million as Other current assets and $20.8 million as Other current liabilities related to our estimate of the final revenue rate with our U.S. Iron Ore and Asia Pacific Iron Ore customers in the Statements of Unaudited Condensed Consolidated Financial Position . At December 31, 2016 , we recorded $10.3 million as Other current assets and $0.5 million as Other current liabilities related to our estimate of the final revenue rate with our U.S. Iron Ore and Asia Pacific Iron Ore customers in the Statements of Unaudited Condensed Consolidated Financial Position . 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 decrease of $35.4 million and $ 19.8 million in Product revenues in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2017 , respectively, related to these arrangements. This compares with a net increase of $1.8 million and $ 0.3 million in Product revenues for the comparable periods in 2016 , respectively. 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 and six months ended June 30, 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 Six Months Ended 2017 2016 2017 2016 Customer Supply Agreements Product revenues 51.9 19.5 69.6 19.9 Provisional Pricing Arrangements Product revenues (35.4 ) 1.8 (19.8 ) 0.3 Commodity Contracts Cost of goods sold and operating expenses — — (1.3 ) — Total $ 16.5 $ 21.3 $ 48.5 $ 20.2 Refer to NOTE 6 - FAIR VALUE MEASUREMENTS for additional information.

CAPITAL STOCK

CAPITAL STOCK	6 Months Ended
	Jun. 30, 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 issuance of $500 million aggregate principal amount of 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 aggregate principal amount of 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. During the second quarter of 2017, we redeemed $35.6 million aggregate principal amount of the 8.25% First Lien Notes due 2020 with the remaining net proceeds from our common share offering.

SHAREHOLDERS' EQUITY

SHAREHOLDERS' EQUITY	6 Months Ended
	Jun. 30, 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 six months ended June 30, 2017 and June 30, 2016 : (In Millions) Cliffs Noncontrolling Interest (Deficit) Total Equity (Deficit) December 31, 2016 $ (1,464.3 ) $ 133.8 $ (1,330.5 ) Comprehensive loss Net income (loss) 3.7 (3.4 ) 0.3 Other comprehensive income (loss) 1.9 (4.6 ) (2.7 ) Total comprehensive income (loss) 5.6 (8.0 ) (2.4 ) Issuance of common shares 661.3 — 661.3 Stock and other incentive plans 8.3 — 8.3 Distributions to noncontrolling interest — (3.4 ) (3.4 ) June 30, 2017 $ (789.1 ) $ 122.4 $ (666.7 ) (In Millions) Cliffs Noncontrolling Total Equity (Deficit) December 31, 2015 $ (1,981.4 ) $ 169.8 $ (1,811.6 ) Comprehensive income Net income 120.8 25.5 146.3 Other comprehensive income 9.0 1.3 10.3 Total comprehensive income 129.8 26.8 156.6 Issuance of common shares 14.4 — 14.4 Stock and other incentive plans 6.5 — 6.5 Distributions of partnership equity — (41.4 ) (41.4 ) Distributions to noncontrolling interest — (3.4 ) (3.4 ) June 30, 2016 $ (1,830.7 ) $ 151.8 $ (1,678.9 ) The following table reflects the changes in Accumulated other comprehensive loss related to Cliffs shareholders’ deficit for June 30, 2017 and June 30, 2016 : (In Millions) Changes in Pension and Other Post-Retirement Benefits, Unrealized Net Gain (Loss) on Foreign Currency Translation Accumulated Other Comprehensive 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 loss 6.4 — 6.4 March 31, 2017 $ (250.9 ) $ 226.6 $ (24.3 ) Other comprehensive loss before reclassifications (0.1 ) (1.5 ) (1.6 ) Net loss reclassified from accumulated other comprehensive loss 6.5 — 6.5 June 30, 2017 $ (244.5 ) $ 225.1 $ (19.4 ) (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 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 reclassified from accumulated other comprehensive loss 6.3 — — — 6.3 March 31, 2016 $ (236.6 ) $ — $ 225.1 $ (0.8 ) $ (12.3 ) Other comprehensive income (loss) before reclassifications (0.4 ) — (2.7 ) 0.1 (3.0 ) Net loss reclassified from accumulated other comprehensive loss 6.3 — — — 6.3 June 30, 2016 $ (230.7 ) $ — $ 222.4 $ (0.7 ) $ (9.0 ) The following table reflects the details about Accumulated other comprehensive loss components related to Cliffs shareholders’ deficit for the three and six months ended June 30, 2017 and 2016 : (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 Six Months Ended 2017 2016 2017 2016 Amortization of pension and postretirement benefit liability: Prior service credits 1 $ (0.1 ) $ (0.4 ) $ (0.2 ) $ (0.7 ) Net actuarial loss 1 6.6 6.7 13.1 13.3 Total before taxes 6.5 6.3 12.9 12.6 — — — — Income tax benefit (expense) Total reclassifications for the period, net of tax $ 6.5 $ 6.3 $ 12.9 $ 12.6 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	6 Months Ended
	Jun. 30, 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 June 30, 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 % As part of a 2014 extension agreement between us and ArcelorMittal, which amended certain terms of the Empire partnership agreement, certain distributions of the partners' equity amounts were required to be made on a quarterly basis beginning in the first quarter of 2015. These equity distributions were made through the termination of the partnership agreement on December 31, 2016. We paid $8.7 million in January 2017 related to 2016 distributions. During the three and six months ended June 30, 2016 , we recorded distributions of $24.4 million and $41.4 million , respectively, under this agreement of which $17.0 million was paid as of June 30, 2016 . In addition, we paid $11.1 million in January 2016 related to 2015 distributions. ArcelorMittal's equity balance in the Empire partnership as of December 31, 2016 was approximately $132.7 million. During the second quarter of 2017, the partners reached an agreement in principle regarding the final distribution of partnership equity. We expect the partnership equity distribution to be made per the partnership agreement in three equal installments over a period of 24 months, commencing upon the finalization of the agreement. This agreement is expected to be finalized during the third quarter of 2017. Product revenues from related parties were as follows: (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Product revenues from related parties $ 227.5 $ 241.6 $ 336.9 $ 345.0 Total product revenues 512.0 452.8 924.8 728.4 Related party product revenue as a percent of total product revenue 44.4 % 53.4 % 36.4 % 47.4 % The following table presents the classification of related party assets and liabilities in the Statements of Unaudited Condensed Consolidated Financial Position as of June 30, 2017 and December 31, 2016 : (In Millions) Balance Sheet Location June 30, 2017 December 31, 2016 Amounts due from related parties Accounts receivable, net $ 18.8 $ 46.9 Customer supply agreements and provisional pricing agreements Other current assets 68.0 26.8 Amounts due to related parties Other current liabilities 15.9 8.7 Certain supply agreements with one U.S. Iron Ore customer provide for supplemental revenue or refunds to the customer based on the customer’s average annual steel pricing or based on the average annual daily market price for hot-rolled coil steel at the time 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	6 Months Ended
	Jun. 30, 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 Six Months Ended 2017 2016 2017 2016 Income from Continuing Operations $ 76.5 $ 29.9 $ 46.2 $ 144.2 Loss (Income) from Continuing Operations Attributable to Noncontrolling Interest 1.7 (16.7 ) 3.4 (25.5 ) Net Income from Continuing Operations Attributable to Cliffs Shareholders $ 78.2 $ 13.2 $ 49.6 $ 118.7 Income (Loss) from Discontinued Operations, net of tax (46.4 ) (0.4 ) (45.9 ) 2.1 Net Income Attributable to Cliffs Shareholders $ 31.8 $ 12.8 $ 3.7 $ 120.8 Weighted Average Number of Shares: Basic 296.1 182.3 280.6 177.0 Employee Stock Plans 4.6 2.3 4.6 1.3 Diluted 300.7 184.6 285.2 178.3 Earnings (Loss) per Common Share Attributable to Continuing operations $ 0.26 $ 0.07 $ 0.18 $ 0.67 Discontinued operations (0.16 ) — (0.16 ) 0.01 $ 0.10 $ 0.07 $ 0.02 $ 0.68 Earnings (Loss) per Common Share Attributable to Continuing operations $ 0.26 $ 0.07 $ 0.17 $ 0.67 Discontinued operations (0.15 ) — (0.16 ) 0.01 $ 0.11 $ 0.07 $ 0.01 $ 0.68

