Cleveland-Cliffs (CLF) 10-K 9 Feb 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Feb. 06, 2017	Jun. 30, 2016
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-K
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		233,074,091
Trading Symbol	clf
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 1,068,236,979

Statements Of Condensed Consoli

Statements Of Condensed Consolidated Financial Position - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
CURRENT ASSETS
Cash and cash equivalents	$ 323.4	$ 285.2
Accounts receivable, net	128.7	40.2
Inventories	178.4	329.6
Supplies and other inventories	91.4	110.4
Loans to and accounts receivables from the Canadian Entities	48.6	72.9
Insurance coverage receivable	0	93.5
Other current assets	54.1	50.9
TOTAL CURRENT ASSETS	824.6	982.7
PROPERTY, PLANT AND EQUIPMENT, NET	984.4	1,059
OTHER ASSETS
OTHER NON-CURRENT ASSETS	114.9	93.8
TOTAL ASSETS	1,923.9	2,135.5
CURRENT LIABILITIES
Accounts payable	107.6	106.3
Accrued employment costs	56.1	53
State and local taxes payable	28.3	35.2
Accrued expenses	41.1	32.4
Accrued interest	40.2	53.3
Accrued royalties	26.2	17.3
Guarantees	0.2	96.5
Insured loss	0	93.5
Other current liabilities	91.4	94.2
TOTAL CURRENT LIABILITIES	391.1	581.7
POSTEMPLOYMENT BENEFIT LIABILITIES
Pensions	245.7	209.7
Other postretirement benefits	34.8	11.3
TOTAL POSTEMPLOYMENT BENEFIT LIABILITIES	280.5	221
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	193.9	231.2
LONG-TERM DEBT	2,175.1	2,699.4
OTHER LIABILITIES	213.8	213.8
TOTAL LIABILITIES	3,254.4	3,947.1
COMMITMENTS AND CONTINGENCIES (SEE NOTE 20)
CLIFFS SHAREHOLDERS' DEFICIT
Preferred Stock - no par value, Class A - 3,000,000 shares authorized, 7 % Series A Mandatory Convertible, Class A, no par value and $1,000 per share liquidation preference (See Note 15), Issued and Outstanding - none issued (2015 - 731,223)	0	731.3
Common Shares - par value $0.125 per share, Authorized - 400,000,000 shares (2015 - 400,000,000 shares); Issued - 238,636,794 shares (2015 - 159,546,224) shares); Outstanding - 233,074,091 shares (2015 - 153,591,930) shares)	29.8	19.8
Capital in excess of par value of shares	3,347	2,298.9
Retained deficit	(4,574.3)	(4,748.4)
Cost of 5,562,703 common shares in treasury (2015 - 5,954,294 shares)	(245.5)	(265)
Accumulated other comprehensive loss	(21.3)	(18)
TOTAL CLIFFS SHAREHOLDERS' DEFICIT	(1,464.3)	(1,981.4)
NONCONTROLLING INTEREST (DEFICIT)	133.8	169.8
TOTAL DEFICIT	(1,330.5)	(1,811.6)
TOTAL LIABILITIES AND DEFICIT	$ 1,923.9	$ 2,135.5

Statements Of Condensed Consol3

Statements Of Condensed Consolidated Financial Position (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Preferred stock, par value	$ 0	$ 0
Cumulative Mandatory Convertible	7.00%	7.00%
Common shares, par value	$ 0.125	$ 0.125
Common shares, authorized (in shares)	400,000,000	400,000,000
Common shares, issued (in shares)	238,636,794	159,546,224
Common shares, outstanding	233,074,091	153,591,930
Common shares in treasury	5,562,703	5,954,294
Preferred Class A [Member]
Class of Stock [Line Items]
Preferred Stock, Liquidation Preference Per Share	$ 1,000	$ 1,000
Preferred stock, shares authorized (in shares)	3,000,000	3,000,000
Preferred Shares, Issued and Outstanding, Shares	0	731,223
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 Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
REVENUES FROM PRODUCT SALES AND SERVICES
Product	$ 1,913.5	$ 1,832.4	$ 3,095.2
Freight and venture partners' cost reimbursements	195.5	180.9	278
TOTAL REVENUES	2,109	2,013.3	3,373.2
COST OF GOODS SOLD AND OPERATING EXPENSES	(1,719.7)	(1,776.8)	(2,487.5)
SALES MARGIN	389.3	236.5	885.7
OTHER OPERATING INCOME (EXPENSE)
Selling, general and administrative expenses	(117.8)	(110)	(154.7)
Impairment of goodwill and other long-lived assets	0	(3.3)	(635.5)
Miscellaneous - net	(30.7)	28.1	34.6
Other operating expense	(148.5)	(85.2)	(755.6)
OPERATING INCOME	240.8	151.3	130.1
OTHER INCOME (EXPENSE)
Interest expense, net	(200.5)	(228.5)	(176.7)
Gain on extinguishment/restructuring of debt	166.3	392.9	16.2
Other non-operating income (expense)	0.4	(2.6)	10.7
TOTAL OTHER INCOME (EXPENSE)	(33.8)	161.8	(149.8)
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES AND EQUITY LOSS FROM VENTURES	207	313.1	(19.7)
INCOME TAX BENEFIT (EXPENSE)	12.2	(169.3)	86
EQUITY LOSS FROM VENTURES, net of tax	0	(0.1)	(9.9)
INCOME FROM CONTINUING OPERATIONS	219.2	143.7	56.4
LOSS FROM DISCONTINUED OPERATIONS, net of tax	(19.9)	(892.1)	(8,368)
NET INCOME (LOSS)	199.3	(748.4)	(8,311.6)
LOSS (INCOME) ATTRIBUTABLE TO NONCONTROLLING INTEREST (Year Ended December 31, 2016 - No loss related to Discontinued Operations, Year Ended December 31, 2015 - Loss of $7.7 million and Year Ended December 31, 2014 - Loss of $1,113.3 million related to Discontinued Operations)	(25.2)	(0.9)	1,087.4
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	174.1	(749.3)	(7,224.2)
PREFERRED STOCK DIVIDENDS	0	(38.4)	(51.2)
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS	$ 174.1	$ (787.7)	$ (7,275.4)
EARNINGS (LOSS) PER COMMON SHARE ATTRIBUTABLE TO CLIFFS SHAREHOLDERS - BASIC
Continuing operations	$ 0.98	$ 0.63	$ (0.14)
Discontinued operations	(0.10)	(5.77)	(47.38)
Earnings (loss) per Common Share Attributable to Cliffs Common Shareholders - Basic:	0.88	(5.14)	(47.52)
EARNINGS (LOSS) PER COMMON SHARE ATTRIBUTABLE TO CLIFFS SHAREHOLDERS - DILUTED
Continuing operations	0.97	0.63	(0.14)
Discontinued operations	(0.10)	(5.76)	(47.38)
Earnings (loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted:	$ 0.87	$ (5.13)	$ (47.52)
AVERAGE NUMBER OF SHARES (IN THOUSANDS)
Basic	197,659	153,230	153,098
Diluted	200,145	153,605	153,098

Statements Of Condensed Consol5

Statements Of Condensed Consolidated Operations (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
LOSS ATTRIBUTABLE TO NONCONTROLLING INTEREST	$ 0	$ 7.7	$ 1,113.3

Statements Of Condensed Consol6

Statements Of Condensed Consolidated Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$ 174.1	$ (749.3)	$ (7,224.2)
OTHER COMPREHENSIVE INCOME (LOSS)
Pension and OPEB liability, net of tax	(19.8)	45.2	(91)
Unrealized net gain (loss) on marketable securities, net of tax	0	1.7	(7.2)
Unrealized net gain (loss) on foreign currency translation	18.6	155.6	(42.3)
Unrealized net gain (loss) on derivative financial instruments, net of tax	(2.6)	20.7	2.8
OTHER COMPREHENSIVE INCOME (LOSS)	(3.8)	223.2	(137.7)
OTHER COMPREHENSIVE LOSS ATTRIBUTABLE TO THE NONCONTROLLING INTEREST	(0.5)	(4.6)	(4.8)
TOTAL COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$ 170.8	$ (521.5)	$ (7,357.1)

Statements Of Condensed Consol7

Statements Of Condensed Consolidated Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
OPERATING ACTIVITIES
Net income (loss)	$ 199.3	$ (748.4)	$ (8,311.6)
Adjustments to reconcile net income (loss) to net cash provided (used) by operating activities:
Depreciation, depletion and amortization	115.4	134	504
Impairment of goodwill and other long-lived assets	0	76.6	9,029.9
Deferred income taxes	0	159.8	(1,153.9)
Changes in deferred revenue and below-market sales contracts	(20.5)	(42.6)	(18)
Gain on extinguishment/restructuring of debt	(166.3)	(392.9)	(16.2)
Loss on deconsolidation, net of cash deconsolidated	17.5	668.3	0
Loss (gain) on sale of North American Coal mines	(2.1)	(9.3)	419.6
Other	32.6	113	(11.6)
Changes in operating assets and liabilities:
Receivables and other assets	43.2	369.1	(82.8)
Product inventories	157.8	(62)	37.8
Payables and accrued expenses	(73.9)	(227.7)	(38.3)
Net cash provided by operating activities	303	37.9	358.9
INVESTING ACTIVITIES
Purchase of property, plant and equipment	(69.1)	(80.8)	(284.1)
Investments in DIP and pre-petition financing	(1.5)	(14)	0
Proceeds from DIP and prepetition financing	8.3	0	0
Proceeds (uses) from sale of North American Coal mines	3.6	(15.2)	155
Other investing activities	0.8	6.8	25.5
Net cash used in investing activities	(57.9)	(103.2)	(103.6)
FINANCING ACTIVITIES
Net proceeds from issuance of common shares	287.4	0	0
Proceeds from first lien notes offering	0	503.5	0
Debt issuance costs	(5.2)	(33.6)	(9)
Borrowings under credit facilities	105	309.8	1,219.5
Repayment under credit facilities	(105)	(309.8)	(1,219.5)
Repayments of equipment loans	(95.6)	(45.4)	(20.9)
Repurchase of debt	(305.4)	(225.9)	(28.8)
Contributions (to)/by joint ventures, net	(3.2)	0.1	(25.7)
Distributions of partnership equity	(59.9)	(40.6)	0
Common stock dividends	0	0	(92.5)
Preferred stock dividends	0	(51.2)	(51.2)
Other financing activities	(24.5)	(45.9)	(60.2)
Net cash provided (used) by financing activities	(206.4)	61	(288.3)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(0.5)	(1.4)	(11.6)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	38.2	(5.7)	(44.6)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	285.2	290.9	335.5
CASH AND CASH EQUIVALENTS AT END OF YEAR	$ 323.4	$ 285.2	$ 290.9

Statements of Consolidated Chan

Statements of Consolidated Changes in Equity - USD ($) $ in Millions	Total	Depositary Shares [Member]	Common Stock [Member]	Capital in Excess of Par Value of Shares [Member]	Retained Earnings [Member]	Common Shares in Treasury [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Preferred Stock, Shares Outstanding		29,300,000
Balance, beginning of period (in shares) at Dec. 31, 2013			153,200,000
Balance, beginning of period at Dec. 31, 2013	$ 6,884.3	$ 731.3	$ 19.8	$ 2,329.5	$ 3,407.3	$ (305.5)	$ (112.9)	$ 814.8
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
NET INCOME (LOSS)	(8,311.6)				(7,224.2)			(1,087.4)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	7,357.1						(132.9)
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	4.8							(4.8)
Other Comprehensive Income (Loss), Net of Tax	(137.7)
Pension and OPEB liability, net of tax	(91)
Unrealized net loss on marketable securities, net of tax	(7.2)
Total comprehensive income (loss)	(8,449.3)							(1,092.2)
Capital contribution by noncontrolling interest to subsidiary	0.1							0.1
Undistributed losses to noncontrolling interest to subsidiary	(25.5)							(25.5)
Stock and other incentive plans	0.1			(19.7)		19.8
Common stock dividends ($0.60 per share)	(92.5)				92.5
Preferred Stock Dividends	(51.3)				(51.3)
Balance, end of period (in shares) at Dec. 31, 2014			153,200,000
Balance, end of period at Dec. 31, 2014	(1,734.3)	$ 731.3	$ 19.8	2,309.8	(3,960.7)	(285.7)	(245.8)	(303)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Preferred Stock, Shares Outstanding		29,300,000
NET INCOME (LOSS)	(748.4)				(749.3)			0.9
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	521.5						227.8
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	4.6							(4.6)
Other Comprehensive Income (Loss), Net of Tax	223.2
Pension and OPEB liability, net of tax	45.2
Unrealized net loss on marketable securities, net of tax	1.7
Total comprehensive income (loss)	(525.2)							(3.7)
Capital contribution by noncontrolling interest to subsidiary	0.2							0.2
Undistributed losses to noncontrolling interest to subsidiary	(0.2)							(0.2)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(51.7)							(51.7)
Deconsolidation, Gain (Loss), Amount	528.2							528.2
Stock and other incentive plans (in shares)			300,000
Stock and other incentive plans	9.8			(10.9)		20.7
Preferred Stock Dividends	$ (38.4)				(38.4)
Balance, end of period (in shares) at Dec. 31, 2015	153,591,930		153,500,000
Balance, end of period at Dec. 31, 2015	$ (1,811.6)	$ 731.3	$ 19.8	2,298.9	(4,748.4)	(265)	(18)	169.8
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Preferred Stock, Shares Outstanding		29,300,000
NET INCOME (LOSS)	199.3				174.1			25.2
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(170.8)						(3.3)
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	0.5							(0.5)
Other Comprehensive Income (Loss), Net of Tax	(3.8)
Pension and OPEB liability, net of tax	(19.8)
Unrealized net loss on marketable securities, net of tax	0
Total comprehensive income (loss)	195.5							24.7
Undistributed losses to noncontrolling interest to subsidiary	(3.2)							(3.2)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(57.5)							(57.5)
Stock and other incentive plans (in shares)			500,000
Stock and other incentive plans	13.7			(5.8)		19.5
Shares issued for debt exchange			8,200,000
Debt for equity exchange (value)	45.2		$ 1	44.2
Stock Issued During Period, Value, Conversion of Convertible Securities	$ 0	$ (731.3)	$ 3.5	727.8
Stock Issued During Period, Shares, Conversion of Units		(29,300,000)	26,500,000
Common Stock, New Shares, Issued	44,400,000		44,400,000
Common stock issuance (value)	$ 287.4		$ 5.5	281.9
Balance, end of period (in shares) at Dec. 31, 2016	233,074,091		233,100,000
Balance, end of period at Dec. 31, 2016	$ (1,330.5)	$ 0	$ 29.8	$ 3,347	$ (4,574.3)	$ (245.5)	$ (21.3)	$ 133.8
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Preferred Stock, Shares Outstanding		0

Statements of Consolidated Cha9

Statements of Consolidated Changes in Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Common stock dividends per share	$ 0	$ 0.60	$ 0.60
Preferred stock dividends per share	$ 0	$ 1.32	$ 1.76

BASIS OF PRESENTATION AND SIGNI

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BUSINESS SUMMARY AND SIGNIFICANT ACCOUNTING POLICIES	NOTE 1 - BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES Nature of Business We are a leading mining and natural resources company in the U.S. We are a major supplier of iron ore pellets to the North American steel industry from our mines and pellet plants located in Michigan and Minnesota. We also operate the Koolyanobbing iron ore mining complex in Western Australia, which provides iron ore to the seaborne market for Asian steel producers. Significant Accounting Policies We consider the following policies to be beneficial in understanding the judgments that are involved in the preparation of our consolidated financial statements and the uncertainties that could impact our financial condition, results of operations and cash flows. Use of Estimates The preparation of financial statements, in conformity with GAAP, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions related to mineral reserves future realizable cash flow; environmental, reclamation and closure obligations; valuation of long-lived assets; valuation of inventory; valuation of post-employment, post-retirement and other employee benefit liabilities; valuation of tax assets; reserves for contingencies and litigation; the fair value of derivative instruments; and the fair value of loans to and accounts receivable from Canadian entities. Actual results could differ from estimates. On an ongoing basis, management reviews estimates. Changes in facts and circumstances may alter such estimates and affect the results of operations and financial position in future periods. Basis of Consolidation The consolidated financial statements include our accounts and the accounts of our wholly owned and majority-owned subsidiaries, including the following operations at December 31, 2016 : 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 Investments in unconsolidated ventures that we have the ability to exercise significant influence over, but not control, are accounted for under the equity method. Hibbing Our 23% ownership interest in Hibbing is recorded as an equity method investment. As of December 31, 2016 and December 31, 2015 , our investment in Hibbing was $8.7 million and $2.4 million , respectively, classified in Other liabilities in the Statements of Consolidated Financial Position . Our share of equity income (loss) is eliminated against consolidated product inventory upon production, and against Cost of goods sold and operating expenses when sold. This effectively reduces our cost for our share of the mining ventures' production cost, reflecting the cost-based nature of our participation in unconsolidated ventures. Noncontrolling Interests Noncontrolling interest is primarily comprised of the 21% noncontrolling interest in the consolidated, but less-than-wholly-owned subsidiary at our Empire mining venture and through the CCAA filing on January 27, 2015, the 17.2% noncontrolling interest in the Bloom Lake operations. Financial results prior to the deconsolidation of the Bloom Lake Group and subsequent expenses directly associated with the Canadian Entities are included in our financial statements. The net loss and income attributable to the noncontrolling interest of the Empire mining venture was $25.2 million and $8.6 million for the years ended December 31, 2016 and December 31, 2015 , respectively. There was no net income or loss attributable to the noncontrolling interest related to Bloom Lake for the year ended December 31, 2016 . This compares with a net loss attributable to the noncontrolling interest related to Bloom Lake of $7.7 million for the year ended December 31, 2015 . See NOTE 14 - DISCONTINUED OPERATIONS for further information. Cash Equivalents Cash and cash equivalents include cash on hand and on deposit as well as all short-term securities held for the primary purpose of general liquidity. We consider investments in highly liquid debt instruments with an original maturity of three months or less from the date of acquisition to be cash equivalents. We routinely monitor and evaluate counterparty credit risk related to the financial institutions by which our short-term investment securities are held. Trade Accounts Receivable and Allowance for Doubtful Accounts Trade accounts receivable are recorded at the invoiced amount and do not bear interest. The allowance for doubtful accounts is our best estimate of the amount of probable credit losses in our existing accounts receivable. We establish provisions for losses on accounts receivable when it is probable that all or part of the outstanding balance will not be collected. We regularly review our accounts receivable balances and establish or adjust the allowance as necessary using the specific identification method. The allowance for doubtful accounts was zero and $7.1 million at December 31, 2016 and 2015 , respectively. There was no bad debt expense for the years ended December 31, 2016 and 2014. There was $7.1 million bad debt expense for the year ended December 31, 2015 . Inventories U.S. Iron Ore U.S. Iron Ore product inventories are stated at the lower of cost or market. Cost of iron ore inventories is determined using the LIFO method. We had approximately 1.5 million long tons and 1.3 million long tons of finished goods stored at ports and customer facilities on the lower Great Lakes to service customers at December 31, 2016 and 2015 , respectively. We maintain ownership of the inventories until title has transferred to the customer, usually when payment is received. Maintaining ownership of the iron ore products at ports on the lower Great Lakes reduces risk of non-payment by customers. Asia Pacific Iron Ore Asia Pacific Iron Ore product inventories are stated at the lower of cost or market. Costs of iron ore inventories are being valued on a weighted average cost basis. We maintain ownership of the inventories until title has transferred to the customer, which generally is when the product is loaded into the vessel. Supplies and Other Inventories Supply inventories include replacement parts, fuel, chemicals and other general supplies, which are expected to be used or consumed in normal operations. Supply inventories also include critical spares. Critical spares are replacement parts for equipment that is critical for the continued operation of the mine or processing facilities. Supply inventories are stated at the lower of cost or market using average cost, less an allowance for obsolete and surplus items. The allowance for obsolete and surplus items was $14.0 million and $31.8 million at December 31, 2016 and 2015 , respectively. The decrease in the allowance for obsolete and surplus items during the year ended December 31, 2016 , was primarily a result of the disposal of Empire's supplies inventory of approximately $17.4 million that was fully reserved for as of the previous year end. Derivative Financial Instruments and Hedging Activities We are exposed to certain risks related to the ongoing operations of our business, including those caused by changes in commodity prices, interest rates and foreign currency exchange rates. We have established policies and procedures, including the use of certain derivative instruments, to manage such risks, if deemed necessary. Derivative financial instruments are recognized as either assets or liabilities in the Statements of Consolidated Financial Position and measured at fair value. For derivative instruments that have not been designated as cash flow hedges, changes in fair value are recorded in the period of the instrument's earnings or losses. Refer to NOTE 13 - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES for further information. Property, Plant and Equipment Our properties are stated at the lower of cost less accumulated depreciation or fair value. Depreciation of plant and equipment is computed principally by the straight-line method based on estimated useful lives, not to exceed the mine lives. The U.S. Iron Ore operations use the double-declining balance method of depreciation for certain mining equipment. The Asia Pacific Iron Ore operation uses the production output method for certain mining equipment. Depreciation is provided over the following estimated useful lives: Asset Class Basis Life Office and information technology Straight line 3 to 15 Years Buildings Straight line 45 Years Mining equipment Straight line/Double declining balance 3 to 20 Years Processing equipment Straight line 10 to 45 Years Electric power facilities Straight line 10 to 45 years Land improvements Straight line 20 to 45 years Asset retirement obligation Straight line Life of mine Depreciation continues to be recognized when operations are idled temporarily. Refer to NOTE 4 - PROPERTY, PLANT AND EQUIPMENT for further information. Capitalized Stripping Costs During the development phase, stripping costs are capitalized as a part of the depreciable cost of building, developing and constructing a mine. These capitalized costs are amortized over the productive life of the mine using the units of production method. The production phase does not commence until the removal of more than a de minimis amount of saleable mineral material occurs in conjunction with the removal of overburden or waste material for purposes of obtaining access to an ore body. The stripping costs incurred in the production phase of a mine are variable production costs included in the costs of the inventory produced (extracted) during the period that the stripping costs are incurred. Stripping costs related to expansion of a mining asset of proven and probable reserves are variable production costs that are included in the costs of the inventory produced during the period that the stripping costs are incurred. Other Intangible Assets and Liabilities Other intangible assets are subject to periodic amortization on a straight-line basis over their estimated useful lives as follows: Intangible Assets Basis Useful Life (years) Permits - Asia Pacific Iron Ore Units of production Life of mine Permits - USIO Straight line Life of mine Asset Impairment Long-Lived Tangible and Intangible Assets We monitor conditions that may affect the carrying value of our long-lived tangible and intangible assets when events and circumstances indicate that the carrying value of the asset groups may not be recoverable. In order to determine if assets have been impaired, assets are grouped and tested at the lowest level for which identifiable, independent cash flows are available ("asset group"). An impairment loss exists when projected undiscounted cash flows are less than the carrying value of the asset group. The measurement of the impairment loss to be recognized is based on the difference between the fair value and the carrying value of the asset group. Fair value can be determined using a market approach, income approach or cost approach. During the year ended December 31, 2016, there were no impairment indicators present; as a result no impairment assessments were required. As a result of the 2015 assessments, there were no material impairment charges related to long-lived tangible or intangible assets at our continuing operations. During 2014, we recorded a long-lived tangible asset impairment charge of $537.8 million and an intangible asset impairment charge of $13.8 million in our Statements of Consolidated Operations related to our continuing operations. Refer to NOTE 4 - PROPERTY, PLANT AND EQUIPMENT , NOTE 12 - GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES and NOTE 6 - FAIR VALUE OF FINANCIAL INSTRUMENTS for further information. Fair Value Measurements Valuation Hierarchy ASC 820, Fair Value Measurements and Disclosures , establishes a three-level valuation hierarchy for classification of fair value measurements. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. Inputs refer broadly to the assumptions that market participants would use in pricing an asset or liability. Inputs may be observable or unobservable. Observable inputs are inputs that reflect the assumptions market participants would use in pricing the asset or liability developed based on market data obtained from independent sources. Unobservable inputs are inputs that reflect our own views about the assumptions market participants would use in pricing the asset or liability developed based on the best information available in the circumstances. The three-tier hierarchy of inputs is summarized below: • Level 1 — Valuation is based upon quoted prices (unadjusted) for identical assets or liabilities in active markets. • Level 2 — Valuation is based upon quoted prices for similar assets and liabilities in active markets, or other inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the financial instrument. • Level 3 — Valuation is based upon other unobservable inputs that are significant to the fair value measurement. The classification of assets and liabilities within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement in its entirety. Valuation methodologies used for assets and liabilities measured at fair value are as follows: Cash Equivalents Where quoted prices are available in an active market, cash equivalents are classified within Level 1 of the valuation hierarchy. Cash equivalents classified in Level 1 at December 31, 2016 and 2015 include money market funds. Valuation of these instruments is determined using a market approach and is based upon unadjusted quoted prices for identical assets in active markets. Derivative Financial Instruments Derivative financial instruments valued using financial models that use as their basis readily observable market parameters are classified within Level 2 of the valuation hierarchy. Such derivative financial instruments include our commodity hedge and foreign currency exchange contracts. Derivative financial instruments that are valued based upon models with significant unobservable market parameters and are normally traded less actively, are classified within Level 3 of the valuation hierarchy. Refer to NOTE 6 - FAIR VALUE OF FINANCIAL INSTRUMENTS and NOTE 7 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information. Pensions and Other Postretirement Benefits We offer defined benefit pension plans, defined contribution pension plans and other postretirement benefit plans, primarily consisting of retiree healthcare benefits, to most employees in North America as part of a total compensation and benefits program. We do not have employee pension or post-retirement benefit obligations at our Asia Pacific Iron Ore operations. We recognize the funded or unfunded status of our postretirement benefit obligations on our December 31, 2016 and 2015 Statements of Consolidated Financial Position based on the difference between the market value of plan assets and the actuarial present value of our retirement obligations on that date, on a plan-by-plan basis. If the plan assets exceed the retirement obligations, the amount of the surplus is recorded as an asset; if the retirement obligations exceed the plan assets, the amount of the underfunded obligations are recorded as a liability. Year-end balance sheet adjustments to postretirement assets and obligations are recorded as Accumulated other comprehensive loss . The actuarial estimates of the PBO and APBO incorporate various assumptions including the discount rates, the rates of increases in compensation, healthcare cost trend rates, mortality, retirement timing and employee turnover. The discount rate is determined based on the prevailing year-end rates for high-grade corporate bonds with a duration matching the expected cash flow timing of the benefit payments from the various plans. The remaining assumptions are based on our estimates of future events by incorporating historical trends and future expectations. The amount of net periodic cost that is recorded in the Statements of Consolidated Operations consists of several components including service cost, interest cost, expected return on plan assets, and amortization of previously unrecognized amounts. Service cost represents the value of the benefits earned in the current year by the participants. Interest cost represents the cost associated with the passage of time. Certain items, such as plan amendments, gains and/or losses resulting from differences between actual and assumed results for demographic and economic factors affecting the obligations and assets of the plans, and changes in other assumptions are subject to deferred recognition for income and expense purposes. The expected return on plan assets is determined utilizing the weighted average of expected returns for plan asset investments in various asset categories based on historical performance, adjusted for current trends. See NOTE 7 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information. Asset Retirement Obligations Asset retirement obligations are recognized when incurred and recorded as liabilities at fair value. The fair value of the liability is determined as the discounted value of the expected future cash flow. The asset retirement obligation is accreted over time through periodic charges to earnings. In addition, the asset retirement cost is capitalized and amortized over the life of the related asset. Reclamation costs are adjusted periodically to reflect changes in the estimated present value resulting from the passage of time and revisions to the estimates of either the timing or amount of the reclamation costs. We review, on an annual basis, unless otherwise deemed necessary, the asset retirement obligation at each mine site in accordance with the provisions of ASC 410, Asset Retirement and Environmental Obligations . We perform an in-depth evaluation of the liability every three years in addition to routine annual assessments. Future reclamation costs for inactive mines are accrued based on management’s best estimate at the end of each period of the costs expected to be incurred at a site. Such cost estimates include, where applicable, ongoing maintenance and monitoring costs. Changes in estimates at inactive mines are reflected in earnings in the period an estimate is revised. See NOTE 11 - ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS for further information. Environmental Remediation Costs We have a formal policy for environmental protection and restoration. Our mining and exploration activities are subject to various laws and regulations governing protection of the environment. We conduct our operations to protect the public health and environment and believe our operations are in compliance with applicable laws and regulations in all material respects. Our environmental liabilities, including obligations for known environmental remediation exposures at active and closed mining operations and other sites, have been recognized based on the estimated cost of investigation and remediation at each site. If the cost only can be estimated as a range of possible amounts with no point in the range being more likely, the minimum of the range is accrued. Future expenditures are not discounted unless the amount and timing of the cash disbursements reasonably can be estimated. It is possible that additional environmental obligations could be incurred, the extent of which cannot be assessed. Potential insurance recoveries have not been reflected in the determination of the liabilities. See NOTE 11 - ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS for further information. Revenue Recognition We sell our products pursuant to comprehensive supply agreements negotiated and executed with our customers. Revenue is recognized from a sale when persuasive evidence of an arrangement exists, the price is fixed or determinable, the product is delivered in accordance with F.O.B. terms, title and risk of loss have transferred to the customer in accordance with the specified provisions of each supply agreement and collection of the sales price reasonably is assured. Our U.S. Iron Ore and Asia Pacific Iron Ore supply agreements provide that title and risk of loss transfer to the customer either upon loading of the vessel, shipment or, as is the case with some of our U.S. Iron Ore supply agreements, when payment is received. Under certain term supply agreements, we ship the product to ports on the lower Great Lakes or to the customers’ facilities prior to the transfer of title. Our rationale for shipping iron ore products to certain customers and retaining title until payment is received for these products is to minimize credit risk exposure. Sales are recorded at a sales price specified in the relevant supply agreements resulting in revenue and a receivable at the time of sale. Upon revenue recognition for provisionally priced sales, a freestanding derivative is created for the difference between the sales price used and expected future settlement price. The derivative, which does not qualify for hedge accounting, is adjusted to fair value through Product revenues as a revenue adjustment each reporting period based upon current market data and forward-looking estimates determined by management until the final sales price is determined. The principal risks associated with recognition of sales on a provisional basis include iron ore price fluctuations between the date initially recorded and the date of final settlement. For revenue recognition, we estimate the future settlement rate; however, if significant changes in iron ore prices occur between the provisional pricing date and the final settlement date, we might be required to either return a portion of the sales proceeds received or bill for the additional sales proceeds due based on the provisional sales price. Refer to NOTE 13 - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES for further information. In addition, certain supply agreements with one customer include provisions for supplemental revenue or refunds based on the customer’s annual steel pricing for the year the product is consumed in the customer’s blast furnaces. We account for this provision as a free standing derivative instrument at the time of sale and record this provision at fair value until the year the product is consumed and the amounts are settled as an adjustment to revenue. Refer to NOTE 13 - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES for further information. Revenue from product sales and services also includes reimbursement for freight charges associated with domestic freight and venture partner cost reimbursements for the U.S. Iron Ore operations and freight associated with CFR based shipments paid on behalf of customers for the Asia Pacific Iron Ore operations. These are included in Freight and venture partners' cost reimbursements separate from Product revenues . Revenue is recognized for the expected reimbursement of services when the services are performed. Deferred Revenue The terms of one of our U.S. Iron Ore pellet supply agreements required supplemental payments to be paid by the customer during the period 2009 through 2012, with the option to defer a portion of the 2009 monthly amount in exchange for interest payments until the deferred amount was repaid in 2013. Installment amounts received under this arrangement in excess of sales were classified as deferred revenue in the Statements of Consolidated Financial Position upon receipt of payment. Revenue is recognized over the life of the supply agreement, which extends until 2022, in equal annual installments. As of December 31, 2016 and 2015 , installment amounts received in excess of sales totaled $77.1 million and $89.9 million , respectively. As of December 31, 2016, deferred revenue of $16.4 million was recorded in Other current liabilities and $64.2 million was recorded as long-term in Other liabilities in the Statements of Consolidated Financial Position . As of December 31, 2015, deferred revenue of $12.8 million was recorded in Other current liabilities and $77.1 million was recorded as long-term in Other liabilities in the Statements of Consolidated Financial Position . In 2016 and 2014, due to the payment terms and the timing of cash receipts near year-end, cash receipts exceeded shipments for certain customers. The shipments were completed early in the subsequent years. We considered whether revenue should be recognized on these sales under the “bill and hold” guidance provided by the SEC Staff; however, based upon the assessment performed, revenue recognition on these transactions totaling $3.4 million and $29.3 million were deferred on the Statements of Consolidated Financial Position for the years ended December 31, 2016 and 2014 , respectively. Cost of Goods Sold Cost of goods sold and operating expenses represents all direct and indirect costs and expenses applicable to the sales of our mining operations. Operating expenses primarily represent the portion of the Tilden mining venture costs for which we do not own; that is, the costs attributable to the share of the mine’s production owned by the other joint venture partner in the Tilden mine. The mining venture functions as a captive cost company; it supplies product only to its owners effectively for the cost of production. Accordingly, the noncontrolling interests’ revenue amounts are stated at cost of production and are offset by an equal amount included in Cost of goods sold and operating expenses resulting in no sales margin reflected for the noncontrolling partner participant. As we are responsible for product fulfillment, we act as a principal in the transaction and, accordingly, record revenue under these arrangements on a gross basis. The following table is a summary of reimbursements in our U.S. Iron Ore operations for the years ended December 31, 2016 , 2015 and 2014 : (In Millions) Year Ended December 31, 2016 2015 2014 Reimbursements for: Freight $ 106.8 $ 105.3 $ 163.0 Venture partners’ cost 68.0 52.0 108.0 Total reimbursements $ 174.8 $ 157.3 $ 271.0 In 2014, we began selling a portion of our Asia Pacific Iron Ore product on a CFR basis. As a result, $20.7 million , $23.6 million and $6.9 million of freight was included in Cost of goods sold and operating expenses for the years ended December 31, 2016, 2015 and 2014, respectively. Where we have joint ownership of a mine, our contracts entitle us to receive royalties and/or management fees, which we earn as the pellets are produced. Repairs and Maintenance Repairs, maintenance and replacement of components are expensed as incurred. The cost of major equipment overhauls is capitalized and depreciated over the estimated useful life, which is the period until the next scheduled overhaul, generally five years. All other planned and unplanned repairs and maintenance costs are expensed when incurred. Share-Based Compensation 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. Consistent with the guidelines of ASC 718, Stock Compensation , a correlation matrix of historic and projected stock prices was developed for both the Company and its predetermined peer group of mining and metals companies. The fair value assumes that performance goals will be achieved. The expected term of the grant represents the time from the grant date to the end of the service period for each of the three plan-year agreements. We estimated 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 plans. The fair value of stock options is estimated on the date of grant using a Black-Scholes model using the grant date price of our common shares and option exercise price, and assumptions regarding the option’s expected term, the volatility of our common shares, the risk-free interest rate, and the dividend yield over the option’s expected term. Upon vesting of share-based compensation awards, we issue shares from treasury shares before issuing new shares. Refer to NOTE 8 - STOCK COMPENSATION PLANS for additional information. Income Taxes Income taxes are based on income for financial reporting purposes, calculated using tax rates by jurisdiction, and reflect a current tax liability or asset for the estimated taxes payable or recoverable on the current year tax return and expected annual changes in deferred taxes. Any interest or penalties on income tax are recognized as a component of income tax expense. We account for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. We record net deferred tax assets to the extent we believe these assets will more likely than not be realized. In making such determination, we consider all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax planning strategies and recent financial results of operations. Accounting for uncertainty in income taxes recognized in the financial statements requires that a tax benefit from an uncertain tax position be recognized when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on technical merits. See NOTE 9 - INCOME TAXES for further information. Discontinued Operations In April 2014, the FASB issued ASU 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity , which changes the criteria for reporting discontinued operations and requires additional disclosures about discontinued operations. The standard requires that an entity report as a discontinued operation only a disposal that represents a strategic shift in operations that has a major effect on its operations and financial results. ASU 2014-08 is effective prospectively for new disposals that occur within annual periods beginning on or after December 15, 2014. Early adoption was permitted and we adopted ASU 2014-08 during the year ended December 31, 2014. North American Coal Operations As we executed our strategy to focus on strengthening our U.S. Iron Ore operations, management determined as of March 31, 2015 that our North American Coal operating segment met the criteria to be classified as held for sale under ASC 205, Presentation of Financial Statements and continued to meet the criteria throughout 2015. In December 2015, we completed the sale of our remaining two metallurgical coal operations, Oak Grove and Pinnacle mines, which marked our exit from the coal business. Our plan to sell the Oak Grove and Pinnacle mine assets represented a strategic shift in our business. For this reason, our previously reported North American Coal operating segment results for all periods, prior to the March 31, 2015 held for sale determination, as well as costs to exit are classified as discontinued operations. Refer to NOTE 14 - DISCONTINUED OPERATIONS for further discussion of our discontinued operations. Canadian Operations As more fully described in NOTE 14 - DISCONTINUED OPERATIONS , in January 2015, we announced that the Bloom Lake Group commenced restructuring proceedings in Montreal, Quebec under the CCAA. At that time, we had suspend

SEGMENT REPORTING

SEGMENT REPORTING	12 Months Ended
	Dec. 31, 2016
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 product revenues in 2016, 2015 or 2014. We have historically evaluated segment performance based on sales margin, defined as revenues less cost of goods sold and operating expenses identifiable to each segment. Additionally, we evaluate segment performance based on EBITDA, defined as net income (loss) before interest, income taxes, depreciation, depletion and amortization, and Adjusted EBITDA, defined as EBITDA excluding certain items such as extinguishment/restructuring of debt, impacts of discontinued operations, foreign currency remeasurement, severance and contractor termination costs, certain supplies inventory write-offs, impairment of goodwill and other long-lived assets and other costs associated with the proxy contest and change in control. 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 is 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 years ended December 31, 2016 , 2015 and 2014 , including a reconciliation of segment sales margin to Income (Loss) from Continuing Operations Before Income Taxes and Equity Loss from Ventures and a reconciliation of Net Income (Loss) to EBITDA and Adjusted EBITDA: (In Millions) 2016 2015 2014 Revenues from product sales and services: U.S. Iron Ore $ 1,554.5 74% $ 1,525.4 76% $ 2,506.5 74% Asia Pacific Iron Ore 554.5 26% 487.9 24% 866.7 26% Total revenues from product sales and services $ 2,109.0 100% $ 2,013.3 100% $ 3,373.2 100% Sales margin: U.S. Iron Ore $ 275.7 $ 227.1 $ 710.4 Asia Pacific Iron Ore 113.6 9.4 121.7 Eliminations with discontinued operations — — 53.6 Sales margin 389.3 236.5 885.7 Other operating expense (148.5 ) (85.2 ) (755.6 ) Other income (expense) (33.8 ) 161.8 (149.8 ) Income (loss) from continuing operations before income taxes and equity loss from ventures $ 207.0 $ 313.1 $ (19.7 ) (In Millions) 2016 2015 2014 Net income (loss) $ 199.3 $ (748.4 ) $ (8,311.6 ) Less: Interest expense, net (200.5 ) (231.4 ) (185.2 ) Income tax benefit (expense) 12.2 (163.3 ) 1,302.0 Depreciation, depletion and amortization (115.4 ) (134.0 ) (504.0 ) Total EBITDA $ 503.0 $ (219.7 ) $ (8,924.4 ) Less: Gain on extinguishment/restructuring of debt $ 166.3 $ 392.9 $ 16.2 Impact of discontinued operations (19.9 ) (892.0 ) (9,332.5 ) Foreign exchange remeasurement (16.8 ) 16.3 29.0 Severance and contractor termination costs (0.1 ) (10.2 ) (23.3 ) Supplies inventory write-off — (16.3 ) — Impairment of goodwill and other long-lived assets — (3.3 ) (635.5 ) Proxy contest and change in control in SG&A — — (26.6 ) Total Adjusted EBITDA $ 373.5 $ 292.9 $ 1,048.3 EBITDA: U.S. Iron Ore $ 342.4 $ 317.6 $ 805.6 Asia Pacific Iron Ore 128.3 35.3 (352.9 ) Other (including discontinued operations) 32.3 (572.6 ) (9,377.1 ) Total EBITDA $ 503.0 $ (219.7 ) $ (8,924.4 ) Adjusted EBITDA: U.S. Iron Ore $ 359.6 $ 352.1 $ 833.5 Asia Pacific Iron Ore 132.9 32.7 252.9 Other (119.0 ) (91.9 ) (38.1 ) Total Adjusted EBITDA $ 373.5 $ 292.9 $ 1,048.3 (In Millions) 2016 2015 2014 Depreciation, depletion and amortization: U.S. Iron Ore $ 84.0 $ 98.9 $ 107.4 Asia Pacific Iron Ore 25.1 25.3 145.9 Other 6.3 6.6 7.7 Total depreciation, depletion and amortization $ 115.4 $ 130.8 $ 261.0 Capital additions 1 : U.S. Iron Ore $ 62.2 $ 58.2 $ 48.4 Asia Pacific Iron Ore 0.2 5.4 10.8 Other 6.1 8.6 6.3 Total capital additions $ 68.5 $ 72.2 $ 65.5 1 Includes capital lease additions and non-cash accruals. Refer to NOTE 17 - CASH FLOW INFORMATION. A summary of assets by segment is as follows: (In Millions) December 31, December 31, 2015 December 31, 2014 Assets: U.S. Iron Ore $ 1,372.5 $ 1,476.4 $ 1,464.9 Asia Pacific Iron Ore 155.1 202.5 306.2 Total segment assets 1,527.6 1,678.9 1,771.1 Corporate 396.3 441.7 666.2 Assets of Discontinued Operations — 14.9 709.9 Total assets $ 1,923.9 $ 2,135.5 $ 3,147.2 Included in the consolidated financial statements are the following amounts relating to geographic location: (In Millions) 2016 2015 2014 Revenue United States $ 1,236.2 $ 1,206.4 $ 1,923.2 China 452.5 370.8 662.7 Canada 267.1 282.4 430.5 Other countries 153.2 153.7 356.8 Total revenue $ 2,109.0 $ 2,013.3 $ 3,373.2 Property, Plant and Equipment, Net United States $ 961.0 $ 1,012.7 $ 998.1 Australia 23.4 46.3 72.4 Total Property, Plant and Equipment, Net $ 984.4 $ 1,059.0 $ 1,070.5 Concentrations in Revenue In 2016 , two customers individually accounted for more than 10% of our consolidated product revenue and in 2015 and 2014 , three customers individually accounted for more than 10% of our consolidated product revenue. Total product revenue from these customers represents approximately $1.1 billion , $ 1.3 billion and $ 1.9 billion of our total consolidated product revenue in 2016 , 2015 and 2014 , respectively, and is attributable to our U.S. Iron Ore business segment. The following table represents the percentage of our total revenue contributed by each category of products and services in 2016 , 2015 and 2014 : 2016 2015 2014 Revenue category Product 91 % 91 % 92 % Freight and venture partners’ cost reimbursements 9 % 9 % 8 % Total revenue 100 % 100 % 100 %

INVENTORIES

INVENTORIES	12 Months Ended
	Dec. 31, 2016
Inventory Disclosure [Abstract]
Inventories	NOTE 3 - INVENTORIES The following table presents the detail of our Inventories in the Statements of Consolidated Financial Position as of December 31, 2016 and 2015 : (In Millions) December 31, 2016 December 31, 2015 Segment Finished Goods Work-in Process Total Inventory Finished Goods Work-in Process Total Inventory U.S. Iron Ore $ 124.4 $ 12.6 $ 137.0 $ 252.3 $ 11.7 $ 264.0 Asia Pacific Iron Ore 23.6 17.8 41.4 20.8 44.8 65.6 Total $ 148.0 $ 30.4 $ 178.4 $ 273.1 $ 56.5 $ 329.6 Asia Pacific Iron Ore had no long-term work-in-process stockpiles at December 31, 2016 . There were $6.8 million long-term work-in-process stockpiles classified as Other non-current assets in the Statements of Consolidated Financial Position as of December 31, 2015 . U.S. Iron Ore The excess of current cost over LIFO cost of iron ore inventories was $78.5 million and $87.8 million at December 31, 2016 and 2015 , respectively. As of December 31, 2016 , the product inventory balance for U.S. Iron Ore declined, resulting in the liquidation of a LIFO layer in 2016. The effect of the inventory reduction was an increase in Cost of goods sold and operating expenses of $8.8 million in the Statements of Consolidated Operations for the year ended December 31, 2016 . As of December 31, 2015 , the product inventory balance for U.S. Iron Ore increased, resulting in a LIFO increment in 2015 . The effect of the inventory build was an increase in Inventories of $118.8 million in the Statements of Consolidated Financial Position for the year ended December 31, 2015 .