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 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 matters: 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 June 30, 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 $50.1 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 as of June 30, 2017 and December 31, 2016 , respectively. During the three months ended June 30, 2017, we became aware that it was probable the Monitor will assert a preference claim of the CCAA estate against the Company. Given that it is probable the claim will be asserted by the Monitor, we have recorded an estimated liability approximately equal to the value of the Company’s related-party claims against the CCAA estate of $50.0 million , classified as C ontingent claims in the Statements of Unaudited Condensed Consolidated Financial Position as of June 30, 2017 and included within Income (Loss) from Discontinued Operations, net of tax in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2017 . Should the Monitor proceed to assert the claim, we believe the Monitor will demand an amount in excess of the value of Cliffs’ related-party claims against the estate. Thus, it is possible that a change in the estimated liability may occur in the future. Cliffs denies it is liable for any amount and will vigorously defend such claim. Additionally, we have liabilities of $38.5 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 June 30, 2017 and December 31, 2016 , respectively. Refer to NOTE 19 - SUBSEQUENT EVENTS for additional information. As of June 30, 2017 , substantially all of the 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, 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	6 Months Ended
	Jun. 30, 2017
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	NOTE 19 - SUBSEQUENT EVENTS On July 18, 2017, all conditions were satisfied to complete a court-supervised sale of the Wabush Scully Mine assets to a third-party buyer. The buyer agreed to provide replacement financial assurance for environmental obligations of the Wabush Scully Mine, thus eliminating the Company's liability. As a result of this arrangement, the remaining guarantee instruments that supported the Wabush Mine environmental obligations are in the process of being cancelled and, as a result, in the third quarter of 2017, the Company will eliminate the Guarantees liability balance recorded as of June 30, 2017 of $38.5 million . We expect the closing of this sale to result in a gain of approximately $30 million during the third quarter of 2017.

BASIS OF PRESENTATION AND SIG26

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 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 June 30, 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 June 30, 2017 and December 31, 2016 , our investment in Hibbing was $6.5 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 our Australian 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. 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, including short-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 and six months ended June 30, 2017 and 2016: (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Remeasurement of short-term intercompany loans $ 1.5 $ (0.1 ) $ 16.6 $ 0.2 Remeasurement of cash and cash equivalents (0.5 ) 0.5 (1.7 ) 1.5 Other remeasurement (1.0 ) (0.2 ) (1.3 ) (2.6 ) Net impact of transaction gains and (losses) resulting from remeasurement — 0.2 13.6 (0.9 )
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): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. 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 No. 2017-07 will impact Statements of Unaudited Condensed Consolidated Operations by changing our classification of the components of pension and OPEB costs; however, it will not impact our Net Income . In February 2016, the FASB issued ASU No. 2016-02, Leases. The new standard requires lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases with the exception of short-term leases. For lessees, leases will continue to be classified as either operating or finance leases in the income statement. The effective date of the new standard for public companies is for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. Early adoption is permitted. The new standard must be adopted using a modified retrospective transition and requires application of the new guidance at the beginning of the earliest comparative period presented. We are currently evaluating the effect the updated standard will have on our consolidated financial statements and related disclosures. Based on our analysis to date, we anticipate the largest impact will be the balance sheet recognition of operating leases. In May 2014, the FASB issued ASU No. 2014-09, Revenues from Contracts with Customers. The new revenue guidance broadly replaces the revenue guidance provided throughout the Codification. The core principle of the revenue guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve that core principle, an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract and (5) recognize revenue when (or as) the entity satisfies a performance obligation. Reporting entities must prepare new disclosures providing qualitative and quantitative information on the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. New disclosures also include qualitative and quantitative information on significant judgments, changes in judgments, and contract acquisition assets. At issuance, ASU No. 2014-09 was effective starting in 2017 for calendar-year public entities, and interim periods within that year. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers: Deferral of the Effective Date, which defers the adoption of ASU No. 2014-09 to annual reporting periods beginning after December 15, 2017, including interim reporting periods within that reporting period. Earlier application is permitted. As of June 30, 2017, we have completed the initial evaluation of the new standard and the related review and assessment of a representative sample of existing contracts with our customers. We determined, on a preliminary basis, that the timing and pattern of revenue recognition for our U.S. Iron Ore contracts will likely change; however, the total amount of revenue recognized during the year should remain substantially the same as under current GAAP. We do not anticipate any significant changes in the timing and pattern of revenue recognition for our Asia Pacific Iron Ore contracts. We anticipate utilizing the modified retrospective transition method. Based on our analysis to date, we anticipate the primary impact of the adoption on our consolidated financial statements will be the additional required disclosures around revenue recognition in the notes to the consolidated financial statements.

BASIS OF PRESENTATION AND SIG27

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 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 and six months ended June 30, 2017 and 2016: (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Remeasurement of short-term intercompany loans $ 1.5 $ (0.1 ) $ 16.6 $ 0.2 Remeasurement of cash and cash equivalents (0.5 ) 0.5 (1.7 ) 1.5 Other remeasurement (1.0 ) (0.2 ) (1.3 ) (2.6 ) Net impact of transaction gains and (losses) resulting from remeasurement — 0.2 13.6 (0.9 )

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Schedule Of Segment Reporting Information, By Segment	The following tables present a summary of our reportable segments for the three and six months ended June 30, 2017 and 2016 , including a reconciliation of segment sales margin to Income from Continuing Operations Before Income Taxes and a reconciliation of Net Income to EBITDA and Adjusted EBITDA: (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Revenues from product sales and services: U.S. Iron Ore $ 471.3 83 % $ 361.7 73 % $ 757.5 73 % $ 547.2 68 % Asia Pacific Iron Ore 98.0 17 % 134.5 27 % 273.4 27 % 254.5 32 % Total revenues from product sales and services $ 569.3 100 % $ 496.2 100 % $ 1,030.9 100 % $ 801.7 100 % Sales margin: U.S. Iron Ore $ 144.2 $ 70.0 $ 192.6 $ 83.2 Asia Pacific Iron Ore 0.9 21.5 48.2 39.2 Sales margin 145.1 91.5 240.8 122.4 Other operating expense (30.5 ) (16.8 ) (44.3 ) (48.0 ) Other income (expense) (35.5 ) (46.9 ) (149.5 ) 75.2 Income from continuing operations before income taxes $ 79.1 $ 27.8 $ 47.0 $ 149.6 (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Net Income $ 30.1 $ 29.5 $ 0.3 $ 146.3 Less: Interest expense, net (31.4 ) (50.7 ) (74.2 ) (107.5 ) Income tax benefit (expense) (2.6 ) 2.1 (0.8 ) (5.4 ) Depreciation, depletion and amortization (21.6 ) (26.9 ) (44.8 ) (62.1 ) EBITDA $ 85.7 $ 105.0 $ 120.1 $ 321.3 Less: Gain (loss) on extinguishment/restructuring of debt (4.9 ) 3.6 (76.8 ) 182.4 Foreign exchange remeasurement — 0.2 13.6 (0.9 ) Impact of discontinued operations (46.4 ) (0.4 ) (45.9 ) 2.1 Severance and contractor termination costs — — — (0.1 ) Adjusted EBITDA $ 137.0 $ 101.6 $ 229.2 $ 137.8 EBITDA: U.S. Iron Ore $ 155.0 $ 94.1 $ 212.9 $ 135.5 Asia Pacific Iron Ore 1.2 26.1 52.6 48.4 Other (70.5 ) (15.2 ) (145.4 ) 137.4 Total EBITDA $ 85.7 $ 105.0 $ 120.1 $ 321.3 Adjusted EBITDA: U.S. Iron Ore $ 161.5 $ 97.2 $ 225.6 $ 143.3 Asia Pacific Iron Ore 3.0 26.5 56.8 49.5 Other (27.5 ) (22.1 ) (53.2 ) (55.0 ) Total Adjusted EBITDA $ 137.0 $ 101.6 $ 229.2 $ 137.8 (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Depreciation, depletion and amortization: U.S. Iron Ore $ 16.7 $ 19.4 $ 33.1 $ 46.3 Asia Pacific Iron Ore 3.3 6.1 8.0 12.9 Other 1.6 1.4 3.7 2.9 Total depreciation, depletion and amortization $ 21.6 $ 26.9 $ 44.8 $ 62.1 Capital additions: U.S. Iron Ore $ 24.6 $ 9.2 $ 51.7 $ 13.7 Asia Pacific Iron Ore 0.6 — 0.8 — Other — 2.1 — 4.4 Total capital additions 1 $ 25.2 $ 11.3 $ 52.5 $ 18.1 1 Includes cash paid for capital additions of $49.4 million and $20.2 million and an increase in non-cash accruals of $3.1 million and a decrease in non-cash accruals of $2.1 million for the six months ended June 30, 2017 and 2016, respectively.
Summary of Assets by Segment	A summary of assets by segment is as follows: (In Millions) June 30, December 31, Assets: U.S. Iron Ore $ 1,525.9 $ 1,372.5 Asia Pacific Iron Ore 157.7 155.1 Total segment assets 1,683.6 1,527.6 Corporate 346.5 396.3 Total assets $ 2,030.1 $ 1,923.9