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	12 Months Ended
	Dec. 31, 2016
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 December 31, 2016 and 2015 : (In Millions) December 31, 2016 2015 Land rights and mineral rights $ 500.5 $ 500.5 Office and information technology 65.1 71.0 Buildings 67.9 60.4 Mining equipment 592.2 594.0 Processing equipment 552.0 516.8 Electric power facilities 49.4 46.4 Land improvements 23.5 24.8 Asset retirement obligation 19.8 87.9 Other 28.1 28.2 Construction in-progress 42.8 40.3 1,941.3 1,970.3 Allowance for depreciation and depletion (956.9 ) (911.3 ) $ 984.4 $ 1,059.0 We recorded depreciation expense of $106.8 million , $119.2 million and $173.0 million in the Statements of Consolidated Operations for the years ended December 31, 2016 , 2015 and 2014 , respectively. For the year ended December 31, 2016 , there were no factors present that indicated the carrying value of certain asset groups would not be recoverable; therefore, there were no impairments during 2016 . Our asset groups consist of the assets and liabilities of our mines and associated reserves. The lowest level of identifiable cash flows largely are at the U.S. Iron Ore and Asia Pacific Iron Ore segment levels. For the year ended December 31, 2015 , although certain factors indicated that the carrying value of certain asset groups may not be recoverable, an assessment was performed and no further impairment was indicated. During the second half of 2014 , due to lower than previously expected profits as a result of decreased iron ore pricing expectations and increased costs, we determined that indicators of impairment with respect to certain of our long-lived assets or asset groups existed. As a result of these assessments during 2014 , we determined that the future cash flows associated with our Asia Pacific Iron Ore asset group and other asset groups were not sufficient to support the recoverability of the carrying value of these productive assets. Accordingly, during 2014 , an other long-lived asset impairment charge of $537.8 million was recorded as Impairment of goodwill and other long-lived assets in the Statements of Consolidated Operations related to property, plant and equipment. The fair value estimates were calculated using income and market approaches. The net book value of the land rights and mineral rights as of December 31, 2016 and 2015 is as follows : (In Millions) December 31, 2016 2015 Land rights $ 11.6 $ 11.6 Mineral rights: Cost $ 488.9 $ 488.9 Depletion (112.2 ) (108.4 ) Net mineral rights $ 376.7 $ 380.5 Accumulated depletion relating to mineral rights, which was recorded using the unit-of-production method, is included in Cost of goods sold and operating expenses . We recorded depletion expense of $3.8 million , $7.4 million and $79.6 million in the Statements of Consolidated Operations for the years ended December 31, 2016 , 2015 and 2014 , respectively. As discussed above, during 2014 we performed impairment assessments with respect to certain of our long-lived assets or asset groups. As a result of these assessments, we recorded an other long-lived asset impairment charge related to mineral rights of $297.2 million associated with our Asia Pacific Iron Ore asset group.

DEBT AND CREDIT FACILITIES

DEBT AND CREDIT FACILITIES	12 Months Ended
	Dec. 31, 2016
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 December 31, 2016 and 2015 : ($ 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 ($ in Millions) December 31, 2015 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 $ (10.5 ) $ (32.1 ) $ 497.4 $544.2 Million 7.75% 2020 Second Lien Notes 15.55% 544.2 (9.5 ) (131.5 ) 403.2 Unsecured Notes $500 Million 3.95% 2018 Senior Notes 6.30% 311.2 (0.9 ) (1.2 ) 309.1 $400 Million 5.90% 2020 Senior Notes 5.98% 290.8 (1.1 ) (0.8 ) 288.9 $500 Million 4.80% 2020 Senior Notes 4.83% 306.7 (1.1 ) (0.4 ) 305.2 $700 Million 4.875% 2021 Senior Notes 4.89% 412.5 (1.7 ) (0.2 ) 410.6 $800 Million 6.25% 2040 Senior Notes 6.34% 492.8 (4.3 ) (5.8 ) 482.7 ABL Facility N/A 550.0 N/A N/A — Fair Value Adjustment to Interest Rate Hedge 2.3 Long-term debt $ 2,699.4 Senior Secured Notes Our First Lien Notes bear interest at a rate of 8.25% per annum. Interest on the First Lien Notes is payable semi-annually in arrears on March 31 and September 30 of each year, commencing on September 30, 2015. The First Lien Notes mature on March 31, 2020 and are secured senior obligations of the Company. Our 1.5 Lien Notes bear interest at a rate of 8.00% per annum. Interest on the 1.5 Lien Notes is payable semi-annually in arrears on March 31 and September 30 of each year, commencing on September 30, 2016. The 1.5 Lien Notes mature on September 30, 2020 and are secured senior obligations of the Company. Our Second Lien Notes bear interest at a rate of 7.75% per annum. Interest on the Second Lien Notes is payable semi-annually in arrears on March 31 and September 30 of each year, commencing on September 30, 2015. The Second Lien Notes mature on March 31, 2020 and are secured senior obligations of the Company. The First Lien Notes are jointly and severally and fully and unconditionally guaranteed on a senior secured basis by substantially all of our material U.S. subsidiaries and are secured (subject in each case to certain exceptions and permitted liens) by (i) a first-priority lien on substantially all of our U.S. assets, other than the ABL Collateral (the "Notes Collateral"), and (ii) a second-priority lien on the U.S. ABL Collateral (as defined below), which is junior to a first-priority lien for the benefit of the lenders under the ABL Facility. The First Lien Notes and guarantees are general senior obligations of the Company and the applicable guarantor; are effectively senior to all of our unsecured indebtedness, to the extent of the value of the collateral; together with other obligations secured equally and ratably with the First Lien Notes, are effectively (i) senior to our existing and future ABL obligations, to the extent and value of the Notes Collateral and (ii) senior to our obligations under the Second Lien Notes, to the extent and value of the collateral; are effectively subordinated to (i) our existing and future ABL obligations, to the extent and value of the ABL Collateral, and (ii) any existing or future indebtedness that is secured by liens on assets that do not constitute a part of the collateral, to the extent of the value of such assets; will rank equally in right of payment with all existing and future senior indebtedness, and any guarantees thereof; will rank equally in priority as to the Notes Collateral with any future debt secured equally and ratably with the First Lien Notes incurred after March 30, 2015; rank senior in right of payment to all existing and future subordinated indebtedness; and structurally subordinated to all existing and future indebtedness and other liabilities of our subsidiaries that do not guarantee the First Lien Notes. The relative priority of the liens securing our First Lien Notes obligations, 1.5 Lien Notes obligations and Second Lien Notes obligations compared to the liens securing our obligations under the ABL Facility and certain other matters relating to the administration of security interests are set forth in intercreditor agreements. The 1.5 and Second Lien Notes have substantially similar terms to those of the First Lien Notes except with respect to their priority security interest in the collateral. The 1.5 Lien Notes are jointly and severally and fully and unconditionally guaranteed on a senior secured basis by substantially all of our material U.S. subsidiaries and are secured (subject in each case to certain exceptions and permitted liens) on (i) a junior first-priority basis by substantially all of our U.S. assets, other than the ABL Collateral, and (ii) a junior second-priority basis by our ABL Collateral, which secures our ABL obligations on a first-priority basis, the First Lien Notes obligations on a senior second-priority basis and the Second Lien Notes obligations on a third-priority basis. The Second Lien Notes are jointly and severally and fully and unconditionally guaranteed on a senior secured basis by substantially all of our material U.S. subsidiaries and are secured (subject in each case to certain exceptions and permitted liens) by (i) a second-priority lien (junior to the First Lien Notes) on substantially all of our U.S. assets, other than the ABL Collateral, and (ii) a third-priority lien (junior to the ABL Facility and the First Lien Notes) on the U.S. ABL Collateral. The terms of the secured notes are governed by the secured notes indentures. The secured notes indentures contain customary covenants that, among other things, limit our ability to incur certain secured indebtedness, create liens on principal property and the capital stock or debt of a subsidiary that owns a principal property, use proceeds of dispositions of collateral, enter into certain sale and leaseback transactions, merge or consolidate with another company and transfer or sell all or substantially all of our assets. Upon the occurrence of a “change of control triggering event,” as defined in the secured notes indentures, we are required to offer to repurchase the secured notes at 101% of the aggregate principal amount thereof, plus any accrued and unpaid interest, if any, to, but excluding, the repurchase date. The secured notes indentures contain 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 secured notes indentures will allow either the trustee or the holders of at least 25% in aggregate principal amount of the then-outstanding applicable series of secured notes issued under the applicable indenture to accelerate, or in certain cases, will automatically cause the acceleration of, the amounts due under such series of secured notes. The following is a summary of redemption prices for each of our secured senior notes: First Lien Notes 1.5 Lien Notes Second Lien Notes Percent of Principal Period Percent of Principal Period Percent of Principal Period Early redemption 1,2 100.00 % Prior to March 31, 2018 100.00 % Prior to September 30, 2017 100.00 % Prior to March 31, 2017 Initial redemption 1 108.25 Beginning on March 31, 2018 104.00 Beginning on September 30, 2017 103.875 Beginning on March 31, 2017 Secondary redemption 1 100.00 Beginning on June 30, 2019 100.00 Beginning on September 30, 2019 100.00 Beginning on March 31, 2019 1 Plus accrued and unpaid interest, if any, up to but excluding the redemption date. 2 Plus a "make-whole" premium. In addition, we may redeem in the aggregate up to 35% of the original aggregate principal amount (calculated after giving effect to any issuance of additional notes) with the net cash proceeds from certain equity offerings at a redemption price of 108.25%, 108.00% and 107.75% for the First, 1.5 and Second Lien Notes, respectively, so long as at least 65% of the original aggregate principal amount of the notes (calculated after giving effect to any issuance of additional notes) issued remain outstanding after each such redemption. Unsecured Senior Notes Our 3.95% senior notes were redeemed in whole on September 16, 2016 at a total redemption price of $301.0 million , which included $283.6 million outstanding aggregate principal. As a result, we recorded a $19.9 million pre-tax loss on full retirement of long-term debt in the third quarter of 2016, which consisted of debt redemption premiums of $17.4 million and expenses of $2.5 million related to the write-off of unamortized debt issuance costs, unamortized bond discount and deferred losses on interest rate swaps. The loss was recorded against the Gain on extinguishment/restructuring of debt in the Statements of Consolidated Operations for the year ended December 31, 2016 . Our 5.90% senior notes are due March 15, 2020. Interest is payable on March 15 and September 15 of each year until maturity. Our 4.80% senior notes are due October 1, 2020. Interest is payable on April 1 and October 1 of each year until maturity. Our 4.875% senior notes are due April 1, 2021. Interest is payable on April 1 and October 1 of each year until maturity. Our 6.25% senior notes are due October 1, 2040. Interest is payable on April 1 and October 1 of each year until maturity. The senior notes are unsecured obligations and rank equally in right of payment with all our other existing and future unsecured and unsubordinated indebtedness. There are no subsidiary guarantees of the interest and principal amounts. The senior notes may be redeemed any time at our option not less than 30 days nor more than 60 days after prior notice is sent to the holders of the applicable series of notes. The senior notes are redeemable at a redemption price equal to the greater of (1) 100% of the principal amount of the notes to be redeemed or (2) the sum of the present values of the remaining scheduled payments of principal and interest on the notes to be redeemed, discounted to the redemption date on a semi-annual basis at the treasury rate plus 50 basis points with respect to the 2018 senior notes, 35 basis points with respect to the 2020 senior notes, 25 basis points with respect to the 2021 senior notes and 40 basis points with respect to the 2040 senior notes, plus, in each case, accrued and unpaid interest to the date of redemption. However, if the 2021 senior notes are redeemed on or after the date that is three months prior to their maturity date, the 2021 senior notes will be redeemed at a redemption price equal to 100% of the principal amount of the notes to be redeemed plus accrued and unpaid interest to the date of redemption. In addition, if a change of control triggering event occurs with respect to the senior notes, as defined in the agreement, we will be required to offer to purchase the notes of the applicable series at a purchase price equal to 101% of the principal amount, plus accrued and unpaid interest, if any, to the date of purchase. The terms of the senior notes contain certain customary covenants; however, there are no financial covenants. ABL Facility On March 30, 2015, we entered into a new senior secured asset-based revolving credit facility with various financial institutions. The ABL Facility will mature upon the earlier of March 30, 2020 or 60 days prior to the maturity of the First Lien Notes and certain other material debt, and provides for up to $550.0 million in borrowings, comprised of (i) a $450.0 million U.S. tranche, including a $250.0 million sublimit for the issuance of letters of credit and a $100.0 million sublimit for U.S. swingline loans, and (ii) a $100.0 million Australian tranche, including a $50.0 million sublimit for the issuance of letters of credit and a $20.0 million sublimit for Australian swingline loans. Availability under both the U.S. tranche and Australian tranche of the ABL Facility is limited to an eligible U.S. borrowing base and Australian borrowing base, as applicable, determined by applying customary advance rates to eligible accounts receivable, inventory and certain mobile equipment. The ABL Facility and certain bank products and hedge obligations are guaranteed by us and certain of our existing wholly-owned U.S. and Australian subsidiaries and are required to be guaranteed by certain of our future U.S. and Australian subsidiaries; provided, however, that the obligations of any U.S. entity will not be guaranteed by any Australian entity. Amounts outstanding under the ABL Facility will be secured by (i) a first-priority security interest in the ABL Collateral, including, in the case of the Australian tranche only, ABL Collateral owned by a borrower or guarantor that is organized under the laws of Australia, and (ii) a third-priority security interest in the Notes Collateral (as defined herein). The priority of the security interests in the ABL Collateral and the Notes Collateral of the lenders under the ABL Facility and the holders of the First Lien Notes are set forth in intercreditor provisions contained in an ABL intercreditor agreement. The ABL Collateral generally consists of the following assets: accounts receivable and other rights to payment, inventory, as-extracted collateral, investment property, certain general intangibles and commercial tort claims, certain mobile equipment, commodities accounts, deposit accounts, securities accounts and other related assets and proceeds and products of each of the foregoing. Borrowings under the ABL Facility bear interest, at our option, at a base rate, an Australian base rate or, if certain conditions are met, a LIBOR rate, in each case plus an applicable margin. The base rate is equal to the greater of the federal funds rate plus ½ of 1% , the LIBOR rate based on a one-month interest period plus 1% and the floating rate announced by BAML as its “prime rate.” The Australian base rate is equal to the LIBOR rate as of 11:00 a.m. on the first business day of each month for a one-month period. The LIBOR rate is a per annum fixed rate equal to LIBOR with respect to the applicable interest period and amount of LIBOR rate loan requested. The ABL Facility contains customary representations and warranties and affirmative and negative covenants including, among others, covenants regarding the maintenance of certain financial ratios if certain conditions are triggered, covenants relating to financial reporting, covenants relating to the payment of dividends on, or purchase or redemption of our capital stock, covenants relating to the incurrence or prepayment of certain debt, covenants relating to the incurrence of liens or encumbrances, compliance with laws, transactions with affiliates, mergers and sales of all or substantially all of our assets and limitations on changes in the nature of our business. The ABL Facility provides for customary events of default, including, among other things, the event of nonpayment of principal, interest, fees, or other amounts, a representation or warranty proving to have been materially incorrect when made, failure to perform or observe certain covenants within a specified period of time, a cross-default to certain material indebtedness, the bankruptcy or insolvency of the Company and certain of its subsidiaries, monetary judgment defaults of a specified amount, invalidity of any loan documentation, a change of control of the Company, and ERISA defaults resulting in liability of a specified amount. In the event of a default by us (beyond any applicable grace or cure period, if any), the administrative agent may and, at the direction of the requisite number of lenders, shall declare all amounts owing under the ABL Facility immediately due and payable, terminate such lenders’ commitments to make loans under the ABL Facility and/or exercise any and all remedies and other rights under the ABL Facility. For certain defaults related to insolvency and receivership, the commitments of the lenders will be automatically terminated and all outstanding loans and other amounts will become immediately due and payable. As of December 31, 2016, we were in compliance with the ABL Facility liquidity requirements and, therefore, the springing financial covenant requiring a minimum fixed charge coverage ratio of 1.0 to 1.0 was not applicable. As of December 31, 2016 , no loans were drawn under the ABL Facility and we had total availability of $333.0 million as a result of borrowing base limitations. As of December 31, 2016 , the principal amount of letter of credit obligations totaled $106.0 million , thereby further reducing available borrowing capacity on our ABL Facility to $227.0 million . As of December 31, 2015 , no loans were drawn under the ABL Facility and we had total availability of $366.0 million as a result of borrowing base limitations. As of December 31, 2015 , the principal amount of letter of credit obligations totaled $186.3 million and commodity hedge obligations totaled $0.5 million , thereby further reducing available borrowing capacity to $179.2 million . Letters of Credit We issued standby letters of credit with certain financial institutions in order to support business obligations including, but not limited to, workers compensation and environmental obligations. As of December 31, 2016 and December 31, 2015 , these letter of credit obligations totaled $106.0 million and $186.3 million , respectively. Debt Extinguishments/Restructurings 1.5 Lien Notes Exchange On March 2, 2016, we entered into an indenture among the Company, the guarantors party thereto and U.S. Bank National Association, as trustee and notes collateral agent, relating to our issuance of $218.5 million aggregate principal amount of 8.00% 1.5 Lien Senior Secured Notes due 2020 (the “1.5 Lien Notes”). The 1.5 Lien Notes were issued in exchange offers for certain of our existing senior notes. We accounted for the 1.5 Lien Notes exchange as a TDR. For an exchange classified as TDR, if the future undiscounted cash flows of the newly issued debt are less than the net carrying value of the original debt, the carrying value of the newly issued debt is adjusted to the future undiscounted cash flow amount, a gain is recorded for the difference and no future interest expense is recorded. All future interest payments on the newly issued debt reduce the carrying value. Accordingly, we recognized a gain of $174.3 million in the Gain on extinguishment/restructuring of debt in the Statements of Consolidated Operations for the year ended December 31, 2016 . As a result, our reported interest expense will be less than the contractual interest payments throughout the term of the 1.5 Lien Notes. Debt issuance costs incurred of $5.2 million related to the notes exchange were expensed and were included in the Gain on extinguishment/restructuring of debt in the Statements of Consolidated Operations for the year ended December 31, 2016 . As of December 31, 2016 , $17.5 million of the undiscounted interest is recorded as current and classified as Other current liabilities in the Statements of Consolidated Financial Position. The following is a summary of the debt exchanged for our $218.5 million 1.5 Lien Notes: ($ In Millions) Debt Extinguished 1.5 Lien Amount Issued Carrying Value 1 Gain on Restructuring 2 $544.2 Million 7.75% 2020 Second Lien Notes $ 114.1 $ 57.0 $ 77.5 $ 6.9 $500 Million 3.95% 2018 Senior Notes 17.6 11.4 15.5 1.8 $400 Million 5.90% 2020 Senior Notes 65.1 26.0 35.4 28.3 $500 Million 4.80% 2020 Senior Notes 44.7 17.9 24.4 19.5 $700 Million 4.875% 2021 Senior Notes 76.3 30.5 41.5 33.3 $800 Million 6.25% 2040 Senior Notes 194.4 75.7 103.0 84.5 $ 512.2 $ 218.5 $ 297.3 $ 174.3 1 Includes undiscounted interest payments 2 Net of amounts expensed for unamortized original issue discount and deferred origination fees Second Lien Notes Exchange On March 30, 2015, we also entered into an indenture among the Company, the guarantors and U.S. Bank National Association, as trustee and notes collateral agent, relating to our issuance of $544.2 million aggregate principal amount of 7.75% second lien senior secured notes due 2020 (the "Second Lien Notes"). The Second Lien Notes were issued in exchange offers for certain of our existing senior notes. The following is a summary of the debt exchanged for our $544.2 million Second Lien Notes: ($ In Millions) Debt Extinguished Second Lien Notes Amount Issued Carrying Value 1 Gain on Restructuring 2 $400 Million 5.90% 2020 Senior Notes $ 67.0 $ 57.5 $ 42.0 $ 24.5 $500 Million 4.80% 2020 Senior Notes 137.8 112.9 82.4 54.6 $700 Million 4.875% 2021 Senior Notes 208.5 170.3 124.3 83.1 $800 Million 6.25% 2040 Senior Notes 261.3 203.5 148.5 107.3 $ 674.6 $ 544.2 $ 397.2 $ 269.5 1 Includes unamortized discounts 2 Net of amounts expensed for unamortized original issue discount and deferred origination fees Debt-for-Equity Exchanges During the year ended December 31, 2016, we entered into a series of privately negotiated exchange agreements whereby we issued an aggregate of 8.2 million common shares in exchange for $10.0 million aggregate principal amount of our 3.95% senior notes due 2018, $20.1 million aggregate principal amount of our 4.80% senior notes due 2020 and $26.8 million aggregate principal amount of our 4.875% senior notes due 2021. There were no exchanges that represented more than 1% of our outstanding common shares during any quarter. Accordingly, we recognized a gain of $11.3 million in Gain on extinguishment/restructuring of debt in the Statements of Consolidated Operations for the year ended December 31, 2016 . Other Debt Redemptions During the year ended December 31, 2016, we purchased with cash $5.0 million of our outstanding 4.80% senior notes, which resulted in a gain on extinguishment of $0.6 million . During the year ended December 31, 2015, we purchased with cash $168.8 million of outstanding 3.95% senior notes, $69.0 million of outstanding 4.875% senior notes, $45.9 million of outstanding 6.25% senior notes, $45.6 million of outstanding 4.80% senior notes, and $37.3 million of outstanding 5.90% senior notes, which resulted in a gain on the extinguishment of debt of $137.1 million . In addition, during 2015, we replaced the revolving credit agreement with our ABL Facility, which resulted in a loss on extinguishment of $13.7 million . Debt Maturities The following represents a summary of our maturities of debt instruments, excluding borrowings on the ABL Facility, based on the principal amounts outstanding at December 31, 2016 : (In Millions) Maturities of Debt 2017 $ — 2018 — 2019 — 2020 1,651.0 2021 309.4 2022 and thereafter 298.4 Total maturities of debt $ 2,258.8

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	NOTE 6 - FAIR VALUE OF FINANCIAL INSTRUMENTS The following represents the assets and liabilities of the Company measured at fair value at December 31, 2016 and 2015 : (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 (In Millions) December 31, 2015 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 $ 30.0 $ — $ — $ 30.0 Derivative assets — — 7.8 7.8 Total $ 30.0 $ — $ 7.8 $ 37.8 Liabilities: Derivative liabilities $ — $ 0.6 $ 3.4 $ 4.0 Total $ — $ 0.6 $ 3.4 $ 4.0 Financial assets classified in Level 1 as of December 31, 2016 and December 31, 2015 , include money market funds, which are included in Cash and cash equivalents . 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. At December 31, 2016 and December 31, 2015 , such derivative financial instruments included our commodity hedge contracts. The derivative financial assets classified within Level 3 at December 31, 2016 and December 31, 2015 primarily relate to a freestanding derivative instrument related to certain supply agreements with one of our U.S. Iron Ore customers. The agreements include provisions for supplemental revenue or refunds based on the customer’s annual steel pricing at the time the product is consumed in the customer’s blast furnaces. We account for this provision as a derivative instrument at the time of sale and adjust this provision to fair value as an adjustment to Product revenues each reporting period until the product is consumed and the amounts are settled. The fair value of the instrument is determined using a market approach based on an estimate of the annual realized price of hot-rolled coil at the steelmaker’s facilities, and takes into consideration current market conditions and nonperformance risk. The Level 3 derivative assets and liabilities also consisted of derivatives related to certain provisional pricing arrangements with our U.S. Iron Ore and Asia Pacific Iron Ore customers at December 31, 2016 and December 31, 2015 . These provisional pricing arrangements specify provisional price calculations, where the pricing mechanisms generally are based on market pricing, with the final revenue rate to be based on market inputs at a specified point in time in the future, per the terms of the supply agreements. The difference between the estimated final revenue at the date of sale and the estimated final revenue rate is characterized as a derivative and is required to be accounted for separately once the revenue has been recognized. The derivative instrument is adjusted to fair value through Product revenues each reporting period based upon current market data and forward-looking estimates provided by management until the final revenue rate is determined. The following table illustrates information about quantitative inputs and assumptions for the derivative assets and derivative liabilities categorized in Level 3 of the fair value hierarchy: Qualitative/Quantitative Information About Level 3 Fair Value Measurements ($ in millions) Fair Value at December 31, 2016 Balance Sheet Location Valuation Technique Unobservable Input Range or Point Estimate (Weighted Average) Provisional Pricing Arrangements $ 10.3 Other current assets Market Approach Management's Estimate of Platts 62% Price $80 $ 0.5 Other current liabilities Customer Supply Agreement $ 21.3 Other current assets Market Approach Hot-Rolled Coil Estimate $505 - $620 ($555) The significant unobservable inputs used in the fair value measurement of the reporting entity’s provisional pricing arrangements are management’s estimates of Platts 62% Price based upon current market data, index pricing, and the customer's average annual steel pricing for hot rolled coil, each of which include forward-looking estimates determined by management. Significant increases or decreases in these inputs would result in a significantly higher or lower fair value measurement, respectively. The significant unobservable input used in the fair value measurement of the reporting entity’s customer supply agreement is the future hot-rolled coil price that is estimated based on current market data, analysts' projections, projections provided by the customer and forward-looking estimates determined by management. Significant increases or decreases in this input would result in a significantly higher or lower fair value measurement, respectively. We recognize any transfers between levels as of the beginning of the reporting period, including both transfers into and out of levels. There were no transfers between Level 1 and Level 2 of the fair value hierarchy during the years ended December 31, 2016 and 2015 . 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 years ended December 31, 2016 and 2015 . (In Millions) Derivative Assets (Level 3) Derivative Liabilities (Level 3) Year Ended Year Ended 2016 2015 2016 2015 Beginning balance - January 1 $ 7.8 $ 63.2 $ (3.4 ) $ (9.5 ) Total gains (losses) Included in earnings 103.8 35.1 (14.1 ) (61.0 ) Settlements (80.0 ) (90.5 ) 17.0 67.1 Transfers into Level 3 — — — — Transfers out of Level 3 — — — — Ending balance - December 31 $ 31.6 $ 7.8 $ (0.5 ) $ (3.4 ) Total gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) on assets still held at the reporting date $ 23.7 $ 29.1 $ (0.5 ) $ (3.4 ) Gains and losses included in earnings are reported in Product revenues in the Statements of Consolidated Operations for the years ended December 31, 2016 and 2015 . The carrying amount for certain financial instruments (e.g. Accounts receivable, net , Accounts payable and Accrued expenses ) approximate fair value and, therefore, have been excluded from the table below. A summary of the carrying amount and fair value of other financial instruments at December 31, 2016 and 2015 were as follows: (In Millions) December 31, 2016 December 31, 2015 Classification Carrying Value Fair Value Carrying Value Fair Value Long-term debt: Secured Notes Senior First Lien Notes—$540 million Level 1 $ 506.3 $ 595.0 $ 497.4 $ 414.5 1.5 Senior Lien Notes—$218 million Level 2 284.2 229.5 — — Senior Second Lien Notes—$544.2 million Level 1 339.1 439.7 403.2 134.7 Unsecured Notes Senior Notes—$400 million Level 1 224.5 219.6 288.9 52.8 Senior Notes—$1.3 billion Level 1 528.4 455.8 787.9 137.4 Senior Notes—$700 million Level 1 308.2 283.1 410.6 69.4 Senior Notes—$500 million Level 1 — — 309.1 87.1 ABL Facility Level 2 — — — — Fair Value Adjustment to Interest Rate Hedge Level 2 1.9 1.9 2.3 2.3 Total long-term debt $ 2,192.6 $ 2,224.6 $ 2,699.4 $ 898.2 The fair value of long-term debt was determined using quoted market prices or discounted cash flows based upon current borrowing rates. Items Measured at Fair Value on a Non-Recurring Basis There were no financial and non-financial assets and liabilities that were measured on a non-recurring fair value basis at December 31, 2016 and 2015.

PENSIONS AND OTHER POSTRETIREME

PENSIONS AND OTHER POSTRETIREMENT BENEFITS	12 Months Ended
	Dec. 31, 2016
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 other postretirement benefit plans, primarily consisting of retiree healthcare benefits, to most employees in the U.S. 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 employees’ years of service and average earnings for a defined period prior to retirement or a minimum formula. Approximately 80.0% of our total U.S. Iron Ore hourly workforce is represented by the USW. We offer retiree medical coverage to hourly retirees of our USW-represented mines. The 2015 USW agreement set fixed monthly medical premiums for participants who retired prior to January 1, 2015. These fixed premiums will expire on December 31, 2018 and revert to increasing premiums based a cost-sharing formula. The agreements also provide for an OPEB cap that limits the amount of contributions that we have to make toward retiree medical insurance coverage for each retiree and spouse of a retiree per calendar year who retired on or after January 1, 2015. The amount of the annual OPEB cap is based upon the gross plan costs we incurred in 2014. The OPEB cap applies to employees who retired on or after January 1, 2015 and does not apply to surviving spouses. The 2015 USW agreement also eliminates retiree medical coverage for USW-represented employees hired after September 1, 2016. In lieu of retiree medical coverage, USW-represented employees hired after September 1, 2016 will receive a 401(k) contribution of $0.50 per hour worked to a restricted Retiree Health Care Account. In addition, we currently provide various levels of retirement health care and OPEB to some full-time employees who meet certain length of service and age requirements (a portion of which is pursuant to collective bargaining agreements). Most plans require retiree contributions and have deductibles, co-pay requirements and benefit limits. Most bargaining unit plans require retiree contributions and co-pays for major medical and prescription drug coverage. There is a cap on our cost for medical coverage under the salaried plans. The annual limit applies to each covered participant and equals $7,000 for coverage prior to age 65, with the retiree’s participation adjusted based on the age at which the retiree’s benefits commence. Beginning in 2015, we changed the delivery of the post-65 salaried retiree medical benefit program, including salaried retirees from our Northshore operation, from an employer sponsored plan to the combination of an employer subsidy plan and an individual supplemental Medicare insurance plan purchased through a Medicare exchange. This allows the program to take full advantage of available government subsidies and more efficient pricing in the Medicare market. For participants at our Northshore operation, the annual limit ranges from $4,020 to $4,500 for coverage prior to age 65. Covered participants pay an amount for coverage equal to the excess of (i) the average cost of coverage for all covered participants, over (ii) the participant’s individual limit, but in no event will the participant’s cost be less than 15.0% of the average cost of coverage for all covered participants. For Northshore participants, the minimum participant cost is a fixed dollar amount. We do not provide OPEB for most salaried employees hired after January 1, 1993. Retiree healthcare coverage is provided through programs administered by insurance companies whose charges are based on benefits paid. The Pinnacle and Oak Grove mines were sold in December 2015, and the liabilities representing vested salaried pension benefits at the time of the sale remained with Cliffs. The sale triggered a curtailment event for the Salaried Pension Plan. Liabilities for other postretirement benefits were transferred as part of the sale, and associated adjustments were made to the Accumulated other comprehensive loss balances as they pertained to Pinnacle and Oak Grove participants in the Hourly OPEB plan. Accordingly, all amounts shown below include retained obligations of vested employees of the North American Coal mines. Further, all disclosures presented include the annual expense, contributions and obligations associated with the retained vested benefits of these participants. The following table summarizes the annual expense (income) recognized related to the retirement plans for 2016 , 2015 and 2014 : (In Millions) 2016 2015 2014 Defined benefit pension plans $ 16.5 $ 23.9 $ 26.2 Defined contribution pension plans 2.8 3.6 4.4 Other postretirement benefits (4.0 ) 4.4 (2.5 ) Total $ 15.3 $ 31.9 $ 28.1 Obligations and Funded Status The following tables and information provide additional disclosures for the years ending December 31, 2016 and 2015 : (In Millions) Pension Benefits Other Benefits Change in benefit obligations: 2016 2015 2016 2015 Benefit obligations — beginning of year $ 910.8 $ 998.0 $ 266.0 $ 295.8 Service cost (excluding expenses) 17.6 22.7 1.7 1.9 Interest cost 30.3 37.7 9.1 11.5 Plan amendments 5.7 — 9.8 — Actuarial (gain) loss 38.1 (67.7 ) (7.2 ) (27.0 ) Benefits paid (70.9 ) (78.7 ) (21.3 ) (20.6 ) Participant contributions — — 6.0 4.0 Federal subsidy on benefits paid — — 0.5 0.4 Curtailment gain — (1.2 ) — — Benefit obligations — end of year $ 931.6 $ 910.8 $ 264.6 $ 266.0 Change in plan assets: Fair value of plan assets — beginning of year $ 700.6 $ 749.8 $ 250.6 $ 269.3 Actual return on plan assets 54.8 (6.4 ) 16.0 (3.9 ) Participant contributions — — 0.5 0.4 Employer contributions 1.2 35.7 1.7 1.3 Asset transfers 0.1 0.2 — — Benefits paid (70.9 ) (78.7 ) (15.8 ) (16.5 ) Fair value of plan assets — end of year $ 685.8 $ 700.6 $ 253.0 $ 250.6 Funded status at December 31: Fair value of plan assets $ 685.8 $ 700.6 $ 253.0 $ 250.6 Benefit obligations (931.6 ) (910.8 ) (264.6 ) (266.0 ) Funded status (plan assets less benefit obligations) $ (245.8 ) $ (210.2 ) $ (11.6 ) $ (15.4 ) Amount recognized at December 31 $ (245.8 ) $ (210.2 ) $ (11.6 ) $ (15.4 ) Amounts recognized in Statements of Financial Position: Noncurrent assets $ — $ — $ 27.3 $ — Current liabilities (0.1 ) (0.5 ) (4.1 ) (4.1 ) Noncurrent liabilities (245.7 ) (209.7 ) (34.8 ) (11.3 ) Total amount recognized $ (245.8 ) $ (210.2 ) $ (11.6 ) $ (15.4 ) Amounts recognized in accumulated other comprehensive loss: Net actuarial loss $ 315.9 $ 290.9 $ 87.0 $ 91.5 Prior service cost (credit) 11.0 7.5 (26.9 ) (39.5 ) Net amount recognized $ 326.9 $ 298.4 $ 60.1 $ 52.0 The estimated amounts that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in 2017: Net actuarial loss $ 21.1 $ 5.0 Prior service cost (credit) 2.6 (3.0 ) Net amount recognized $ 23.7 $ 2.0 (In Millions) 2016 Pension Plans Other Benefits Salaried Hourly Mining SERP Total Salaried Hourly Total Fair value of plan assets $ 242.9 $ 436.9 $ 6.0 $ — $ 685.8 $ — $ 253.0 $ 253.0 Benefit obligation (351.9 ) (565.6 ) (10.0 ) (4.1 ) (931.6 ) (37.6 ) (227.0 ) (264.6 ) Funded status $ (109.0 ) $ (128.7 ) $ (4.0 ) $ (4.1 ) $ (245.8 ) $ (37.6 ) $ 26.0 $ (11.6 ) 2015 Pension Plans Other Benefits Salaried Hourly Mining SERP Total Salaried Hourly Total Fair value of plan assets $ 258.3 $ 436.7 $ 5.6 $ — $ 700.6 $ — $ 250.6 $ 250.6 Benefit obligation (340.0 ) (558.6 ) (8.6 ) (3.6 ) (910.8 ) (38.2 ) (227.8 ) (266.0 ) Funded status $ (81.7 ) $ (121.9 ) $ (3.0 ) $ (3.6 ) $ (210.2 ) $ (38.2 ) $ 22.8 $ (15.4 ) The accumulated benefit obligation for all defined benefit pension plans was $922.0 million and $898.9 million at December 31, 2016 and 2015 , respectively. The increase in the accumulated benefit obligation primarily is a result of a decrease in the discount rates. Components of Net Periodic Benefit Cost (In Millions) Pension Benefits Other Benefits 2016 2015 2014 2016 2015 2014 Service cost $ 17.6 $ 22.7 $ 26.1 $ 1.7 $ 6.4 $ 1.8 Interest cost 30.3 37.7 40.3 9.1 13.4 11.9 Expected return on plan assets (54.7 ) (59.8 ) (58.1 ) (17.1 ) (18.3 ) (17.1 ) Amortization: Prior service costs (credits) 2.2 2.3 2.5 (3.7 ) (3.7 ) (3.6 ) Net actuarial loss 21.1 20.8 14.0 6.0 6.6 4.5 Curtailments and settlements — 0.2 1.4 — — — Net periodic benefit cost (credit) $ 16.5 $ 23.9 $ 26.2 $ (4.0 ) $ 4.4 $ (2.5 ) Curtailment effects — (1.2 ) — — — — Current year actuarial (gain)/loss 37.8 (0.7 ) 109.7 (8.1 ) 0.2 22.2 Amortization of net loss (21.1 ) (21.0 ) (15.4 ) (6.0 ) (6.6 ) (4.5 ) Current year prior service (credit) cost 5.7 — — 9.8 — (0.9 ) Amortization of prior service (cost) credit (2.2 ) (2.3 ) (2.5 ) 3.7 3.7 3.6 Total recognized in other comprehensive income (loss) $ 20.2 $ (25.2 ) $ 91.8 $ (0.6 ) $ (2.7 ) $ 20.4 Total recognized in net periodic cost and other comprehensive income (loss) $ 36.7 $ (1.3 ) $ 118.0 $ (4.6 ) $ 1.7 $ 17.9 Additional Information (In Millions) Pension Benefits Other Benefits 2016 2015 2014 2016 2015 2014 Effect of change in mine ownership & noncontrolling interest $ 14.2 $ 48.4 $ 51.2 $ 5.9 $ 5.5 $ 5.9 Actual return on plan assets 54.8 (6.4 ) 59.1 16.0 (3.9 ) 31.9 Assumptions The discount rate for determining PBO is determined individually for each plan as noted in the assumption chart below. The discount rates are determined by matching the projected cash flows used to determine the PBO and APBO to a projected yield curve of 696 Aa graded bonds in the 40 th to 90 th percentiles. These bonds are either noncallable or callable with make-whole provisions. The decreases in discount rates due to market conditions resulted in increases of $22.0 million and $8.6 million for the pension and other postretirement benefit plans, respectively, to the plans PBO. Effective January 1, 2016, we changed the approach used to calculate the service and interest components of net periodic benefit cost. Previously, we calculated the service and interest components utilizing a single weighted-average discount rate derived from the yield curve used to measure the PBO. We have elected an alternative approach that utilizes a full yield curve approach in the estimation of these components by applying the specific spot rates along the yield curve used in the determination of the benefit obligation to their underlying projected cash flows. The change resulted in a decrease to our net periodic benefit cost of $8.2 million and $1.8 million for our pension plans and OPEB plans, respectively for the year ended December 31, 2016. On December 31, 2016, the assumed mortality improvement projection was changed from generational scale MP-2015 to generational scale MP-2016. The healthy mortality assumption remains the RP-2014 mortality tables with blue collar adjustments for the Iron Hourly and Hourly PRW plans, with white collar adjustments for the SERP and Salaried PRW Plan, and without collar adjustments for the Salaried and Ore Mining. The adoption of the new projection scale resulted in decreases to our PBO totaling approximately $13.1 million or 1.4% for the pension plans and $4.9 million or 1.8% for the OPEB plans. Weighted-average assumptions used to determine benefit obligations at December 31 were: Pension Benefits Other Benefits 2016 2015 2016 2015 Discount rate Iron Hourly Pension Plan 4.02 % 4.27 % N/A % N/A % Salaried Pension Plan 3.92 4.12 N/A N/A Ore Mining Pension Plan 4.04 4.28 N/A N/A SERP 3.90 4.22 N/A N/A Hourly OPEB Plan N/A N/A 4.02 4.32 Salaried OPEB Plan N/A N/A 3.99 4.22 Salaried rate of compensation increase 3.00 3.00 3.00 3.00 Hourly rate of compensation increase 2.00 2.00 N/A N/A Weighted-average assumptions used to determine net benefit cost for the years 2016 , 2015 and 2014 were: Pension Benefits Other Benefits 2016 2015 2014 2016 2015 2014 Obligation Discount Rate Iron Hourly Pension Plan 4.27 % 3.83 % 4.57 % N/A % N/A % N/A % Salaried Pension Plan 4.13 3.83 4.57 N/A N/A N/A Ore Mining Pension Plan 4.28 3.83 4.57 N/A N/A N/A SERP 4.01 3.83 4.57 N/A N/A N/A Hourly OPEB Plan N/A N/A N/A 4.32 3.83 4.57 Salaried OPEB Plan N/A N/A N/A 4.22 3.83 4.57 Service Cost Discount Rate Iron Hourly Pension Plan 4.66 3.83 4.57 N/A N/A N/A Salaried Pension Plan 4.14 3.83 4.57 N/A N/A N/A Ore Mining Pension Plan 4.60 3.83 4.57 N/A N/A N/A SERP 3.87 3.83 4.57 N/A N/A N/A Hourly OPEB Plan N/A N/A N/A 4.56 3.83 4.57 Salaried OPEB Plan N/A N/A N/A 4.63 3.83 4.57 Interest Cost Discount Rate Iron Hourly Pension Plan 3.46 3.83 4.57 N/A N/A N/A Salaried Pension Plan 3.21 3.83 4.57 N/A N/A N/A Ore Mining Pension Plan 3.48 3.83 4.57 N/A N/A N/A SERP 3.30 3.83 4.57 N/A N/A N/A Hourly OPEB Plan N/A N/A N/A 3.48 3.83 4.57 Salaried OPEB Plan N/A N/A N/A 3.31 3.83 4.57 Expected return on plan assets 8.25 8.25 8.25 7.00 7.00 7.00 Salaried rate of compensation increase 3.00 3.00 4.00 3.00 3.00 4.00 Hourly rate of compensation increase 2.00 2.50 3.00 N/A N/A N/A Assumed health care cost trend rates at December 31 were: 2016 2015 Health care cost trend rate assumed for next year 6.50 % 6.75 % Ultimate health care cost trend rate 5.00 5.00 Year that the ultimate rate is reached 2023 2023 Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A change of one percentage point in assumed health care cost trend rates would have the following effects: (In Millions) Increase Decrease Effect on total of service and interest cost $ 1.3 $ (1.0 ) Effect on postretirement benefit obligation 23.4 (19.6 ) Plan Assets Our financial objectives with respect to our pension and VEBA plan assets are to fully fund the actuarial accrued liability for each of the plans, to maximize investment returns within reasonable and prudent levels of risk, and to maintain sufficient liquidity to meet benefit obligations on a timely basis. Our investment objective is to outperform the expected ROA assumption used in the plans’ actuarial reports over the life of the plans. The expected ROA takes into account historical returns and estimated future long-term returns based on capital market assumptions applied to the asset allocation strategy. The expected return is net of investment expenses paid by the plans. In addition, investment performance is monitored on a quarterly basis by benchmarking to various indices and metrics for the one-, three- and five-year periods. The asset allocation strategy is determined through a detailed analysis of assets and liabilities by plan, which defines the overall risk that is acceptable with regard to the expected level and variability of portfolio returns, surplus (assets compared to liabilities), contributions and pension expense. The asset allocation review process involves simulating capital market behaviors including global asset class performance, inflation and interest rates in order to evaluate various asset allocation scenarios and determine the asset mix with the highest likelihood of meeting financial objectives. The process includes factoring in the current funded status and likely future funded status levels of the plans by taking into account expected growth or decline in the contributions over time. The asset allocation strategy varies by plan. The following table reflects the actual asset allocations for pension and VEBA plan assets as of December 31, 2016 and 2015 , as well as the 2017 weighted average target asset allocations as of December 31, 2016 . Equity investments include securities in large-cap, mid-cap and small-cap companies located in the U.S. and worldwide. Fixed income investments primarily include corporate bonds and government debt securities. Alternative investments include hedge funds, private equity, structured credit and real estate. Pension Assets VEBA Assets Asset Category 2017 Target Allocation Percentage of Plan Assets at December 31, 2017 Target Allocation Percentage of Plan Assets at December 31, 2016 2015 2016 2015 Equity securities 45.0 % 43.2 % 44.0 % 8.0 % 8.4 % 8.8 % Fixed income 28.0 % 26.4 % 27.7 % 80.1 % 78.3 % 78.2 % Hedge funds 5.0 % 5.9 % 5.8 % 4.2 % 4.4 % 4.5 % Private equity 7.0 % 5.3 % 4.7 % 2.6 % 1.7 % 2.2 % Structured credit 7.5 % 9.3 % 8.9 % 2.1 % 2.7 % 2.3 % Real estate 7.5 % 9.0 % 8.2 % 3.0 % 4.4 % 4.0 % Cash — % 0.9 % 0.7 % — % 0.1 % — % Total 100.0 % 100.0 % 100.0 % 100.0 % 100.0 % 100.0 % Pension The fair values of our pension plan assets at December 31, 2016 and 2015 by asset category are as follows: (In Millions) December 31, 2016 Asset Category Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Equity securities: U.S. large-cap $ 144.7 $ — $ — $ 144.7 U.S. small/mid-cap 39.9 — — 39.9 International 111.8 — — 111.8 Fixed income 157.5 23.7 — 181.2 Hedge funds — — 40.6 40.6 Private equity — — 36.1 36.1 Structured credit — — 63.8 63.8 Real estate — — 61.9 61.9 Cash 5.8 — — 5.8 Total $ 459.7 $ 23.7 $ 202.4 $ 685.8 (In Millions) December 31, 2015 Asset Category Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Equity securities: U.S. large-cap $ 150.5 $ — $ — $ 150.5 U.S. small/mid-cap 40.6 — — 40.6 International 116.8 — — 116.8 Fixed income 166.3 27.9 — 194.2 Hedge funds — — 40.7 40.7 Private equity — — 33.1 33.1 Structured credit — — 62.1 62.1 Real estate — — 57.5 57.5 Cash 5.1 — — 5.1 Total $ 479.3 $ 27.9 $ 193.4 $ 700.6 Following is a description of the inputs and valuation methodologies used to measure the fair value of our plan assets. Equity Securities Equity securities classified as Level 1 investments include U.S. large-, small- and mid-cap investments and international equity. These investments are comprised of securities listed on an exchange, market or automated quotation system for which quotations are readily available. The valuation of these securities is determined using a market approach, and is based upon unadjusted quoted prices for identical assets in active markets. Fixed Income Fixed income securities classified as Level 1 investments include bonds and government debt securities. These investments are comprised of securities listed on an exchange, market or automated quotation system for which quotations are readily available. The valuation of these securities is determined using a market approach, and is based upon unadjusted quoted prices for identical assets in active markets. Also included in Fixed Income is a portfolio of U.S. Treasury STRIPS, which are zero-coupon bearing fixed income securities backed by the full faith and credit of the U.S. government. The securities sell at a discount to par because there are no incremental coupon payments. STRIPS are not issued directly by the Treasury, but rather are created by a financial institution, government securities broker or government securities dealer. Liquidity on the issue varies depending on various market conditions; however, in general the STRIPS market is slightly less liquid than that of the U.S. Treasury Bond market. The STRIPS are priced daily through a bond pricing vendor and are classified as Level 2. Hedge Funds Hedge funds are alternative investments comprised of direct or indirect investment in offshore hedge funds with an investment objective to achieve an attractive risk-adjusted return with moderate volatility and moderate directional market exposure over a full market cycle. The valuation techniques used to measure fair value attempt to maximize the use of observable inputs and minimize the use of unobservable inputs. Considerable judgment is required to interpret the factors used to develop estimates of fair value. Valuations of the underlying investment funds are obtained and reviewed. The securities that are valued by the funds are interests in the investment funds and not the underlying holdings of such investment funds. Thus, the inputs used to value the investments in each of the underlying funds may differ from the inputs used to value the underlying holdings of such funds. During the fourth quarter of 2016, a total redemption request for a tender of 100% of the position was executed and is to be reinvested into another fund within this asset category. The tender was effective as of December 31, 2016, with the funds targeted for distribution and reinvestment during the first quarter of 2017. In determining the fair value of a security, the fund managers may consider any information that is deemed relevant, which may include one or more of the following factors regarding the portfolio security, if appropriate: type of security or asset; cost at the date of purchase; size of holding; last trade price; most recent valuation; fundamental analytical data relating to the investment in the security; nature and duration of any restriction on the disposition of the security; evaluation of the factors that influence the market in which the security is purchased or sold; financial statements of the issuer; discount from market value of unrestricted securities of the same class at the time of purchase; special reports prepared by analysts; information as to any transactions or offers with respect to the security; existence of merger proposals or tender offers affecting the security; price and extent of public trading in similar securities of the issuer or compatible companies and other relevant matters; changes in interest rates; observations from financial institutions; domestic or foreign government actions or pronouncements; other recent events; existence of shelf registration for restricted securities; existence of any undertaking to register the security; and other acceptable methods of valuing portfolio securities. Private Equity Funds Private equity funds are alternative investments that represent direct or indirect investments in partnerships, venture funds or a diversified pool of private investment vehicles (fund of funds). Investment commitments are made in private equity funds based on an asset allocation strategy, and capital calls are made over the life of the funds to fund the commitments. As of December 31, 2016, remaining commitments total $37.9 million for both our pension and other benefits. Committed amounts are funded from plan assets when capital calls are made. Investment commitments are not pre-funded in reserve accounts. The valuation of investments in private equity funds initially is performed by the underlying fund managers. In determining the fair value, the fund managers may consider any information that is deemed relevant, which may include: type of security or asset; cost at the date of purchase; size of holding; last trade price; most recent valuation; fundamental analytical data relating to the investment in the security; nature and duration of any restriction on the disposition of the security; evaluation of the factors that influence the market in which the security is purchased or sold; financial statements of the issuer; discount from market value of unrestricted securities of the same class at the time of purchase; special reports prepared by analysts; information as to any transactions or offers with respect to the security; existence of merger proposals or tender offers affecting the security; price and extent of public trading in similar securities of the issuer or compatible companies and other relevant matters; changes in interest rates; observations from financial institutions; domestic or foreign government actions or pronouncements; other recent events; existence of shelf registration for restricted securities; existence of any undertaking to register the security; and other acceptable methods of valuing portfolio securities. The valuations are obtained from the underlying fund managers, and the valuation methodology and process is reviewed for consistent application and adherence to policies. Considerable judgment is required to interpret the factors used to develop estimates of fair value. Private equity investments are valued quarterly and recorded on a one-quarter lag. For alternative investment values reported on a lag, current market information is reviewed for any material changes in values at the reporting date. Capital distributions for the funds do not occur on a regular frequency. Liquidation of these investments would require sale of the partnership interest. Structured Credit Structured credit investments are alternative investments comprised of collateralized debt obligations and other structured credit investments that are priced based on valuations provided by independent, third-party pricing agents, if available. Such values generally reflect the last reported sales price if the security is actively traded. The third-party pricing agents may also value structured credit investments at an evaluated bid price by employing methodologies that utilize actual market transactions, broker-supplied valuations, or other methodologies designed to identify the market value of such securities. Such methodologies generally consider such factors as security prices, yields, maturities, call features, ratings and developments relating to specific securities in arriving at valuations. Securities listed on a securities exchange, market or automated quotation system for which quotations are readily available are valued at the last quoted sale price on the primary exchange or market on which they are traded. Debt obligations with remaining maturities of 60 days or less may be valued at amortized cost, which approximates fair value. Structured credit investments are valued monthly and recorded on a one-month lag. For alternative investment values reported on a lag, current market information is reviewed for any material changes in values at the reporting date. Historically, redemption requests have been considered quarterly, subject to notice of 90 days , although the advisor is currently only requiring notice of 65 days. Real Estate The real estate portfolio for the pension plans is an alternative investment primarily comprised of two funds with strategic categories of real estate investments. All real estate holdings are appraised externally at least annually, and appraisals are conducted by reputable, independent appraisal firms that are members of the Appraisal Institute. All external appraisals are performed in accordance with the Uniform Standards of Professional Appraisal Practices. The property valuations and assumptions of each property are reviewed quarterly by the investment advisor and values are adjusted if there has been a significant change in circumstances relating to the property since the last external appraisal. The valuation methodology utilized in determining the fair value is consistent with the best practices prevailing within the real estate appraisal and real estate investment management industries, including the Real Estate Information Standards, and standards promulgated by the National Council of Real Estate Investment Fiduciaries, the National Association of Real Estate Investment Fiduciaries, and the National Association of Real Estate Managers. In addition, the investment advisor may cause additional appraisals to be performed. Two of the funds’ fair values are updated monthly, and there is no lag in reported values. Redemption requests for these two funds are considered on a quarterly basis, subject to notice of 45 days . During the fourth quarter of 2016, a notice of full redemption request for a tender of 100% of one fund position was executed and is to be invested into the other fund. The redemption was included in the fourth quarter queue and the funds are targeted for distribution and reinvestment during the first quarter of 2017. The real estate fund of funds investment for the Empire, Tilden, Hibbing and United Taconite VEBA plans invests in pooled investment vehicles that in turn invest in commercial real estate properties. Valuations are performed quarterly and financial statements are prepared on a semi-annual basis, with annual audited statements. Asset values for this fund are reported with a one-quarter lag and current market information is reviewed for any material changes in values at the reporting date. In most cases, values are based on valuations reported by underlying fund managers or other independent third-party sources, but the fund has discretion to use other valuation methods, subject to compliance with ERISA. Valuations are typically estimates and subject to upward or downward revision based on each underlying fund’s annual audit. Withdrawals are permitted on the last business day of each quarter subject to a 65 -day prior written notice. The following represents the effect of fair value measurements using significant unobservable inputs (Level 3) on changes in plan assets for the years ended December 31, 2016 and 2015 : (In Millions) Year Ended December 31, 2016 Hedge Funds Private Equity Funds Structured Credit Fund Real Estate Total Beginning balance — January 1, 2016 $ 40.7 $ 33.1 $ 62.1 $ 57.5 $ 193.4 Actual return on plan assets: Relating to assets still held at the reporting date (0.1 ) (2.7 ) 10.0 5.1 12.3 Relating to assets sold during the period — 3.7 (0.3 ) (0.1 ) 3.3 Purchases — 8.0 — — 8.0 Sales — (6.0 ) (8.0 ) (0.6 ) (14.6 ) Ending balance — December 31, 2016 $ 40.6 $ 36.1 $ 63.8 $ 61.9 $ 202.4 (In Millions) Year Ended December 31, 2015 Hedge Funds Private Equity Funds Structured Credit Fund Real Estate Total Beginning balance — January 1, 2015 $ 41.5 $ 31.2 $ 65.4 $ 50.0 $ 188.1 Actual return on plan assets: Relating to assets still held at the reporting date (0.8 ) 1.5 (3.3 ) 8.1 5.5 Relating to assets sold during the period — 2.5 — — 2.5 Purchases — 5.7 — — 5.7 Sales — (7.8 ) — (0.6 ) (8.4 ) Ending balance — December 31, 2015 $ 40.7 $ 33.1 $ 62.1 $ 57.5 $ 193.4 VEBA Assets for other benefits include VEBA trusts pursuant to bargaining agreements that are available to fund retired employees’ life insurance obligations and medical benefits. The fair values of our other benefit plan assets at December 31, 2016 and 2015 by asset category are as follows: (In Millions) December 31, 2016 Asset Category Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Equity securities: U.S. large-cap $ 10.6 $ — $ — $ 10.6 U.S. small/mid-cap 2.7 — — 2.7 International 8.1 — — 8.1 Fixed income 162.0 35.9 — 197.9 Hedge funds — — 11.2 11.2 Private equity — — 4.3 4.3 Structured credit — — 6.9 6.9 Real estate — — 11.1 11.1 Cash 0.2 — — 0.2 Total $ 183.6 $ 35.9 $ 33.5 $ 253.0 (In Millions) December 31, 2015 Asset Category Quoted Prices in Active Significant Other Significant Total Equity securities: U.S. large-cap $ 11.1 $ — $ — $ 11.1 U.S. small/mid-cap 2.8 — — 2.8 International 8.2 — — 8.2 Fixed income 158.1 37.9 — 196.0 Hedge funds — — 11.2 11.2 Private equity — — 5.5 5.5 Structured credit — — 5.8 5.8 Real estate — — 10.0 10.0 Cash — — — — Total $ 180.2 $ 37.9 $ 32.5 $ 250.6 Refer to the pension asset discussion above for further information regarding the inputs and valuation methodologies used to measure the fair value of each respective category of plan assets. The following represents the effect of fair value measurements using significant unobservable inputs (Level 3) on changes in plan assets for the year ended December 31, 2016 and 2015 : (In Millions) Year Ended December 31, 2016 Hedge Funds Private Equity Funds Structured Credit Fund Real Estate Total Beginning balance — January 1, 2016 $ 11.2 $ 5.5 $ 5.8 $ 10.0 $ 32.5 Actual return on plan assets: Relating to assets still held at the reporting date — (0.3 ) 1.1 1.1 1.9 Relating to assets sold during the period — 0.1 — — 0.1 Purchases — — — — — Sales — (1.0 ) — — (1.0 ) Ending balance — December 31, 2016 $ 11.2 $ 4.3 $ 6.9 $ 11.1 $ 33.5 (In Millions) Year Ended December 31, 2015 Hedge Funds Private Equity Funds Structured Credit Fund Real Estate Total Beginning balance — January 1, 2015 $ 11.5 $ 6.2 $ 6.1 $ 8.7 $ 32.5 Actual return on plan assets: Relating to assets still held at the reporting date (0.3 ) 0.3 (0.3 ) 1.3 1.0 Relating to assets sold during the period — 0.4 — — 0.4 Purchases — 0.1 — — 0.1 Sales — (1.5 ) — — (1.5 ) Ending balance — December 31, 2015 $ 11.2 $ 5.5 $ 5.8 $ 10.0 $ 32.5 Contributions Annual contributions to the pension plans are made within income tax deductibility restrictions in accordance with statutory regulations. In the event of plan termination, the plan sponsors could be required to fund additional shutdown and early retirement obl

STOCK COMPENSATION PLANS

STOCK COMPENSATION PLANS	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK COMPENSATION PLANS	NOTE 8 - STOCK COMPENSATION PLANS At December 31, 2016 , we have outstanding awards under two share-based compensation plans, which are described below. The compensation cost that has been charged against income for those plans was $14.2 million , $13.9 million and $21.5 million in 2016 , 2015 and 2014 , respectively, which primarily was recorded in Selling, general and administrative expenses in the Statements of Consolidated Operations. The total income tax benefit recognized in the Statements of Consolidated Operations for share-based compensation arrangements was $7.5 million for 2014 . There was no income tax benefit recognized for the year ended December 31, 2016 and 2015 , due to the full valuation allowance. Employees’ Plans The 2015 Equity Plan was approved by our Board of Directors on March 26, 2015 and by our shareholders on May 19, 2015. The 2015 Equity Plan replaced the 2012 Equity Plan. The maximum number of shares that may be issued under the 2015 Equity Plan is 12.9 million common shares. No additional grants were issued from the 2012 Amended Equity Plan after the date of approval of the 2015 Equity Plan; however, all awards previously granted under the 2012 Amended Equity Plan will continue in full force and effect in accordance with the terms of outstanding awards. During the first quarter of 2016, the Compensation and Organization Committee of the Board of Directors approved grants under the 2015 Equity Plan of 3.4 million restricted share units to certain officers and employees with a grant date of February 23, 2016. The restricted share units granted under this award are subject to continued employment through the vesting date of December 31, 2018. During the third quarter of 2015, the Compensation Committee approved grants under the 2015 Equity Plan of 1.5 million restricted share units to certain officers and employees with a grant date of September 10, 2015. The restricted share units granted under this award are subject to continued employment through the vesting date of December 15, 2017. During the first quarter of 2015, the Compensation Committee approved grants under the 2012 Equity Plan to certain officers and employees for the 2015 to 2017 performance period. Shares granted under the awards consisted of 0.9 million performance shares, 0.9 million restricted share units and 0.4 million stock options. On February 10, 2014, upon recommendation by the Compensation Committee, our Board of Directors approved and adopted, subject to the approval of our shareholders at the 2014 Annual Meeting, the 2012 Equity Plan. The principal reason for amending and restating the 2012 Equity Plan was to increase the number of common shares available for issuance by 5.0 million common shares. This amended plan was approved by our shareholders at the 2014 Annual Meeting held on July 29, 2014. Subsequent to our 2014 Annual Meeting of Shareholders, where shareholders elected six new directors, our board changed substantially. Such an event constituted a change in control pursuant to our incentive equity plans and applicable award agreements. As a result, all of the outstanding and unvested equity incentives awarded to participants prior to October 2013 became vested. Accordingly, this resulted in recognizing $11.7 million of additional equity-based compensation expense in the accompanying financial statements, representing the remaining unrecognized compensation expense of the awards. For any equity grants awarded after September 2013, the vesting of all such grants was accelerated and paid in cash following each participant's qualifying termination of employment associated with the change in control and as long as the common shares were not substituted with a replacement award. This liability for additional double-trigger payments for share-based compensation in cash expired on August 6, 2016. Performance Shares The outstanding performance share or unit grants vest over a period of three years and are intended to be paid out in common shares or cash in certain circumstances. Performance is measured on the basis of relative TSR for the period and measured against the constituents of the S&P Metals and Mining ETF Index at the beginning of the relevant performance period. The final payouts for the outstanding performance period grants will vary from 0% to 200% of the original grant depending on whether and to what extent the Company achieves certain objectives and performance goals as established by the Compensation Committee. Following is a summary of our performance share award agreements currently outstanding : Performance Performance Shares Granted Estimated Forfeitures Expected to Vest Grant Date Performance Period 2015 410,105 157,979 252,126 February 9, 2015 1/1/2015 - 12/31/2017 2015 464,470 82,636 381,834 January 12, 2015 1/1/2015 - 12/31/2017 2014 1 188,510 188,510 — July 29, 2014 1/1/2014 - 12/31/2016 2014 1 80,560 80,560 — May 12, 2014 1/1/2014 - 12/31/2016 2014 1 230,265 230,265 — February 10, 2014 1/1/2014 - 12/31/2016 1 The performance shares granted in 2014 will have a payout of 0% of the original grant based on the final performance evaluation versus the performance goals that were established in the grants. Performance-Based Restricted Stock Units For the outstanding 400,000 performance-based restricted stock units that were granted on November 17, 2014, the award may be earned and settled based upon certain VWAP performance for the Company’s common shares, (Threshold VWAP, Target VWAP, or Maximum VWAP) for any period of ninety (90) consecutive calendar days during a performance period commencing August 7, 2014 and ending December 31, 2017. Restricted Share Units All of the outstanding restricted share units are subject to continued employment, are retention based, and are payable in common shares or cash in certain circumstances at a time determined by the Compensation Committee at its discretion. The outstanding restricted share units that were granted in 2015, with the exception of the 2015 special retention awards that have a 27 months vesting period, have or will vest in equal thirds on each of December 31, 2016, December 31, 2017 and December 31, 2018. The outstanding restricted share units that were granted in 2016, cliff vest in three years on December 31, 2019. Stock Options The stock options that were granted during the first quarter of 2015 vest on December 31, 2017, subject to continued employment through the vesting date, are exercisable at a strike price of $7.70 after the vesting date and expire on January 12, 2025 . The stock options that were granted on November 17, 2014 vest in equal thirds on each of December 31, 2015, December 31, 2016 and December 31, 2017 subject to continued employment through each vesting date, and are exercisable cumulatively at a strike price of $13.83 after each vesting date and expire on November 17, 2021 . Employee Stock Purchase Plan On March 26, 2015, upon recommendation by the Compensation Committee, our Board of Directors approved and adopted, subject to the approval of Cliffs' shareholders at the 2015 Annual Meeting, the Cliffs Natural Resources Inc. 2015 Employee Stock Purchase Plan. This plan was approved by our shareholders at the 2015 Annual Meeting held May 19, 2015. 10 million common shares have been reserved for issuance under this plan; however, as of December 31, 2016, this program has not been made active and no common shares have been purchased. We sought shareholder approval of this plan for the purpose of qualifying the reserved common shares for special tax treatment under Section 423 of the Internal Revenue Code of 1986, as amended. Nonemployee Directors Equity Grants During 2016, our nonemployee directors were entitled to receive restricted share awards under the Directors’ Plan. For 2016, nonemployee directors were granted a number of restricted shares, with a value equal to $85,000 , based on the closing price of our common shares on April 27, 2016, the date of the 2016 Annual Meeting, subject to any deferral election and pursuant to the terms of the Directors’ Plan and an award agreement, effective on April 27, 2016. For the last three years, Equity Grant shares have been awarded to elected or re-elected nonemployee Directors as follows: Year of Grant Restricted Equity Grant Shares Deferred Equity Grant Shares 2014 73,635 — 2015 109,408 25,248 2016 135,038 29,583 Starting in July, 2015, the Governance and Nominating Committee recommended, and the Board adopted, a Nonemployee Director Retainer Share Election Program pursuant to which nonemployee directors may elect to receive all or any portion of their annual retainer and any other fees earned in cash in Cliffs' common shares. Election is voluntary and irrevocable for the applicable election period and shares issued under this program must be held for six months from the issuance date. The number of shares received each quarter are calculated by dividing the value of the quarterly cash retainer amount by the closing market price of the date of payment. Other Information The following table summarizes the share-based compensation expense that we recorded for continuing operations in 2016 , 2015 and 2014 : (In Millions, except per share amounts) 2016 2015 2014 Cost of goods sold and operating expenses $ 2.1 $ 4.0 $ 5.6 Selling, general and administrative expenses 12.1 9.9 15.9 Reduction of operating income from continuing operations before income taxes and equity loss from ventures 14.2 13.9 21.5 Income tax benefit 1 — — (7.5 ) Reduction of net income attributable to Cliffs shareholders $ 14.2 $ 13.9 $ 14.0 Reduction of earnings per share attributable to Cliffs shareholders: Basic $ 0.07 $ 0.09 $ 0.09 Diluted $ 0.07 $ 0.09 $ 0.09 1 No income tax benefit for the year ended December 31, 2016 and December 31, 2015, due to the full valuation allowance. Determination of Fair Value Performance Shares 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 historical and projected stock prices was developed for both the Company and our predetermined peer group of mining and metals companies. The fair value assumes that performance goals will be achieved. The expected term of the grant represents the time from the grant date to the end of the service period for each of the three plan-year agreements. We estimate the volatility of our common shares and that of the peer group of mining and metals companies using daily price intervals for all companies. The risk-free interest rate is the rate at the grant date on zero-coupon government bonds, with a term commensurate with the remaining life of the performance period. No performance shares were granted in 2016 , therefore no fair value analysis was required. Stock Options The fair value of each stock option grant is estimated on the date of grant using a Black-Scholes valuation model. The expected term of the option grant is determined using the simplified method. We estimate the volatility of our common shares using historical stock prices with consistent frequency over the most recent historical period equal to the option’s expected term. The risk-free interest rate is the rate at the grant date on zero-coupon government bonds, with a term commensurate with the expected term. No stock options were granted in 2016 , therefore no fair value analysis was required. Restricted Share Units The fair value of the restricted share units is determined based on the closing price of our common shares on the grant date. Stock option, restricted share awards and performance share activity under our long-term equity plans and Directors’ Plans are as follows: 2016 2015 2014 Shares Shares Shares Stock options: Outstanding at beginning of year 607,489 250,000 — Granted during the year — 412,710 250,000 Forfeited/canceled (7,619 ) (55,221 ) — Outstanding at end of year 599,870 607,489 250,000 Restricted awards: Outstanding and restricted at beginning of year 2,338,070 523,176 586,084 Granted during the year 3,571,337 2,482,415 531,030 Vested (271,988 ) (477,157 ) (423,822 ) Forfeited/canceled (175,636 ) (190,364 ) (170,116 ) Outstanding and restricted at end of year 5,461,783 2,338,070 523,176 Performance shares: Outstanding at beginning of year 1,496,489 1,072,376 1,040,453 Granted during the year — 874,575 1,233,685 Issued 1 (59,260 ) (242,920 ) (796,624 ) Forfeited/canceled (68,760 ) (207,542 ) (405,138 ) Outstanding at end of year 1,368,469 1,496,489 1,072,376 Vested or expected to vest as of December 31, 2016 6,716,979 Directors’ retainer and voluntary shares: Outstanding at beginning of year — — 7,329 Granted during the year — — 2,281 Vested — — (9,610 ) Outstanding at end of year — — — Reserved for future grants or awards at end of year: Employee plans 6,514,038 Directors’ plans 676,678 Total 7,190,716 1 The performance shares granted in 2014 will have a payout of 0% of the original grant based on the final performance evaluation versus the performance goals that were established in the grants. These shares are not included in this number because they expire and will be ultimately forfeited in February 2017. For the year ended December 31, 2015, the shares vesting due to the change in control were paid out in cash, at target, and valued as of the respective participants' termination dates. For the year ended December 31, 2014, the shares vesting on December 31, 2013 were valued as of February 10, 2014, and the shares vesting due to the change in a majority of our Board of Directors that triggered the acceleration of vesting and payout of outstanding equity grants under our equity plans on August 6, 2014 were paid out in cash, at target, and valued as of that date. A summary of our outstanding share-based awards as of December 31, 2016 is shown below: Shares Weighted Average Grant Date Fair Value Outstanding, beginning of year 4,442,048 $ 8.93 Granted 3,571,337 $ 1.93 Vested (331,248 ) $ 11.25 Forfeited/expired (252,015 ) $ 5.90 Outstanding, end of year 7,430,122 $ 5.55 A summary of our stock option grants vested or expected to vest as of December 31, 2016 is shown below: Shares Weighted-Average Exercise Price Aggregate Intrinsic Value Weighted-Average Remaining Contractual Term (Years) Expected to vest 417,914 $ 8.88 $ 239,640 7.43 Exercisable 166,667 $ 13.83 $ — 4.88 The total compensation cost related to outstanding awards not yet recognized is $14.7 million at December 31, 2016 . The weighted average remaining period for the awards outstanding at December 31, 2016 is approximately 1.8 years.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 9 - INCOME TAXES Income (Loss) from Continuing Operations Before Income Taxes and Equity Loss from Ventures includes the following components: (In Millions) 2016 2015 2014 United States $ 124.9 $ 314.2 $ (447.5 ) Foreign 82.1 (1.1 ) 427.8 $ 207.0 $ 313.1 $ (19.7 ) The components of the provision (benefit) for income taxes on continuing operations consist of the following: (In Millions) 2016 2015 2014 Current provision (benefit): United States federal $ (11.1 ) $ 8.2 $ (125.2 ) United States state & local (0.5 ) 0.3 (0.6 ) Foreign (0.1 ) 0.9 11.7 (11.7 ) 9.4 (114.1 ) Deferred provision (benefit): United States federal (0.5 ) 165.8 20.4 United States state & local — — (24.9 ) Foreign — (5.9 ) 32.6 (0.5 ) 159.9 28.1 Total provision (benefit) on income (loss) from continuing operations $ (12.2 ) $ 169.3 $ (86.0 ) Reconciliation of our income tax attributable to continuing operations computed at the U.S. federal statutory rate is as follows: (In Millions) 2016 2015 2014 Tax at U.S. statutory rate of 35% $ 72.5 35.0 % $ 109.6 35.0 % $ (6.9 ) 35.0 % Increase (decrease) due to: Impact of tax law change 149.1 72.0 — — 13.0 (66.0 ) Valuation allowance build/(reversal) on tax benefits recorded in prior years (142.6 ) (68.9 ) 165.8 52.9 15.2 (77.2 ) Tax uncertainties (11.3 ) (5.5 ) 84.1 26.9 — — Valuation allowance build/(reversal) in current year 93.9 45.4 (104.6 ) (33.4 ) 318.3 (1,615.7 ) Prior year adjustments in current year (11.8 ) (5.7 ) 5.9 1.9 (6.3 ) 32.1 Worthless stock deduction (73.4 ) (35.5 ) — — — — Impact of foreign operations (42.7 ) (20.6 ) (53.9 ) (17.2 ) 51.4 (260.9 ) Percentage depletion in excess of cost depletion (36.1 ) (17.4 ) (34.9 ) (11.1 ) (87.9 ) 446.2 Non-taxable income related to noncontrolling interests (8.8 ) (4.2 ) (3.0 ) (1.0 ) (9.4 ) 47.7 State taxes, net 0.4 0.2 0.2 0.1 (25.4 ) 128.9 Settlement of financial guaranty — — — — (347.1 ) 1,761.9 Income not subject to tax — — — — (27.7 ) 140.6 Goodwill impairment — — — — 22.7 (115.2 ) Other items — net (1.4 ) (0.7 ) 0.1 — 4.1 (20.9 ) Provision for income tax (benefit) expense and effective income tax rate including discrete items $ (12.2 ) (5.9 )% $ 169.3 54.1 % $ (86.0 ) 436.5 % The components of income taxes for other than continuing operations consisted of the following: (In Millions) 2016 2015 2014 Other comprehensive (income) loss: Pension/OPEB liability $ — $ — $ 37.1 Mark-to-market adjustments — 0.3 3.6 Other 0.5 5.9 0.2 Total $ 0.5 $ 6.2 $ 40.9 Paid in capital — stock based compensation $ — $ — $ (4.8 ) Discontinued Operations $ — $ (6.0 ) $ (1,216.0 ) Significant components of our deferred tax assets and liabilities as of December 31, 2016 and 2015 are as follows: (In Millions) 2016 2015 Deferred tax assets: Pensions $ 114.6 $ 106.6 Postretirement benefits other than pensions 35.2 36.5 Alternative minimum tax credit carryforwards 251.2 218.7 Deferred income 44.5 57.2 Financial instruments 71.3 — Investments in ventures — 4.9 Asset retirement obligations 22.3 5.3 Operating loss carryforwards 2,699.7 2,791.6 Property, plant and equipment and mineral rights 181.2 189.8 State and local 59.2 59.9 Lease liabilities 12.9 18.3 Other liabilities 108.3 148.9 Total deferred tax assets before valuation allowance 3,600.4 3,637.7 Deferred tax asset valuation allowance (3,334.8 ) (3,372.5 ) Net deferred tax assets 265.6 265.2 Deferred tax liabilities: Property, plant and equipment and mineral rights (34.0 ) (35.5 ) Investment in ventures (203.1 ) (206.6 ) Intangible assets (1.0 ) (1.5 ) Product inventories (3.4 ) (2.5 ) Other assets (24.1 ) (19.1 ) Total deferred tax liabilities (265.6 ) (265.2 ) Net deferred tax assets (liabilities) $ — $ — At December 31, 2016 and 2015 , we had $251.2 million and $218.7 million , respectively, of gross deferred tax assets related to U.S. alternative minimum tax credits that can be carried forward indefinitely. We had gross domestic (including states) and foreign net operating loss carryforwards, inclusive of discontinued operations, of $3.7 billion and $6.9 billion , respectively, at December 31, 2016 . We had gross domestic and foreign net operating loss carryforwards at December 31, 2015 of $3.9 billion and $11.1 billion , respectively. The U.S. Federal net operating losses will begin to expire in 2035 and state net operating losses will begin to expire in 2019. The foreign net operating losses can be carried forward indefinitely. We had foreign tax credit carryforwards of $5.8 million at December 31, 2016 and December 31, 2015 . The foreign tax credit carryforwards will begin to expire in 2020. Additionally, there is a net operating loss carryforward, inclusive of discontinued operations, of $1.4 billion for Alternative Minimum Tax. No benefit has been recorded in the financials for this attribute as ASC 740, Income Taxes , does not allow for the recording of deferred taxes under alternative taxing systems. We recorded a $37.7 million net decrease in the valuation allowance of certain deferred tax assets. Of this amount, a $149.1 million decrease was due to the change in the Luxembourg statutory rate and a $33.1 million decrease resulted from prior year adjustments due to a change in estimate of the 2015 net operating loss. Offsetting increases to the valuation allowance included a $104.9 million increase related to the recording of deferred tax assets due to current year operating activities and a $39.6 million increase related to the close of audits. At December 31, 2016 and 2015 , we had no cumulative undistributed earnings of foreign subsidiaries included in consolidated retained earnings. Accordingly, no provision has been made for U.S. deferred taxes related to future repatriation of earnings. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows: (In Millions) 2016 2015 2014 Unrecognized tax benefits balance as of January 1 $ 156.2 $ 72.6 $ 71.8 Increases/(decreases) for tax positions in prior years (61.0 ) 6.7 — Increases for tax positions in current year 0.2 78.5 5.9 Decrease due to foreign exchange — — (0.2 ) Settlements (64.7 ) (1.1 ) — Lapses in statutes of limitations — (0.5 ) (3.7 ) Other — — (1.2 ) Unrecognized tax benefits balance as of December 31 $ 30.7 $ 156.2 $ 72.6 At December 31, 2016 and 2015 , we had $30.7 million and $156.2 million , respectively, of unrecognized tax benefits recorded. Of this amount, $8.3 million and $21.5 million , respectively, were recorded in Other liabilities and $22.4 million and $134.7 million , respectively, were recorded as Other non-current assets in the Statements of Consolidated Financial Position for both years. If the $30.7 million were recognized, only $8.3 million would impact the effective tax rate. We do not expect that the amount of unrecognized benefits will change significantly within the next 12 months. At December 31, 2016 and 2015 , we had $0.8 million and $2.1 million , respectively, of accrued interest and penalties related to the unrecognized tax benefits recorded in Other liabilities in the Statements of Consolidated Financial Position. Tax years 2012 and forward remain subject to examination for the U.S. and Australia. Tax years 2008 and forward remain subject to examination for Canada.