INVENTORIES (Tables)

INVENTORIES (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : (In Millions) June 30, 2017 December 31, 2016 Segment Finished Goods Work-in Process Total Inventory Finished Goods Work-in Process Total Inventory U.S. Iron Ore $ 238.3 $ 14.3 $ 252.6 $ 124.4 $ 12.6 $ 137.0 Asia Pacific Iron Ore 22.7 12.3 35.0 23.6 17.8 41.4 Total $ 261.0 $ 26.6 $ 287.6 $ 148.0 $ 30.4 $ 178.4

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : (In Millions) June 30, December 31, Land rights and mineral rights $ 500.7 $ 500.5 Office and information technology 66.0 65.1 Buildings 71.8 67.9 Mining equipment 600.1 592.2 Processing equipment 621.5 552.0 Electric power facilities 54.0 49.4 Land improvements 23.8 23.5 Asset retirement obligation 19.7 19.8 Other 28.7 28.1 Construction in-progress 19.8 42.8 2,006.1 1,941.3 Allowance for depreciation and depletion (1,007.0 ) (956.9 ) $ 999.1 $ 984.4

DEBT AND CREDIT FACILITIES (Tab

DEBT AND CREDIT FACILITIES (Tables)	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Schedule Of Long-Term Debt	The following represents a summary of our long-term debt as of June 30, 2017 and December 31, 2016 : (In Millions) June 30, 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% $ 504.4 $ (6.3 ) $ (20.7 ) $ 477.4 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 (8.1 ) — 491.9 $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 1.6 Long-term debt $ 1,611.8 (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 six months ended June 30, 2017 and the respective gain (loss) on extinguishment for the three and six months ended June 30, 2017 : (In Millions) Gain (Loss) on Extinguishment 1 Debt Extinguished Three Months Ended Six Months Ended Secured Notes $540 Million 8.25% 2020 First Lien Notes $ 35.6 $ (4.9 ) $ (4.9 ) $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 ) $ 1,106.4 $ (4.9 ) $ (76.8 ) 1 Includes write-off of undiscounted interest, unamortized discounts and debt issuance costs. In addition, this includes premiums paid of $2.9 million and $47.6 million related to the redemption of our notes for the three and six months ended June 30, 2017, respectively.
Schedule of Maturities of Long-term Debt	Debt Maturities The following represents a summary of our maturities of debt instruments, excluding borrowings under the ABL Facility, based on the principal amounts outstanding at June 30, 2017 : (In Millions) Maturities of Debt 2017 (July 1 - December 31) $ — 2018 — 2019 — 2020 715.7 2021 138.4 2022 — 2023 and thereafter 798.4 Total maturities of debt $ 1,652.5

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : (In Millions) June 30, 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 $ 40.0 $ 120.0 $ — $ 160.0 Derivative assets — — 72.5 72.5 Total $ 40.0 $ 120.0 $ 72.5 $ 232.5 Liabilities: Derivative liabilities $ — $ — $ 20.8 $ 20.8 Total $ — $ — $ 20.8 $ 20.8 (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 Total $ 177.0 $ 1.5 $ 31.6 $ 210.1 Liabilities: Derivative liabilities $ — $ — $ 0.5 $ 0.5 Total $ — $ — $ 0.5 $ 0.5
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 June 30, 2017 Balance Sheet Location Valuation Technique Unobservable Input Range or Point Estimate (Weighted Average) Provisional pricing arrangements $ 6.1 Other current assets Market Approach Management's Estimate of Platts 62% Price per dry metric ton $60 - $75 Market Hot-Rolled Coil Steel Estimate $580 - $660 Provisional pricing arrangements $ 20.8 Other current liabilities Market Approach Management's Estimate of Platts 62% Price per dry metric ton $60 - $75 Customer supply agreements $ 66.4 Other current assets Market Approach Customer Hot-Rolled Steel Estimate $541 - $630 Market Hot-Rolled Coil Steel Estimate $580 - $660
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation	(In Millions) Level 3 Assets Three Months Ended Six Months Ended 2017 2016 2017 2016 Beginning balance $ 59.4 $ 9.0 $ 31.6 $ 7.8 Total gains (losses) Included in earnings 53.3 34.5 95.4 45.7 Settlements (40.2 ) (17.7 ) (54.5 ) (27.7 ) Ending balance - June 30 $ 72.5 $ 25.8 $ 72.5 $ 25.8 Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date $ 20.1 $ 21.6 $ 53.3 $ 21.9
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	(In Millions) Level 3 Liabilities Three Months Ended Six Months Ended 2017 2016 2017 2016 Beginning balance $ (9.1 ) $ (6.2 ) $ (0.5 ) $ (3.4 ) Total gains (losses) Included in earnings (36.8 ) (2.8 ) (45.5 ) (8.4 ) Settlements 25.1 6.4 25.2 9.2 Ending balance - June 30 $ (20.8 ) $ (2.6 ) $ (20.8 ) $ (2.6 ) Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date $ (11.7 ) $ (0.7 ) $ (20.8 ) $ (2.6 )
Schedule Of Carrying Value And Fair Value Of Financial Instruments	A summary of the carrying amount and fair value of other financial instruments at June 30, 2017 and December 31, 2016 were as follows: (In Millions) June 30, 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 $ 477.4 $ 550.0 $ 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 1 491.9 473.8 — — Senior Notes—$400 million Level 1 88.5 86.0 224.5 219.6 Senior Notes—$1.3 billion Level 1 414.5 339.7 528.4 455.8 Senior Notes—$700 million Level 1 137.9 131.6 308.2 283.1 ABL Facility Level 2 — — — — Fair value adjustment to interest rate hedge Level 2 1.6 1.6 1.9 1.9 Total long-term debt $ 1,611.8 $ 1,582.7 $ 2,192.6 $ 2,224.6
Fair Value Measurements, Nonrecurring [Table Text Block]	Items Measured at Fair Value on a Non-Recurring Basis The following tables present information about the financial assets and liabilities that were measured on a fair value basis at June 30, 2017 and December 31, 2016 for the Canadian Entities. The tables also indicate the fair value hierarchy of the valuation techniques used to determine such fair value. (In Millions) June 30, 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 Total Gains Assets: Loans to and accounts receivables from the Canadian Entities $ — $ — $ 50.1 $ 50.1 $ 1.5 Liabilities: Guarantees $ — $ — $ 38.5 $ 38.5 $ 1.3 (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 Total Gains (Losses) Assets: Loans to and accounts receivables from the Canadian Entities $ — $ — $ 48.6 $ 48.6 $ (17.5 ) Liabilities: Guarantees $ — $ — $ 37.2 $ 37.2 $ 0.4