LEASE OBLIGATIONS

LEASE OBLIGATIONS	12 Months Ended
	Dec. 31, 2016
Leases [Abstract]
LEASE OBLIGATIONS	NOTE 10 - LEASE OBLIGATIONS We lease certain mining, production and other equipment under operating and capital leases. The 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 $7.6 million , $12.0 million and $17.8 million for the years ended December 31, 2016 , 2015 and 2014 , respectively. Capital lease assets were $29.3 million and $32.5 million at December 31, 2016 and 2015, respectively. Corresponding accumulated amortization of capital leases included in respective allowances for depreciation were $13.1 million and $8.7 million at December 31, 2016 and 2015 , respectively. Future minimum payments under capital leases and non-cancellable operating leases at December 31, 2016 are as follows: (In Millions) Capital Leases Operating Leases 2017 $ 22.0 $ 6.9 2018 17.9 5.6 2019 9.9 3.0 2020 9.0 2.9 2021 8.3 3.0 2022 and thereafter 0.7 — Total minimum lease payments $ 67.8 $ 21.4 Amounts representing interest 12.0 Present value of net minimum lease payments 1 $ 55.8 1 The total is comprised of $17.4 million and $38.4 million classified as Other current liabilities and Other liabilities, respectively, in the Statements of Consolidated Financial Position at December 31, 2016.

ENVIRONMENTAL AND MINE CLOSURE

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	12 Months Ended
	Dec. 31, 2016
Asset Retirement Obligation Disclosure [Abstract]
Environmental Loss Contingency And Mine Closure Obligation Disclosure [Text Block]	NOTE 11 - ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS We had environmental and mine closure liabilities of $206.8 million and $234.0 million at December 31, 2016 and 2015 , respectively. Payments in 2016 and 2015 were $2.4 million and $2.6 million , respectively. The following is a summary of the obligations as of December 31, 2016 and 2015 : (In Millions) December 31, 2016 2015 Environmental $ 2.8 $ 3.6 Mine closure U.S. Iron Ore 1 187.8 214.0 Asia Pacific Iron Ore 16.2 16.4 Total mine closure 204.0 230.4 Total environmental and mine closure obligations 206.8 234.0 Less current portion 12.9 2.8 Long-term environmental and mine closure obligations $ 193.9 $ 231.2 1 U.S. Iron Ore includes our active operating mines, our indefinitely idled Empire mine and a closed mine formerly operating as LTVSMC. Environmental Our mining and exploration activities are subject to various laws and regulations governing the protection of the environment. We conduct our operations to protect the public health and environment and believe our operations are in compliance with applicable laws and regulations in all material respects. Our environmental liabilities of $2.8 million and $3.6 million at December 31, 2016 and 2015 , respectively, including obligations for known environmental remediation exposures at various active and closed mining operations and other sites, have been recognized based on the estimated cost of investigation and remediation at each site. If the cost can only be estimated as a range of possible amounts with no specific amount being more likely, the minimum of the range is accrued. Future expenditures are not discounted unless the amount and timing of the cash disbursements readily are known. Potential insurance recoveries have not been reflected. Additional environmental obligations could be incurred, the extent of which cannot be assessed. Mine Closure Our mine closure obligations of $204.0 million and $230.4 million at December 31, 2016 and 2015 , respectively, include our U.S. Iron Ore mines and our Asia Pacific Iron Ore mine. The accrued closure obligation for our mining operations provides for contractual and legal obligations associated with the eventual closure of the mining operations. We performed a detailed assessment of our asset retirement obligations related to our active mining locations most recently in 2014 in accordance with our accounting policy, which requires us to perform an in-depth evaluation of the liability every three years in addition to routine annual assessments. Management periodically performs an assessment of the obligation to determine the adequacy of the liability in relation to the closure activities still required at the LTVSMC site. The LTVSMC closure liability was $25.5 million and $24.1 million at December 31, 2016 and 2015 , respectively. We are anticipating MPCA to reissue the NPDES permits for this facility in the future that could modify the closure liability, but the scale of that change will not be understood until reissuance of the permits. For the assessments performed, we determined the obligations based on detailed estimates adjusted for factors that a market participant would consider (i.e., inflation, overhead and profit) and then discounted the obligation using the current credit-adjusted risk-free interest rate based on the corresponding life of mine. The estimate also incorporates incremental increases in the closure cost estimates and changes in estimates of mine lives. The closure date for each location was determined based on the exhaustion date of the remaining iron ore reserves. 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 years ended December 31, 2016 and 2015 : (In Millions) December 31, 2016 2015 Asset retirement obligation at beginning of period $ 230.4 $ 165.3 Accretion expense 14.0 7.7 Remediation payments (2.2 ) — Exchange rate changes (0.2 ) (1.1 ) Revision in estimated cash flows (38.0 ) 58.5 Asset retirement obligation at end of period $ 204.0 $ 230.4 The revisions in estimated cash flows recorded during the year ended December 31, 2016 relate 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. The revisions in estimated cash flows recorded during the year ended December 31, 2015 related primarily to revisions in the timing of the estimated cash flows and the technology associated with required storm water management systems expected to be implemented subsequent to the indefinite idling of the Empire mine, which resulted in an increase in the asset retirement obligation of $45.2 million .

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES	NOTE 12 - GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES Goodwill Goodwill represents the excess purchase price paid over the fair value of the net assets of acquired companies and is not subject to amortization. We assign goodwill arising from acquired companies to the reporting units that are expected to benefit from the synergies of the acquisition. Our reporting units are either at the operating segment level or a component one level below our operating segments that constitutes a business for which management generally reviews production and financial results of that component. Decisions often are made as to capital expenditures, investments and production plans at the component level as part of the ongoing management of the related operating segment. We have determined that our Asia Pacific Iron Ore operating segment constitutes a separate reporting unit and that Northshore within our U.S. Iron Ore operating segment constitutes a reporting unit. Goodwill is allocated among and evaluated for impairment at the reporting unit level in the fourth quarter of each year or as circumstances occur that potentially indicate that the carrying amount of these assets may exceed their fair value. For the years ended December 31, 2016 and 2015 , there were no goodwill impairment charges. During the third quarter of 2014, a goodwill impairment charge of $73.5 million was recorded for our Asia Pacific Iron Ore reporting segment. The impairment charge was a result of downward long-term pricing estimates as determined through management's long-range planning process. The carrying amount of goodwill for the years ended December 31, 2016 and December 31, 2015 was $2.0 million and related to our U.S. Iron Ore operating segment. Other Intangible Assets and Liabilities Following is a summary of intangible assets and liabilities as of December 31, 2016 and December 31, 2015 : (In Millions) December 31, 2016 December 31, 2015 Classification Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Definite-lived intangible assets: Permits Other non-current assets $ 78.4 $ (24.6 ) $ 53.8 $ 78.4 $ (20.2 ) $ 58.2 Total intangible assets $ 78.4 $ (24.6 ) $ 53.8 $ 78.4 $ (20.2 ) $ 58.2 Below-market sales contracts Other current liabilities $ — $ — $ — $ (23.1 ) $ — $ (23.1 ) Below-market sales contracts Other liabilities — — — (205.8 ) 205.8 — Total below-market sales contracts $ — $ — $ — $ (228.9 ) $ 205.8 $ (23.1 ) Amortization expense relating to intangible assets was $4.8 million , $4.2 million and $8.4 million for the years ended December 31, 2016 , 2015 and 2014 , respectively, and is recognized in Cost of goods sold and operating expenses in the Statements of Consolidated Operations . During the year ended December 31, 2014, an impairment charge of $13.8 million was recorded related to the permits intangible asset and is recognized in Impairment of goodwill and other long-lived assets in the Statements of Consolidated Operations . There were no impairment charges recorded for definite-lived intangible assets in 2016 or 2015. The estimated amortization expense relating to intangible assets for each of the five succeeding years is as follows: (In Millions) Amount Year Ending December 31 2017 1.9 2018 1.9 2019 2.0 2020 1.6 2021 1.0 Total $ 8.4 The below-market sales contract was historically classified as a liability and was recognized over the term of the underlying contract, which expired December 31, 2016. As a result, there will be no future impact to Product revenues for the succeeding fiscal years relating to this contract. For the years ended December 31, 2016 , 2015 and 2014 , we recognized $23.1 million per year in Product revenues related to below-market sales contracts.

DERIVATIVE INSTRUMENTS AND HEDG

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	12 Months Ended
	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	NOTE 13 - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES The following table presents the fair value of our derivative instruments and the classification of each in the Statements of Consolidated Financial Position as of December 31, 2016 and December 31, 2015 : (In Millions) Derivative Assets Derivative Liabilities December 31, 2016 December 31, 2015 December 31, 2016 December 31, 2015 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 21.3 Other current assets 5.8 — — Provisional Pricing Arrangements Other current assets 10.3 Other current assets 2.0 Other current liabilities 0.5 Other current liabilities 3.4 Commodity Contracts Other current assets 1.5 — — Other current liabilities 0.6 Total derivatives not designated as hedging instruments under ASC 815: $ 33.1 $ 7.8 $ 0.5 $ 4.0 Derivatives Not Designated as Hedging Instruments Customer Supply Agreements Most of our U.S. Iron Ore long-term supply agreements are comprised of a base price with annual price adjustment factors. The base price is the primary component of the purchase price for each contract. The indexed price adjustment factors are integral to the iron ore supply contracts and vary based on the agreement, but typically include adjustments based upon changes in the Platts 62% Price, along with pellet premiums, published Platts international indexed freight rates and changes in specified Producer Price Indices, including those for industrial commodities, energy and steel. The pricing adjustments generally operate in the same manner, with each factor typically comprising a portion of the price adjustment, although the weighting of each factor varies based upon the specific terms of each agreement. In most cases, these adjustment factors have not been finalized at the time our product is sold. In these cases, we historically have estimated the adjustment factors at each reporting period based upon the best third-party information available. The estimates are then adjusted to actual when the information has been finalized. The price adjustment factors have been evaluated to determine if they contain embedded derivatives. The price adjustment factors share the same economic characteristics and risks as the host contract and are integral to the host contract as inflation adjustments; accordingly, they have not been separately valued as derivative instruments. A certain supply agreement with one U.S. Iron Ore customer provides for supplemental revenue or refunds to the customer based on the customer’s average annual steel pricing at the time the product is consumed in the customer’s blast furnace. The supplemental pricing is characterized as a freestanding derivative and is required to be accounted for separately once the product is shipped. The derivative instrument, which is finalized based on a future price, is adjusted to fair value as a revenue adjustment each reporting period until the pellets are consumed and the amounts are settled. We recognized $41.7 million , $27.1 million and $187.8 million as Product revenues in the Statements of Consolidated Operations for the years ended December 31, 2016 , 2015 and 2014 , respectively, related to the supplemental payments. The fair value of the pricing factors were $21.3 million and $5.8 million in Other current assets in the December 31, 2016 and December 31, 2015 Statements of Consolidated Financial Position , respectively. Provisional Pricing Arrangements Certain of our U.S. Iron Ore and Asia Pacific Iron Ore customer supply agreements specify provisional price calculations, where the pricing mechanisms generally are based on market pricing, with the final revenue rate to be based on market inputs at a specified period in time in the future, per the terms of the supply agreements. U.S. Iron Ore sales revenue is primarily recognized when cash is received. For U.S. Iron Ore sales, the difference between the provisionally agreed-upon price and the estimated final revenue rate is characterized as a freestanding derivative and must be accounted for separately once the provisional revenue has been recognized. Asia Pacific Iron Ore sales revenue is recorded initially at the provisionally agreed-upon price with the pricing provision embedded in the receivable. The pricing provision is an embedded derivative that must be bifurcated and accounted for separately from the receivable. Subsequently, the derivative instruments for both U.S. Iron Ore and Asia Pacific Iron Ore are adjusted to fair value through Product revenues each reporting period based upon current market data and forward-looking estimates provided by management until the final revenue rate is determined. At December 31, 2016 and December 31, 2015 , we recorded $10.3 million and $2.0 million , respectively, as Other current assets in the Statements of Consolidated Financial Position related to our estimate of the final revenue rate with any of our customers. At December 31, 2016 and December 31, 2015 , we recorded $0.5 million and $3.4 million , respectively, as Other current liabilities in the Statements of Consolidated Financial Position related to our estimate of final revenue rate with our U.S. Iron Ore and Asia Pacific Iron Ore customers. These amounts represent the difference between the provisional price agreed upon with our customers based on the supply agreement terms and our estimate of the final revenue rate based on the price calculations established in the supply agreements. We recognized a net $49.0 million increase in Product revenues in the Statements of Consolidated Operations for the year ended December 31, 2016 related to these arrangements. This compares with a net $1.4 million decrease and a net $9.5 million decrease in Product revenues for the comparable periods in 2015 and 2014 . The following summarizes the effect of our derivatives that are not designated as hedging instruments in the Statements of Consolidated Operations for the years ended December 31, 2016 , 2015 and 2014 : (In Millions) Derivatives Not Designated as Hedging Instruments Location of Gain (Loss) Recognized in Income on Derivative Amount of Gain/(Loss) Recognized in Income on Derivative Year Ended 2016 2015 2014 Customer Supply Agreements Product revenues $ 41.7 $ 27.1 $ 187.8 Provisional Pricing Arrangements Product revenues 49.0 (1.4 ) (9.5 ) Foreign Exchange Contracts Other non-operating income (expense) — (3.6 ) — Foreign Exchange Contracts Product revenues — (12.6 ) — Commodity Contracts Cost of goods sold and operating expenses 1.9 (4.0 ) — Total $ 92.6 $ 5.5 $ 178.3 Refer to NOTE 6 - FAIR VALUE OF FINANCIAL INSTRUMENTS for additional information.

DISCONTINUED OPERATIONS

DISCONTINUED OPERATIONS	12 Months Ended
	Dec. 31, 2016
Discontinued Operations and Disposal Groups [Abstract]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	NOTE 14 - DISCONTINUED OPERATIONS The information below sets forth selected financial information related to operating results of our businesses classified as discontinued operations. While the reclassification of revenues and expenses related to discontinued operations from prior periods have no impact upon previously reported net income, the Statements of Consolidated Operations present the revenues and expenses that were reclassified from the specified line items to discontinued operations. The chart below provides an asset group breakout for each financial statement line impacted by discontinued operations. (In Millions) Canadian Operations North American Coal Eastern Canadian Iron Ore Other Total Canadian Operations Total of Discontinued Operations Statements of Consolidated Operations Loss from Discontinued Operations, net of tax YTD $ (2.4 ) $ (17.5 ) $ — $ (17.5 ) $ (19.9 ) Loss from Discontinued Operations, net of tax YTD $ (152.4 ) $ (638.7 ) $ (101.0 ) $ (739.7 ) $ (892.1 ) Loss from Discontinued Operations, net of tax YTD $ (1,134.5 ) $ (6,952.9 ) $ (280.6 ) $ (7,233.5 ) $ (8,368.0 ) Statements of Consolidated Financial Position Other current liabilities As of $ 6.0 $ — $ — $ — $ 6.0 Other current assets As of $ 14.9 $ — $ — $ — $ 14.9 Other current liabilities As of $ 6.9 $ — $ — $ — $ 6.9 Non-Cash Operating and Investing Activities Depreciation, depletion and amortization YTD $ 3.2 $ — $ — $ — $ 3.2 Purchase of property, plant and equipment YTD $ 15.9 $ — $ — $ — $ 15.9 Impairment of goodwill and other long-lived assets YTD $ 73.4 $ — $ — $ — $ 73.4 Depreciation, depletion and amortization YTD $ 106.9 $ 135.6 $ 0.5 $ 136.1 $ 243.0 Purchase of property, plant and equipment YTD $ 29.9 $ 190.3 $ — $ 190.3 $ 220.2 Impairment of goodwill and other long-lived assets YTD $ 857.5 $ 7,269.2 $ 267.6 $ 7,536.8 $ 8,394.3 North American Coal Operations Background As of March 31, 2015, management determined that our North American Coal operating segment met the criteria to be classified as held for sale under ASC 205, Presentation of Financial Statements. The North American Coal segment continued to meet the criteria throughout 2015 until we sold our held for sale North American Coal operations during the fourth quarter of 2015. As such, all current and historical North American Coal operating segment results are included in our financial statements and classified within discontinued operations. In the first quarter of 2015, as part of the held for sale classification assigned to North American Coal, an impairment of $73.4 million was recorded. The impairment charge was to reduce the assets to their estimated fair value which was determined based on potential sales scenarios. No further impairment was recorded in 2015. We sold all the remaining North American Coal operations during the fourth quarter of 2015. On December 22, 2015, we closed the sale of our remaining North American Coal business, which included Pinnacle mine in West Virginia and Oak Grove mine in Alabama. Pinnacle mine and Oak Grove mine were sold to Seneca and the deal structure was a sale of equity interests of our remaining coal business. Additionally, Seneca may pay Cliffs an earn-out of up to $50 million contingent upon the terms of a revenue sharing agreement which extends through the year 2020. However, we have not recorded a gain contingency in relation to this earn-out. We recorded the results of this sale within Loss from Discontinued Operations, net of tax for the year ended December 31, 2015. On December 31, 2014, we completed the sale of our CLCC assets in West Virginia to Coronado Coal II, LLC, an affiliate of Coronado Coal LLC, for $174.0 million in cash and the assumption of certain liabilities, of which $155.0 million was collected as of December 31, 2014. We recorded the results of this sale in our fourth quarter earnings within Loss from Discontinued Operations, net of tax as the transaction closed on December 31, 2014. Loss on Discontinued Operations The sale of our Oak Grove and Pinnacle mines on December 22, 2015 completed a strategic shift in our business. Our previously reported North American Coal operating segment results for all periods, prior to the March 31, 2015 held for sale determination, are classified as discontinued operations. Historical results also include our CLCC assets, which were sold during the fourth quarter of 2014. (In Millions) Year Ended Loss from Discontinued Operations 2016 2015 2014 Revenues from product sales and services $ — $ 392.9 $ 687.1 Cost of goods sold and operating expenses — (449.2 ) (822.9 ) Sales margin — (56.3 ) (135.8 ) Other operating expense (4.5 ) (30.4 ) (20.8 ) Gain (loss) on sale of coal mines 2.1 9.3 (419.6 ) Other expense — (1.8 ) (3.0 ) Loss from discontinued operations before income taxes (2.4 ) (79.2 ) (579.2 ) Impairment of long-lived assets — (73.4 ) (857.5 ) Income tax benefit — 0.2 302.2 Loss from discontinued operations, net of tax $ (2.4 ) $ (152.4 ) $ (1,134.5 ) Items Measured at Fair Value on a Non-Recurring Basis The following table presents information about the impairment charge on non-financial assets that was measured on a fair value basis at March 31, 2015 for the North American Coal operations. There were no financial and non-financial assets and liabilities that were measured on a non-recurring fair value basis at December 31, 2016 for the North American Coal operations. The table also indicates the fair value hierarchy of the valuation techniques used to determine such fair value. (In Millions) March 31, 2015 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 Losses Assets: Other long-lived assets - Property, plant and equipment and Mineral rights: North American Coal operating unit $ — $ — $ 20.4 $ 20.4 $ 73.4 $ — $ — $ 20.4 $ 20.4 $ 73.4 In the first quarter of 2015, as part of the held for sale classification assigned to North American Coal, an impairment charge of $73.4 million was recorded. The impairment charge was to reduce the assets to their estimated fair value which was determined based on potential sales scenarios. We determined the fair value and recoverability of our North American Coal operating segment by comparing the estimated fair value of the underlying assets and liabilities to the estimated sales price of the operating segment held for sale. No further impairment was recorded in 2015. Recorded Assets and Liabilities (In Millions) Assets and Liabilities of Discontinued Operations 1 December 31, December 31, Other current assets $ — $ 14.9 Total assets of discontinued operations $ — $ 14.9 Accrued liabilities $ 1.1 $ — Other current liabilities 4.9 6.9 Total liabilities of discontinued operations $ 6.0 $ 6.9 1 At December 31, 2016 and 2015, we also recorded $2.1 million and $7.8 million, respectively, of contingent liabilities associated with our exit from the coal business recorded on our parent company. As part of the CLCC asset sale during the fourth quarter of 2014, there was an amount placed in escrow to cover decreases in working capital, indemnity obligations and regulatory liabilities. During the year ended December 31, 2016, $10.3 million was released to us from escrow. There was no amount held in escrow at December 31, 2016 and $14.9 million at December 31, 2015 recorded within Other current assets on the Statements of Consolidated Financial Position . Income Taxes We have recognized no tax expense or benefit for the year ended December 31, 2016 in Loss from Discontinued Operations, net of tax , related to our North American Coal investments. For the years ended December 31, 2015 and 2014, we have recognized a tax benefit of $ 0.2 million and $302.2 million , respectively, in Loss from Discontinued Operations, net of tax , related to a loss on our North American Coal investments. The benefit for the year ended December 31, 2014 is primarily the result of the impairment of long-lived assets in the third quarter of 2014. Canadian Operations Background On November 30, 2013, we suspended indefinitely our Chromite Project in Northern Ontario. The Chromite Project remained suspended throughout 2014 and until final sale in 2015. Our Wabush Scully iron ore mine in Newfoundland and Labrador was idled by the end of the first quarter of 2014 and subsequently began to commence permanent closure in the fourth quarter of 2014. During 2014, we also limited exploration spending on the Labrador Trough South property in Québec. In November 2014, we announced that we were pursuing exit options for our Eastern Canadian Iron Ore operations. In December 2014, iron ore production at the Bloom Lake mine was suspended and the Bloom Lake mine was placed in "care-and-maintenance" mode. Together, the suspension of exploration efforts, shutdown of the Wabush Scully mine and the cessation of operations at our Bloom Lake mine represented a complete curtailment of our Canadian operations. On January 27, 2015, we announced the Bloom Filing under the CCAA with the Québec Court in Montreal. At that time, the Bloom Lake Group was no longer generating revenues and was not able to meet its obligations as they came due. The Bloom Filing addressed the Bloom Lake Group's immediate liquidity issues and permitted the Bloom Lake Group to preserve and protect its assets for the benefit of all stakeholders while restructuring and sale options are explored. As part of the CCAA process, the Court approved the appointment of a Monitor and certain other financial advisors. Additionally, on May 20, 2015, we announced the Wabush Filing with the Court under the CCAA. 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 of each of their businesses and operations. The Wabush Group was no longer generating revenues and was not able to meet its obligations as they came due. The inclusion of the Wabush Group in the existing Bloom Filing facilitated a more comprehensive restructuring and sale process of both the Bloom Lake Group and the Wabush Group, which collectively included mine, port and rail assets. The Wabush Filing also mitigates various legacy related long-term liabilities associated with the Wabush Group. As part of the Wabush Filing, the Court approved the appointment of a Monitor and certain other financial advisors. The Monitor of the Wabush Group is also the Monitor of the Bloom Lake Group. As a result of the Bloom Filing on January 27, 2015, we no longer have a controlling interest in the Bloom Lake Group. For that reason, we deconsolidated the Bloom Lake Group and certain other wholly-owned subsidiaries effective January 27, 2015, which resulted in a pretax impairment loss on deconsolidation and other charges, totaling $818.7 million that was recorded in the first quarter of 2015. The pretax loss on deconsolidation includes the derecognition of the carrying amounts of the Bloom Lake Group and certain other wholly-owned subsidiaries' assets, liabilities and accumulated other comprehensive loss and the recording of our remaining interests at fair value. As a result of the Wabush Filing, we deconsolidated certain Wabush Group wholly-owned subsidiaries effective May 20, 2015. The certain wholly-owned subsidiaries that were deconsolidated effective May 20, 2015 are Wabush Group entities that were not deconsolidated as part of the deconsolidation effective January 27, 2015 as discussed previously in this section. This deconsolidation, effective May 20, 2015, resulted in a pretax gain on deconsolidation and other charges, totaling $134.7 million . The pretax gain on deconsolidation includes the derecognition of the carrying amounts of these certain deconsolidated Wabush Group wholly-owned subsidiaries' assets, liabilities and accumulated other comprehensive loss and the adjustment of our remaining interests in the Canadian Entities to fair value. Subsequent to each of the deconsolidations discussed above, we utilized the cost method to account for our investment in the Canadian Entities, which has been reflected as zero in our Statements of Consolidated Financial Position as of December 31, 2016 and 2015 based on the estimated fair value of the Canadian Entities' net assets. Loans to and accounts receivable from the Canadian Entities are recorded at an estimated fair value of $48.6 million and $72.9 million classified as Loans to and accounts receivables from the Canadian Entities in the Statements of Consolidated Financial Position as of December 31, 2016 and 2015, respectively. The Loans to and accounts receivables from the Canadian Entities balance reflects our current estimate. We continue to update the estimate as the CCAA proceedings progress. The December 31, 2016 balance reflects recent developments, including finalized liquidation values for completed asset sales and updates for the expected allocation of proceeds for those sales, updates for ongoing costs incurred by the estate that will be held back from the final distribution, and the repayment of the DIP financing. Status of CCAA Proceedings On March 8, 2016, certain of the Canadian Entities completed the sale of their port and rail assets located in Pointe-Noire, Quebec to Societe Ferroviaire et Portuaire de Pointe-Noire S.E.C., an affiliate of Investissement Quebec, for C$66.75 million in cash and the assumption of certain liabilities. On April 11, 2016, certain of the Canadian Entities completed the sale of the Bloom Lake mine and Labrador Trough South mineral claims located in Quebec, as well as certain rail assets located in Newfoundland & Labrador, to Quebec Iron Ore Inc., an affiliate of Champion Iron Mines Limited, for C$10.5 million in cash and the assumption of certain liabilities. As of December 31, 2016, the majority of assets available to the estate have been liquidated. The CCAA proceedings are still ongoing and the Monitor is evaluating all claims into the estate including our related party claims. Currently, there is uncertainty as to the amount of the distribution that will be made to the creditors of the estate, including, if any to Cliffs, and whether Cliffs could be held liable for claims that may be asserted by or on behalf of the Bloom Lake Group or the Wabush Group or by their respective representatives against non-debtor affiliates of the Bloom Lake Group and the Wabush Group. After repayment of the DIP financing, payment of sales expenses, taxes and the costs of the CCAA proceedings to date, the net proceeds from these and certain other divestitures by the Canadian Entities are currently being held by the Monitor, on behalf of the Canadian Entities, to fund the accrued and ongoing costs of the CCAA proceedings and for eventual distribution to creditors of the Canadian Entities pending further order of the Montreal Court. Loss on Discontinued Operations Our Canadian exit represents a strategic shift in our business. For this reason, our previously reported Eastern Canadian Iron Ore and Ferroalloys operating segment results for all periods prior to the respective deconsolidations, as well as costs to exit, are classified as discontinued operations. (In Millions) Year Ended December 31, Loss from Discontinued Operations 2016 2015 2014 Revenues from product sales and services $ — $ 11.3 $ 563.5 Cost of goods sold and operating expenses — (11.1 ) (808.4 ) Eliminations with continuing operations — — (53.6 ) Sales margin — 0.2 (298.5 ) Other operating expense — (33.8 ) (306.3 ) Other expense — (1.0 ) (5.6 ) Loss from discontinued operations before income taxes — (34.6 ) (610.4 ) Loss from deconsolidation (17.5 ) (710.9 ) — Impairment of long-lived assets — — (7,536.8 ) Income tax benefit — 5.8 913.7 Loss from discontinued operations, net of tax $ (17.5 ) $ (739.7 ) $ (7,233.5 ) Canadian Entities loss from deconsolidation totaled $17.5 million and $710.9 million for the year ended December 31, 2016 and 2015, respectively and included the following: (In Millions) Year Ended December 31, Year Ended December 31, 2016 2015 Investment impairment on deconsolidation 1 $ (17.5 ) $ (507.8 ) Guarantees and contingent liabilities — (203.1 ) Total loss from deconsolidation $ (17.5 ) $ (710.9 ) 1 Includes the adjustment to fair value of our remaining interest in the Canadian Entities. We have no gain or loss from deconsolidation attributable to contingent liabilities for the year ended December 31, 2016 compared to a loss of $203.1 million for the year ended December 31, 2015. As a result of the deconsolidation, we recorded accrued expenses for the estimated probable loss related to claims that may be asserted against us, primarily under guarantees of certain debt arrangements and leases for a loss on deconsolidation of $203.1 million , for the year ended December 31, 2015. Investments in the Canadian Entities We continue to indirectly own a majority of the interest in the Canadian Entities but have deconsolidated those entities because we no longer have a controlling interest as a result of the Bloom Filing and the Wabush Filing. At the respective dates of deconsolidation, January 27, 2015 or May 20, 2015 and subsequently at each reporting period, we adjusted our investment in the Canadian Entities to fair value with a corresponding charge to Loss from Discontinued Operations, net of tax . As the estimated amount of the Canadian Entities' liabilities exceeded the estimated fair value of the assets available for distribution to its creditors, the fair value of Cliffs’ equity investment is approximately zero . Amounts Receivable from the Canadian Entities Prior to the deconsolidations, various Cliffs wholly-owned entities made loans to the Canadian Entities for the purpose of funding its 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 in our consolidated financial statements. Additionally, we procured funding subsequent to the deconsolidation through the DIP financing. 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 $48.6 million and $72.9 million classified as Loans to and accounts receivables from the Canadian Entities in the Statements of Consolidated Financial Position at December 31, 2016 and 2015, respectively. Guarantees and Contingent Liabilities Certain liabilities, consisting primarily of equipment loans and environmental obligations of the Canadian Entities, were secured through corporate guarantees and standby letters of credit. As of December 31, 2016 , we have liabilities of $0.2 million and $37.0 million , respectively, in our consolidated results, classified as Guarantees and Other liabilities in the Statements of Consolidated Financial Position . As of December 31, 2015, we have liabilities of $96.5 million and $35.9 million , respectively, in our consolidated results, classified as Guarantees and Other liabilities in the Statements of Consolidated Financial Position . Contingencies The recorded expenses include an accrual for the estimated probable loss related to claims that may be asserted against us. Our estimates involve significant judgment. Our estimates are based on currently available information, an assessment of the validity of certain claims and estimated payments by the Canadian Entities. We are not able to reasonably estimate a range of possible losses in excess of the accrual because there are significant factual and legal issues to be resolved. We believe that it is reasonably possible that future changes to our estimates of loss and the ultimate amount paid on these claims could be material to our results of operations in future periods. Any such losses would be reported in discontinued operations. Items Measured at Fair Value on a Non-Recurring Basis The following table presents information about the financial assets and liabilities that were measured on a fair value basis at December 31, 2016 and 2015 for the Canadian Entities. The table also indicates the fair value hierarchy of the valuation techniques used to determine such fair value. (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 Losses Assets: Loans to and accounts receivables from the Canadian Entities $ — $ — $ 48.6 $ 48.6 $ 17.5 Liabilities: Guarantees and contingent liabilities $ — $ — $ 37.2 $ 37.2 $ — (In Millions) December 31, 2015 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 Losses Assets: Loans to and accounts receivables from the Canadian Entities $ — $ — $ 72.9 $ 72.9 $ 507.8 Liabilities: Guarantees and contingent liabilities $ — $ — $ 132.4 $ 132.4 $ 203.1 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 and contingent liabilities at book value, which best approximated fair value. Outstanding liabilities include accounts payable and other liabilities, forward commitments, unsubordinated related party payables, lease liabilities and other potential claims. Potential claims include an accrual for the estimated probable loss related to claims that may be asserted against the Bloom Lake Group and Wabush Group under certain contracts. Claimants may seek damages or other related relief as a result of the Canadian Entities' exit from Canada. Based on our estimates, the fair value of liabilities exceeds the fair value of assets. 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 contingent liability exposure described previously. Pre-Petition Financing Prior to the Wabush Filing on May 20, 2015, a secured credit facility (the "Pre-Petition financing") was put into place to provide support to the Wabush Group for ongoing business activities until the DIP financing was in place. There was a total of $7.2 million drawn and outstanding under the Pre-Petition financing funded by Wabush Iron Co. Limited’s parent company, Cliffs Mining Company as of December 31, 2016 and 2015. Our estimated recovery of the Pre-Petition financing is included within the Loans to and accounts receivables from the Canadian Entities of $48.6 million . The Pre-Petition financing is secured by certain equipment of the Wabush Group. DIP Financing In connection with the Wabush Filing on May 20, 2015, the Montreal Court approved an agreement to provide the DIP financing to the Wabush Group, which provided for borrowings under the facility up to $10.0 million . As of December 31, 2015, there was $6.8 million drawn and outstanding under the DIP financing funded by Wabush Iron Co. Limited’s parent company, Cliffs Mining Company. During the three months ended March 31, 2016, the Wabush Group made an additional draw of $1.5 million . We subsequently received a repayment of $8.3 million and as a result, there was no outstanding balance due under the DIP financing arrangement from Wabush Iron Co. Limited’s parent company, Cliffs Mining Company as of December 31, 2016 . Income Taxes We have recognized no tax expense or benefit for the year ended December 31, 2016 in Loss from Discontinued Operations, net of tax , related to our Canadian investments. For the years ended December 31, 2015 and 2014, we recognized a tax benefit of $ 5.8 million and $913.7 million , respectively, in Loss from Discontinued Operations, net of tax . The benefit for the year ended December 31, 2014 was the result of the impairment of long-lived assets in the third quarter of 2014 offset by the placement of a valuation allowance against the Canadian operations net deferred tax assets.