PENSIONS AND OTHER POSTRETIRE33

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Tables)	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 2017 and 2016 : Defined Benefit Pension Costs (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Service cost $ 4.7 $ 4.5 $ 9.5 $ 9.0 Interest cost 7.5 7.5 15.0 14.9 Expected return on plan assets (13.6 ) (13.7 ) (27.1 ) (27.4 ) Amortization: Prior service costs 0.7 0.5 1.3 1.1 Net actuarial loss 5.3 5.3 10.6 10.5 Net periodic benefit cost $ 4.6 $ 4.1 $ 9.3 $ 8.1 Other Postretirement Benefits Credit (In Millions) Three Months Ended Six Months Ended 2017 2016 2017 2016 Service cost $ 0.5 $ 0.4 $ 1.0 $ 0.9 Interest cost 2.2 2.3 4.3 4.5 Expected return on plan assets (4.5 ) (4.3 ) (8.9 ) (8.5 ) Amortization: Prior service credits (0.8 ) (0.9 ) (1.5 ) (1.8 ) Net actuarial loss 1.3 1.4 2.5 2.8 Net periodic benefit credit $ (1.3 ) $ (1.1 ) $ (2.6 ) $ (2.1 )

STOCK COMPENSATION PLANS STOCK

STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Tables)	6 Months Ended
	Jun. 30, 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 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% June 26, 2017 $ 6.64 2.51 92.8% 1.45% —% $ 10.74 161.75%

LEASE OBLIGATIONS (Tables)

LEASE OBLIGATIONS (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2017 are as follows: (In Millions) Capital Leases Operating Leases 2017 (July 1 - December 31) $ 11.7 $ 3.6 2018 18.9 5.8 2019 10.5 2.9 2020 9.5 2.9 2021 8.8 3.0 2022 and thereafter 0.6 — Total minimum lease payments $ 60.0 $ 18.2 Amounts representing interest 10.0 Present value of net minimum lease payments 1 $ 50.0 1 The total is comprised of $17.4 million and $32.6 million classified as Other current liabilities and Other liabilities , respectively, in the Statements of Unaudited Condensed Consolidated Financial Position at June 30, 2017.

ENVIRONMENTAL AND MINE CLOSUR36

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Tables)	6 Months Ended
	Jun. 30, 2017
Environmental Remediation Obligations [Abstract]
Summary Of Mine Closure Obligations	The following is a summary of the obligations as of June 30, 2017 and December 31, 2016 : (In Millions) June 30, December 31, Environmental $ 2.8 $ 2.8 Mine closure U.S. Iron Ore 1 193.6 187.8 Asia Pacific Iron Ore 17.7 16.2 Total mine closure 211.3 204.0 Total environmental and mine closure obligations 214.1 206.8 Less current portion 12.2 12.9 Long-term environmental and mine closure obligations $ 201.9 $ 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 six months ended June 30, 2017 and for the year ended December 31, 2016 : (In Millions) June 30, December 31, 2016 Asset retirement obligation at beginning of period $ 204.0 $ 230.4 Accretion expense 7.1 14.0 Remediation payments (0.8 ) (2.2 ) Exchange rate changes 1.0 (0.2 ) Revision in estimated cash flows — (38.0 ) Asset retirement obligation at end of period $ 211.3 $ 204.0

GOODWILL AND OTHER INTANGIBLE37

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Tables)	6 Months Ended
	Jun. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule Of Finite-Lived Intangible Assets By Major Class	The following table is a summary of definite-lived intangible assets as of June 30, 2017 and December 31, 2016 : (In Millions) June 30, 2017 December 31, 2016 Classification Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Permits Other non-current assets $ 78.8 $ (25.6 ) $ 53.2 $ 78.4 $ (24.6 ) $ 53.8

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : (In Millions) Derivative Assets Derivative Liabilities June 30, 2017 December 31, 2016 June 30, 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 agreements Other current assets 66.4 Other current assets 21.3 — — Provisional pricing arrangements Other current assets 6.1 Other current assets 10.3 Other current liabilities 20.8 Other current liabilities 0.5 Commodity contracts — Other current assets 1.5 — — Total derivatives not designated as hedging instruments under ASC 815 $ 72.5 $ 33.1 $ 20.8 $ 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 and six months ended June 30, 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 Six Months Ended 2017 2016 2017 2016 Customer Supply Agreements Product revenues 51.9 19.5 69.6 19.9 Provisional Pricing Arrangements Product revenues (35.4 ) 1.8 (19.8 ) 0.3 Commodity Contracts Cost of goods sold and operating expenses — — (1.3 ) — Total $ 16.5 $ 21.3 $ 48.5 $ 20.2

SHAREHOLDERS' EQUITY Shareholde

SHAREHOLDERS' EQUITY Shareholders' Equity (Tables)	6 Months Ended
	Jun. 30, 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 six months ended June 30, 2017 and June 30, 2016 : (In Millions) Cliffs Noncontrolling Interest (Deficit) Total Equity (Deficit) December 31, 2016 $ (1,464.3 ) $ 133.8 $ (1,330.5 ) Comprehensive loss Net income (loss) 3.7 (3.4 ) 0.3 Other comprehensive income (loss) 1.9 (4.6 ) (2.7 ) Total comprehensive income (loss) 5.6 (8.0 ) (2.4 ) Issuance of common shares 661.3 — 661.3 Stock and other incentive plans 8.3 — 8.3 Distributions to noncontrolling interest — (3.4 ) (3.4 ) June 30, 2017 $ (789.1 ) $ 122.4 $ (666.7 ) (In Millions) Cliffs Noncontrolling Total Equity (Deficit) December 31, 2015 $ (1,981.4 ) $ 169.8 $ (1,811.6 ) Comprehensive income Net income 120.8 25.5 146.3 Other comprehensive income 9.0 1.3 10.3 Total comprehensive income 129.8 26.8 156.6 Issuance of common shares 14.4 — 14.4 Stock and other incentive plans 6.5 — 6.5 Distributions of partnership equity — (41.4 ) (41.4 ) Distributions to noncontrolling interest — (3.4 ) (3.4 ) June 30, 2016 $ (1,830.7 ) $ 151.8 $ (1,678.9 )
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table reflects the changes in Accumulated other comprehensive loss related to Cliffs shareholders’ deficit for June 30, 2017 and June 30, 2016 : (In Millions) Changes in Pension and Other Post-Retirement Benefits, Unrealized Net Gain (Loss) on Foreign Currency Translation Accumulated Other Comprehensive 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 loss 6.4 — 6.4 March 31, 2017 $ (250.9 ) $ 226.6 $ (24.3 ) Other comprehensive loss before reclassifications (0.1 ) (1.5 ) (1.6 ) Net loss reclassified from accumulated other comprehensive loss 6.5 — 6.5 June 30, 2017 $ (244.5 ) $ 225.1 $ (19.4 ) (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 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 reclassified from accumulated other comprehensive loss 6.3 — — — 6.3 March 31, 2016 $ (236.6 ) $ — $ 225.1 $ (0.8 ) $ (12.3 ) Other comprehensive income (loss) before reclassifications (0.4 ) — (2.7 ) 0.1 (3.0 ) Net loss reclassified from accumulated other comprehensive loss 6.3 — — — 6.3 June 30, 2016 $ (230.7 ) $ — $ 222.4 $ (0.7 ) $ (9.0 )
Details of Accumulated Other Comprehensive Income (Loss) Components	The following table reflects the details about Accumulated other comprehensive loss components related to Cliffs shareholders’ deficit for the three and six months ended June 30, 2017 and 2016 : (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 Six Months Ended 2017 2016 2017 2016 Amortization of pension and postretirement benefit liability: Prior service credits 1 $ (0.1 ) $ (0.4 ) $ (0.2 ) $ (0.7 ) Net actuarial loss 1 6.6 6.7 13.1 13.3 Total before taxes 6.5 6.3 12.9 12.6 — — — — Income tax benefit (expense) Total reclassifications for the period, net of tax $ 6.5 $ 6.3 $ 12.9 $ 12.6 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)	6 Months Ended
	Jun. 30, 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 June 30, 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 Six Months Ended 2017 2016 2017 2016 Product revenues from related parties $ 227.5 $ 241.6 $ 336.9 $ 345.0 Total product revenues 512.0 452.8 924.8 728.4 Related party product revenue as a percent of total product revenue 44.4 % 53.4 % 36.4 % 47.4 %
Summary of Balance Sheet Presentation [Table Text Block]	The following table presents the classification of related party assets and liabilities in the Statements of Unaudited Condensed Consolidated Financial Position as of June 30, 2017 and December 31, 2016 : (In Millions) Balance Sheet Location June 30, 2017 December 31, 2016 Amounts due from related parties Accounts receivable, net $ 18.8 $ 46.9 Customer supply agreements and provisional pricing agreements Other current assets 68.0 26.8 Amounts due to related parties Other current liabilities 15.9 8.7

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 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 Six Months Ended 2017 2016 2017 2016 Income from Continuing Operations $ 76.5 $ 29.9 $ 46.2 $ 144.2 Loss (Income) from Continuing Operations Attributable to Noncontrolling Interest 1.7 (16.7 ) 3.4 (25.5 ) Net Income from Continuing Operations Attributable to Cliffs Shareholders $ 78.2 $ 13.2 $ 49.6 $ 118.7 Income (Loss) from Discontinued Operations, net of tax (46.4 ) (0.4 ) (45.9 ) 2.1 Net Income Attributable to Cliffs Shareholders $ 31.8 $ 12.8 $ 3.7 $ 120.8 Weighted Average Number of Shares: Basic 296.1 182.3 280.6 177.0 Employee Stock Plans 4.6 2.3 4.6 1.3 Diluted 300.7 184.6 285.2 178.3 Earnings (Loss) per Common Share Attributable to Continuing operations $ 0.26 $ 0.07 $ 0.18 $ 0.67 Discontinued operations (0.16 ) — (0.16 ) 0.01 $ 0.10 $ 0.07 $ 0.02 $ 0.68 Earnings (Loss) per Common Share Attributable to Continuing operations $ 0.26 $ 0.07 $ 0.17 $ 0.67 Discontinued operations (0.15 ) — (0.16 ) 0.01 $ 0.11 $ 0.07 $ 0.01 $ 0.68

BASIS OF PRESENTATION AND SIG42

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) - Hibbing [Member] - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Other Noncurrent Assets [Member]
Related Party Transaction [Line Items]
Ownership interest, equity method investment	23.00%	23.00%
Other Noncurrent Liabilities [Member]
Related Party Transaction [Line Items]
Equity Method Investments	$ 6.5	$ 8.7

BASIS OF PRESENTATION AND SIG43

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)	6 Months Ended
	Jun. 30, 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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Foreign Currency Transaction Gain (Loss), before Tax	$ 0	$ 0.2	$ 13.6	$ (0.9)
Short-term intercompany loan [Member]
Foreign Currency Transaction Gain (Loss), before Tax	1.5	(0.1)	16.6	0.2
Cash and Cash Equivalents [Member]
Foreign Currency Transaction Gain (Loss), before Tax	(0.5)	0.5	(1.7)	1.5
Other Remeasurement
Foreign Currency Transaction Gain (Loss), before Tax	$ (1)	$ (0.2)	$ (1.3)	$ (2.6)

SEGMENT REPORTING (Schedule Of

SEGMENT REPORTING (Schedule Of Segment Reporting Information, By Segment) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	100.00%	100.00%	100.00%	100.00%
Revenues from product sales and services	$ 569.3	$ 496.2	$ 1,030.9	$ 801.7
Sales margin	145.1	91.5	240.8	122.4
Other operating expense	(30.5)	(16.8)	(44.3)	(48)
Other income (expense)	(35.5)	(46.9)	(149.5)	75.2
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	79.1	27.8	47	149.6
Net Income	30.1	29.5	0.3	146.3
Interest expense, net	(31.4)	(50.7)	(74.2)	(107.5)
Income tax benefit (expense)	(2.6)	2.1	(0.8)	(5.4)
Depreciation, depletion and amortization	21.6	26.9	44.8	62.1
EBITDA	85.7	105	120.1	321.3
Gain (loss) on extinguishment/restructuring of debt	(4.9)	3.6	(76.8)	182.4
Adjusted EBITDA	137	101.6	229.2	137.8
Property, Plant and Equipment, Additions	$ 25.2	$ 11.3	52.5	18.1
Payments To Acquire Property Plant And Equipment Net			49.4	20.2
Capital Expenditures Incurred but Not yet Paid			$ 3.1	$ (2.1)
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	83.00%	73.00%	73.00%	68.00%
Revenues from product sales and services	$ 471.3	$ 361.7	$ 757.5	$ 547.2
Sales margin	144.2	70	192.6	83.2
Depreciation, depletion and amortization	16.7	19.4	33.1	46.3
EBITDA	155	94.1	212.9	135.5
Adjusted EBITDA	161.5	97.2	225.6	143.3
Property, Plant and Equipment, Additions	$ 24.6	$ 9.2	$ 51.7	$ 13.7
Asia Pacific Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	17.00%	27.00%	27.00%	32.00%
Revenues from product sales and services	$ 98	$ 134.5	$ 273.4	$ 254.5
Sales margin	0.9	21.5	48.2	39.2
Depreciation, depletion and amortization	3.3	6.1	8	12.9
EBITDA	1.2	26.1	52.6	48.4
Adjusted EBITDA	3	26.5	56.8	49.5
Property, Plant and Equipment, Additions	0.6	0	0.8	0
All Other Segments [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization	1.6	1.4	3.7	2.9
EBITDA	(70.5)	(15.2)	(145.4)	137.4
Adjusted EBITDA	(27.5)	(22.1)	(53.2)	(55)
Property, Plant and Equipment, Additions	0	2.1	0	4.4
EBITDA Calculation [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization	21.6	26.9	44.8	62.1
Adjusted EBITDA Calculation [Member]
Segment Reporting Information [Line Items]
Impact of discontinued operations	(46.4)	(0.4)	(45.9)	2.1
Severance and contractor termination costs	0	0	0	(0.1)
Foreign exchange remeasurement	$ 0	$ 0.2	$ 13.6	$ (0.9)

SEGMENT REPORTING Segment Repor

SEGMENT REPORTING Segment Reporting (Summary of Assets by Segment) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Assets	$ 2,030.1	$ 1,923.9
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Assets	1,525.9	1,372.5
Asia Pacific Iron Ore [Member]
Segment Reporting Information [Line Items]
Assets	157.7	155.1
Total Segment Assets [Member]
Segment Reporting Information [Line Items]
Assets	1,683.6	1,527.6
Corporate [Member]
Segment Reporting Information [Line Items]
Assets	$ 346.5	$ 396.3

INVENTORIES (Schedule Of Invent

INVENTORIES (Schedule Of Inventories) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Inventory, Net [Abstract]
Finished Goods	$ 261	$ 148
Work-in Process	26.6	30.4
Total Inventory	287.6	178.4
U.S. Iron Ore [Member]
Inventory, Net [Abstract]
Finished Goods	238.3	124.4
Work-in Process	14.3	12.6
Total Inventory	252.6	137
Asia Pacific Iron Ore [Member]
Inventory, Net [Abstract]
Finished Goods	22.7	23.6
Work-in Process	12.3	17.8
Total Inventory	$ 35	$ 41.4

PROPERTY, PLANT AND EQUIPMENT48

PROPERTY, PLANT AND EQUIPMENT (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Property, Plant and Equipment [Abstract]
Depreciation and depletion	$ 21.2	$ 25.7	$ 43.8	$ 59.5