CAPITAL STOCK

CAPITAL STOCK	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
CAPITAL STOCK	NOTE 15 - CAPITAL STOCK Preferred Shares Conversion to Common Shares On January 4, 2016, we announced that our Board of Directors determined the final quarterly dividend of our Preferred Shares would not be paid in cash, but instead, pursuant to the terms of the Preferred Shares, the conversion rate was increased such that holders of the Preferred Shares received additional common shares in lieu of the accrued dividend at the time of the mandatory conversion on February 1, 2016. The number of common shares in the aggregate that were issued in lieu of the final dividend was 1.3 million . This resulted in an effective conversion rate of 0.9052 common shares, rather than 0.8621 common shares, per depositary share, e ach representing a 1/40 th of a Preferred Share. Prior to the mandatory conversion, holders of the depositary shares were entitled to a proportional fractional interest in the rights and preferences of the Series A preferred shares, including conversion, dividend, liquidation and voting rights, subject to the provisions of the deposit agreement. The Series A preferred shares were convertible, at the option of the holder, at the minimum conversion rate of 28.1480 of our common shares (equivalent to 0.7037 of our common shares per depositary share) at any time prior to February 1, 2016 or other than during a fundamental change conversion period, subject to anti-dilution adjustments. If not converted prior to that time, each Series A preferred share converted automatically on February 1, 2016 into between 28.1480 and 34.4840 common shares, par value $0.125 per share, subject to anti-dilution adjustments. The number of common shares issued on conversion was determined based on the average VWAP per share of our common shares during the 20 trading day period beginning on, and including, the 23 rd scheduled trading day prior to February 1, 2016, subject to customary anti-dilution adjustments. Upon conversion on February 1, 2016, an aggregate of 26.5 million common shares were issued, representing 25.2 million common shares issuable upon conversion and 1.3 million that were issued in lieu of a final cash dividend. Dividends On March 27, 2015, July 1, 2015 and September 10, 2015, our Board of Directors declared the quarterly cash dividend of $17.50 per Preferred Share, which is equivalent to approximately $0.44 per depositary share. The cash dividend was paid on May 1, 2015, August 3, 2015 and November 2, 2015 to our shareholders of record as of the close of business on April 15, 2015, July 15, 2015 and October 15, 2015, respectively. On February 11, 2014, May 13, 2014, September 8, 2014 and November 19, 2014, our Board of Directors declared the quarterly cash dividend of $ 17.50 per Preferred Share, which is equivalent to approximately $ 0.44 per depositary share. The cash dividend was paid on May 1, 2014 , August 1, 2014 , November 3, 2014 and February 2, 2015 , to our Preferred Shareholders of record as of the close of business on April 15, 2014 , July 15, 2014 , October 15, 2014 and January 15, 2015 , respectively. On February 11, 2013, our Board of Directors approved a reduction to our quarterly cash dividend rate by 76% to $0.15 per share. The cash dividend of $0.15 per share was paid on March 3, 2014, June 3, 2014, September 2, 2014 and December 1, 2014 to our common shareholders of record as of close of business on February 21, 2014, May 23, 2014, August 15, 2014 and November 15, 2014. On January 26, 2015, we announced that our Board of Directors had decided to eliminate the quarterly dividend of $0.15 per share on our common shares. The decision was applicable to the first quarter of 2015 and all subsequent quarters. Debt-for-Equity Exchanges During the year ended December 31, 2016, we entered into a series of privately negotiated exchange agreements whereby we issued an aggregate of 8.2 million common shares in exchange for $10.0 million aggregate principal amount of our 3.95% senior notes due 2018, $20.1 million aggregate principal amount of our 4.80% senior notes due 2020 and $26.8 million aggregate principal amount of our 4.875% senior notes due 2021. There were no exchanges that represented more than 1% of our outstanding common shares during any quarter. Accordingly, we recognized a gain of $11.3 million in Gain on extinguishment/restructuring of debt in the Statements of Consolidated Operations for the year ended December 31, 2016 . The issuances of the common shares in exchange for our senior notes due 2018, 2020 and 2021 were made in reliance on the exemption from registration provided in Section 3(a)(9) of the Securities Act. Common Share Public Offering On August 10, 2016, we issued 44.4 million common shares in an underwritten public offering. We received net proceeds of approximately $287.6 million at a public offering price of $6.75 per common share. The proceeds from the issuance of our common shares were used to fully redeem our senior notes due 2018.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
ACCUMLATED OTHER COMPREHENSIVE INCOME (LOSS)	NOTE 16 - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The components of Accumulated other comprehensive loss within Cliffs shareholders’ deficit and related tax effects allocated to each are shown below as of December 31, 2016 , 2015 and 2014: (In Millions) Pre-tax Amount Tax Benefit (Provision) After-tax Amount As of December 31, 2014: Postretirement benefit liability $ (425.3 ) $ 134.2 $ (291.1 ) Foreign currency translation adjustments 64.4 — 64.4 Unrealized net loss on derivative financial instruments (25.9 ) 7.8 (18.1 ) Unrealized gain (loss) on securities (1.3 ) 0.3 (1.0 ) $ (388.1 ) $ 142.3 $ (245.8 ) As of December 31, 2015: Postretirement benefit liability $ (364.8 ) $ 123.4 $ (241.4 ) Foreign currency translation adjustments 220.7 — 220.7 Unrealized net gain on derivative financial instruments 2.2 0.4 2.6 Unrealized gain on securities 0.1 — 0.1 $ (141.8 ) $ 123.8 $ (18.0 ) As of December 31, 2016: Postretirement benefit liability $ (384.0 ) $ 123.4 $ (260.6 ) Foreign currency translation adjustments 239.3 — 239.3 $ (144.7 ) $ 123.4 $ (21.3 ) The following tables reflect the changes in Accumulated other comprehensive loss related to Cliffs shareholders’ equity for December 31, 2016 , 2015 and 2014: (In Millions) Postretirement Benefit Liability, net of tax Unrealized Net Gain (Loss) on Securities, net of tax Unrealized Net Gain (Loss) on Foreign Currency Translation Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax Accumulated Other Comprehensive Income (Loss) Balance December 31, 2015 $ (241.4 ) $ 0.1 $ 220.7 $ 2.6 $ (18.0 ) Other comprehensive income (loss) before reclassifications (44.8 ) (0.1 ) 18.4 (3.3 ) (29.8 ) Net loss reclassified from accumulated other comprehensive income (loss) 25.6 — 0.2 0.7 26.5 Balance December 31, 2016 $ (260.6 ) $ — $ 239.3 $ — $ (21.3 ) (In Millions) Postretirement Benefit Liability, net of tax Unrealized Net Gain (Loss) on Securities, net of tax Unrealized Net Gain (Loss) on Foreign Currency Translation Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax Accumulated Other Comprehensive Income (Loss) Balance December 31, 2014 $ (291.1 ) $ (1.0 ) $ 64.4 $ (18.1 ) $ (245.8 ) Other comprehensive income (loss) before reclassifications 9.1 5.4 (26.4 ) 1.9 (10.0 ) Net loss (gain) reclassified from accumulated other comprehensive income (loss) 40.6 (4.3 ) 182.7 18.8 237.8 Balance December 31, 2015 $ (241.4 ) $ 0.1 $ 220.7 $ 2.6 $ (18.0 ) (In Millions) Postretirement Benefit Liability, net of tax Unrealized Net Gain (Loss) on Securities, net of tax Unrealized Net Gain (Loss) on Foreign Currency Translation Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax Accumulated Other Comprehensive Income (Loss) Balance December 31, 2013 $ (204.9 ) $ 6.2 $ 106.7 $ (20.9 ) $ (112.9 ) Other comprehensive income (loss) before reclassifications (97.0 ) 1.3 (42.3 ) (28.2 ) (166.2 ) Net loss (gain) reclassified from accumulated other comprehensive income (loss) 10.8 (8.5 ) — 31.0 33.3 Balance December 31, 2014 $ (291.1 ) $ (1.0 ) $ 64.4 $ (18.1 ) $ (245.8 ) The following table reflects the details about Accumulated other comprehensive loss components related to Cliffs shareholders’ equity for the years ended December 31, 2016 , 2015 and 2014: (In Millions) Details about Accumulated Other Comprehensive Income (Loss) Components Amount of (Gain)/Loss Reclassified into Income Affected Line Item in the Statement of Consolidated Operations Year Ended Year Ended Year Ended December 31, 2014 Amortization of Pension and Postretirement Benefit Liability: Prior service costs 1 $ (1.5 ) $ (1.4 ) $ (1.1 ) Net actuarial loss 1 27.1 27.4 18.5 Curtailments/Settlements 1 — 0.2 1.4 Effect of deconsolidation 2 — 15.1 — Loss from Discontinued Operations, net of tax 25.6 41.3 18.8 Total before taxes — (0.7 ) (5.8 ) Income tax benefit (expense) $ 25.6 $ 40.6 $ 13.0 Net of taxes Unrealized loss on marketable securities: Sale of marketable securities $ — $ (2.6 ) $ (11.4 ) Other non-operating income (expense) Impairment — (2.0 ) (0.5 ) Other non-operating income (expense) — (4.6 ) (11.9 ) Total before taxes — 0.3 3.4 Income tax benefit (expense) $ — $ (4.3 ) $ (8.5 ) Net of taxes Unrealized gain on foreign currency translation: Dissolution of entity $ 0.2 $ — $ — Other non-operating income (expense) Effect of deconsolidation 3 — 182.7 — Loss from Discontinued Operations, net of tax $ 0.2 $ 182.7 $ — Net of taxes Unrealized gain on derivative financial instruments: Treasury lock $ 1.2 $ — $ — Gain on extinguishment/restructuring of debt Australian dollar foreign exchange contracts — 26.9 18.9 Product revenues Canadian dollar foreign exchange contracts — — 26.7 Cost of goods sold and operating expenses 1.2 26.9 45.6 Total before taxes (0.5 ) (8.1 ) (14.6 ) Income tax benefit (expense) $ 0.7 $ 18.8 $ 31.0 Net of taxes Total Reclassifications for the Period $ 26.5 $ 237.8 $ 35.5 1 These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. See NOTE 7 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information. 2 Represents Canadian postretirement benefit liabilities that were deconsolidated. See NOTE 14 - DISCONTINUED OPERATIONS for further information. 3 Represents Canadian accumulated currency translation adjustments that were deconsolidated. See NOTE 14 - DISCONTINUED OPERATIONS for further information.

CASH FLOW INFORMATION

CASH FLOW INFORMATION	12 Months Ended
	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Cash Flow Information	NOTE 17 - CASH FLOW INFORMATION A reconciliation of capital additions to cash paid for capital expenditures for the years ended December 31, 2016 , 2015 and 2014 is as follows: (In Millions) Year Ended December 31, 2016 2015 2014 Capital additions 1 $ 68.5 $ 96.7 $ 235.5 Cash paid for capital expenditures 69.1 80.8 284.1 Difference $ (0.6 ) $ 15.9 $ (48.6 ) Non-cash accruals $ (0.6 ) $ 14.4 $ (58.5 ) Capital leases — 1.5 9.9 Total $ (0.6 ) $ 15.9 $ (48.6 ) 1 Includes capital additions of $68.5 million related to continuing operations for the year ended December 31, 2016. Includes capital additions of $72.2 million and $24.5 million related to continuing operations and discontinued operations, respectively, for the year ended December 31, 2015. Includes capital additions of $65.5 million and $170.0 million related to continuing operations and discontinued operations, respectively, for the year ended December 31, 2014. Cash payments for interest and income taxes in 2016 , 2015 and 2014 are as follows: (In Millions) 2016 2015 2014 Taxes paid on income $ 6.0 $ 5.0 $ 47.3 Income tax refunds 1 5.4 211.4 54.7 Interest paid on debt obligations 2 184.0 185.6 176.5 1 Includes income tax refunds that relate to the deconsolidated Canadian Entities for the year ended December 31, 2014 of $47.8 million. 2 Includes interest paid on the corporate guarantees of the equipment loans that relate to discontinued operations for the years ended December 31, 2016, 2015 and 2014 of $1.4 million, $4.8 million and $6.1 million, respectively.

RELATED PARTIES

RELATED PARTIES	12 Months Ended
	Dec. 31, 2016
Related Party Transactions [Abstract]
RELATED PARTIES	NOTE 18 - RELATED PARTIES Two of our four operating U.S. iron ore mines and our indefinitely-idled Empire mine are owned with various joint venture partners 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 or more of the joint venture partners are also our customers. The following is a summary of the mine ownership of these iron ore mines at December 31, 2016 : Mine Cliffs Natural Resources ArcelorMittal U.S. Steel Empire 79.0 % 21.0 % — Tilden 85.0 % — 15.0 % Hibbing 23.0 % 62.3 % 14.7 % ArcelorMittal has a unilateral right to put its interest in the Empire mine to us, but has not exercised this right to date. Furthermore, as part of a 2014 extension agreement between us and ArcelorMittal, which amended certain terms of the Empire partnership agreement, certain minimum distributions of the partners’ equity amounts were required to be made on a quarterly basis beginning in the first quarter of 2015 and continued through January 2017. The partnership dissolved on December 31, 2016 and the partners are in discussion regarding distribution of the remaining assets and/or equity interest, if any, in the partnership. During the year ended December 31, 2016 , we recorded distributions of $57.5 million to ArcelorMittal under this agreement, of which $48.8 million was paid as of December 31, 2016 . During the year ended December 31, 2015, we recorded distributions of $51.7 million under this agreement, of which $40.6 million was paid as of December 31, 2015. Product revenues from related parties were as follows: (In Millions) Year Ended December 31, 2016 2015 2014 Product revenues from related parties $ 830.1 $ 671.1 $ 1,011.4 Total product revenues 1,913.5 1,832.4 3,095.2 Related party product revenue as a percent of total product revenue 43.4 % 36.6 % 32.7 % Amounts due from related parties recorded in Accounts receivable, net and Other current assets , including trade accounts receivable, a customer supply agreement and provisional pricing arrangements, were $73.8 million and $15.8 million at December 31, 2016 and 2015 , respectively. Amounts due to related parties recorded in Other current liabilities , including provisional pricing arrangements and liabilities to related parties, were $8.7 million and $14.5 million at December 31, 2016 and 2015 , respectively. A supply agreement with one of our customers includes provisions for supplemental revenue or refunds based on the customer’s annual steel pricing for the year the product is consumed in the customer’s blast furnace. The supplemental pricing is characterized as a freestanding derivative. Refer to NOTE 13 - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES for further information.

EARNINGS PER SHARE

EARNINGS PER SHARE	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
EARNINGS PER SHARE	NOTE 19 - EARNINGS PER SHARE The following table summarizes the computation of basic and diluted earnings per share attributable to Cliffs shareholders: (In Millions, Except Per Share Amounts) Year Ended December 31, 2016 2015 2014 Income from Continuing Operations $ 219.2 $ 143.7 $ 56.4 Income from Continuing Operations Attributable to (25.2 ) (8.6 ) (25.9 ) Net Income from Continuing Operations $ 194.0 $ 135.1 $ 30.5 Loss from Discontinued Operations, net of tax (19.9 ) (884.4 ) (7,254.7 ) NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS $ 174.1 $ (749.3 ) $ (7,224.2 ) PREFERRED STOCK DIVIDENDS — (38.4 ) (51.2 ) NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS $ 174.1 $ (787.7 ) $ (7,275.4 ) Weighted Average Number of Shares: Basic 197.7 153.2 153.1 Employee Stock Plans 2.4 0.4 — Diluted 200.1 153.6 153.1 Earnings (loss) per Common Share Attributable to Continuing operations $ 0.98 $ 0.63 $ (0.14 ) Discontinued operations (0.10 ) (5.77 ) (47.38 ) $ 0.88 $ (5.14 ) $ (47.52 ) Earnings (loss) per Common Share Attributable to Continuing operations $ 0.97 $ 0.63 $ (0.14 ) Discontinued operations (0.10 ) (5.76 ) (47.38 ) $ 0.87 $ (5.13 ) $ (47.52 ) The diluted earnings per share calculation excludes 25.3 million and 25.2 million depositary shares that were anti-dilutive for the year ended December 31, 2015 and 2014, respectively. Additionally, the diluted earnings per share calculation also excludes 0.7 million of equity plan awards that were anti-dilutive for the year ended December 31, 2014.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	NOTE 20 - COMMITMENTS AND CONTINGENCIES Contingencies Litigation We are currently a 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, litigation is 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 of the period in which the ruling occurs, or future periods. However, we do not believe that any pending litigation, not covered by insurance, will result in a material liability in relation to our consolidated financial statements . 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 approximately $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. As of December 31, 2016, this potential liability of $13.6 million is included in our Statements of Consolidated Financial Position as part of Other current liabilities . 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. 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. Environmental Matters We had environmental liabilities of $2.8 million and $3.6 million at December 31, 2016 and 2015 , respectively, including obligations for known environmental remediation exposures at active and closed mining operations and other sites. These amounts have been recognized based on the estimated cost of investigation and remediation at each site, and include site studies, design and implementation of remediation plans, legal and consulting fees, and post-remediation monitoring and related activities. If the cost can only be estimated as a range of possible amounts with no specific amount being more likely, the minimum of the range is accrued. Future expenditures are not discounted unless the amount and timing of the cash disbursements are readily known. Potential insurance recoveries have not been reflected. Additional environmental obligations could be incurred, the extent of which cannot be assessed. The amount of our ultimate liability with respect to these matters may be affected by several uncertainties, primarily the ultimate cost of required remediation and the extent to which other responsible parties contribute. Refer to NOTE 11 - ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS for further information. Tax Matters The calculation of our tax liabilities involves dealing with uncertainties in the application of complex tax regulations. We recognize liabilities for anticipated tax audit issues based on our estimate of whether, and the extent to which, additional taxes will be due. If we ultimately determine that payment of these amounts is unnecessary, we reverse the liability and recognize a tax benefit during the period in which we determine that the liability is no longer necessary. We also recognize tax benefits to the extent that it is more likely than not that our positions will be sustained when challenged by the taxing authorities. To the extent we prevail in matters for which liabilities have been established, or are required to pay amounts in excess of our liabilities, our effective tax rate in a given period could be materially affected. An unfavorable tax settlement would require use of our cash and result in an increase in our effective tax rate in the year of resolution. A favorable tax settlement would be recognized as a reduction in our effective tax rate in the year of resolution. Refer to NOTE 9 - INCOME TAXES for further information.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
	Dec. 31, 2016
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	NOTE 21 - SUBSEQUENT EVENTS We have evaluated subsequent events through the date of financial issuance.

QUARTERLY RESULTS OF OPERATIONS

QUARTERLY RESULTS OF OPERATIONS - (UNAUDITED)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information [Text Block]	NOTE 22 - QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) The sum of quarterly EPS may not equal EPS for the year due to discrete quarterly calculations. (In Millions, Except Per Share Amounts) 2016 Quarters First Second Third Fourth Year Revenues from product sales and services $ 305.5 $ 496.2 $ 553.3 $ 754.0 $ 2,109.0 Sales margin 30.9 91.5 85.4 181.5 389.3 Income (Loss) from Continuing Operations $ 114.3 $ 29.9 $ (25.1 ) $ 100.1 $ 219.2 Loss (Income) from Continuing Operations (8.8 ) (16.7 ) 2.0 (1.7 ) (25.2 ) Net Income (Loss) from Continuing Operations 105.5 13.2 (23.1 ) 98.4 194.0 Income (Loss) from Discontinued Operations, net of tax 2.5 (0.4 ) (2.7 ) (19.3 ) (19.9 ) NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS $ 108.0 $ 12.8 $ (25.8 ) $ 79.1 $ 174.1 Earnings (loss) per common share attributable to Cliffs common shareholders — Basic: Continuing Operations $ 0.61 $ 0.07 $ (0.11 ) $ 0.43 $ 0.98 Discontinued Operations 0.01 — (0.01 ) (0.08 ) (0.10 ) $ 0.62 $ 0.07 $ (0.12 ) $ 0.35 $ 0.88 Earnings (loss) per common share attributable to Cliffs common shareholders — Diluted: Continuing Operations $ 0.61 $ 0.07 $ (0.11 ) $ 0.42 $ 0.97 Discontinued Operations 0.01 — (0.01 ) (0.08 ) (0.10 ) $ 0.62 $ 0.07 $ (0.12 ) $ 0.34 $ 0.87 The diluted earnings per share calculation for the third quarter of 2016 exclude equity plan awards of 3.0 million that were anti-dilutive. There was no anti-dilution in the first, second or fourth quarter of 2016. (In Millions, Except Per Share Amounts) 2015 Quarters First Second Third Fourth Year Revenues from product sales and services $ 446.0 $ 498.1 $ 593.2 $ 476.0 $ 2,013.3 Sales margin 80.8 57.3 55.1 43.3 236.5 Income (Loss) from Continuing Operations $ 166.8 $ (38.2 ) $ 49.9 $ (34.8 ) $ 143.7 Loss (Income) from Continuing Operations 1.9 (5.0 ) 4.6 (2.4 ) (8.6 ) Net Income (Loss) from Continuing Operations $ 168.7 $ (43.2 ) $ 54.5 $ (37.2 ) $ 135.1 Income (Loss) from Discontinued Operations, net of tax (928.5 ) 103.4 (43.9 ) (23.1 ) (884.4 ) NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS $ (759.8 ) $ 60.2 $ 10.6 $ (60.3 ) $ (749.3 ) PREFERRED STOCK DIVIDENDS (12.8 ) — (25.6 ) — (38.4 ) NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS (772.6 ) 60.2 (15.0 ) (60.3 ) (787.7 ) Earnings (loss) per common share attributable to Cliffs common shareholders — Basic: Continuing Operations $ 1.02 $ (0.28 ) $ 0.19 $ (0.24 ) $ 0.63 Discontinued Operations (6.06 ) 0.67 (0.29 ) (0.15 ) (5.77 ) $ (5.04 ) $ 0.39 $ (0.10 ) $ (0.39 ) $ (5.14 ) Earnings (loss) per common share attributable to Continuing Operations $ 0.94 $ (0.28 ) $ 0.19 $ (0.24 ) $ 0.63 Discontinued Operations (5.20 ) 0.67 (0.29 ) (0.15 ) (5.76 ) $ (4.26 ) $ 0.39 $ (0.10 ) $ (0.39 ) $ (5.13 ) The diluted earnings per share calculation for the second, third and fourth quarter of 2015 exclude depositary shares that were anti-dilutive ranging between 25.2 million and 25.6 million and equity plan awards ranging between 0.1 million and 0.3 million that were anti-dilutive. There was no anti-dilution in the first quarter of 2015.

BASIS OF PRESENTATION AND SIG32

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements, in conformity with GAAP, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions related to mineral reserves future realizable cash flow; environmental, reclamation and closure obligations; valuation of long-lived assets; valuation of inventory; valuation of post-employment, post-retirement and other employee benefit liabilities; valuation of tax assets; reserves for contingencies and litigation; the fair value of derivative instruments; and the fair value of loans to and accounts receivable from Canadian entities. Actual results could differ from estimates. On an ongoing basis, management reviews estimates. Changes in facts and circumstances may alter such estimates and affect the results of operations and financial position in future periods.
Basis Of Consolidation	Basis of Consolidation The consolidated financial statements include our accounts and the accounts of our wholly owned and majority-owned subsidiaries, including the following operations at December 31, 2016 : 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 Investments in unconsolidated ventures that we have the ability to exercise significant influence over, but not control, are accounted for under the equity method. Hibbing Our 23% ownership interest in Hibbing is recorded as an equity method investment. As of December 31, 2016 and December 31, 2015 , our investment in Hibbing was $8.7 million and $2.4 million , respectively, classified in Other liabilities in the Statements of Consolidated Financial Position . Our share of equity income (loss) is eliminated against consolidated product inventory upon production, and against Cost of goods sold and operating expenses when sold. This effectively reduces our cost for our share of the mining ventures' production cost, reflecting the cost-based nature of our participation in unconsolidated ventures.
Noncontrolling Interests [Policy Text Block]	Noncontrolling Interests Noncontrolling interest is primarily comprised of the 21% noncontrolling interest in the consolidated, but less-than-wholly-owned subsidiary at our Empire mining venture and through the CCAA filing on January 27, 2015, the 17.2% noncontrolling interest in the Bloom Lake operations. Financial results prior to the deconsolidation of the Bloom Lake Group and subsequent expenses directly associated with the Canadian Entities are included in our financial statements. The net loss and income attributable to the noncontrolling interest of the Empire mining venture was $25.2 million and $8.6 million for the years ended December 31, 2016 and December 31, 2015 , respectively. There was no net income or loss attributable to the noncontrolling interest related to Bloom Lake for the year ended December 31, 2016 . This compares with a net loss attributable to the noncontrolling interest related to Bloom Lake of $7.7 million for the year ended December 31, 2015 . See NOTE 14 - DISCONTINUED OPERATIONS for further information.
Cash and Cash Equivalents	Cash Equivalents Cash and cash equivalents include cash on hand and on deposit as well as all short-term securities held for the primary purpose of general liquidity. We consider investments in highly liquid debt instruments with an original maturity of three months or less from the date of acquisition to be cash equivalents. We routinely monitor and evaluate counterparty credit risk related to the financial institutions by which our short-term investment securities are held.
Trade and Other Accounts Receivable	Trade Accounts Receivable and Allowance for Doubtful Accounts Trade accounts receivable are recorded at the invoiced amount and do not bear interest. The allowance for doubtful accounts is our best estimate of the amount of probable credit losses in our existing accounts receivable. We establish provisions for losses on accounts receivable when it is probable that all or part of the outstanding balance will not be collected. We regularly review our accounts receivable balances and establish or adjust the allowance as necessary using the specific identification method. The allowance for doubtful accounts was zero and $7.1 million at December 31, 2016 and 2015 , respectively. There was no bad debt expense for the years ended December 31, 2016 and 2014. There was $7.1 million bad debt expense for the year ended December 31, 2015 .
Inventory	Inventories U.S. Iron Ore U.S. Iron Ore product inventories are stated at the lower of cost or market. Cost of iron ore inventories is determined using the LIFO method. We had approximately 1.5 million long tons and 1.3 million long tons of finished goods stored at ports and customer facilities on the lower Great Lakes to service customers at December 31, 2016 and 2015 , respectively. We maintain ownership of the inventories until title has transferred to the customer, usually when payment is received. Maintaining ownership of the iron ore products at ports on the lower Great Lakes reduces risk of non-payment by customers. Asia Pacific Iron Ore Asia Pacific Iron Ore product inventories are stated at the lower of cost or market. Costs of iron ore inventories are being valued on a weighted average cost basis. We maintain ownership of the inventories until title has transferred to the customer, which generally is when the product is loaded into the vessel.
Inventory Supplies	Supplies and Other Inventories Supply inventories include replacement parts, fuel, chemicals and other general supplies, which are expected to be used or consumed in normal operations. Supply inventories also include critical spares. Critical spares are replacement parts for equipment that is critical for the continued operation of the mine or processing facilities. Supply inventories are stated at the lower of cost or market using average cost, less an allowance for obsolete and surplus items. The allowance for obsolete and surplus items was $14.0 million and $31.8 million at December 31, 2016 and 2015 , respectively.
Derivatives	Derivative Financial Instruments and Hedging Activities We are exposed to certain risks related to the ongoing operations of our business, including those caused by changes in commodity prices, interest rates and foreign currency exchange rates. We have established policies and procedures, including the use of certain derivative instruments, to manage such risks, if deemed necessary. Derivative financial instruments are recognized as either assets or liabilities in the Statements of Consolidated Financial Position and measured at fair value. For derivative instruments that have not been designated as cash flow hedges, changes in fair value are recorded in the period of the instrument's earnings or losses. Refer to NOTE 13 - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES for further information.
Property, Plant and Equipment	Property, Plant and Equipment Our properties are stated at the lower of cost less accumulated depreciation or fair value. Depreciation of plant and equipment is computed principally by the straight-line method based on estimated useful lives, not to exceed the mine lives. The U.S. Iron Ore operations use the double-declining balance method of depreciation for certain mining equipment. The Asia Pacific Iron Ore operation uses the production output method for certain mining equipment. Depreciation is provided over the following estimated useful lives: Asset Class Basis Life Office and information technology Straight line 3 to 15 Years Buildings Straight line 45 Years Mining equipment Straight line/Double declining balance 3 to 20 Years Processing equipment Straight line 10 to 45 Years Electric power facilities Straight line 10 to 45 years Land improvements Straight line 20 to 45 years Asset retirement obligation Straight line Life of mine Depreciation continues to be recognized when operations are idled temporarily. Refer to NOTE 4 - PROPERTY, PLANT AND EQUIPMENT for further information.
Capitalized Stripping Costs	Capitalized Stripping Costs During the development phase, stripping costs are capitalized as a part of the depreciable cost of building, developing and constructing a mine. These capitalized costs are amortized over the productive life of the mine using the units of production method. The production phase does not commence until the removal of more than a de minimis amount of saleable mineral material occurs in conjunction with the removal of overburden or waste material for purposes of obtaining access to an ore body. The stripping costs incurred in the production phase of a mine are variable production costs included in the costs of the inventory produced (extracted) during the period that the stripping costs are incurred. Stripping costs related to expansion of a mining asset of proven and probable reserves are variable production costs that are included in the costs of the inventory produced during the period that the stripping costs are incurred.
Other Intangible Assets and Liabilities	Other Intangible Assets and Liabilities Other intangible assets are subject to periodic amortization on a straight-line basis over their estimated useful lives as follows: Intangible Assets Basis Useful Life (years) Permits - Asia Pacific Iron Ore Units of production Life of mine Permits - USIO Straight line Life of mine
Impairment or Disposal of Long-Lived Assets	Asset Impairment Long-Lived Tangible and Intangible Assets We monitor conditions that may affect the carrying value of our long-lived tangible and intangible assets when events and circumstances indicate that the carrying value of the asset groups may not be recoverable. In order to determine if assets have been impaired, assets are grouped and tested at the lowest level for which identifiable, independent cash flows are available ("asset group"). An impairment loss exists when projected undiscounted cash flows are less than the carrying value of the asset group. The measurement of the impairment loss to be recognized is based on the difference between the fair value and the carrying value of the asset group. Fair value can be determined using a market approach, income approach or cost approach. During the year ended December 31, 2016, there were no impairment indicators present; as a result no impairment assessments were required. As a result of the 2015 assessments, there were no material impairment charges related to long-lived tangible or intangible assets at our continuing operations. During 2014, we recorded a long-lived tangible asset impairment charge of $537.8 million and an intangible asset impairment charge of $13.8 million in our Statements of Consolidated Operations related to our continuing operations. Refer to NOTE 4 - PROPERTY, PLANT AND EQUIPMENT , NOTE 12 - GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES and NOTE 6 - FAIR VALUE OF FINANCIAL INSTRUMENTS for further information.
Fair Value of Financial Instruments	Fair Value Measurements Valuation Hierarchy ASC 820, Fair Value Measurements and Disclosures , establishes a three-level valuation hierarchy for classification of fair value measurements. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. Inputs refer broadly to the assumptions that market participants would use in pricing an asset or liability. Inputs may be observable or unobservable. Observable inputs are inputs that reflect the assumptions market participants would use in pricing the asset or liability developed based on market data obtained from independent sources. Unobservable inputs are inputs that reflect our own views about the assumptions market participants would use in pricing the asset or liability developed based on the best information available in the circumstances. The three-tier hierarchy of inputs is summarized below: • Level 1 — Valuation is based upon quoted prices (unadjusted) for identical assets or liabilities in active markets. • Level 2 — Valuation is based upon quoted prices for similar assets and liabilities in active markets, or other inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the financial instrument. • Level 3 — Valuation is based upon other unobservable inputs that are significant to the fair value measurement. The classification of assets and liabilities within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement in its entirety. Valuation methodologies used for assets and liabilities measured at fair value are as follows: Cash Equivalents Where quoted prices are available in an active market, cash equivalents are classified within Level 1 of the valuation hierarchy. Cash equivalents classified in Level 1 at December 31, 2016 and 2015 include money market funds. Valuation of these instruments is determined using a market approach and is based upon unadjusted quoted prices for identical assets in active markets. Derivative Financial Instruments Derivative financial instruments valued using financial models that use as their basis readily observable market parameters are classified within Level 2 of the valuation hierarchy. Such derivative financial instruments include our commodity hedge and foreign currency exchange contracts. Derivative financial instruments that are valued based upon models with significant unobservable market parameters and are normally traded less actively, are classified within Level 3 of the valuation hierarchy. Refer to NOTE 6 - FAIR VALUE OF FINANCIAL INSTRUMENTS and NOTE 7 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.
Pension and Other Postretirement Plans	Pensions and Other Postretirement Benefits We offer defined benefit pension plans, defined contribution pension plans and other postretirement benefit plans, primarily consisting of retiree healthcare benefits, to most employees in North America as part of a total compensation and benefits program. We do not have employee pension or post-retirement benefit obligations at our Asia Pacific Iron Ore operations. We recognize the funded or unfunded status of our postretirement benefit obligations on our December 31, 2016 and 2015 Statements of Consolidated Financial Position based on the difference between the market value of plan assets and the actuarial present value of our retirement obligations on that date, on a plan-by-plan basis. If the plan assets exceed the retirement obligations, the amount of the surplus is recorded as an asset; if the retirement obligations exceed the plan assets, the amount of the underfunded obligations are recorded as a liability. Year-end balance sheet adjustments to postretirement assets and obligations are recorded as Accumulated other comprehensive loss . The actuarial estimates of the PBO and APBO incorporate various assumptions including the discount rates, the rates of increases in compensation, healthcare cost trend rates, mortality, retirement timing and employee turnover. The discount rate is determined based on the prevailing year-end rates for high-grade corporate bonds with a duration matching the expected cash flow timing of the benefit payments from the various plans. The remaining assumptions are based on our estimates of future events by incorporating historical trends and future expectations. The amount of net periodic cost that is recorded in the Statements of Consolidated Operations consists of several components including service cost, interest cost, expected return on plan assets, and amortization of previously unrecognized amounts. Service cost represents the value of the benefits earned in the current year by the participants. Interest cost represents the cost associated with the passage of time. Certain items, such as plan amendments, gains and/or losses resulting from differences between actual and assumed results for demographic and economic factors affecting the obligations and assets of the plans, and changes in other assumptions are subject to deferred recognition for income and expense purposes. The expected return on plan assets is determined utilizing the weighted average of expected returns for plan asset investments in various asset categories based on historical performance, adjusted for current trends. See NOTE 7 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.
Asset Retirement Obligations	Asset Retirement Obligations Asset retirement obligations are recognized when incurred and recorded as liabilities at fair value. The fair value of the liability is determined as the discounted value of the expected future cash flow. The asset retirement obligation is accreted over time through periodic charges to earnings. In addition, the asset retirement cost is capitalized and amortized over the life of the related asset. Reclamation costs are adjusted periodically to reflect changes in the estimated present value resulting from the passage of time and revisions to the estimates of either the timing or amount of the reclamation costs. We review, on an annual basis, unless otherwise deemed necessary, the asset retirement obligation at each mine site in accordance with the provisions of ASC 410, Asset Retirement and Environmental Obligations . We perform an in-depth evaluation of the liability every three years in addition to routine annual assessments. Future reclamation costs for inactive mines are accrued based on management’s best estimate at the end of each period of the costs expected to be incurred at a site. Such cost estimates include, where applicable, ongoing maintenance and monitoring costs. Changes in estimates at inactive mines are reflected in earnings in the period an estimate is revised. See NOTE 11 - ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS for further information.
Environmental Costs	Environmental Remediation Costs We have a formal policy for environmental protection and restoration. Our mining and exploration activities are subject to various laws and regulations governing protection of the environment. We conduct our operations to protect the public health and environment and believe our operations are in compliance with applicable laws and regulations in all material respects. Our environmental liabilities, including obligations for known environmental remediation exposures at active and closed mining operations and other sites, have been recognized based on the estimated cost of investigation and remediation at each site. If the cost only can be estimated as a range of possible amounts with no point in the range being more likely, the minimum of the range is accrued. Future expenditures are not discounted unless the amount and timing of the cash disbursements reasonably can be estimated. It is possible that additional environmental obligations could be incurred, the extent of which cannot be assessed. Potential insurance recoveries have not been reflected in the determination of the liabilities. See NOTE 11 - ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS for further information.
Revenue Recognition	Revenue Recognition We sell our products pursuant to comprehensive supply agreements negotiated and executed with our customers. Revenue is recognized from a sale when persuasive evidence of an arrangement exists, the price is fixed or determinable, the product is delivered in accordance with F.O.B. terms, title and risk of loss have transferred to the customer in accordance with the specified provisions of each supply agreement and collection of the sales price reasonably is assured. Our U.S. Iron Ore and Asia Pacific Iron Ore supply agreements provide that title and risk of loss transfer to the customer either upon loading of the vessel, shipment or, as is the case with some of our U.S. Iron Ore supply agreements, when payment is received. Under certain term supply agreements, we ship the product to ports on the lower Great Lakes or to the customers’ facilities prior to the transfer of title. Our rationale for shipping iron ore products to certain customers and retaining title until payment is received for these products is to minimize credit risk exposure. Sales are recorded at a sales price specified in the relevant supply agreements resulting in revenue and a receivable at the time of sale. Upon revenue recognition for provisionally priced sales, a freestanding derivative is created for the difference between the sales price used and expected future settlement price. The derivative, which does not qualify for hedge accounting, is adjusted to fair value through Product revenues as a revenue adjustment each reporting period based upon current market data and forward-looking estimates determined by management until the final sales price is determined. The principal risks associated with recognition of sales on a provisional basis include iron ore price fluctuations between the date initially recorded and the date of final settlement. For revenue recognition, we estimate the future settlement rate; however, if significant changes in iron ore prices occur between the provisional pricing date and the final settlement date, we might be required to either return a portion of the sales proceeds received or bill for the additional sales proceeds due based on the provisional sales price. Refer to NOTE 13 - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES for further information. In addition, certain supply agreements with one customer include provisions for supplemental revenue or refunds based on the customer’s annual steel pricing for the year the product is consumed in the customer’s blast furnaces. We account for this provision as a free standing derivative instrument at the time of sale and record this provision at fair value until the year the product is consumed and the amounts are settled as an adjustment to revenue. Refer to NOTE 13 - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES for further information. Revenue from product sales and services also includes reimbursement for freight charges associated with domestic freight and venture partner cost reimbursements for the U.S. Iron Ore operations and freight associated with CFR based shipments paid on behalf of customers for the Asia Pacific Iron Ore operations. These are included in Freight and venture partners' cost reimbursements separate from Product revenues . Revenue is recognized for the expected reimbursement of services when the services are performed.
Revenue Recognition, Deferred Revenue	Deferred Revenue The terms of one of our U.S. Iron Ore pellet supply agreements required supplemental payments to be paid by the customer during the period 2009 through 2012, with the option to defer a portion of the 2009 monthly amount in exchange for interest payments until the deferred amount was repaid in 2013. Installment amounts received under this arrangement in excess of sales were classified as deferred revenue in the Statements of Consolidated Financial Position upon receipt of payment. Revenue is recognized over the life of the supply agreement, which extends until 2022, in equal annual installments. As of December 31, 2016 and 2015 , installment amounts received in excess of sales totaled $77.1 million and $89.9 million , respectively. As of December 31, 2016, deferred revenue of $16.4 million was recorded in Other current liabilities and $64.2 million was recorded as long-term in Other liabilities in the Statements of Consolidated Financial Position . As of December 31, 2015, deferred revenue of $12.8 million was recorded in Other current liabilities and $77.1 million was recorded as long-term in Other liabilities in the Statements of Consolidated Financial Position . In 2016 and 2014, due to the payment terms and the timing of cash receipts near year-end, cash receipts exceeded shipments for certain customers. The shipments were completed early in the subsequent years. We considered whether revenue should be recognized on these sales under the “bill and hold” guidance provided by the SEC Staff; however, based upon the assessment performed, revenue recognition on these transactions totaling $3.4 million and $29.3 million were deferred on the Statements of Consolidated Financial Position for the years ended December 31, 2016 and 2014 , respectively.
Cost of Sales	Cost of Goods Sold Cost of goods sold and operating expenses represents all direct and indirect costs and expenses applicable to the sales of our mining operations. Operating expenses primarily represent the portion of the Tilden mining venture costs for which we do not own; that is, the costs attributable to the share of the mine’s production owned by the other joint venture partner in the Tilden mine. The mining venture functions as a captive cost company; it supplies product only to its owners effectively for the cost of production. Accordingly, the noncontrolling interests’ revenue amounts are stated at cost of production and are offset by an equal amount included in Cost of goods sold and operating expenses resulting in no sales margin reflected for the noncontrolling partner participant. As we are responsible for product fulfillment, we act as a principal in the transaction and, accordingly, record revenue under these arrangements on a gross basis. The following table is a summary of reimbursements in our U.S. Iron Ore operations for the years ended December 31, 2016 , 2015 and 2014 : (In Millions) Year Ended December 31, 2016 2015 2014 Reimbursements for: Freight $ 106.8 $ 105.3 $ 163.0 Venture partners’ cost 68.0 52.0 108.0 Total reimbursements $ 174.8 $ 157.3 $ 271.0 In 2014, we began selling a portion of our Asia Pacific Iron Ore product on a CFR basis. As a result, $20.7 million , $23.6 million and $6.9 million of freight was included in Cost of goods sold and operating expenses for the years ended December 31, 2016, 2015 and 2014, respectively. Where we have joint ownership of a mine, our contracts entitle us to receive royalties and/or management fees, which we earn as the pellets are produced.
Repairs And Maintenance	Repairs and Maintenance Repairs, maintenance and replacement of components are expensed as incurred. The cost of major equipment overhauls is capitalized and depreciated over the estimated useful life, which is the period until the next scheduled overhaul, generally five years. All other planned and unplanned repairs and maintenance costs are expensed when incurred.
Share-based Compensation, Option and Incentive Plans	Share-Based Compensation 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. Consistent with the guidelines of ASC 718, Stock Compensation , a correlation matrix of historic and projected stock prices was developed for both the Company and its predetermined peer group of mining and metals companies. The fair value assumes that performance goals will be achieved. The expected term of the grant represents the time from the grant date to the end of the service period for each of the three plan-year agreements. We estimated 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 plans. The fair value of stock options is estimated on the date of grant using a Black-Scholes model using the grant date price of our common shares and option exercise price, and assumptions regarding the option’s expected term, the volatility of our common shares, the risk-free interest rate, and the dividend yield over the option’s expected term. Upon vesting of share-based compensation awards, we issue shares from treasury shares before issuing new shares. Refer to NOTE 8 - STOCK COMPENSATION PLANS for additional information.
Income Tax	Income Taxes Income taxes are based on income for financial reporting purposes, calculated using tax rates by jurisdiction, and reflect a current tax liability or asset for the estimated taxes payable or recoverable on the current year tax return and expected annual changes in deferred taxes. Any interest or penalties on income tax are recognized as a component of income tax expense. We account for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. We record net deferred tax assets to the extent we believe these assets will more likely than not be realized. In making such determination, we consider all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax planning strategies and recent financial results of operations. Accounting for uncertainty in income taxes recognized in the financial statements requires that a tax benefit from an uncertain tax position be recognized when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on technical merits. See NOTE 9 - INCOME TAXES for further information.
Discontinued Operations	Discontinued Operations In April 2014, the FASB issued ASU 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity , which changes the criteria for reporting discontinued operations and requires additional disclosures about discontinued operations. The standard requires that an entity report as a discontinued operation only a disposal that represents a strategic shift in operations that has a major effect on its operations and financial results. ASU 2014-08 is effective prospectively for new disposals that occur within annual periods beginning on or after December 15, 2014. Early adoption was permitted and we adopted ASU 2014-08 during the year ended December 31, 2014. North American Coal Operations As we executed our strategy to focus on strengthening our U.S. Iron Ore operations, management determined as of March 31, 2015 that our North American Coal operating segment met the criteria to be classified as held for sale under ASC 205, Presentation of Financial Statements and continued to meet the criteria throughout 2015. In December 2015, we completed the sale of our remaining two metallurgical coal operations, Oak Grove and Pinnacle mines, which marked our exit from the coal business. Our plan to sell the Oak Grove and Pinnacle mine assets represented a strategic shift in our business. For this reason, our previously reported North American Coal operating segment results for all periods, prior to the March 31, 2015 held for sale determination, as well as costs to exit are classified as discontinued operations. Refer to NOTE 14 - DISCONTINUED OPERATIONS for further discussion of our discontinued operations. Canadian Operations As more fully described in NOTE 14 - DISCONTINUED OPERATIONS , in January 2015, we announced that the Bloom Lake Group commenced restructuring proceedings in Montreal, Quebec under the CCAA. At that time, we had suspended Bloom Lake operations and for several months had been exploring options to sell certain of our Canadian assets, among other initiatives. 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 restructuring proceedings in Montreal, Quebec under the CCAA which resulted in the deconsolidation of the remaining Wabush Group entities that were not previously deconsolidated. The Wabush Group was no longer generating revenues and was not able to meet its obligations as they came due. 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 of each of their businesses and operations. Our Canadian exit represents a strategic shift in our business. For this reason, our previously reported Eastern Canadian Iron Ore and Ferroalloys operating segment results for all periods prior to the respective deconsolidations as well as costs to exit are classified as discontinued operations.
Foreign Currency Transactions and Translations	Foreign Currency Our financial statements are prepared with the U.S. dollar as the reporting currency. The functional currency of our Australian subsidiaries is the Australian dollar. The functional currency of all other international subsidiaries is the U.S. dollar. The financial statements of international subsidiaries are translated into U.S. dollars using the exchange rate at each balance sheet date for assets and liabilities and a weighted average exchange rate for each period for revenues, expenses, gains and losses. Where the local currency is the functional currency, translation adjustments are recorded as Accumulated other comprehensive loss . Income taxes generally are not provided for foreign currency translation adjustments. To the extent that monetary assets and liabilities, inclusive of short-term and certain long-term intercompany loans, are recorded in a currency other than the functional currency, these amounts are remeasured each reporting period, with the resulting gain or loss being recorded in the Statements of Consolidated Operations . Transaction gains and losses resulting from remeasurement of intercompany loans are included in Miscellaneous - net in our Statements of Consolidated Operations . The following represents the net gain related to impact of transaction gains and losses resulting from remeasurement for the years ended December 31, 2016 , 2015 and 2014: (In Millions) 2016 2015 2014 Remeasurement of intercompany loans $ (16.6 ) $ 11.5 $ 19.7 Remeasurement of cash and cash equivalents (1.0 ) 1.5 10.6 Other remeasurement 0.8 3.3 (1.3 ) Net gain (loss) related to impact of transaction gains and losses resulting from remeasurement (16.8 ) 16.3 29.0
Earnings Per Share	Earnings Per Share We present both basic and diluted earnings per share amounts for continuing operations and discontinued operations. Basic earnings per share amounts are calculated by dividing Net Income (Loss) from Continuing Operations Attributable to Cliffs Shareholders less any paid or declared but unpaid dividends on our depositary shares by the weighted average number of common shares outstanding during the period presented. Diluted earnings per share amounts are calculated by dividing Net Income (Loss) from Continuing Operations Attributable to Cliffs Shareholders by the weighted average number of common shares, common share equivalents under stock plans using the treasury stock method and the number of common shares that would be issued under an assumed conversion of our outstanding depositary shares, each representing a 1/40th interest in a share of our Series A Mandatory Convertible Preferred Stock, Class A, under the if-converted method. We currently do not have any outstanding depositary shares. Historically, when we have had outstanding depositary shares, they were convertible into common shares based on the volume weighted average of closing prices of our common shares over the 20 consecutive trading day period ending on the third day immediately preceding the end of that reporting period. Common share equivalents are excluded from EPS computations in the periods in which they have an anti-dilutive effect. See NOTE 19 - EARNINGS PER SHARE for further information.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Issued and Adopted In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230) Classification of Certain Cash Receipts and Cash Payment s. The new standard addresses eight specific changes to how cash receipts and cash payments are presented and classified in the statement of cash flows. The guidance is effective for interim and annual reporting periods beginning after December 15, 2017, and early adoption is permitted. We have adopted the guidance for the period ended December 31, 2016 and have applied this amended accounting guidance to the Statements of Consolidated Cash Flows for all periods presented. The adoption of ASU 2016-15 did not have an impact on prior results reported in the Statements of Consolidated Cash Flows . In August 2014, the FASB issued ASU 2014-15, Disclosure of Uncertainties About an Entity's Ability to Continue as a Going Concern . ASU 2014-15 explicitly requires management to assess an entity's ability to continue as a going concern, and to provide related footnote disclosure in certain circumstances. ASU 2014-15 is intended to define management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. Specifically, ASU 2014-15 provides a definition of the term "substantial doubt" and requires an assessment for a period of one year after the date that the financial statements are issued (or available to be issued). It also requires certain disclosures when substantial doubt is alleviated as a result of consideration of management’s plans and requires an express statement and other disclosures when substantial doubt is not alleviated. The new standard is effective for all entities in the first annual period ending after December 15, 2016 and for annual periods and interim periods thereafter. We have adopted the guidance for the year ended December 31, 2016. The adoption of ASU 2014-15 did not impact our disclosures in 2016. In October 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes. This update simplifies the presentation of deferred income taxes, by requiring that deferred tax liabilities and assets be classified as non-current in a classified statement of financial position. This update is effective for financial statements issued for annual periods beginning after December 15, 2016, and interim periods within those annual periods; however, early adoption was permitted. This guidance can also be applied either prospectively to all deferred tax liabilities and assets or retrospectively to all periods presented. We adopted the guidance during the year ended December 31, 2015 and have applied this amended accounting guidance to our deferred tax liabilities and assets for all periods presented. The adoption of ASU 2015-17 did not have an impact on our Statements of Consolidated Operations or Statements of Consolidated Cash Flows . The impact of the adoption of the guidance resulted in any current deferred tax assets or liabilities being reclassified to non-current deferred tax assets or liabilities on the Statements of Consolidated Financial Position . Issued and Not Effective 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. Lessor accounting is similar to the current model but updated to align with certain changes to the lessee model. 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 that the updated standard will have on our consolidated financial statements and related disclosures. In May 2014, the FASB issued ASU 2014-09, R e venues 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. The new revenue guidance also requires the capitalization of certain contract acquisition costs. 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 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 2015-14, Revenue from Contracts with Customers: Deferral of the Effective Date, which defers the adoption of ASU 2014-09 to annual reporting periods beginning after December 15, 2017, including interim reporting periods within that reporting period. Earlier application is permitted only as of annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. During the fourth quarter of 2016, we completed the initial evaluation of the new standard and the related assessment and review of a representative sample of existing revenue contracts with our customers. We determined, on a preliminary basis, that although the timing and pattern of revenue recognition may change, the amount of revenue recognized during the year should remain substantially the same. We anticipate utilizing the full retrospective transition method. 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 SIG33