PROPERTY, PLANT AND EQUIPMENT49

PROPERTY, PLANT AND EQUIPMENT (Value Of Each Of The Major Classes Of Consolidated Depreciable Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 2,006.1	$ 1,941.3
Allowance for depreciation and depletion	(1,007)	(956.9)
Property, plant and equipment, net	999.1	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	66	65.1
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	71.8	67.9
Mining Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	600.1	592.2
Processing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	621.5	552
Electric Power Facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	54	49.4
Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	23.8	23.5
Asset Retirement Obligation [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	19.7	19.8
Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	28.7	28.1
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 19.8	$ 42.8

DEBT AND CREDIT FACILITIES (Nar

DEBT AND CREDIT FACILITIES (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	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	$ (4,900,000)	$ 3,600,000	(76,800,000)	$ 182,400,000
Debt redemption premiums paid	2,900,000		47,600,000
$500 Million 5.75% 2025 Senior Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Par Value	$ 500,000,000		$ 500,000,000
Debt Instrument, Interest Rate, Effective Percentage	5.75%		5.75%
Note Redemption Price, Percent of Principal Amount to be Redeemed	100.00%		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
Unamortized Debt Issuance Expense	$ 8,100,000		$ 8,100,000
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility, amount outstanding	0		0		$ 0
Line of Credit Facility, Maximum Borrowing Capacity	296,600,000		296,600,000		333,000,000
Debt Instrument, Par Value	550,000,000		550,000,000		550,000,000
Letters of credit outstanding	82,500,000		82,500,000		106,000,000
Credit facility remaining capacity	$ 214,100,000		$ 214,100,000		$ 227,000,000

DEBT AND CREDIT FACILITIES (Sch

DEBT AND CREDIT FACILITIES (Schedule Of Long-Term Debt) (Details) - USD ($)	Jun. 30, 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	$ 1,611,800,000	$ 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	$ 504,400,000	$ 540,000,000
Unamortized Debt Issuance Expense	(6,300,000)	(8,000,000)
Debt Instrument, Unamortized Discount	(20,700,000)	(25,700,000)
Long-term Debt	$ 477,400,000	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	(8,100,000)
Debt Instrument, Unamortized Discount	0
Long-term Debt	$ 491,900,000
$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	$ 1,600,000	$ 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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount			$ 1,106.4
Gain (loss) on extinguishment/restructuring of debt	$ (4.9)	$ 3.6	(76.8)	$ 182.4
$540 Million 8.25% 2020 Lien Notes [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount			35.6
Gain (loss) on extinguishment/restructuring of debt	(4.9)		(4.9)
$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	0		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	0		(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	0		(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	0		(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	$ 0		$ (2.8)

DEBT AND CREDIT FACILITIES DE53

DEBT AND CREDIT FACILITIES DEBT AND CREDIT FACILITIES (Schedule of Debt Maturities) (Details) $ in Millions	Jun. 30, 2017USD ($)
Debt Disclosure [Abstract]
2017 (July 1 - December 31)	$ 0
Debt Maturities 2018	0
Debt Maturities 2019	0
Debt Maturities 2020	715.7
Debt Maturities 2021	138.4
Debt Maturities 2022	0
2023 and thereafter	798.4
Total maturities of debt	$ 1,652.5

FAIR VALUE MEASUREMENTS (Narrat

FAIR VALUE MEASUREMENTS (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets And Liabilities Components [Line Items]
Cash equivalents	$ 160	$ 177
Management Estimate of 62% Fe	62.00%
Derivative Asset	$ 72.5	33.1
Derivative Liability	20.8	0.5
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Cash equivalents	40	177
Derivative Asset	0	0
Derivative Liability	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Cash equivalents	120	0
Derivative Asset	0	1.5
Derivative Liability	0	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Cash equivalents	0	0
Derivative Asset	72.5	31.6
Derivative Liability	20.8	0.5
Not Designated as Hedging Instrument [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Derivative Asset	72.5	33.1
Derivative Liability	20.8	0.5
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	66.4	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	6.1	10.3
Other Current Liabilities [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 Liability	$ 20.8	$ 0.5

FAIR VALUE MEASUREMENTS FAIR VA

FAIR VALUE MEASUREMENTS FAIR VALUE MEASUREMENTS (Fair Value of Assets and Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	$ 160	$ 177
Derivative Asset	72.5	33.1
Total Asset	232.5	210.1
Derivative Liability	20.8	0.5
Total Liability	20.8	0.5
Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	40	177
Derivative Asset	0	0
Total Asset	40	177
Derivative Liability	0	0
Total Liability	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	120	0
Derivative Asset	0	1.5
Total Asset	120	1.5
Derivative Liability	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	72.5	31.6
Total Asset	72.5	31.6
Derivative Liability	20.8	0.5
Total Liability	$ 20.8	$ 0.5

FAIR VALUE MEASUREMENTS (Schedu

FAIR VALUE MEASUREMENTS (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Details) - USD ($)	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	$ 20,800,000	$ 500,000
Derivative Asset	$ 72,500,000	33,100,000
Management Estimate of 62% Fe	62.00%
Not Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	$ 20,800,000	500,000
Derivative Asset	72,500,000	33,100,000
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	20,800,000	500,000
Derivative Asset	$ 72,500,000	31,600,000
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	$ 72
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] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	60
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] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	75
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	634
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] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	580
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] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	660
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	634
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	580
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	660
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Customer's 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	578
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Customer's 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	541
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Customer's 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	6,100,000	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	66,400,000	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	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	20,800,000	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	$ 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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 59.4	$ 9	$ 31.6	$ 7.8
Total gains (losses)
Included in earnings	53.3	34.5	95.4	45.7
Settlements	(40.2)	(17.7)	(54.5)	(27.7)
Ending balance - June 30	72.5	25.8	72.5	25.8
Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date	20.1	21.6	53.3	21.9
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	(9.1)	(6.2)	(0.5)	(3.4)
Total gains (losses)
Included in earnings	(36.8)	(2.8)	(45.5)	(8.4)
Settlements	25.1	6.4	25.2	9.2
Ending balance - June 30	(20.8)	(2.6)	(20.8)	(2.6)
Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date	$ (11.7)	$ (0.7)	$ (20.8)	$ (2.6)

FAIR VALUE MEASUREMENTS (Carryi

FAIR VALUE MEASUREMENTS (Carrying Value And Fair Value Of Financial Instruments Disclosure) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Interest Rate Swap [Member]
Long-term debt:
Fair Value Adjustment to Interest Rate Hedge	$ 1.6	$ 1.9
Carrying Value [Member] | Fair Value, Inputs, Level 2 [Member]
Long-term debt:
Total long-term debt, fair value	1,611.8	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	1.6	1.9
Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]
Long-term debt:
Total long-term debt, fair value	1,582.7	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	1.6	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	0	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	0	544.2
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] | $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] | 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	477.4	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] | $500 Million 5.75% 2025 Senior Notes [Member]
Long-term debt:
Total long-term debt, fair value	491.9	0
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 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	550	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] | $500 Million 5.75% 2025 Senior Notes [Member]
Long-term debt:
Total long-term debt, fair value	473.8	0
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	86	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	339.7	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	131.6	283.1
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

FAIR VALUE MEASUREMENTS FAIR 59

FAIR VALUE MEASUREMENTS FAIR VALUE MEASUREMENTS (Fair Value Measurements, Nonrecurring) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 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	$ 50.1	$ 48.6
Fair Value, Asset, Measured on a Nonrecurring Basis, Gain (Loss) Included in Earnings	1.5	(17.5)
Contingent Liabilities recognized in Consolidated Financials	38.5	37.2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	1.3	0.4
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	50.1	48.6
Contingent Liabilities recognized in Consolidated Financials	$ 38.5	$ 37.2

PENSIONS AND OTHER POSTRETIRE60

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Plans, Defined Benefit [Member]
Definted Benefit Plan Disclosure [Line Items]
Pension Contributions	$ 2.3	$ 0	$ 2.3	$ 0.3
Other Postretirement Benefit Plans, Defined Benefit [Member]
Definted Benefit Plan Disclosure [Line Items]
OPEB Contributions	$ 0	$ 0	$ 0	$ 0

PENSIONS AND OTHER POSTRETIRE61

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Estimated Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 4.7	$ 4.5	$ 9.5	$ 9
Interest cost	7.5	7.5	15	14.9
Expected return on plan assets	(13.6)	(13.7)	(27.1)	(27.4)
Prior service credits	0.7	0.5	1.3	1.1
Net actuarial loss	5.3	5.3	10.6	10.5
Net periodic benefit credit	4.6	4.1	9.3	8.1
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	1	0.9
Interest cost	2.2	2.3	4.3	4.5
Expected return on plan assets	(4.5)	(4.3)	(8.9)	(8.5)
Prior service credits	(0.8)	(0.9)	(1.5)	(1.8)
Net actuarial loss	1.3	1.4	2.5	2.8
Net periodic benefit credit	$ (1.3)	$ (1.1)	$ (2.6)	$ (2.1)

STOCK COMPENSATION PLANS (Narra

STOCK COMPENSATION PLANS (Narrative) (Details) - shares shares in Millions	3 Months Ended
	Jun. 30, 2017	Mar. 31, 2017
Restricted Stock Units (RSUs) [Member] | A&R 2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of restricted shares granted	0.5
Restricted Stock Units (RSUs) [Member] | 2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of restricted shares granted		0.6
Performance Shares [Member] | A&R 2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of restricted shares granted	0.2
Performance Shares [Member] | 2015 Equity Plan [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] | 2015 Equity Plan [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] | 2015 Equity Plan [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 STOC63

STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Assumptions Utilized to Estimate Fair Value for Performance Share Grants) (Details) - $ / shares	3 Months Ended
	Jun. 30, 2017	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Date Market Price	$ 6.64	$ 11.67
Average Expected Term	2 years 6 months 2 days	2 years 10 months 9 days
Expected Volatility	92.80%	92.10%
Risk-Free Interest Rate	1.45%	1.51%
Dividend Yield	0.00%	0.00%
Fair Value	$ 10.74	$ 19.69
Fair Value (Percent of Grant Date Market Price)	161.75%	168.72%

INCOME TAXES (Narrative) (Detai

INCOME TAXES (Narrative) (Details)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Percent	1.30%	3.10%
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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Leases [Abstract]
Operating lease expense	$ 1.8	$ 2.2	$ 3.5	$ 4.6

LEASE OBLIGATIONS (Future Minim

LEASE OBLIGATIONS (Future Minimum Lease Payments) (Details) $ in Millions	Jun. 30, 2017USD ($)
Capital Leases
2017 (July 1 - December 31)	$ 11.7
2,018	18.9
2,019	10.5
2,020	9.5
2,021	8.8
2022 and thereafter	0.6
Total minimum lease payments	60
Amounts representing interest	10
Present value of net minimum lease payments	50
Operating Leases
2017 (July 1 - December 31)	3.6
2,018	5.8
2,019	2.9
2,020	2.9
2,021	3
2022 and thereafter	0
Total minimum lease payments	18.2
Other Current Liabilities [Member]
Capital Leases
Present value of net minimum lease payments	17.4
Other Liabilities [Member]
Capital Leases
Present value of net minimum lease payments	$ 32.6

ENVIRONMENTAL AND MINE CLOSUR67

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)T	Jun. 30, 2017USD ($)
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	$ 214.1

ENVIRONMENTAL AND MINE CLOSUR68

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Summary Of Mine Closure Obligations) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Environmental	$ 2.8	$ 2.8
Environmental Loss Contingency And Mine Reclamation And Closing Liability Current	12.2	12.9
Environmental Loss Contingency And Mine Reclamation And Closing Liability Noncurrent	201.9	193.9
U.S. Iron Ore [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	193.6	187.8
Asia Pacific Iron Ore [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	17.7	16.2
North American Coal [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	211.3	204
Eastern Canadian Iron Ore [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	$ 214.1	$ 206.8

ENVIRONMENTAL AND MINE CLOSUR69

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Asset Retirement Obligation Disclosure) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Asset Retirement Obligation [Roll Forward]
Asset retirement obligation at beginning of period	$ 204	$ 230.4
Accretion expense	7.1	14
Asset Retirement Obligation, Liabilities Settled	(0.8)	(2.2)
Exchange rate changes	1	(0.2)
Revision in estimated cash flows		(38)
Asset retirement obligation at end of period	$ 211.3	$ 204

GOODWILL AND OTHER INTANGIBLE70

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Cost of Sales [Member]
Goodwill [Line Items]
Amortization expense relating to intangible assets	$ 0.4	$ 1.2	$ 1	$ 2.6
U.S. Iron Ore [Member]
Goodwill [Line Items]
Goodwill	$ 2		$ 2		$ 2

GOODWILL AND OTHER INTANGIBLE71

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Schedule Of Finite-Lived Intangible Assets By Major Class) (Details) - Permits [Member] - Other Assets [Member] - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	$ 78.8	$ 78.4
Definite lived intangible assets - Accumulated Amortization	(25.6)	(24.6)
Definite lived intangible assets - Net Carrying Amount	$ 53.2	$ 53.8

DERIVATIVE INSTRUMENTS (Narrati

DERIVATIVE INSTRUMENTS (Narrative) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Customer Supply Agreement [Member] | Product Revenues [Member]
Derivative [Line Items]
Amount of gain/(loss) recognized in income on derivative	$ 51.4	$ 19.5	$ 69.2	$ 19.9
Customer Supply Agreement [Member] | Derivative Financial Instruments, Assets [Member]
Derivative [Line Items]
Derivative assets	66.4		66.4		$ 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	(35.4)	$ 1.8	(19.8)	$ 0.3
Provisional Pricing Arrangements [Member] | U S Iron Ore And Asia Pacific Iron Ore [Member] | Derivative Financial Instruments, Assets [Member]
Derivative [Line Items]
Derivative assets	6.1		6.1		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	$ 20.8		$ 20.8		$ 0.5

DERIVATIVE INSTRUMENTS (Schedul

DERIVATIVE INSTRUMENTS (Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative Asset	$ 72.5	$ 33.1
Derivative Liability	20.8	0.5
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	72.5	33.1
Derivative Liability	20.8	0.5
Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	72.5	31.6
Derivative Liability	20.8	0.5
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Customer Supply Agreement [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	66.4	21.3
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Customer Supply Agreement [Member] | Derivative Financial Instruments, Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	0	0
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	6.1	10.3
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	20.8	0.5
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0	1.5
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	$ 0	$ 0

DERIVATIVE INSTRUMENTS (Sched74

DERIVATIVE INSTRUMENTS (Schedule Of Derivatives Not Designated As Hedging Instruments) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 16.5	$ 21.3	$ 48.5	$ 20.2
Commodity Contract [Member] | Other Nonoperating Income (Expense) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	0	(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	51.9	19.5	69.6	19.9
Provisional Pricing Arrangements [Member] | Product Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ (35.4)	$ 1.8	$ (19.8)	$ 0.3

CAPITAL STOCK (Details)

CAPITAL STOCK (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Feb. 09, 2017	Dec. 31, 2016
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	1,106.4
$500 Million 5.75% 2025 Senior Notes [Member]
Class of Stock [Line Items]
Debt Instrument, Par Value	500
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
$540 Million 8.25% 2020 Lien Notes [Member]
Class of Stock [Line Items]
Debt Instrument, Par Value	504.4			$ 540
Extinguishment of Debt, Amount	$ 35.6