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2016
Schedule Of Subsidiaries	The consolidated financial statements include our accounts and the accounts of our wholly owned and majority-owned subsidiaries, including the following operations at December 31, 2016 : 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
Depreciation Disclosure [Table Text Block]	Depreciation is provided over the following estimated useful lives: Asset Class Basis Life Office and information technology Straight line 3 to 15 Years Buildings Straight line 45 Years Mining equipment Straight line/Double declining balance 3 to 20 Years Processing equipment Straight line 10 to 45 Years Electric power facilities Straight line 10 to 45 years Land improvements Straight line 20 to 45 years Asset retirement obligation Straight line Life of mine
Estimated Useful Lives Of Intangible Assets Subject To Periodic Amortization On Straight Line Basis Table [Text Block]	Other intangible assets are subject to periodic amortization on a straight-line basis over their estimated useful lives as follows: Intangible Assets Basis Useful Life (years) Permits - Asia Pacific Iron Ore Units of production Life of mine Permits - USIO Straight line Life of mine
Reimbursements Revenue Disclosure [Table Text Block]	The following table is a summary of reimbursements in our U.S. Iron Ore operations for the years ended December 31, 2016 , 2015 and 2014 : (In Millions) Year Ended December 31, 2016 2015 2014 Reimbursements for: Freight $ 106.8 $ 105.3 $ 163.0 Venture partners’ cost 68.0 52.0 108.0 Total reimbursements $ 174.8 $ 157.3 $ 271.0
Foreign Currency Transaction [Table Text Block]	The following represents the net gain related to impact of transaction gains and losses resulting from remeasurement for the years ended December 31, 2016 , 2015 and 2014: (In Millions) 2016 2015 2014 Remeasurement of intercompany loans $ (16.6 ) $ 11.5 $ 19.7 Remeasurement of cash and cash equivalents (1.0 ) 1.5 10.6 Other remeasurement 0.8 3.3 (1.3 ) Net gain (loss) related to impact of transaction gains and losses resulting from remeasurement (16.8 ) 16.3 29.0

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Schedule Of Segment Reporting Information, By Segment	The following tables present a summary of our reportable segments for the years ended December 31, 2016 , 2015 and 2014 , including a reconciliation of segment sales margin to Income (Loss) from Continuing Operations Before Income Taxes and Equity Loss from Ventures and a reconciliation of Net Income (Loss) to EBITDA and Adjusted EBITDA: (In Millions) 2016 2015 2014 Revenues from product sales and services: U.S. Iron Ore $ 1,554.5 74% $ 1,525.4 76% $ 2,506.5 74% Asia Pacific Iron Ore 554.5 26% 487.9 24% 866.7 26% Total revenues from product sales and services $ 2,109.0 100% $ 2,013.3 100% $ 3,373.2 100% Sales margin: U.S. Iron Ore $ 275.7 $ 227.1 $ 710.4 Asia Pacific Iron Ore 113.6 9.4 121.7 Eliminations with discontinued operations — — 53.6 Sales margin 389.3 236.5 885.7 Other operating expense (148.5 ) (85.2 ) (755.6 ) Other income (expense) (33.8 ) 161.8 (149.8 ) Income (loss) from continuing operations before income taxes and equity loss from ventures $ 207.0 $ 313.1 $ (19.7 ) (In Millions) 2016 2015 2014 Net income (loss) $ 199.3 $ (748.4 ) $ (8,311.6 ) Less: Interest expense, net (200.5 ) (231.4 ) (185.2 ) Income tax benefit (expense) 12.2 (163.3 ) 1,302.0 Depreciation, depletion and amortization (115.4 ) (134.0 ) (504.0 ) Total EBITDA $ 503.0 $ (219.7 ) $ (8,924.4 ) Less: Gain on extinguishment/restructuring of debt $ 166.3 $ 392.9 $ 16.2 Impact of discontinued operations (19.9 ) (892.0 ) (9,332.5 ) Foreign exchange remeasurement (16.8 ) 16.3 29.0 Severance and contractor termination costs (0.1 ) (10.2 ) (23.3 ) Supplies inventory write-off — (16.3 ) — Impairment of goodwill and other long-lived assets — (3.3 ) (635.5 ) Proxy contest and change in control in SG&A — — (26.6 ) Total Adjusted EBITDA $ 373.5 $ 292.9 $ 1,048.3 EBITDA: U.S. Iron Ore $ 342.4 $ 317.6 $ 805.6 Asia Pacific Iron Ore 128.3 35.3 (352.9 ) Other (including discontinued operations) 32.3 (572.6 ) (9,377.1 ) Total EBITDA $ 503.0 $ (219.7 ) $ (8,924.4 ) Adjusted EBITDA: U.S. Iron Ore $ 359.6 $ 352.1 $ 833.5 Asia Pacific Iron Ore 132.9 32.7 252.9 Other (119.0 ) (91.9 ) (38.1 ) Total Adjusted EBITDA $ 373.5 $ 292.9 $ 1,048.3 (In Millions) 2016 2015 2014 Depreciation, depletion and amortization: U.S. Iron Ore $ 84.0 $ 98.9 $ 107.4 Asia Pacific Iron Ore 25.1 25.3 145.9 Other 6.3 6.6 7.7 Total depreciation, depletion and amortization $ 115.4 $ 130.8 $ 261.0 Capital additions 1 : U.S. Iron Ore $ 62.2 $ 58.2 $ 48.4 Asia Pacific Iron Ore 0.2 5.4 10.8 Other 6.1 8.6 6.3 Total capital additions $ 68.5 $ 72.2 $ 65.5 1 Includes capital lease additions and non-cash accruals. Refer to NOTE 17 - CASH FLOW INFORMATION.
Summary of Assets by Segment	A summary of assets by segment is as follows: (In Millions) December 31, December 31, 2015 December 31, 2014 Assets: U.S. Iron Ore $ 1,372.5 $ 1,476.4 $ 1,464.9 Asia Pacific Iron Ore 155.1 202.5 306.2 Total segment assets 1,527.6 1,678.9 1,771.1 Corporate 396.3 441.7 666.2 Assets of Discontinued Operations — 14.9 709.9 Total assets $ 1,923.9 $ 2,135.5 $ 3,147.2
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas	Included in the consolidated financial statements are the following amounts relating to geographic location: (In Millions) 2016 2015 2014 Revenue United States $ 1,236.2 $ 1,206.4 $ 1,923.2 China 452.5 370.8 662.7 Canada 267.1 282.4 430.5 Other countries 153.2 153.7 356.8 Total revenue $ 2,109.0 $ 2,013.3 $ 3,373.2 Property, Plant and Equipment, Net United States $ 961.0 $ 1,012.7 $ 998.1 Australia 23.4 46.3 72.4 Total Property, Plant and Equipment, Net $ 984.4 $ 1,059.0 $ 1,070.5
Revenue from External Customers by Products and Services	The following table represents the percentage of our total revenue contributed by each category of products and services in 2016 , 2015 and 2014 : 2016 2015 2014 Revenue category Product 91 % 91 % 92 % Freight and venture partners’ cost reimbursements 9 % 9 % 8 % Total revenue 100 % 100 % 100 %

INVENTORIES (Tables)

INVENTORIES (Tables)	12 Months Ended
	Dec. 31, 2016
Inventory Disclosure [Abstract]
Schedule Of Inventories	The following table presents the detail of our Inventories in the Statements of Consolidated Financial Position as of December 31, 2016 and 2015 : (In Millions) December 31, 2016 December 31, 2015 Segment Finished Goods Work-in Process Total Inventory Finished Goods Work-in Process Total Inventory U.S. Iron Ore $ 124.4 $ 12.6 $ 137.0 $ 252.3 $ 11.7 $ 264.0 Asia Pacific Iron Ore 23.6 17.8 41.4 20.8 44.8 65.6 Total $ 148.0 $ 30.4 $ 178.4 $ 273.1 $ 56.5 $ 329.6

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	12 Months Ended
	Dec. 31, 2016
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 December 31, 2016 and 2015 : (In Millions) December 31, 2016 2015 Land rights and mineral rights $ 500.5 $ 500.5 Office and information technology 65.1 71.0 Buildings 67.9 60.4 Mining equipment 592.2 594.0 Processing equipment 552.0 516.8 Electric power facilities 49.4 46.4 Land improvements 23.5 24.8 Asset retirement obligation 19.8 87.9 Other 28.1 28.2 Construction in-progress 42.8 40.3 1,941.3 1,970.3 Allowance for depreciation and depletion (956.9 ) (911.3 ) $ 984.4 $ 1,059.0
Book Value of Land and Mineral Rights Disclosure [Table Text Block]	The net book value of the land rights and mineral rights as of December 31, 2016 and 2015 is as follows : (In Millions) December 31, 2016 2015 Land rights $ 11.6 $ 11.6 Mineral rights: Cost $ 488.9 $ 488.9 Depletion (112.2 ) (108.4 ) Net mineral rights $ 376.7 $ 380.5

DEBT AND CREDIT FACILITIES (Tab

DEBT AND CREDIT FACILITIES (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Schedule Of Long-Term Debt	The following represents a summary of our long-term debt as of December 31, 2016 and 2015 : ($ 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 ($ in Millions) December 31, 2015 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 $ (10.5 ) $ (32.1 ) $ 497.4 $544.2 Million 7.75% 2020 Second Lien Notes 15.55% 544.2 (9.5 ) (131.5 ) 403.2 Unsecured Notes $500 Million 3.95% 2018 Senior Notes 6.30% 311.2 (0.9 ) (1.2 ) 309.1 $400 Million 5.90% 2020 Senior Notes 5.98% 290.8 (1.1 ) (0.8 ) 288.9 $500 Million 4.80% 2020 Senior Notes 4.83% 306.7 (1.1 ) (0.4 ) 305.2 $700 Million 4.875% 2021 Senior Notes 4.89% 412.5 (1.7 ) (0.2 ) 410.6 $800 Million 6.25% 2040 Senior Notes 6.34% 492.8 (4.3 ) (5.8 ) 482.7 ABL Facility N/A 550.0 N/A N/A — Fair Value Adjustment to Interest Rate Hedge 2.3 Long-term debt $ 2,699.4
Debt Instrument Redemption [Table Text Block]	The following is a summary of redemption prices for each of our secured senior notes: First Lien Notes 1.5 Lien Notes Second Lien Notes Percent of Principal Period Percent of Principal Period Percent of Principal Period Early redemption 1,2 100.00 % Prior to March 31, 2018 100.00 % Prior to September 30, 2017 100.00 % Prior to March 31, 2017 Initial redemption 1 108.25 Beginning on March 31, 2018 104.00 Beginning on September 30, 2017 103.875 Beginning on March 31, 2017 Secondary redemption 1 100.00 Beginning on June 30, 2019 100.00 Beginning on September 30, 2019 100.00 Beginning on March 31, 2019 1 Plus accrued and unpaid interest, if any, up to but excluding the redemption date. 2 Plus a "make-whole" premium. In addition, we may redeem in the aggregate up to 35% of the original aggregate principal amount (calculated after giving effect to any issuance of additional notes) with the net cash proceeds from certain equity offerings at a redemption price of 108.25%, 108.00% and 107.75% for the First, 1.5 and Second Lien Notes, respectively, so long as at least 65% of the original aggregate principal amount of the notes (calculated after giving effect to any issuance of additional notes) issued remain outstanding after each such redemption.
$218.5 1.5 Lien Notes Exchange [Table Text Block]	The following is a summary of the debt exchanged for our $218.5 million 1.5 Lien Notes: ($ In Millions) Debt Extinguished 1.5 Lien Amount Issued Carrying Value 1 Gain on Restructuring 2 $544.2 Million 7.75% 2020 Second Lien Notes $ 114.1 $ 57.0 $ 77.5 $ 6.9 $500 Million 3.95% 2018 Senior Notes 17.6 11.4 15.5 1.8 $400 Million 5.90% 2020 Senior Notes 65.1 26.0 35.4 28.3 $500 Million 4.80% 2020 Senior Notes 44.7 17.9 24.4 19.5 $700 Million 4.875% 2021 Senior Notes 76.3 30.5 41.5 33.3 $800 Million 6.25% 2040 Senior Notes 194.4 75.7 103.0 84.5 $ 512.2 $ 218.5 $ 297.3 $ 174.3 1 Includes undiscounted interest payments 2 Net of amounts expensed for unamortized original issue discount and deferred origination fees
$544.2 2nd Lien Notes Exchange [Table Text Block]	The following is a summary of the debt exchanged for our $544.2 million Second Lien Notes: ($ In Millions) Debt Extinguished Second Lien Notes Amount Issued Carrying Value 1 Gain on Restructuring 2 $400 Million 5.90% 2020 Senior Notes $ 67.0 $ 57.5 $ 42.0 $ 24.5 $500 Million 4.80% 2020 Senior Notes 137.8 112.9 82.4 54.6 $700 Million 4.875% 2021 Senior Notes 208.5 170.3 124.3 83.1 $800 Million 6.25% 2040 Senior Notes 261.3 203.5 148.5 107.3 $ 674.6 $ 544.2 $ 397.2 $ 269.5 1 Includes unamortized discounts 2 Net of amounts expensed for unamortized original issue discount and deferred origination fees
Schedule of Maturities of Long-term Debt [Table Text Block]	Debt Maturities The following represents a summary of our maturities of debt instruments, excluding borrowings on the ABL Facility, based on the principal amounts outstanding at December 31, 2016 : (In Millions) Maturities of Debt 2017 $ — 2018 — 2019 — 2020 1,651.0 2021 309.4 2022 and thereafter 298.4 Total maturities of debt $ 2,258.8

FAIR VALUE OF FINANCIAL INSTR38

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Dec. 31, 2016
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 December 31, 2016 and 2015 : (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 (In Millions) December 31, 2015 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 $ 30.0 $ — $ — $ 30.0 Derivative assets — — 7.8 7.8 Total $ 30.0 $ — $ 7.8 $ 37.8 Liabilities: Derivative liabilities $ — $ 0.6 $ 3.4 $ 4.0 Total $ — $ 0.6 $ 3.4 $ 4.0
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Recurring and Nonrecurring, Valuation Techniques	The following table illustrates information about quantitative inputs and assumptions for the derivative assets and derivative liabilities categorized in Level 3 of the fair value hierarchy: Qualitative/Quantitative Information About Level 3 Fair Value Measurements ($ in millions) Fair Value at December 31, 2016 Balance Sheet Location Valuation Technique Unobservable Input Range or Point Estimate (Weighted Average) Provisional Pricing Arrangements $ 10.3 Other current assets Market Approach Management's Estimate of Platts 62% Price $80 $ 0.5 Other current liabilities Customer Supply Agreement $ 21.3 Other current assets Market Approach Hot-Rolled Coil Estimate $505 - $620 ($555)
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation	The following tables represent a reconciliation of the changes in fair value of financial instruments measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the years ended December 31, 2016 and 2015 . (In Millions) Derivative Assets (Level 3) Derivative Liabilities (Level 3) Year Ended Year Ended 2016 2015 2016 2015 Beginning balance - January 1 $ 7.8 $ 63.2 $ (3.4 ) $ (9.5 ) Total gains (losses) Included in earnings 103.8 35.1 (14.1 ) (61.0 ) Settlements (80.0 ) (90.5 ) 17.0 67.1 Transfers into Level 3 — — — — Transfers out of Level 3 — — — — Ending balance - December 31 $ 31.6 $ 7.8 $ (0.5 ) $ (3.4 ) Total gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) on assets still held at the reporting date $ 23.7 $ 29.1 $ (0.5 ) $ (3.4 )
Schedule Of Carrying Value And Fair Value Of Financial Instruments	A summary of the carrying amount and fair value of other financial instruments at December 31, 2016 and 2015 were as follows: (In Millions) December 31, 2016 December 31, 2015 Classification Carrying Value Fair Value Carrying Value Fair Value Long-term debt: Secured Notes Senior First Lien Notes—$540 million Level 1 $ 506.3 $ 595.0 $ 497.4 $ 414.5 1.5 Senior Lien Notes—$218 million Level 2 284.2 229.5 — — Senior Second Lien Notes—$544.2 million Level 1 339.1 439.7 403.2 134.7 Unsecured Notes Senior Notes—$400 million Level 1 224.5 219.6 288.9 52.8 Senior Notes—$1.3 billion Level 1 528.4 455.8 787.9 137.4 Senior Notes—$700 million Level 1 308.2 283.1 410.6 69.4 Senior Notes—$500 million Level 1 — — 309.1 87.1 ABL Facility Level 2 — — — — Fair Value Adjustment to Interest Rate Hedge Level 2 1.9 1.9 2.3 2.3 Total long-term debt $ 2,192.6 $ 2,224.6 $ 2,699.4 $ 898.2
Fair Value Measurements, Nonrecurring	There were no financial and non-financial assets and liabilities that were measured on a non-recurring fair value basis at December 31, 2016 and 2015.

PENSIONS AND OTHER POSTRETIRE39

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Tables)	12 Months Ended
	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Retirement And Defined Compensation Plans Disclosures [Table Text Block]	The following table summarizes the annual expense (income) recognized related to the retirement plans for 2016 , 2015 and 2014 : (In Millions) 2016 2015 2014 Defined benefit pension plans $ 16.5 $ 23.9 $ 26.2 Defined contribution pension plans 2.8 3.6 4.4 Other postretirement benefits (4.0 ) 4.4 (2.5 ) Total $ 15.3 $ 31.9 $ 28.1
Obligations and Funded Status	The following tables and information provide additional disclosures for the years ending December 31, 2016 and 2015 : (In Millions) Pension Benefits Other Benefits Change in benefit obligations: 2016 2015 2016 2015 Benefit obligations — beginning of year $ 910.8 $ 998.0 $ 266.0 $ 295.8 Service cost (excluding expenses) 17.6 22.7 1.7 1.9 Interest cost 30.3 37.7 9.1 11.5 Plan amendments 5.7 — 9.8 — Actuarial (gain) loss 38.1 (67.7 ) (7.2 ) (27.0 ) Benefits paid (70.9 ) (78.7 ) (21.3 ) (20.6 ) Participant contributions — — 6.0 4.0 Federal subsidy on benefits paid — — 0.5 0.4 Curtailment gain — (1.2 ) — — Benefit obligations — end of year $ 931.6 $ 910.8 $ 264.6 $ 266.0 Change in plan assets: Fair value of plan assets — beginning of year $ 700.6 $ 749.8 $ 250.6 $ 269.3 Actual return on plan assets 54.8 (6.4 ) 16.0 (3.9 ) Participant contributions — — 0.5 0.4 Employer contributions 1.2 35.7 1.7 1.3 Asset transfers 0.1 0.2 — — Benefits paid (70.9 ) (78.7 ) (15.8 ) (16.5 ) Fair value of plan assets — end of year $ 685.8 $ 700.6 $ 253.0 $ 250.6 Funded status at December 31: Fair value of plan assets $ 685.8 $ 700.6 $ 253.0 $ 250.6 Benefit obligations (931.6 ) (910.8 ) (264.6 ) (266.0 ) Funded status (plan assets less benefit obligations) $ (245.8 ) $ (210.2 ) $ (11.6 ) $ (15.4 ) Amount recognized at December 31 $ (245.8 ) $ (210.2 ) $ (11.6 ) $ (15.4 ) Amounts recognized in Statements of Financial Position: Noncurrent assets $ — $ — $ 27.3 $ — Current liabilities (0.1 ) (0.5 ) (4.1 ) (4.1 ) Noncurrent liabilities (245.7 ) (209.7 ) (34.8 ) (11.3 ) Total amount recognized $ (245.8 ) $ (210.2 ) $ (11.6 ) $ (15.4 ) Amounts recognized in accumulated other comprehensive loss: Net actuarial loss $ 315.9 $ 290.9 $ 87.0 $ 91.5 Prior service cost (credit) 11.0 7.5 (26.9 ) (39.5 ) Net amount recognized $ 326.9 $ 298.4 $ 60.1 $ 52.0 The estimated amounts that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in 2017: Net actuarial loss $ 21.1 $ 5.0 Prior service cost (credit) 2.6 (3.0 ) Net amount recognized $ 23.7 $ 2.0
Fair Value Of Plan Assets, Benefit Obligation And Funded Status	(In Millions) 2016 Pension Plans Other Benefits Salaried Hourly Mining SERP Total Salaried Hourly Total Fair value of plan assets $ 242.9 $ 436.9 $ 6.0 $ — $ 685.8 $ — $ 253.0 $ 253.0 Benefit obligation (351.9 ) (565.6 ) (10.0 ) (4.1 ) (931.6 ) (37.6 ) (227.0 ) (264.6 ) Funded status $ (109.0 ) $ (128.7 ) $ (4.0 ) $ (4.1 ) $ (245.8 ) $ (37.6 ) $ 26.0 $ (11.6 ) 2015 Pension Plans Other Benefits Salaried Hourly Mining SERP Total Salaried Hourly Total Fair value of plan assets $ 258.3 $ 436.7 $ 5.6 $ — $ 700.6 $ — $ 250.6 $ 250.6 Benefit obligation (340.0 ) (558.6 ) (8.6 ) (3.6 ) (910.8 ) (38.2 ) (227.8 ) (266.0 ) Funded status $ (81.7 ) $ (121.9 ) $ (3.0 ) $ (3.6 ) $ (210.2 ) $ (38.2 ) $ 22.8 $ (15.4 )
Components Of Net Periodic Benefit Cost	Components of Net Periodic Benefit Cost (In Millions) Pension Benefits Other Benefits 2016 2015 2014 2016 2015 2014 Service cost $ 17.6 $ 22.7 $ 26.1 $ 1.7 $ 6.4 $ 1.8 Interest cost 30.3 37.7 40.3 9.1 13.4 11.9 Expected return on plan assets (54.7 ) (59.8 ) (58.1 ) (17.1 ) (18.3 ) (17.1 ) Amortization: Prior service costs (credits) 2.2 2.3 2.5 (3.7 ) (3.7 ) (3.6 ) Net actuarial loss 21.1 20.8 14.0 6.0 6.6 4.5 Curtailments and settlements — 0.2 1.4 — — — Net periodic benefit cost (credit) $ 16.5 $ 23.9 $ 26.2 $ (4.0 ) $ 4.4 $ (2.5 ) Curtailment effects — (1.2 ) — — — — Current year actuarial (gain)/loss 37.8 (0.7 ) 109.7 (8.1 ) 0.2 22.2 Amortization of net loss (21.1 ) (21.0 ) (15.4 ) (6.0 ) (6.6 ) (4.5 ) Current year prior service (credit) cost 5.7 — — 9.8 — (0.9 ) Amortization of prior service (cost) credit (2.2 ) (2.3 ) (2.5 ) 3.7 3.7 3.6 Total recognized in other comprehensive income (loss) $ 20.2 $ (25.2 ) $ 91.8 $ (0.6 ) $ (2.7 ) $ 20.4 Total recognized in net periodic cost and other comprehensive income (loss) $ 36.7 $ (1.3 ) $ 118.0 $ (4.6 ) $ 1.7 $ 17.9
Additional Information	Additional Information (In Millions) Pension Benefits Other Benefits 2016 2015 2014 2016 2015 2014 Effect of change in mine ownership & noncontrolling interest $ 14.2 $ 48.4 $ 51.2 $ 5.9 $ 5.5 $ 5.9 Actual return on plan assets 54.8 (6.4 ) 59.1 16.0 (3.9 ) 31.9
Weighted-Average Assumptions Used to Determine Benefit Obligations	Weighted-average assumptions used to determine benefit obligations at December 31 were: Pension Benefits Other Benefits 2016 2015 2016 2015 Discount rate Iron Hourly Pension Plan 4.02 % 4.27 % N/A % N/A % Salaried Pension Plan 3.92 4.12 N/A N/A Ore Mining Pension Plan 4.04 4.28 N/A N/A SERP 3.90 4.22 N/A N/A Hourly OPEB Plan N/A N/A 4.02 4.32 Salaried OPEB Plan N/A N/A 3.99 4.22 Salaried rate of compensation increase 3.00 3.00 3.00 3.00 Hourly rate of compensation increase 2.00 2.00 N/A N/A
Weighted-Average Assumptions Used To Determine Net Benefit Costs	Weighted-average assumptions used to determine net benefit cost for the years 2016 , 2015 and 2014 were: Pension Benefits Other Benefits 2016 2015 2014 2016 2015 2014 Obligation Discount Rate Iron Hourly Pension Plan 4.27 % 3.83 % 4.57 % N/A % N/A % N/A % Salaried Pension Plan 4.13 3.83 4.57 N/A N/A N/A Ore Mining Pension Plan 4.28 3.83 4.57 N/A N/A N/A SERP 4.01 3.83 4.57 N/A N/A N/A Hourly OPEB Plan N/A N/A N/A 4.32 3.83 4.57 Salaried OPEB Plan N/A N/A N/A 4.22 3.83 4.57 Service Cost Discount Rate Iron Hourly Pension Plan 4.66 3.83 4.57 N/A N/A N/A Salaried Pension Plan 4.14 3.83 4.57 N/A N/A N/A Ore Mining Pension Plan 4.60 3.83 4.57 N/A N/A N/A SERP 3.87 3.83 4.57 N/A N/A N/A Hourly OPEB Plan N/A N/A N/A 4.56 3.83 4.57 Salaried OPEB Plan N/A N/A N/A 4.63 3.83 4.57 Interest Cost Discount Rate Iron Hourly Pension Plan 3.46 3.83 4.57 N/A N/A N/A Salaried Pension Plan 3.21 3.83 4.57 N/A N/A N/A Ore Mining Pension Plan 3.48 3.83 4.57 N/A N/A N/A SERP 3.30 3.83 4.57 N/A N/A N/A Hourly OPEB Plan N/A N/A N/A 3.48 3.83 4.57 Salaried OPEB Plan N/A N/A N/A 3.31 3.83 4.57 Expected return on plan assets 8.25 8.25 8.25 7.00 7.00 7.00 Salaried rate of compensation increase 3.00 3.00 4.00 3.00 3.00 4.00 Hourly rate of compensation increase 2.00 2.50 3.00 N/A N/A N/A
Assumed Health Care Cost Trend Rates	Assumed health care cost trend rates at December 31 were: 2016 2015 Health care cost trend rate assumed for next year 6.50 % 6.75 % Ultimate health care cost trend rate 5.00 5.00 Year that the ultimate rate is reached 2023 2023
Effect of One Percentage Point Change in Assumed Health Care Cost Trend Rates	A change of one percentage point in assumed health care cost trend rates would have the following effects: (In Millions) Increase Decrease Effect on total of service and interest cost $ 1.3 $ (1.0 ) Effect on postretirement benefit obligation 23.4 (19.6 )
Plan Assets and Asset Allocation	The following table reflects the actual asset allocations for pension and VEBA plan assets as of December 31, 2016 and 2015 , as well as the 2017 weighted average target asset allocations as of December 31, 2016 . Equity investments include securities in large-cap, mid-cap and small-cap companies located in the U.S. and worldwide. Fixed income investments primarily include corporate bonds and government debt securities. Alternative investments include hedge funds, private equity, structured credit and real estate. Pension Assets VEBA Assets Asset Category 2017 Target Allocation Percentage of Plan Assets at December 31, 2017 Target Allocation Percentage of Plan Assets at December 31, 2016 2015 2016 2015 Equity securities 45.0 % 43.2 % 44.0 % 8.0 % 8.4 % 8.8 % Fixed income 28.0 % 26.4 % 27.7 % 80.1 % 78.3 % 78.2 % Hedge funds 5.0 % 5.9 % 5.8 % 4.2 % 4.4 % 4.5 % Private equity 7.0 % 5.3 % 4.7 % 2.6 % 1.7 % 2.2 % Structured credit 7.5 % 9.3 % 8.9 % 2.1 % 2.7 % 2.3 % Real estate 7.5 % 9.0 % 8.2 % 3.0 % 4.4 % 4.0 % Cash — % 0.9 % 0.7 % — % 0.1 % — % Total 100.0 % 100.0 % 100.0 % 100.0 % 100.0 % 100.0 %
Fair Value, Assets and Liabilities Measured on Recurring Basis	Pension The fair values of our pension plan assets at December 31, 2016 and 2015 by asset category are as follows: (In Millions) December 31, 2016 Asset Category Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Equity securities: U.S. large-cap $ 144.7 $ — $ — $ 144.7 U.S. small/mid-cap 39.9 — — 39.9 International 111.8 — — 111.8 Fixed income 157.5 23.7 — 181.2 Hedge funds — — 40.6 40.6 Private equity — — 36.1 36.1 Structured credit — — 63.8 63.8 Real estate — — 61.9 61.9 Cash 5.8 — — 5.8 Total $ 459.7 $ 23.7 $ 202.4 $ 685.8 (In Millions) December 31, 2015 Asset Category Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Equity securities: U.S. large-cap $ 150.5 $ — $ — $ 150.5 U.S. small/mid-cap 40.6 — — 40.6 International 116.8 — — 116.8 Fixed income 166.3 27.9 — 194.2 Hedge funds — — 40.7 40.7 Private equity — — 33.1 33.1 Structured credit — — 62.1 62.1 Real estate — — 57.5 57.5 Cash 5.1 — — 5.1 Total $ 479.3 $ 27.9 $ 193.4 $ 700.6
Effect of Fair Value Measurements Using Significant Unobservable Inputs on Changes in Plan Assets	The following represents the effect of fair value measurements using significant unobservable inputs (Level 3) on changes in plan assets for the years ended December 31, 2016 and 2015 : (In Millions) Year Ended December 31, 2016 Hedge Funds Private Equity Funds Structured Credit Fund Real Estate Total Beginning balance — January 1, 2016 $ 40.7 $ 33.1 $ 62.1 $ 57.5 $ 193.4 Actual return on plan assets: Relating to assets still held at the reporting date (0.1 ) (2.7 ) 10.0 5.1 12.3 Relating to assets sold during the period — 3.7 (0.3 ) (0.1 ) 3.3 Purchases — 8.0 — — 8.0 Sales — (6.0 ) (8.0 ) (0.6 ) (14.6 ) Ending balance — December 31, 2016 $ 40.6 $ 36.1 $ 63.8 $ 61.9 $ 202.4 (In Millions) Year Ended December 31, 2015 Hedge Funds Private Equity Funds Structured Credit Fund Real Estate Total Beginning balance — January 1, 2015 $ 41.5 $ 31.2 $ 65.4 $ 50.0 $ 188.1 Actual return on plan assets: Relating to assets still held at the reporting date (0.8 ) 1.5 (3.3 ) 8.1 5.5 Relating to assets sold during the period — 2.5 — — 2.5 Purchases — 5.7 — — 5.7 Sales — (7.8 ) — (0.6 ) (8.4 ) Ending balance — December 31, 2015 $ 40.7 $ 33.1 $ 62.1 $ 57.5 $ 193.4
Schedule Of Annual Contributions	(In Millions) Pension Benefits Other Benefits Company Contributions VEBA Direct Payments Total 2015 $ 35.7 $ — $ 3.5 $ 3.5 2016 1.2 — 1.1 1.1 2017 (Expected) 1 24.5 — 4.1 4.1 1 Pursuant to the bargaining agreement, benefits can be paid from VEBA trusts that are at least 70% funded (all VEBA trusts are over 70% funded at December 31, 2016). Funding obligations have been suspended as Hibbing's, UTAC's, Tilden's and Empire's share of the value of their respective trust assets have reached 90% of their obligation.
Estimated Net Periodic Benefit Cost	Estimated Cost for 2017 For 2017 , we estimate net periodic benefit cost as follows: (In Millions) Defined benefit pension plans $ 18.6 Other postretirement benefits (5.3 ) Total $ 13.3
Estimated Future Benefit Payments	Estimated Future Benefit Payments (In Millions) Pension Benefits Other Benefits Gross Company Benefits Less Medicare Subsidy Net Company Payments 2017 $ 77.3 $ 19.7 $ 0.6 $ 19.1 2018 64.8 20.0 0.7 19.3 2019 63.3 19.1 0.8 18.3 2020 63.0 18.4 0.9 17.5 2021 62.4 17.6 0.9 16.7 2022-2026 308.0 81.8 5.2 76.6
Other Potential Benefit Obligations	Other Potential Benefit Obligations While the foregoing reflects our obligation, our total exposure in the event of non-performance is potentially greater. Following is a summary comparison of the total obligation: (In Millions) December 31, 2016 Defined Benefit Pensions Other Benefits Fair value of plan assets $ 685.8 $ 253.0 Benefit obligation (931.6 ) (264.6 ) Underfunded status of plan $ (245.8 ) $ (11.6 ) Additional shutdown and early retirement benefits $ 22.1 $ 2.2
Veba Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value, Assets and Liabilities Measured on Recurring Basis	The fair values of our other benefit plan assets at December 31, 2016 and 2015 by asset category are as follows: (In Millions) December 31, 2016 Asset Category Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Equity securities: U.S. large-cap $ 10.6 $ — $ — $ 10.6 U.S. small/mid-cap 2.7 — — 2.7 International 8.1 — — 8.1 Fixed income 162.0 35.9 — 197.9 Hedge funds — — 11.2 11.2 Private equity — — 4.3 4.3 Structured credit — — 6.9 6.9 Real estate — — 11.1 11.1 Cash 0.2 — — 0.2 Total $ 183.6 $ 35.9 $ 33.5 $ 253.0 (In Millions) December 31, 2015 Asset Category Quoted Prices in Active Significant Other Significant Total Equity securities: U.S. large-cap $ 11.1 $ — $ — $ 11.1 U.S. small/mid-cap 2.8 — — 2.8 International 8.2 — — 8.2 Fixed income 158.1 37.9 — 196.0 Hedge funds — — 11.2 11.2 Private equity — — 5.5 5.5 Structured credit — — 5.8 5.8 Real estate — — 10.0 10.0 Cash — — — — Total $ 180.2 $ 37.9 $ 32.5 $ 250.6
Effect of Fair Value Measurements Using Significant Unobservable Inputs on Changes in Plan Assets	The following represents the effect of fair value measurements using significant unobservable inputs (Level 3) on changes in plan assets for the year ended December 31, 2016 and 2015 : (In Millions) Year Ended December 31, 2016 Hedge Funds Private Equity Funds Structured Credit Fund Real Estate Total Beginning balance — January 1, 2016 $ 11.2 $ 5.5 $ 5.8 $ 10.0 $ 32.5 Actual return on plan assets: Relating to assets still held at the reporting date — (0.3 ) 1.1 1.1 1.9 Relating to assets sold during the period — 0.1 — — 0.1 Purchases — — — — — Sales — (1.0 ) — — (1.0 ) Ending balance — December 31, 2016 $ 11.2 $ 4.3 $ 6.9 $ 11.1 $ 33.5 (In Millions) Year Ended December 31, 2015 Hedge Funds Private Equity Funds Structured Credit Fund Real Estate Total Beginning balance — January 1, 2015 $ 11.5 $ 6.2 $ 6.1 $ 8.7 $ 32.5 Actual return on plan assets: Relating to assets still held at the reporting date (0.3 ) 0.3 (0.3 ) 1.3 1.0 Relating to assets sold during the period — 0.4 — — 0.4 Purchases — 0.1 — — 0.1 Sales — (1.5 ) — — (1.5 ) Ending balance — December 31, 2015 $ 11.2 $ 5.5 $ 5.8 $ 10.0 $ 32.5