SHAREHOLDERS' EQUITY Narrative

SHAREHOLDERS' EQUITY Narrative (Details)	Jun. 30, 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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Stockholders' Equity Attributable to Parent	$ (789.1)		$ (789.1)		$ (1,464.3)
Stockholders' Equity Attributable to Noncontrolling Interest	122.4		122.4		133.8
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(666.7)	$ (1,678.9)	(666.7)	$ (1,678.9)	(1,330.5)	$ (1,811.6)
NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	31.8	12.8	3.7	120.8
INCOME (LOSS) ATTRIBUTABLE TO NONCONTROLLING INTEREST	(1.7)	16.7	(3.4)	25.5
Net Income	30.1	29.5	0.3	146.3
Other comprehensive income (loss)	36.7	16.1	5.6	129.8
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	0.4	0.7	(4.6)	1.3
Other Comprehensive Income (Loss), Net of Tax	5.3	4	(2.7)	10.3
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest			(2.4)	156.6
Stock and Other Incentive Plans			8.3	6.5
Distributions to partnership equity				(41.4)
Distributions to noncontrolling interest			(3.4)	(3.4)
Cliffs Shareholders Equity [Member]
Stockholders' Equity Attributable to Parent	(789.1)	(1,830.7)	(789.1)	(1,830.7)	(1,464.3)	(1,981.4)
NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS			3.7	120.8
Other comprehensive income (loss)			1.9	9
TOTAL COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS			5.6	129.8
Stock and Other Incentive Plans			8.3	6.5
Distributions to partnership equity				0
Distributions to noncontrolling interest			0	0
Noncontrolling Interest [Member]
Stockholders' Equity Attributable to Noncontrolling Interest	$ 122.4	$ 151.8	122.4	151.8	$ 133.8	$ 169.8
INCOME (LOSS) ATTRIBUTABLE TO NONCONTROLLING INTEREST			(3.4)	25.5
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest			(4.6)	1.3
OTHER COMPREHENSIVE LOSS (INCOME) ATTRIBUTABLE TO THE NONCONTROLLING INTEREST			(8)	26.8
Stock and Other Incentive Plans			0	0
Distributions to partnership equity				(41.4)
Distributions to noncontrolling interest			(3.4)	(3.4)
Common Stock [Member]
Stock Issued During Period, Value, New Issues			661.3	14.4
Common Stock [Member] | Cliffs Shareholders Equity [Member]
Stock Issued During Period, Value, New Issues			661.3	14.4
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				6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		$ (1,330.5)		$ (1,811.6)	$ (1,330.5)	$ (1,811.6)
Ending Balance	$ (666.7)		$ (1,678.9)		(666.7)	(1,678.9)
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	(250.9)	(260.6)	(236.6)	(241.4)	(260.6)	(241.4)
Other comprehensive income (loss) before reclassifications	(0.1)	3.3	(0.4)	(1.5)
Net loss reclassified from accumulated other comprehensive income (loss)	6.5	6.4	6.3	6.3
Ending Balance	(244.5)	(250.9)	(230.7)	(236.6)	(244.5)	(230.7)
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	0.1		0.1
Other comprehensive income (loss) before reclassifications			0	(0.1)
Net loss reclassified from accumulated other comprehensive income (loss)			0	0
Ending Balance			0	0		0
Unrealized Net Gain (Loss) on Foreign Currency Translation [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	226.6	239.3	225.1	220.7	239.3	220.7
Other comprehensive income (loss) before reclassifications	(1.5)	(12.7)	(2.7)	4.4
Net loss reclassified from accumulated other comprehensive income (loss)	0	0	0	0
Ending Balance	225.1	226.6	222.4	225.1	225.1	222.4
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			(0.8)	2.6		2.6
Other comprehensive income (loss) before reclassifications			0.1	(3.4)
Net loss reclassified from accumulated other comprehensive income (loss)			0	0
Ending Balance			(0.7)	(0.8)		(0.7)
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(24.3)	(21.3)	(12.3)	(18)	(21.3)	(18)
Other comprehensive income (loss) before reclassifications	(1.6)	(9.4)	(3)	(0.6)
Net loss reclassified from accumulated other comprehensive income (loss)	6.5	6.4	6.3	6.3
Ending Balance	$ (19.4)	$ (24.3)	$ (9)	$ (12.3)	$ (19.4)	$ (9)

SHAREHOLDERS' EQUITY Details of

SHAREHOLDERS' EQUITY Details of Accumulated Other Comprehensive Income (Loss) Components (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 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	$ 6.5		$ 6.3		$ 12.9	$ 12.6
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	6.5	$ 6.4	6.3	$ 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)		(0.2)	(0.7)
Defined Benefit Plan, Amortization of Gains (Losses)	6.6		6.7		13.1	13.3
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	6.5		6.3		12.9	12.6
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax	$ 0		$ 0		$ 0	$ 0

RELATED PARTIES (Narrative) (De

RELATED PARTIES (Narrative) (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2016USD ($)	Jun. 30, 2017Facility	Jun. 30, 2016USD ($)	Mar. 31, 2017USD ($)	Mar. 31, 2016USD ($)
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	$ 24.4		$ 41.4
Paid Distributions of Partners' Equity Amounts	$ 17		$ 17

RELATED PARTIES (Summary Of Oth

RELATED PARTIES (Summary Of Other Ownership Interests) (Details)	Jun. 30, 2017	Dec. 31, 2016
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%	23.00%

RELATED PARTIES (Summary Of Rel

RELATED PARTIES (Summary Of Related Party Transactions Table Disclosure) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Related Party Transactions [Abstract]
Product revenues from related parties	$ 227.5	$ 241.6	$ 336.9	$ 345
Product	$ 512	$ 452.8	$ 924.8	$ 728.4
Related party product revenue as a percent of total product revenue	44.40%	53.40%	36.40%	47.40%

RELATED PARTIES RELATED PARTIES

RELATED PARTIES RELATED PARTIES (Summary of Balance Sheet Presentation) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Due to Related Parties, Current	$ 15.9	$ 8.7
Trade Accounts Receivable [Member]
Related Party Transaction [Line Items]
Due from Related Parties, Current	18.8	46.9
Other Current Assets [Member]
Related Party Transaction [Line Items]
Due from Related Parties, Current	$ 68	$ 26.8

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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Income from Continuing Operations	$ 76.5	$ 29.9	$ 46.2	$ 144.2
Loss (Income) from Continuing Operations Attributable to Noncontrolling Interest	1.7	(16.7)	3.4	(25.5)
Net Income from Continuing Operations Attributable to Cliffs Shareholders	78.2	13.2	49.6	118.7
Income (Loss) from Discontinued Operations, net of tax	(46.4)	(0.4)	(45.9)	2.1
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$ 31.8	$ 12.8	$ 3.7	$ 120.8
Weighted Average Number of Shares:
Basic	296.1	182.3	280.6	177
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	4.6	2.3	4.6	1.3
Diluted	300.7	184.6	285.2	178.3
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Basic:
Continuing operations (in dollars per share)	$ 0.26	$ 0.07	$ 0.18	$ 0.67
Discontinued operations (in dollars per share)	(0.16)	0	(0.16)	0.01
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Basic (in dollars per share)	0.10	0.07	0.02	0.68
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted:
Continuing operations (in dollars per share)	0.26	0.07	0.17	0.67
Discontinued operations (in dollars per share)	(0.15)	0	(0.16)	0.01
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted (in dollars per share)	$ 0.11	$ 0.07	$ 0.01	$ 0.68

COMMITMENTS AND CONTINGENCIES N

COMMITMENTS AND CONTINGENCIES Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Loans to and accounts receivable from the Canadian Entities	$ 50.1	$ 48.6
Contingent claims	50	0
Contingent Liabilities recognized in Consolidated Financials	38.5	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	50.1	48.6
Contingent Liabilities recognized in Consolidated Financials	$ 38.5	$ 37.2

SUBSEQUENT EVENTS SUBSEQUENT EV

SUBSEQUENT EVENTS SUBSEQUENT EVENTS (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2017	Jul. 18, 2017	Jun. 30, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
Contingent Liabilities recognized in Consolidated Financials			$ 38.5	$ 37.2
Wabush Scully Mine Sale [Domain]
Subsequent Event [Line Items]
Contingent Liabilities recognized in Consolidated Financials		$ 38.5
Scenario, Forecast [Member] | Wabush Scully Mine Sale [Domain]
Subsequent Event [Line Items]
Gain on Sale of Wabush Scully Mine	$ 30