STOCK COMPENSATION PLANS (Table

STOCK COMPENSATION PLANS (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Incentive Plans Disclosure [Table Text Block]	Following is a summary of our performance share award agreements currently outstanding : Performance Performance Shares Granted Estimated Forfeitures Expected to Vest Grant Date Performance Period 2015 410,105 157,979 252,126 February 9, 2015 1/1/2015 - 12/31/2017 2015 464,470 82,636 381,834 January 12, 2015 1/1/2015 - 12/31/2017 2014 1 188,510 188,510 — July 29, 2014 1/1/2014 - 12/31/2016 2014 1 80,560 80,560 — May 12, 2014 1/1/2014 - 12/31/2016 2014 1 230,265 230,265 — February 10, 2014 1/1/2014 - 12/31/2016 1 The performance shares granted in 2014 will have a payout of 0% of the original grant based on the final performance evaluation versus the performance goals that were established in the grants.
Incentive Compensation and Other Benefit Plans for Employees and Directors [Table Text Block]	For the last three years, Equity Grant shares have been awarded to elected or re-elected nonemployee Directors as follows: Year of Grant Restricted Equity Grant Shares Deferred Equity Grant Shares 2014 73,635 — 2015 109,408 25,248 2016 135,038 29,583
Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block]	The following table summarizes the share-based compensation expense that we recorded for continuing operations in 2016 , 2015 and 2014 : (In Millions, except per share amounts) 2016 2015 2014 Cost of goods sold and operating expenses $ 2.1 $ 4.0 $ 5.6 Selling, general and administrative expenses 12.1 9.9 15.9 Reduction of operating income from continuing operations before income taxes and equity loss from ventures 14.2 13.9 21.5 Income tax benefit 1 — — (7.5 ) Reduction of net income attributable to Cliffs shareholders $ 14.2 $ 13.9 $ 14.0 Reduction of earnings per share attributable to Cliffs shareholders: Basic $ 0.07 $ 0.09 $ 0.09 Diluted $ 0.07 $ 0.09 $ 0.09 1 No income tax benefit for the year ended December 31, 2016 and December 31, 2015, due to the full valuation allowance.
Schedule Of Share-Based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions	No performance shares were granted in 2016 , therefore no fair value analysis was required.
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]	No stock options were granted in 2016 , therefore no fair value analysis was required.
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]	Stock option, restricted share awards and performance share activity under our long-term equity plans and Directors’ Plans are as follows: 2016 2015 2014 Shares Shares Shares Stock options: Outstanding at beginning of year 607,489 250,000 — Granted during the year — 412,710 250,000 Forfeited/canceled (7,619 ) (55,221 ) — Outstanding at end of year 599,870 607,489 250,000 Restricted awards: Outstanding and restricted at beginning of year 2,338,070 523,176 586,084 Granted during the year 3,571,337 2,482,415 531,030 Vested (271,988 ) (477,157 ) (423,822 ) Forfeited/canceled (175,636 ) (190,364 ) (170,116 ) Outstanding and restricted at end of year 5,461,783 2,338,070 523,176 Performance shares: Outstanding at beginning of year 1,496,489 1,072,376 1,040,453 Granted during the year — 874,575 1,233,685 Issued 1 (59,260 ) (242,920 ) (796,624 ) Forfeited/canceled (68,760 ) (207,542 ) (405,138 ) Outstanding at end of year 1,368,469 1,496,489 1,072,376 Vested or expected to vest as of December 31, 2016 6,716,979 Directors’ retainer and voluntary shares: Outstanding at beginning of year — — 7,329 Granted during the year — — 2,281 Vested — — (9,610 ) Outstanding at end of year — — — Reserved for future grants or awards at end of year: Employee plans 6,514,038 Directors’ plans 676,678 Total 7,190,716 1 The performance shares granted in 2014 will have a payout of 0% of the original grant based on the final performance evaluation versus the performance goals that were established in the grants. These shares are not included in this number because they expire and will be ultimately forfeited in February 2017. For the year ended December 31, 2015, the shares vesting due to the change in control were paid out in cash, at target, and valued as of the respective participants' termination dates. For the year ended December 31, 2014, the shares vesting on December 31, 2013 were valued as of February 10, 2014, and the shares vesting due to the change in a majority of our Board of Directors that triggered the acceleration of vesting and payout of outstanding equity grants under our equity plans on August 6, 2014 were paid out in cash, at target, and valued as of that date.
Employee Stock Awards Outstanding [Table Text Block]	A summary of our outstanding share-based awards as of December 31, 2016 is shown below: Shares Weighted Average Grant Date Fair Value Outstanding, beginning of year 4,442,048 $ 8.93 Granted 3,571,337 $ 1.93 Vested (331,248 ) $ 11.25 Forfeited/expired (252,015 ) $ 5.90 Outstanding, end of year 7,430,122 $ 5.55
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	A summary of our stock option grants vested or expected to vest as of December 31, 2016 is shown below: Shares Weighted-Average Exercise Price Aggregate Intrinsic Value Weighted-Average Remaining Contractual Term (Years) Expected to vest 417,914 $ 8.88 $ 239,640 7.43 Exercisable 166,667 $ 13.83 $ — 4.88

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Contingency [Line Items]
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]	Income (Loss) from Continuing Operations Before Income Taxes and Equity Loss from Ventures includes the following components: (In Millions) 2016 2015 2014 United States $ 124.9 $ 314.2 $ (447.5 ) Foreign 82.1 (1.1 ) 427.8 $ 207.0 $ 313.1 $ (19.7 )
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	The components of the provision (benefit) for income taxes on continuing operations consist of the following: (In Millions) 2016 2015 2014 Current provision (benefit): United States federal $ (11.1 ) $ 8.2 $ (125.2 ) United States state & local (0.5 ) 0.3 (0.6 ) Foreign (0.1 ) 0.9 11.7 (11.7 ) 9.4 (114.1 ) Deferred provision (benefit): United States federal (0.5 ) 165.8 20.4 United States state & local — — (24.9 ) Foreign — (5.9 ) 32.6 (0.5 ) 159.9 28.1 Total provision (benefit) on income (loss) from continuing operations $ (12.2 ) $ 169.3 $ (86.0 )
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Reconciliation of our income tax attributable to continuing operations computed at the U.S. federal statutory rate is as follows: (In Millions) 2016 2015 2014 Tax at U.S. statutory rate of 35% $ 72.5 35.0 % $ 109.6 35.0 % $ (6.9 ) 35.0 % Increase (decrease) due to: Impact of tax law change 149.1 72.0 — — 13.0 (66.0 ) Valuation allowance build/(reversal) on tax benefits recorded in prior years (142.6 ) (68.9 ) 165.8 52.9 15.2 (77.2 ) Tax uncertainties (11.3 ) (5.5 ) 84.1 26.9 — — Valuation allowance build/(reversal) in current year 93.9 45.4 (104.6 ) (33.4 ) 318.3 (1,615.7 ) Prior year adjustments in current year (11.8 ) (5.7 ) 5.9 1.9 (6.3 ) 32.1 Worthless stock deduction (73.4 ) (35.5 ) — — — — Impact of foreign operations (42.7 ) (20.6 ) (53.9 ) (17.2 ) 51.4 (260.9 ) Percentage depletion in excess of cost depletion (36.1 ) (17.4 ) (34.9 ) (11.1 ) (87.9 ) 446.2 Non-taxable income related to noncontrolling interests (8.8 ) (4.2 ) (3.0 ) (1.0 ) (9.4 ) 47.7 State taxes, net 0.4 0.2 0.2 0.1 (25.4 ) 128.9 Settlement of financial guaranty — — — — (347.1 ) 1,761.9 Income not subject to tax — — — — (27.7 ) 140.6 Goodwill impairment — — — — 22.7 (115.2 ) Other items — net (1.4 ) (0.7 ) 0.1 — 4.1 (20.9 ) Provision for income tax (benefit) expense and effective income tax rate including discrete items $ (12.2 ) (5.9 )% $ 169.3 54.1 % $ (86.0 ) 436.5 %
Income Taxes Other Than Continuing Operations Disclosure Text Block [Table Text Block]	The components of income taxes for other than continuing operations consisted of the following: (In Millions) 2016 2015 2014 Other comprehensive (income) loss: Pension/OPEB liability $ — $ — $ 37.1 Mark-to-market adjustments — 0.3 3.6 Other 0.5 5.9 0.2 Total $ 0.5 $ 6.2 $ 40.9 Paid in capital — stock based compensation $ — $ — $ (4.8 ) Discontinued Operations $ — $ (6.0 ) $ (1,216.0 )
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	Significant components of our deferred tax assets and liabilities as of December 31, 2016 and 2015 are as follows: (In Millions) 2016 2015 Deferred tax assets: Pensions $ 114.6 $ 106.6 Postretirement benefits other than pensions 35.2 36.5 Alternative minimum tax credit carryforwards 251.2 218.7 Deferred income 44.5 57.2 Financial instruments 71.3 — Investments in ventures — 4.9 Asset retirement obligations 22.3 5.3 Operating loss carryforwards 2,699.7 2,791.6 Property, plant and equipment and mineral rights 181.2 189.8 State and local 59.2 59.9 Lease liabilities 12.9 18.3 Other liabilities 108.3 148.9 Total deferred tax assets before valuation allowance 3,600.4 3,637.7 Deferred tax asset valuation allowance (3,334.8 ) (3,372.5 ) Net deferred tax assets 265.6 265.2 Deferred tax liabilities: Property, plant and equipment and mineral rights (34.0 ) (35.5 ) Investment in ventures (203.1 ) (206.6 ) Intangible assets (1.0 ) (1.5 ) Product inventories (3.4 ) (2.5 ) Other assets (24.1 ) (19.1 ) Total deferred tax liabilities (265.6 ) (265.2 ) Net deferred tax assets (liabilities) $ — $ —
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows: (In Millions) 2016 2015 2014 Unrecognized tax benefits balance as of January 1 $ 156.2 $ 72.6 $ 71.8 Increases/(decreases) for tax positions in prior years (61.0 ) 6.7 — Increases for tax positions in current year 0.2 78.5 5.9 Decrease due to foreign exchange — — (0.2 ) Settlements (64.7 ) (1.1 ) — Lapses in statutes of limitations — (0.5 ) (3.7 ) Other — — (1.2 ) Unrecognized tax benefits balance as of December 31 $ 30.7 $ 156.2 $ 72.6

LEASE OBLIGATIONS (Tables)

LEASE OBLIGATIONS (Tables)	12 Months Ended
	Dec. 31, 2016
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 December 31, 2016 are as follows: (In Millions) Capital Leases Operating Leases 2017 $ 22.0 $ 6.9 2018 17.9 5.6 2019 9.9 3.0 2020 9.0 2.9 2021 8.3 3.0 2022 and thereafter 0.7 — Total minimum lease payments $ 67.8 $ 21.4 Amounts representing interest 12.0 Present value of net minimum lease payments 1 $ 55.8 1 The total is comprised of $17.4 million and $38.4 million classified as Other current liabilities and Other liabilities, respectively, in the Statements of Consolidated Financial Position at December 31, 2016.

ENVIRONMENTAL AND MINE CLOSUR43

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Tables)	12 Months Ended
	Dec. 31, 2016
Environmental Remediation Obligations [Abstract]
Schedule of Environmental Loss Contingencies and Asset Retirement Obligations [Table Text Block]	The following is a summary of the obligations as of December 31, 2016 and 2015 : (In Millions) December 31, 2016 2015 Environmental $ 2.8 $ 3.6 Mine closure U.S. Iron Ore 1 187.8 214.0 Asia Pacific Iron Ore 16.2 16.4 Total mine closure 204.0 230.4 Total environmental and mine closure obligations 206.8 234.0 Less current portion 12.9 2.8 Long-term environmental and mine closure obligations $ 193.9 $ 231.2 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 Obligations	The following represents a roll forward of our asset retirement obligation liability for the years ended December 31, 2016 and 2015 : (In Millions) December 31, 2016 2015 Asset retirement obligation at beginning of period $ 230.4 $ 165.3 Accretion expense 14.0 7.7 Remediation payments (2.2 ) — Exchange rate changes (0.2 ) (1.1 ) Revision in estimated cash flows (38.0 ) 58.5 Asset retirement obligation at end of period $ 204.0 $ 230.4

GOODWILL AND OTHER INTANGIBLE44

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Tables)	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule Of Finite-Lived Intangible Assets By Major Class	Following is a summary of intangible assets and liabilities as of December 31, 2016 and December 31, 2015 : (In Millions) December 31, 2016 December 31, 2015 Classification Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Definite-lived intangible assets: Permits Other non-current assets $ 78.4 $ (24.6 ) $ 53.8 $ 78.4 $ (20.2 ) $ 58.2 Total intangible assets $ 78.4 $ (24.6 ) $ 53.8 $ 78.4 $ (20.2 ) $ 58.2 Below-market sales contracts Other current liabilities $ — $ — $ — $ (23.1 ) $ — $ (23.1 ) Below-market sales contracts Other liabilities — — — (205.8 ) 205.8 — Total below-market sales contracts $ — $ — $ — $ (228.9 ) $ 205.8 $ (23.1 )
Estimated Amortization Expense Relating To Intangible Assets	The estimated amortization expense relating to intangible assets for each of the five succeeding years is as follows: (In Millions) Amount Year Ending December 31 2017 1.9 2018 1.9 2019 2.0 2020 1.6 2021 1.0 Total $ 8.4

DERIVATIVE INSTRUMENTS AND HE45

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Tables)	12 Months Ended
	Dec. 31, 2016
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 Consolidated Financial Position as of December 31, 2016 and December 31, 2015 : (In Millions) Derivative Assets Derivative Liabilities December 31, 2016 December 31, 2015 December 31, 2016 December 31, 2015 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 21.3 Other current assets 5.8 — — Provisional Pricing Arrangements Other current assets 10.3 Other current assets 2.0 Other current liabilities 0.5 Other current liabilities 3.4 Commodity Contracts Other current assets 1.5 — — Other current liabilities 0.6 Total derivatives not designated as hedging instruments under ASC 815: $ 33.1 $ 7.8 $ 0.5 $ 4.0
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 Consolidated Operations for the years ended December 31, 2016 , 2015 and 2014 : (In Millions) Derivatives Not Designated as Hedging Instruments Location of Gain (Loss) Recognized in Income on Derivative Amount of Gain/(Loss) Recognized in Income on Derivative Year Ended 2016 2015 2014 Customer Supply Agreements Product revenues $ 41.7 $ 27.1 $ 187.8 Provisional Pricing Arrangements Product revenues 49.0 (1.4 ) (9.5 ) Foreign Exchange Contracts Other non-operating income (expense) — (3.6 ) — Foreign Exchange Contracts Product revenues — (12.6 ) — Commodity Contracts Cost of goods sold and operating expenses 1.9 (4.0 ) — Total $ 92.6 $ 5.5 $ 178.3

DISCONTINUED OPERATIONS (Tables

DISCONTINUED OPERATIONS (Tables)	12 Months Ended
	Dec. 31, 2016
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block]	(In Millions) Canadian Operations North American Coal Eastern Canadian Iron Ore Other Total Canadian Operations Total of Discontinued Operations Statements of Consolidated Operations Loss from Discontinued Operations, net of tax YTD $ (2.4 ) $ (17.5 ) $ — $ (17.5 ) $ (19.9 ) Loss from Discontinued Operations, net of tax YTD $ (152.4 ) $ (638.7 ) $ (101.0 ) $ (739.7 ) $ (892.1 ) Loss from Discontinued Operations, net of tax YTD $ (1,134.5 ) $ (6,952.9 ) $ (280.6 ) $ (7,233.5 ) $ (8,368.0 ) Statements of Consolidated Financial Position Other current liabilities As of $ 6.0 $ — $ — $ — $ 6.0 Other current assets As of $ 14.9 $ — $ — $ — $ 14.9 Other current liabilities As of $ 6.9 $ — $ — $ — $ 6.9 Non-Cash Operating and Investing Activities Depreciation, depletion and amortization YTD $ 3.2 $ — $ — $ — $ 3.2 Purchase of property, plant and equipment YTD $ 15.9 $ — $ — $ — $ 15.9 Impairment of goodwill and other long-lived assets YTD $ 73.4 $ — $ — $ — $ 73.4 Depreciation, depletion and amortization YTD $ 106.9 $ 135.6 $ 0.5 $ 136.1 $ 243.0 Purchase of property, plant and equipment YTD $ 29.9 $ 190.3 $ — $ 190.3 $ 220.2 Impairment of goodwill and other long-lived assets YTD $ 857.5 $ 7,269.2 $ 267.6 $ 7,536.8 $ 8,394.3
North American Coal [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Schedule of Disposal Groups, including Discontinued Operations, Income Statement [Table Text Block]	Loss on Discontinued Operations The sale of our Oak Grove and Pinnacle mines on December 22, 2015 completed a strategic shift in our business. Our previously reported North American Coal operating segment results for all periods, prior to the March 31, 2015 held for sale determination, are classified as discontinued operations. Historical results also include our CLCC assets, which were sold during the fourth quarter of 2014. (In Millions) Year Ended Loss from Discontinued Operations 2016 2015 2014 Revenues from product sales and services $ — $ 392.9 $ 687.1 Cost of goods sold and operating expenses — (449.2 ) (822.9 ) Sales margin — (56.3 ) (135.8 ) Other operating expense (4.5 ) (30.4 ) (20.8 ) Gain (loss) on sale of coal mines 2.1 9.3 (419.6 ) Other expense — (1.8 ) (3.0 ) Loss from discontinued operations before income taxes (2.4 ) (79.2 ) (579.2 ) Impairment of long-lived assets — (73.4 ) (857.5 ) Income tax benefit — 0.2 302.2 Loss from discontinued operations, net of tax $ (2.4 ) $ (152.4 ) $ (1,134.5 )
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Table Text Block]	Items Measured at Fair Value on a Non-Recurring Basis The following table presents information about the impairment charge on non-financial assets that was measured on a fair value basis at March 31, 2015 for the North American Coal operations. There were no financial and non-financial assets and liabilities that were measured on a non-recurring fair value basis at December 31, 2016 for the North American Coal operations. The table also indicates the fair value hierarchy of the valuation techniques used to determine such fair value. (In Millions) March 31, 2015 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 Losses Assets: Other long-lived assets - Property, plant and equipment and Mineral rights: North American Coal operating unit $ — $ — $ 20.4 $ 20.4 $ 73.4 $ — $ — $ 20.4 $ 20.4 $ 73.4
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Table Text Block]	Recorded Assets and Liabilities (In Millions) Assets and Liabilities of Discontinued Operations 1 December 31, December 31, Other current assets $ — $ 14.9 Total assets of discontinued operations $ — $ 14.9 Accrued liabilities $ 1.1 $ — Other current liabilities 4.9 6.9 Total liabilities of discontinued operations $ 6.0 $ 6.9 1 At December 31, 2016 and 2015, we also recorded $2.1 million and $7.8 million, respectively, of contingent liabilities associated with our exit from the coal business recorded on our parent company.
Canadian Entities [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Schedule of Disposal Groups, including Discontinued Operations, Income Statement [Table Text Block]	Loss on Discontinued Operations Our Canadian exit represents a strategic shift in our business. For this reason, our previously reported Eastern Canadian Iron Ore and Ferroalloys operating segment results for all periods prior to the respective deconsolidations, as well as costs to exit, are classified as discontinued operations. (In Millions) Year Ended December 31, Loss from Discontinued Operations 2016 2015 2014 Revenues from product sales and services $ — $ 11.3 $ 563.5 Cost of goods sold and operating expenses — (11.1 ) (808.4 ) Eliminations with continuing operations — — (53.6 ) Sales margin — 0.2 (298.5 ) Other operating expense — (33.8 ) (306.3 ) Other expense — (1.0 ) (5.6 ) Loss from discontinued operations before income taxes — (34.6 ) (610.4 ) Loss from deconsolidation (17.5 ) (710.9 ) — Impairment of long-lived assets — — (7,536.8 ) Income tax benefit — 5.8 913.7 Loss from discontinued operations, net of tax $ (17.5 ) $ (739.7 ) $ (7,233.5 )
PreTax Exit Costs [Table Text Block]	Canadian Entities loss from deconsolidation totaled $17.5 million and $710.9 million for the year ended December 31, 2016 and 2015, respectively and included the following: (In Millions) Year Ended December 31, Year Ended December 31, 2016 2015 Investment impairment on deconsolidation 1 $ (17.5 ) $ (507.8 ) Guarantees and contingent liabilities — (203.1 ) Total loss from deconsolidation $ (17.5 ) $ (710.9 ) 1 Includes the adjustment to fair value of our remaining interest in the Canadian Entities.
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Table Text Block]	Items Measured at Fair Value on a Non-Recurring Basis The following table presents information about the financial assets and liabilities that were measured on a fair value basis at December 31, 2016 and 2015 for the Canadian Entities. The table also indicates the fair value hierarchy of the valuation techniques used to determine such fair value. (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 Losses Assets: Loans to and accounts receivables from the Canadian Entities $ — $ — $ 48.6 $ 48.6 $ 17.5 Liabilities: Guarantees and contingent liabilities $ — $ — $ 37.2 $ 37.2 $ — (In Millions) December 31, 2015 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 Losses Assets: Loans to and accounts receivables from the Canadian Entities $ — $ — $ 72.9 $ 72.9 $ 507.8 Liabilities: Guarantees and contingent liabilities $ — $ — $ 132.4 $ 132.4 $ 203.1

ACCUMULATED OTHER COMPREHENSI47

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) ACCUMULATED OTHERCOMPREHENSIVE INCOME (LOSS) (Tables)	12 Months Ended
	Dec. 31, 2016
Schedule of Accumulate Other Comprehensive Income (Loss) and Related Tax Effects [Table Text Block]	The components of Accumulated other comprehensive loss within Cliffs shareholders’ deficit and related tax effects allocated to each are shown below as of December 31, 2016 , 2015 and 2014: (In Millions) Pre-tax Amount Tax Benefit (Provision) After-tax Amount As of December 31, 2014: Postretirement benefit liability $ (425.3 ) $ 134.2 $ (291.1 ) Foreign currency translation adjustments 64.4 — 64.4 Unrealized net loss on derivative financial instruments (25.9 ) 7.8 (18.1 ) Unrealized gain (loss) on securities (1.3 ) 0.3 (1.0 ) $ (388.1 ) $ 142.3 $ (245.8 ) As of December 31, 2015: Postretirement benefit liability $ (364.8 ) $ 123.4 $ (241.4 ) Foreign currency translation adjustments 220.7 — 220.7 Unrealized net gain on derivative financial instruments 2.2 0.4 2.6 Unrealized gain on securities 0.1 — 0.1 $ (141.8 ) $ 123.8 $ (18.0 ) As of December 31, 2016: Postretirement benefit liability $ (384.0 ) $ 123.4 $ (260.6 ) Foreign currency translation adjustments 239.3 — 239.3 $ (144.7 ) $ 123.4 $ (21.3 )
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following tables reflect the changes in Accumulated other comprehensive loss related to Cliffs shareholders’ equity for December 31, 2016 , 2015 and 2014: (In Millions) Postretirement Benefit Liability, net of tax Unrealized Net Gain (Loss) on Securities, net of tax Unrealized Net Gain (Loss) on Foreign Currency Translation Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax Accumulated Other Comprehensive Income (Loss) Balance December 31, 2015 $ (241.4 ) $ 0.1 $ 220.7 $ 2.6 $ (18.0 ) Other comprehensive income (loss) before reclassifications (44.8 ) (0.1 ) 18.4 (3.3 ) (29.8 ) Net loss reclassified from accumulated other comprehensive income (loss) 25.6 — 0.2 0.7 26.5 Balance December 31, 2016 $ (260.6 ) $ — $ 239.3 $ — $ (21.3 ) (In Millions) Postretirement Benefit Liability, net of tax Unrealized Net Gain (Loss) on Securities, net of tax Unrealized Net Gain (Loss) on Foreign Currency Translation Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax Accumulated Other Comprehensive Income (Loss) Balance December 31, 2014 $ (291.1 ) $ (1.0 ) $ 64.4 $ (18.1 ) $ (245.8 ) Other comprehensive income (loss) before reclassifications 9.1 5.4 (26.4 ) 1.9 (10.0 ) Net loss (gain) reclassified from accumulated other comprehensive income (loss) 40.6 (4.3 ) 182.7 18.8 237.8 Balance December 31, 2015 $ (241.4 ) $ 0.1 $ 220.7 $ 2.6 $ (18.0 ) (In Millions) Postretirement Benefit Liability, net of tax Unrealized Net Gain (Loss) on Securities, net of tax Unrealized Net Gain (Loss) on Foreign Currency Translation Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax Accumulated Other Comprehensive Income (Loss) Balance December 31, 2013 $ (204.9 ) $ 6.2 $ 106.7 $ (20.9 ) $ (112.9 ) Other comprehensive income (loss) before reclassifications (97.0 ) 1.3 (42.3 ) (28.2 ) (166.2 ) Net loss (gain) reclassified from accumulated other comprehensive income (loss) 10.8 (8.5 ) — 31.0 33.3 Balance December 31, 2014 $ (291.1 ) $ (1.0 ) $ 64.4 $ (18.1 ) $ (245.8 )
Details of Accumulated Other Comprehensive Income (Loss) Components [Table Text Block]	The following table reflects the details about Accumulated other comprehensive loss components related to Cliffs shareholders’ equity for the years ended December 31, 2016 , 2015 and 2014: (In Millions) Details about Accumulated Other Comprehensive Income (Loss) Components Amount of (Gain)/Loss Reclassified into Income Affected Line Item in the Statement of Consolidated Operations Year Ended Year Ended Year Ended December 31, 2014 Amortization of Pension and Postretirement Benefit Liability: Prior service costs 1 $ (1.5 ) $ (1.4 ) $ (1.1 ) Net actuarial loss 1 27.1 27.4 18.5 Curtailments/Settlements 1 — 0.2 1.4 Effect of deconsolidation 2 — 15.1 — Loss from Discontinued Operations, net of tax 25.6 41.3 18.8 Total before taxes — (0.7 ) (5.8 ) Income tax benefit (expense) $ 25.6 $ 40.6 $ 13.0 Net of taxes Unrealized loss on marketable securities: Sale of marketable securities $ — $ (2.6 ) $ (11.4 ) Other non-operating income (expense) Impairment — (2.0 ) (0.5 ) Other non-operating income (expense) — (4.6 ) (11.9 ) Total before taxes — 0.3 3.4 Income tax benefit (expense) $ — $ (4.3 ) $ (8.5 ) Net of taxes Unrealized gain on foreign currency translation: Dissolution of entity $ 0.2 $ — $ — Other non-operating income (expense) Effect of deconsolidation 3 — 182.7 — Loss from Discontinued Operations, net of tax $ 0.2 $ 182.7 $ — Net of taxes Unrealized gain on derivative financial instruments: Treasury lock $ 1.2 $ — $ — Gain on extinguishment/restructuring of debt Australian dollar foreign exchange contracts — 26.9 18.9 Product revenues Canadian dollar foreign exchange contracts — — 26.7 Cost of goods sold and operating expenses 1.2 26.9 45.6 Total before taxes (0.5 ) (8.1 ) (14.6 ) Income tax benefit (expense) $ 0.7 $ 18.8 $ 31.0 Net of taxes Total Reclassifications for the Period $ 26.5 $ 237.8 $ 35.5 1 These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. See NOTE 7 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information. 2 Represents Canadian postretirement benefit liabilities that were deconsolidated. See NOTE 14 - DISCONTINUED OPERATIONS for further information. 3 Represents Canadian accumulated currency translation adjustments that were deconsolidated. See NOTE 14 - DISCONTINUED OPERATIONS for further information.

CASH FLOW INFORMATION (Tables)

CASH FLOW INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2016
Supplemental Cash Flow Disclosures	A reconciliation of capital additions to cash paid for capital expenditures for the years ended December 31, 2016 , 2015 and 2014 is as follows: (In Millions) Year Ended December 31, 2016 2015 2014 Capital additions 1 $ 68.5 $ 96.7 $ 235.5 Cash paid for capital expenditures 69.1 80.8 284.1 Difference $ (0.6 ) $ 15.9 $ (48.6 ) Non-cash accruals $ (0.6 ) $ 14.4 $ (58.5 ) Capital leases — 1.5 9.9 Total $ (0.6 ) $ 15.9 $ (48.6 ) 1 Includes capital additions of $68.5 million related to continuing operations for the year ended December 31, 2016. Includes capital additions of $72.2 million and $24.5 million related to continuing operations and discontinued operations, respectively, for the year ended December 31, 2015. Includes capital additions of $65.5 million and $170.0 million related to continuing operations and discontinued operations, respectively, for the year ended December 31, 2014. Cash payments for interest and income taxes in 2016 , 2015 and 2014 are as follows: (In Millions) 2016 2015 2014 Taxes paid on income $ 6.0 $ 5.0 $ 47.3 Income tax refunds 1 5.4 211.4 54.7 Interest paid on debt obligations 2 184.0 185.6 176.5 1 Includes income tax refunds that relate to the deconsolidated Canadian Entities for the year ended December 31, 2014 of $47.8 million. 2 Includes interest paid on the corporate guarantees of the equipment loans that relate to discontinued operations for the years ended December 31, 2016, 2015 and 2014 of $1.4 million, $4.8 million and $6.1 million, respectively.

RELATED PARTIES (Tables)

RELATED PARTIES (Tables)	12 Months Ended
	Dec. 31, 2016
Related Party Transactions [Abstract]
Summary Of Other Ownership Interests	The following is a summary of the mine ownership of these iron ore mines at December 31, 2016 : Mine Cliffs Natural Resources ArcelorMittal U.S. Steel 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) Year Ended December 31, 2016 2015 2014 Product revenues from related parties $ 830.1 $ 671.1 $ 1,011.4 Total product revenues 1,913.5 1,832.4 3,095.2 Related party product revenue as a percent of total product revenue 43.4 % 36.6 % 32.7 %

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Earnings Per Share Computation	The following table summarizes the computation of basic and diluted earnings per share attributable to Cliffs shareholders: (In Millions, Except Per Share Amounts) Year Ended December 31, 2016 2015 2014 Income from Continuing Operations $ 219.2 $ 143.7 $ 56.4 Income from Continuing Operations Attributable to (25.2 ) (8.6 ) (25.9 ) Net Income from Continuing Operations $ 194.0 $ 135.1 $ 30.5 Loss from Discontinued Operations, net of tax (19.9 ) (884.4 ) (7,254.7 ) NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS $ 174.1 $ (749.3 ) $ (7,224.2 ) PREFERRED STOCK DIVIDENDS — (38.4 ) (51.2 ) NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS $ 174.1 $ (787.7 ) $ (7,275.4 ) Weighted Average Number of Shares: Basic 197.7 153.2 153.1 Employee Stock Plans 2.4 0.4 — Diluted 200.1 153.6 153.1 Earnings (loss) per Common Share Attributable to Continuing operations $ 0.98 $ 0.63 $ (0.14 ) Discontinued operations (0.10 ) (5.77 ) (47.38 ) $ 0.88 $ (5.14 ) $ (47.52 ) Earnings (loss) per Common Share Attributable to Continuing operations $ 0.97 $ 0.63 $ (0.14 ) Discontinued operations (0.10 ) (5.76 ) (47.38 ) $ 0.87 $ (5.13 ) $ (47.52 ) The diluted earnings per share calculation excludes 25.3 million and 25.2 million depositary shares that were anti-dilutive for the year ended December 31, 2015 and 2014, respectively. Additionally, the diluted earnings per share calculation also excludes 0.7 million of equity plan awards that were anti-dilutive for the year ended December 31, 2014.

QUARTERLY RESULTS OF OPERATIO51

QUARTERLY RESULTS OF OPERATIONS (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information [Table Text Block]	The sum of quarterly EPS may not equal EPS for the year due to discrete quarterly calculations. (In Millions, Except Per Share Amounts) 2016 Quarters First Second Third Fourth Year Revenues from product sales and services $ 305.5 $ 496.2 $ 553.3 $ 754.0 $ 2,109.0 Sales margin 30.9 91.5 85.4 181.5 389.3 Income (Loss) from Continuing Operations $ 114.3 $ 29.9 $ (25.1 ) $ 100.1 $ 219.2 Loss (Income) from Continuing Operations (8.8 ) (16.7 ) 2.0 (1.7 ) (25.2 ) Net Income (Loss) from Continuing Operations 105.5 13.2 (23.1 ) 98.4 194.0 Income (Loss) from Discontinued Operations, net of tax 2.5 (0.4 ) (2.7 ) (19.3 ) (19.9 ) NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS $ 108.0 $ 12.8 $ (25.8 ) $ 79.1 $ 174.1 Earnings (loss) per common share attributable to Cliffs common shareholders — Basic: Continuing Operations $ 0.61 $ 0.07 $ (0.11 ) $ 0.43 $ 0.98 Discontinued Operations 0.01 — (0.01 ) (0.08 ) (0.10 ) $ 0.62 $ 0.07 $ (0.12 ) $ 0.35 $ 0.88 Earnings (loss) per common share attributable to Cliffs common shareholders — Diluted: Continuing Operations $ 0.61 $ 0.07 $ (0.11 ) $ 0.42 $ 0.97 Discontinued Operations 0.01 — (0.01 ) (0.08 ) (0.10 ) $ 0.62 $ 0.07 $ (0.12 ) $ 0.34 $ 0.87 The diluted earnings per share calculation for the third quarter of 2016 exclude equity plan awards of 3.0 million that were anti-dilutive. There was no anti-dilution in the first, second or fourth quarter of 2016. (In Millions, Except Per Share Amounts) 2015 Quarters First Second Third Fourth Year Revenues from product sales and services $ 446.0 $ 498.1 $ 593.2 $ 476.0 $ 2,013.3 Sales margin 80.8 57.3 55.1 43.3 236.5 Income (Loss) from Continuing Operations $ 166.8 $ (38.2 ) $ 49.9 $ (34.8 ) $ 143.7 Loss (Income) from Continuing Operations 1.9 (5.0 ) 4.6 (2.4 ) (8.6 ) Net Income (Loss) from Continuing Operations $ 168.7 $ (43.2 ) $ 54.5 $ (37.2 ) $ 135.1 Income (Loss) from Discontinued Operations, net of tax (928.5 ) 103.4 (43.9 ) (23.1 ) (884.4 ) NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS $ (759.8 ) $ 60.2 $ 10.6 $ (60.3 ) $ (749.3 ) PREFERRED STOCK DIVIDENDS (12.8 ) — (25.6 ) — (38.4 ) NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS (772.6 ) 60.2 (15.0 ) (60.3 ) (787.7 ) Earnings (loss) per common share attributable to Cliffs common shareholders — Basic: Continuing Operations $ 1.02 $ (0.28 ) $ 0.19 $ (0.24 ) $ 0.63 Discontinued Operations (6.06 ) 0.67 (0.29 ) (0.15 ) (5.77 ) $ (5.04 ) $ 0.39 $ (0.10 ) $ (0.39 ) $ (5.14 ) Earnings (loss) per common share attributable to Continuing Operations $ 0.94 $ (0.28 ) $ 0.19 $ (0.24 ) $ 0.63 Discontinued Operations (5.20 ) 0.67 (0.29 ) (0.15 ) (5.76 ) $ (4.26 ) $ 0.39 $ (0.10 ) $ (0.39 ) $ (5.13 ) The diluted earnings per share calculation for the second, third and fourth quarter of 2015 exclude depositary shares that were anti-dilutive ranging between 25.2 million and 25.6 million and equity plan awards ranging between 0.1 million and 0.3 million that were anti-dilutive. There was no anti-dilution in the first quarter of 2015.

BASIS OF PRESENTATION AND SIG52

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) T in Millions	12 Months Ended
	Dec. 31, 2016USD ($)T	Dec. 31, 2015USD ($)T	Dec. 31, 2014USD ($)
Related Party Transaction [Line Items]
Net Income (Loss) Attributable to Noncontrolling Interest	$ 25,200,000	$ 900,000	$ (1,087,400,000)
LOSS ATTRIBUTABLE TO NONCONTROLLING INTEREST	0	7,700,000	1,113,300,000
Allowance for Doubtful Accounts Receivable	0	7,100,000
Provision for Doubtful Accounts	0	7,100,000	0
Inventory Valuation Reserves	14,000,000	31,800,000
Disposal of supplies inventory	17,400,000
Tangible Asset Impairment Charges	0	0	537,800,000
Impairment of Intangible Assets (Excluding Goodwill)			13,800,000
Freight and venture partners' cost reimbursements	$ 195,500,000	$ 180,900,000	278,000,000
Trading Day Window Determining Number of Common Shares Issuable on Conversion	20
U.S. Iron Ore [Member]
Related Party Transaction [Line Items]
Quantity Of Finished Goods | T	1.5	1.3
Freight and venture partners' cost reimbursements	$ 174,800,000	$ 157,300,000	271,000,000
Asia Pacific [Member]
Related Party Transaction [Line Items]
Freight and venture partners' cost reimbursements	$ 20,700,000	23,600,000	6,900,000
Empire [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	21.00%
Net Income (Loss) Attributable to Noncontrolling Interest		(8,600,000)
Bloom Lake [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	17.00%
Investments in Ventures [Member] | Hibbing [Member]
Related Party Transaction [Line Items]
Ownership interest, equity method investment	23.00%
Other Noncurrent Liabilities [Member] | Hibbing [Member]
Related Party Transaction [Line Items]
Equity Method Investments	$ (8,700,000)	(2,400,000)
Take or Pay Contracts [Member]
Related Party Transaction [Line Items]
Deferred Revenue	3,400,000		$ 29,300,000
Customer Supplemental Payments [Member] | U.S. Iron Ore [Member]
Related Party Transaction [Line Items]
Deferred Revenue	77,100,000	89,900,000
Deferred Revenue, Current	16,400,000	12,800,000
Deferred Revenue, Noncurrent	$ 64,200,000	$ 77,100,000

BASIS OF PRESENTATION AND SIG53

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)	12 Months Ended
	Dec. 31, 2016
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 SIG54

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Depreciation Methods and Useful Lives) (Details)	12 Months Ended
	Dec. 31, 2016
Building [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	45 years
Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	20 years
Other Machinery and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Other Machinery and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	45 years
Electric Power Facilities [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Electric Power Facilities [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	45 years
Land Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	20 years
Land Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	45 years
Computer Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Computer Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	15 years

BASIS OF PRESENTATION AND SIG55

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Revenue Reimbursement) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Freight and venture partners' cost reimbursements	$ 195.5	$ 180.9	$ 278
U.S. Iron Ore [Member]
Freight and venture partners' cost reimbursements	174.8	157.3	271
U.S. Iron Ore [Member] | Freight Revenue [Member]
Freight and venture partners' cost reimbursements	106.8	105.3	163
U.S. Iron Ore [Member] | Co-venturer [Member]
Freight and venture partners' cost reimbursements	$ 68	$ 52	$ 108

BASIS OF PRESENTATION AND SIG56

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Transaction Gains (Losses) Resulting from Remeasurement) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Foreign Currency Transaction Gain (Loss), before Tax	$ 0.8	$ 3.3	$ (1.3)
Transaction Gains and Losses Resulting from Remeasurement [Member]
Foreign Currency Transaction Gain (Loss), before Tax	(16.8)	16.3	29
Cash and Cash Equivalents [Member]
Foreign Currency Transaction Gain (Loss), before Tax	(1)	1.5	10.6
Intercompany loan [Member]
Foreign Currency Transaction Gain (Loss), before Tax	$ (16.6)	$ 11.5	$ 19.7

SEGMENT REPORTING (Narrative) (

SEGMENT REPORTING (Narrative) (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2016USD ($)customer	Dec. 31, 2015USD ($)customer	Dec. 31, 2014USD ($)customer
Segment Reporting Information [Line Items]
Revenues	$ 754	$ 553.3	$ 496.2	$ 305.5	$ 476	$ 593.2	$ 498.1	$ 446	$ 2,109	$ 2,013.3	$ 3,373.2
Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
Segment Reporting Information [Line Items]
Number of Customers | customer									2	3	3
Concentration Risk, Percentage										10.00%	10.00%
Revenues									$ 1,100	$ 1,300	$ 1,900

SEGMENT REPORTING (Schedule Of

SEGMENT REPORTING (Schedule Of Segment Reporting Information, By Segment) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues from product sales and services	$ 754	$ 553.3	$ 496.2	$ 305.5	$ 476	$ 593.2	$ 498.1	$ 446	$ 2,109	$ 2,013.3	$ 3,373.2
Revenues from producet sales and services, percent									100.00%	100.00%	100.00%
SALES MARGIN	$ 181.5	$ 85.4	$ 91.5	$ 30.9	$ 43.3	$ 55.1	$ 57.3	$ 80.8	$ 389.3	$ 236.5	$ 885.7
Other operating expense									(148.5)	(85.2)	(755.6)
Other expense									(33.8)	161.8	(149.8)
Income (loss) from continuing operations before income taxes and equity loss from ventures									207	313.1	(19.7)
Net income (loss)									199.3	(748.4)	(8,311.6)
Interest Income (Expense), net, including Discontinued Operations									(200.5)	(231.4)	(185.2)
Income Tax Expense (Benefit), including Discontinued Operations									12.2	(163.3)	1,302
Depreciation, depletion and amortization									(115.4)	(134)	(504)
EBITDA									503	(219.7)	(8,924.4)
Gain on extinguishment/restructuring of debt									166.3	392.9	16.2
Asset Impairment Charges									0	3.3	635.5
Adjusted EBITDA									373.5	292.9	1,048.3
Depreciation, Depletion and Amortization excluding Depreciation, Amortization and Depletion expense for Discontinued Operations									115.4	130.8	261
Capital Additions									68.5	72.2	65.5
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from product sales and services									$ 1,554.5	$ 1,525.4	$ 2,506.5
Revenues from producet sales and services, percent									74.00%	76.00%	74.00%
SALES MARGIN									$ 275.7	$ 227.1	$ 710.4
Depreciation, depletion and amortization									(84)	(98.9)	(107.4)
EBITDA									342.4	317.6	805.6
Adjusted EBITDA									359.6	352.1	833.5
Capital Additions									62.2	58.2	48.4
Asia Pacific Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from product sales and services									$ 554.5	$ 487.9	$ 866.7
Revenues from producet sales and services, percent									26.00%	24.00%	26.00%
SALES MARGIN									$ 113.6	$ 9.4	$ 121.7
Depreciation, depletion and amortization									(25.1)	(25.3)	(145.9)
EBITDA									128.3	35.3	(352.9)
Adjusted EBITDA									132.9	32.7	252.9
Capital Additions									0.2	5.4	10.8
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Eliminations with Discontinued Operations									0	0	53.6
All Other Segments [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization									(6.3)	(6.6)	(7.7)
Capital Additions									6.1	8.6	6.3
Other Segment [Member]
Segment Reporting Information [Line Items]
EBITDA									32.3	(572.6)	(9,377.1)
Adjusted EBITDA									(119)	(91.9)	(38.1)
EBITDA Calculation [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization									(115.4)	(134)	(504)
Adjusted EBITDA Calculation [Member]
Segment Reporting Information [Line Items]
Impact of Discontinued Operations									(19.9)	(892)	(9,332.5)
Foreign Exchange Remeasurement									(16.8)	16.3	29
Severance Costs									(0.1)	(10.2)	(23.3)
Inventory Write-down									0	(16.3)	0
Proxy contest and change in control costs in SG&A									$ 0	$ 0	$ (26.6)

SEGMENT REPORTING SEGMENT REPOR

SEGMENT REPORTING SEGMENT REPORTING (Summary of Assets by Segment) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Assets	$ 1,923.9	$ 2,135.5	$ 3,147.2
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Assets	1,372.5	1,476.4	1,464.9
Asia Pacific Iron Ore [Member]
Segment Reporting Information [Line Items]
Assets	155.1	202.5	306.2
Total Segment Assets [Member]
Segment Reporting Information [Line Items]
Assets	1,527.6	1,678.9	1,771.1
Corporate [Member]
Segment Reporting Information [Line Items]
Assets	396.3	441.7	666.2
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Disposal Group, Including Discontinued Operation, Assets	$ 0	$ 14.9	$ 709.9

SEGMENT REPORTING SEGMENTS REPO

SEGMENT REPORTING SEGMENTS REPORTING (Revenue by Geographical Location) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 754	$ 553.3	$ 496.2	$ 305.5	$ 476	$ 593.2	$ 498.1	$ 446	$ 2,109	$ 2,013.3	$ 3,373.2
PROPERTY, PLANT AND EQUIPMENT, NET	984.4				1,059				984.4	1,059	1,070.5
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									1,236.2	1,206.4	1,923.2
PROPERTY, PLANT AND EQUIPMENT, NET	961				1,012.7				961	1,012.7	998.1
Australia
Revenues from External Customers and Long-Lived Assets [Line Items]
PROPERTY, PLANT AND EQUIPMENT, NET	$ 23.4				$ 46.3				23.4	46.3	72.4
China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									452.5	370.8	662.7
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									267.1	282.4	430.5
Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 153.2	$ 153.7	$ 356.8

SEGMENT REPORTING SEGMENT REP61

SEGMENT REPORTING SEGMENT REPORTING (Revenue from External Customers by Products and Services) (Details) - Sales Revenue, Net [Member] - Product Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue from External Customer [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%
Iron Ore Revenue [Member]
Revenue from External Customer [Line Items]
Concentration Risk, Percentage	91.00%	91.00%	92.00%
Freight and Venture Partners' Cost Reimbursements [Member]
Revenue from External Customer [Line Items]
Concentration Risk, Percentage	9.00%	9.00%	8.00%

INVENTORIES (Narrative) (Detail

INVENTORIES (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Inventory [Line Items]
Cost of Goods Sold	$ 8,800,000
Asia Pacific Iron Ore [Member]
Inventory [Line Items]
Other Inventory, Noncurrent	0	$ 6,800,000
U.S. Iron Ore [Member]
Inventory [Line Items]
Inventory, LIFO Reserve	$ 78,500,000	87,800,000
Increase in Inventories due to build up of LIFO layers		$ 118,800,000

INVENTORIES (Schedule Of Invent

INVENTORIES (Schedule Of Inventories) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Inventory, Net [Abstract]
Finished Goods	$ 148	$ 273.1
Work-in Process	30.4	56.5
Total Inventory	178.4	329.6
U.S. Iron Ore [Member]
Inventory, Net [Abstract]
Finished Goods	124.4	252.3
Work-in Process	12.6	11.7
Total Inventory	137	264
Asia Pacific Iron Ore [Member]
Inventory, Net [Abstract]
Finished Goods	23.6	20.8
Work-in Process	17.8	44.8
Total Inventory	$ 41.4	$ 65.6

PROPERTY, PLANT AND EQUIPMENT64

PROPERTY, PLANT AND EQUIPMENT (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Depreciation	$ 106,800,000	$ 119,200,000	$ 173,000,000
Tangible Asset Impairment Charges	0	0	537,800,000
Depletion	$ 3,800,000	$ 7,400,000	79,600,000
Land Rights And Mineral Rights [Member]
Property, Plant and Equipment [Line Items]
Tangible Asset Impairment Charges			$ 297.2

PROPERTY, PLANT AND EQUIPMENT65

PROPERTY, PLANT AND EQUIPMENT (Value Of Each Of The Major Classes Of Consolidated Depreciable Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,941.3	$ 1,970.3
Accumulated Depreciation and Depletion, Property, Plant and Equipment	956.9	911.3
Property, plant and equipment, net	984.4	1,059	$ 1,070.5
Land Rights And Mineral Rights [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	500.5	500.5
Office And Information Technology [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	65.1	71
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	67.9	60.4
Mining Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	592.2	594
Processing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	552	516.8
Electric Power Facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	49.4	46.4
Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	23.5	24.8
Asset Retirement Obligation [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	19.8	87.9
Other Assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	28.1	28.2
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 42.8	$ 40.3

PROPERTY, PLANT AND EQUIPMENT P

PROPERTY, PLANT AND EQUIPMENT PROPERTY, PLANT AND EQUIPMENT (Book Value of Land and Mineral Rights Disclosure) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Land Rights	$ 11.6	$ 11.6
Mineral Rights [Abstract]
Mineral Properties, Gross	488.9	488.9
Mineral Properties, Accumulated Depletion	(112.2)	(108.4)
Mineral Properties, Net	$ 376.7	$ 380.5

DEBT AND CREDIT FACILITIES (Nar

DEBT AND CREDIT FACILITIES (Narrative) (Details) shares in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2016USD ($)shares	Sep. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Sep. 16, 2016USD ($)
Line of Credit Facility [Line Items]
Gain on extinguishment/restructuring of debt					$ (166,300,000)	$ (392,900,000)	$ (16,200,000)
Payments of Debt Issuance Costs					5,200,000	33,600,000	$ 9,000,000
Long-term Debt, Current Maturities	$ 17,500,000				$ 17,500,000
Common Shares Issued in Debt to Equity Exchange | shares	8.2				8.2
Debt Instrument, Face Amount Exchanged			$ 512,200,000	$ 674,600,000
$540 Million 8.25% 2020 First Lien Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.25%				8.25%
Debt Instrument, Par Value	$ 540,000,000				$ 540,000,000	540,000,000
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.00%				8.00%
Debt Instrument, Par Value	$ 218,500,000		218,500,000		$ 218,500,000
$544.2 Million 7.75% 2020 Second Lien Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.75%				7.75%
Debt Instrument, Par Value	$ 430,100,000			544,200,000	$ 430,100,000	544,200,000
Debt Instrument, Face Amount Exchanged			114,100,000
Secured Debt [Member]
Line of Credit Facility [Line Items]
Repurchase price if triggering event occurs					1.01
In the Event of Default Amount that will Accelerate					0.25
$500 Million 3.95% 2018 Senior Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.95%				3.95%
Debt Instrument, Par Value						311,200,000
Gain on extinguishment/restructuring of debt		$ 19,900,000
Amortization of Debt Discount (Premium)		17,400,000
Debt Redemption Expenses		2,500,000
Basis points	50				50
Debt Instrument, Face Amount Exchanged			17,600,000
Debt Instrument, Repurchased Face Amount						168,800,000
$400 Million 5.90% 2020 Senior Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.90%				5.90%
Debt Instrument, Par Value	$ 225,600,000				$ 225,600,000	290,800,000
Basis points	35				35
Debt Instrument, Face Amount Exchanged			65,100,000	67,000,000
Debt Instrument, Repurchased Face Amount						37,300,000
$500 Million 4.80% 2020 Senior Notes[Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.80%				4.80%
Debt Instrument, Par Value	$ 236,800,000				$ 236,800,000	306,700,000
Gain on extinguishment/restructuring of debt	(600,000)
Debt Instrument, Face Amount Exchanged			44,700,000	137,800,000
Debt Instrument, Repurchased Face Amount	$ 5,000,000				$ 5,000,000	45,600,000
$700 Million 4.875% 2021 Senior Notes[Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.875%				4.875%
Debt Instrument, Par Value	$ 309,400,000				$ 309,400,000	412,500,000
Basis points	25				25
Debt Instrument, Face Amount Exchanged			76,300,000	208,500,000
Debt Instrument, Repurchased Face Amount						69,000,000
$800 Million 6.25% 2040 Senior Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.25%				6.25%
Debt Instrument, Par Value	$ 298,400,000				$ 298,400,000	492,800,000
Basis points	40				40
Debt Instrument, Face Amount Exchanged			194,400,000	261,300,000
Debt Instrument, Repurchased Face Amount						45,900,000
Unsecured Debt [Member]
Line of Credit Facility [Line Items]
Repurchase price if triggering event occurs					1.01
Note Redemption Price, Percent of Principal Amount to be Redeemed	100.00%				100.00%
Unsecured Debt [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Time Period During Which Senior Notes May Be Redeemed at Company's Option, Number of Days From When Prior Notice Sent to Holders					60 days
Unsecured Debt [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Time Period During Which Senior Notes May Be Redeemed at Company's Option, Number of Days From When Prior Notice Sent to Holders					30 days
ABL Facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Par Value	$ 550,000,000				$ 550,000,000
U.S. Tranche	450,000,000				450,000,000
Sublimit for Issuers of Letters of Credit for U.S. Tranche	250,000,000				250,000,000
Sublimit for U.S. Swingline Loans	100,000,000				100,000,000
Australian Tranche	100,000,000				100,000,000
Sublimit for Issuance of Letters of Credit for Australian Tranche	50,000,000				50,000,000
Sublimit for Australian Swingline Loans	20,000,000				$ 20,000,000
LIBOR Rate Based on a One-month interest period plus 1 percent					0.01
Fixed Charge Coverage Ratio					1
Credit facility, amount outstanding	0				$ 0	0
Line of Credit Facility, Remaining Borrowing Capacity	227,000,000				227,000,000	179,200,000
Revolving credit facility, borrowing capacity	333,000,000				$ 333,000,000	366,000,000
ABL Facility [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Base Rate					0.01
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Credit facility, amount outstanding	106,000,000				$ 106,000,000	186,300,000
Hedge Obligations [Member]
Line of Credit Facility [Line Items]
Credit facility, amount outstanding						500,000
Debt Repurchase [Member]
Line of Credit Facility [Line Items]
Gain on extinguishment/restructuring of debt						(137,100,000)
Debt Repurchase [Member] | $500 Million 3.95% 2018 Senior Notes [Member]
Line of Credit Facility [Line Items]
Redemption Price								$ 301,000,000
Debt Instrument, Par Value		$ 283,600,000
Exchange of Debt [Member] | $218.5 Million 8.00% 2020 1.5 Lien Notes [Member]
Line of Credit Facility [Line Items]
Gain on extinguishment/restructuring of debt					(174,300,000)
Exchange of Debt [Member] | $544.2 Million 7.75% 2020 Second Lien Notes [Member]
Line of Credit Facility [Line Items]
Gain on extinguishment/restructuring of debt			(6,900,000)			(269,500,000)
Exchange of Debt [Member] | $500 Million 3.95% 2018 Senior Notes [Member]
Line of Credit Facility [Line Items]
Gain on extinguishment/restructuring of debt			(1,800,000)
Exchange of Debt [Member] | $400 Million 5.90% 2020 Senior Notes [Member]
Line of Credit Facility [Line Items]
Gain on extinguishment/restructuring of debt			(28,300,000)	(24,500,000)
Exchange of Debt [Member] | $500 Million 4.80% 2020 Senior Notes[Member]
Line of Credit Facility [Line Items]
Gain on extinguishment/restructuring of debt			(19,500,000)	(54,600,000)
Exchange of Debt [Member] | $700 Million 4.875% 2021 Senior Notes[Member]
Line of Credit Facility [Line Items]
Gain on extinguishment/restructuring of debt			(33,300,000)	(83,100,000)
Exchange of Debt [Member] | $800 Million 6.25% 2040 Senior Notes [Member]
Line of Credit Facility [Line Items]
Gain on extinguishment/restructuring of debt			$ (84,500,000)	$ (107,300,000)
Exchange of Debt for Equity [Member]
Line of Credit Facility [Line Items]
Gain on extinguishment/restructuring of debt	(11,300,000)
Exchange of Debt for Equity [Member] | $218.5 Million 8.00% 2020 1.5 Lien Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount Exchanged	20,100,000				20,100,000
Exchange of Debt for Equity [Member] | $500 Million 3.95% 2018 Senior Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount Exchanged	10,000,000				10,000,000
Exchange of Debt for Equity [Member] | $700 Million 4.875% 2021 Senior Notes[Member]
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount Exchanged	$ 26,800,000				$ 26,800,000
Credit Facility Extinguishment [Member]
Line of Credit Facility [Line Items]
Gain on extinguishment/restructuring of debt						$ (13,700,000)

DEBT AND CREDIT FACILITIES (Sch

DEBT AND CREDIT FACILITIES (Schedule Of Long-Term Debt) (Details) - USD ($)	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Debt Instrument [Line Items]
Long-term Debt	$ 2,192,600,000		$ 2,699,400,000
Long-term Debt, Current Maturities	17,500,000
LONG-TERM DEBT	$ 2,175,100,000		2,699,400,000
$540 Million 8.25% 2020 First Lien Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.25%
Debt Instrument, Face Amount	$ 540,000,000		$ 540,000,000
Imputed interest rate	9.97%		9.97%
Debt Instrument, Par Value	$ 540,000,000		$ 540,000,000
Unamortized Debt Issuance Expense	(8,000,000)		(10,500,000)
Debt Instrument, Unamortized Discount	(25,700,000)		(32,100,000)
Long-term Debt	$ 506,300,000		497,400,000
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.00%
Debt Instrument, Face Amount	$ 218,500,000		218,500,000
Debt Instrument, Par Value	218,500,000	$ 218,500,000
Unamortized Debt Issuance Expense	0
Debt Instrument, Unamortized Discount	65,700,000
Long-term Debt	$ 284,200,000
$544.2 Million 7.75% 2020 Second Lien Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.75%
Debt Instrument, Face Amount	$ 544,200,000		$ 544,200,000
Imputed interest rate	15.55%		15.55%
Debt Instrument, Par Value	$ 430,100,000		$ 544,200,000	$ 544,200,000
Unamortized Debt Issuance Expense	(5,800,000)		(9,500,000)
Debt Instrument, Unamortized Discount	(85,200,000)		(131,500,000)
Long-term Debt	$ 339,100,000		403,200,000
$500 Million 3.95% 2018 Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.95%
Debt Instrument, Face Amount	$ 500,000,000		$ 500,000,000
Imputed interest rate			6.30%
Debt Instrument, Par Value			$ 311,200,000
Unamortized Debt Issuance Expense			(900,000)
Debt Instrument, Unamortized Discount			(1,200,000)
Long-term Debt	$ 0		309,100,000
$400 Million 5.90% 2020 Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.90%
Debt Instrument, Face Amount	$ 400,000,000		$ 400,000,000
Imputed interest rate	5.98%		5.98%
Debt Instrument, Par Value	$ 225,600,000		$ 290,800,000
Unamortized Debt Issuance Expense	(600,000)		(1,100,000)
Debt Instrument, Unamortized Discount	(500,000)		(800,000)
Long-term Debt	$ 224,500,000		$ 288,900,000
$500 Million 4.80% 2020 Senior Notes[Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.80%
Debt Instrument, Face Amount	$ 500,000,000
Imputed interest rate	4.83%		4.83%
Debt Instrument, Par Value	$ 236,800,000		$ 306,700,000
Unamortized Debt Issuance Expense	(700,000)		(1,100,000)
Debt Instrument, Unamortized Discount	(200,000)		(400,000)
Long-term Debt	$ 235,900,000		305,200,000
$700 Million 4.875% 2021 Senior Notes[Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.875%
Debt Instrument, Face Amount	$ 700,000,000		$ 700,000,000
Imputed interest rate	4.89%		4.89%
Debt Instrument, Par Value	$ 309,400,000		$ 412,500,000
Unamortized Debt Issuance Expense	(1,000,000)		(1,700,000)
Debt Instrument, Unamortized Discount	(200,000)		(200,000)
Long-term Debt	$ 308,200,000		$ 410,600,000
$800 Million 6.25% 2040 Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.25%
Debt Instrument, Face Amount	$ 800,000,000
Imputed interest rate	6.34%		6.34%
Debt Instrument, Par Value	$ 298,400,000		$ 492,800,000
Unamortized Debt Issuance Expense	(2,500,000)		(4,300,000)
Debt Instrument, Unamortized Discount	(3,400,000)		(5,800,000)
Long-term Debt	292,500,000		482,700,000
ABL Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Par Value	550,000,000
Credit facility, amount outstanding	0		0
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Fair Value Adjustment to Interest Rate Hedge	$ 1,900,000		$ 2,300,000

DEBT AND CREDIT FACILITIES DEBT

DEBT AND CREDIT FACILITIES DEBT AND CREDIT FACILITIES (Debt Redemption) (Details)	12 Months Ended
	Dec. 31, 2016
$540 Million 8.25% 2020 First Lien Notes [Member]
Debt Instrument, Redemption [Line Items]
Early Redemption Price	1
Initial Redemption Price	1.0825
Secondary Redemption Price	1
Amount in aggregate that can be redeemed on or prior to March 31, 2018	0.3500
Amount to Remain Outstanding Prior to March 31, 2018	0.6500
Redemption Price of 35 percent or less of Outstanding	1.0825
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member]
Debt Instrument, Redemption [Line Items]
Early Redemption Price	1
Initial Redemption Price	1.04
Secondary Redemption Price	1
Amount in aggregate that can be redeemed on or prior to September 30, 2017	0.3500
Amount to Remain Outstanding Prior to September 30, 2017	0.6500
Redemption Price of 35 percent or less of Outstanding	1.0800
$544.2 Million 7.75% 2020 Second Lien Notes [Member]
Debt Instrument, Redemption [Line Items]
Early Redemption Price	1
Initial Redemption Price	1.03875
Secondary Redemption Price	1
Amount in aggregate that can be redeemed on or prior to March 31, 2017	0.3500
Amount to Remain Outstanding Prior to March 30, 2017	0.6500
Redemption Price of 35 percent or less of Outstanding	1.0775

DEBT AND CREDIT FACILITIES DE70

DEBT AND CREDIT FACILITIES DEBT AND CREDIT FACILITIES (Debt Restructuring) (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Extinguishment of Debt [Line Items]
Debt Instrument, Face Amount Exchanged			$ 512.2	$ 674.6
Gain on extinguishment/restructuring of debt					$ 166.3	$ 392.9	$ 16.2
$544.2 Million 7.75% 2020 Second Lien Notes [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Face Amount Exchanged			114.1
Debt Instrument, Face Amount Received in Debt Exchange of $400M 5.90% Notes				57.5
Debt Instrument, Face Amount Received in Debt Exchange of $500M 4.80% Notes				112.9
Debt instrument, Face Amount Received in Debt Exchange of $700M 4.875% Notes				170.3
Debt Instrument, Face Amount Received in Debt Exchange of $800M 6.25% Notes				203.5
Debt Instrument, Carrying Amount Received in Debt Exchange of $400M 5.90% Notes				42
Debt Instrument, Carrying Value Received in Debt Exchange of $500M 4.80% Notes				82.4
Debt instrument, Carrying Value Received in Debt Exchange of $700M 4.875% Notes				124.3
Debt Instrument, Carrying Value Received in Debt Exchange of $800M 6.25% Notes				148.5
Debt Instrument, Par Value	$ 430.1			544.2	430.1	544.2
Debt, carrying value				397.2
$544.2 Million 7.75% 2020 Second Lien Notes [Member] | Exchange of Debt [Member]
Extinguishment of Debt [Line Items]
Gain on extinguishment/restructuring of debt			6.9			269.5
Five Hundred Million Three Point Nine Five Two Thousand Eighteen Senior Note [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Face Amount Exchanged			17.6
Gain on extinguishment/restructuring of debt		$ (19.9)
Debt Instrument, Par Value						311.2
Five Hundred Million Three Point Nine Five Two Thousand Eighteen Senior Note [Member] | Exchange of Debt [Member]
Extinguishment of Debt [Line Items]
Gain on extinguishment/restructuring of debt			1.8
Four Hundred Million Five Point Nine Zero Two Thousand And Twenty Senior Note [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Face Amount Exchanged			65.1	67
Debt Instrument, Par Value	225.6				225.6	290.8
Four Hundred Million Five Point Nine Zero Two Thousand And Twenty Senior Note [Member] | Exchange of Debt [Member]
Extinguishment of Debt [Line Items]
Gain on extinguishment/restructuring of debt			28.3	24.5
$500 Million 4.80% 2020 Senior Notes[Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Face Amount Exchanged			44.7	137.8
Gain on extinguishment/restructuring of debt	0.6
Debt Instrument, Par Value	236.8				236.8	306.7
$500 Million 4.80% 2020 Senior Notes[Member] | Exchange of Debt [Member]
Extinguishment of Debt [Line Items]
Gain on extinguishment/restructuring of debt			19.5	54.6
$700 Million 4.875% 2021 Senior Notes[Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Face Amount Exchanged			76.3	208.5
Debt Instrument, Par Value	309.4				309.4	412.5
$700 Million 4.875% 2021 Senior Notes[Member] | Exchange of Debt [Member]
Extinguishment of Debt [Line Items]
Gain on extinguishment/restructuring of debt			33.3	83.1
$800 Million 6.25% 2040 Senior Notes [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Face Amount Exchanged			194.4	261.3
Debt Instrument, Par Value	298.4				298.4	$ 492.8
$800 Million 6.25% 2040 Senior Notes [Member] | Exchange of Debt [Member]
Extinguishment of Debt [Line Items]
Gain on extinguishment/restructuring of debt			84.5	$ 107.3
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Face Amount Received in Debt Exchange of $544M 7.75% Notes			57
Debt Instrument, Face Amount Received in Debt Exchange of $500M 3.95% Notes			11.4
Debt Instrument, Face Amount Received in Debt Exchange of $400M 5.90% Notes			26
Debt Instrument, Face Amount Received in Debt Exchange of $500M 4.80% Notes			17.9
Debt instrument, Face Amount Received in Debt Exchange of $700M 4.875% Notes			30.5
Debt Instrument, Face Amount Received in Debt Exchange of $800M 6.25% Notes			75.7
Debt Instrument, Carrying Amount Received in Debt Exchange of $544.2M 7.75% Notes			77.5
Debt Instrument, Carrying Amount Received in Debt Exchange of $500M 3.95% Notes			15.5
Debt Instrument, Carrying Amount Received in Debt Exchange of $400M 5.90% Notes			35.4
Debt Instrument, Carrying Value Received in Debt Exchange of $500M 4.80% Notes			24.4
Debt instrument, Carrying Value Received in Debt Exchange of $700M 4.875% Notes			41.5
Debt Instrument, Carrying Value Received in Debt Exchange of $800M 6.25% Notes			103
Debt Instrument, Par Value	$ 218.5		218.5		218.5
Debt, carrying value			$ 297.3
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member] | Exchange of Debt [Member]
Extinguishment of Debt [Line Items]
Gain on extinguishment/restructuring of debt					$ 174.3

DEBT AND CREDIT FACILITIES DE71

DEBT AND CREDIT FACILITIES DEBT AND CREDIT FACILITIES (Schedule of Debt Maturities) (Details) $ in Millions	Dec. 31, 2016USD ($)
Debt Disclosure [Abstract]
Debt Maturities 2017	$ 0
Debt Maturities 2018	0
Debt Maturities 2019	0
Debt Maturities 2020	1,651
Debt Maturities 2021	309.4
Debt Maturities 2022 and After	298.4
Long-term Debt, Maturities, Total	$ 2,258.8

FAIR VALUE OF FINANCIAL INSTR72

FAIR VALUE OF FINANCIAL INSTRUMENTS (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Management Estimate of 62% Fe	62.00%	62.00%

FAIR VALUE OF FINANCIAL INSTR73

FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value Of Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets:
Cash equivalents	$ 177	$ 30
Derivative Asset	33.1	7.8
Total Asset	210.1	37.8
Liabilities:
Derivative Liability	0.5	4
Total Liability	0.5	4
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents	177	30
Derivative Asset	0	0
Total Asset	177	30
Liabilities:
Derivative Liability	0	0
Total Liability	0	0
Fair Value, Inputs, Level 2 [Member]
Assets:
Cash equivalents	0	0
Derivative Asset	1.5	0
Total Asset	1.5	0
Liabilities:
Derivative Liability	0	0.6
Total Liability	0	0.6
Fair Value, Inputs, Level 3 [Member]
Assets:
Cash equivalents	0	0
Derivative Asset	31.6	7.8
Total Asset	31.6	7.8
Liabilities:
Derivative Liability	0.5	3.4
Total Liability	$ 0.5	$ 3.4

FAIR VALUE OF FINANCIAL INSTR74

FAIR VALUE OF FINANCIAL INSTRUMENTS (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Management Estimate of 62% Fe	62.00%	62.00%
Not Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, fair value	$ 33,100,000	$ 7,800,000
Derivative liability, fair value	500,000	4,000,000
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% Fe [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	80
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	620
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	505
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	555
Other Current Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, fair value	500,000	3,400,000
Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, fair value	10,300,000	2,000,000
Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, fair value	$ 21,300,000	$ 5,800,000

FAIR VALUE OF FINANCIAL INSTR75

FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value, Assets and Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance - January 1	$ 7.8	$ 63.2
Total gains
Included in earnings	103.8	35.1
Settlements	(80)	(90.5)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance - December 31	31.6	7.8
Total gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) on assets still held at the reporting date	23.7	29.1
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance - January 1	(3.4)	(9.5)
Total gains
Included in earnings	(14.1)	(61)
Settlements	17	67.1
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance - September 30	(0.5)	(3.4)
Total gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) on liabilities still held at the reporting date	$ (0.5)	$ (3.4)

FAIR VALUE OF FINANCIAL INSTR76

FAIR VALUE OF FINANCIAL INSTRUMENTS (Carrying Value And Fair Value Of Financial Instruments Disclosure) (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Long-term debt:
LONG-TERM DEBT	$ 2,175,100,000	$ 2,699,400,000
Long-term Debt, Fair Value	2,224,600,000	898,200,000
$540 Million 8.25% 2020 First Lien Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	540,000,000	540,000,000
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	218,500,000	218,500,000
$544.2 Million 7.75% 2020 Second Lien Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	544,200,000	544,200,000
$400 Million 5.90% 2020 Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	400,000,000	400,000,000
Senior Notes - $1.3 Billion [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	1,300,000,000	1,300,000,000
$700 Million 4.875% 2021 Senior Notes[Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	700,000,000	700,000,000
$500 Million 3.95% 2018 Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	500,000,000	500,000,000
Interest Rate Swap [Member]
Long-term debt:
Fair Value Adjustment to Interest Rate Hedge	1,900,000	2,300,000
Fair Value, Inputs, Level 2 [Member] | ABL Facility [Member]
Long-term debt:
Revolving loan, fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Long-term debt:
Fair Value Adjustment to Interest Rate Hedge	1,900,000	2,300,000
Fair Value, Inputs, Level 1 [Member] | $540 Million 8.25% 2020 First Lien Notes [Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	595,000,000	414,500,000
Fair Value, Inputs, Level 1 [Member] | $544.2 Million 7.75% 2020 Second Lien Notes [Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	439,700,000	134,700,000
Fair Value, Inputs, Level 1 [Member] | $400 Million 5.90% 2020 Senior Notes [Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	219,600,000	52,800,000
Fair Value, Inputs, Level 1 [Member] | Senior Notes - $1.3 Billion [Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	455,800,000	137,400,000
Fair Value, Inputs, Level 1 [Member] | $700 Million 4.875% 2021 Senior Notes[Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	283,100,000	69,400,000
Fair Value, Inputs, Level 1 [Member] | $500 Million 3.95% 2018 Senior Notes [Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	0	87,100,000
Reported Value Measurement [Member]
Long-term debt:
LONG-TERM DEBT	2,192,600,000	2,699,400,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | ABL Facility [Member]
Long-term debt:
Senior notes, carrying value	0	0
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Long-term debt:
Fair Value Adjustment to Interest Rate Hedge	1,900,000	2,300,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | $540 Million 8.25% 2020 First Lien Notes [Member]
Long-term debt:
Senior notes, carrying value	506,300,000	497,400,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | $544.2 Million 7.75% 2020 Second Lien Notes [Member]
Long-term debt:
Senior notes, carrying value	339,100,000	403,200,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | $400 Million 5.90% 2020 Senior Notes [Member]
Long-term debt:
Senior notes, carrying value	224,500,000	288,900,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Senior Notes - $1.3 Billion [Member]
Long-term debt:
Senior notes, carrying value	528,400,000	787,900,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | $700 Million 4.875% 2021 Senior Notes[Member]
Long-term debt:
Senior notes, carrying value	308,200,000	410,600,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | $500 Million 3.95% 2018 Senior Notes [Member]
Long-term debt:
Senior notes, carrying value		$ 309,100,000
Senior Notes [Member] | Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | $218.5 Million 8.00% 2020 1.5 Lien Notes [Member]
Long-term debt:
Long-term Debt, Fair Value	284,200,000
Senior Notes [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | $218.5 Million 8.00% 2020 1.5 Lien Notes [Member]
Long-term debt:
Long-term Debt, Fair Value	$ 229,500,000

PENSIONS AND OTHER POSTRETIRE77

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Minimum participants percentage	15.00%
Defined Benefit Plan, Accumulated Benefit Obligation	$ 922,000,000	$ 898,900,000
Reserve for investment commitments	$ 37,900,000
Structured Finance [Member]
Defined Benefit Plan Disclosure [Line Items]
Redemption request notice period, days	90 days
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Redemption request notice period, days	45 days
Withdrawal request notice period, days	65 days
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Decrease in Projected Benefit Obligation due to Market Conditions	$ 22,000,000
Reduction in net periodic benefit expense	8,200,000
Increase in Projected Benefit Obligation due to new mortality tables	$ 13,100,000
Percentage Increase in Projected Benefit Obligation due to new mortality tables	1.40%
Participant contributions	$ 0	0
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Decrease in Projected Benefit Obligation due to Market Conditions	8,600,000
Reduction in net periodic benefit expense	1,800,000
Increase in Projected Benefit Obligation due to new mortality tables	$ 4,900,000
Percentage Increase in Projected Benefit Obligation due to new mortality tables	2.00%
Participant contributions	$ 6,000,000	$ 4,000,000
Tilden, Empire, Hibbing and United Taconite [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of total workforce covered by labor contract	80.00%
Prior To Age65 [Member] | Defined Benefit Postretirement Health Coverage [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Annual limit on medical coverage for each participant	$ 7,000
Prior To Age65 [Member] | Minimum [Member] | Defined Benefit Postretirement Health Coverage [Member] | Northshore [Member]
Defined Benefit Plan Disclosure [Line Items]
Annual limit on medical coverage for each participant	4,020
Prior To Age65 [Member] | Maximum [Member] | Defined Benefit Postretirement Health Coverage [Member] | Northshore [Member]
Defined Benefit Plan Disclosure [Line Items]
Annual limit on medical coverage for each participant	$ 4,500

PENSIONS AND OTHER POSTRETIRE78

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Annual Costs Related to Retirement Plans) (Details) - Pension Benefits [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plans	$ 16.5	$ 23.9	$ 26.2
Defined contribution pension plans	2.8	3.6	4.4
Other Postretirement Benefit Expense	(4)	4.4	(2.5)
Total	$ 15.3	$ 31.9	$ 28.1

PENSIONS AND OTHER POSTRETIRE79

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Benefit Obligations, Fair Value of Plan Assets, and Net Funded Status) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets — beginning of year	$ 193.4	$ 188.1
Employer contributions	1.1	3.5
Fair value of plan assets — end of year	202.4	193.4	$ 188.1
Funded status at December 31:
Defined Benefit Plan, Fair Value of Plan Assets	193.4	188.1	188.1	$ 202.4	$ 193.4
Amounts recognized in Statements of Financial Position:
Assets, Current				824.6	982.7
Noncurrent liabilities				(280.5)	(221)
Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligations — beginning of year	(910.8)	(998)
Service cost (excluding expenses)	17.6	22.7	26.1
Interest cost	30.3	37.7	40.3
Plan amendments	5.7	0
Actuarial loss	(21.1)	(20.8)	(14)
Defined Benefit Plan, Change in Actuarial (gain) loss	38.1	(67.7)
Benefits paid	(70.9)	(78.7)
Participant contributions	0	0
Federal subsidy on benefits paid	0	0
Benefit obligations — end of year	(931.6)	(910.8)	(998)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets — beginning of year	700.6	749.8
Actual return on plan assets	54.8	(6.4)	59.1
Participant contributions	0	0
Employer contributions	1.2	35.7
Assets Transferred to (from) Plan	0.1	0.2
Fair value of plan assets — end of year	685.8	700.6	749.8
Funded status at December 31:
Defined Benefit Plan, Fair Value of Plan Assets	700.6	749.8	749.8	685.8	700.6
Defined Benefit Plan, Benefit Obligation	(910.8)	(998)	(998)	(931.6)	(910.8)
Defined Benefit Plan, Funded Status of Plan				(245.8)	(210.2)
Total amount recognized				(245.8)	(210.2)
Amounts recognized in Statements of Financial Position:
Assets, Current				0	0
Current liabilities				(0.1)	(0.5)
Noncurrent liabilities				(245.7)	(209.7)
Total amount recognized				(245.8)	(210.2)
Amounts recognized in accumulated other comprehensive income:
Prior service cost				11	7.5
Net actuarial loss				315.9	290.9
Net amount recognized				326.9	298.4
The estimated amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost:
Net actuarial loss	21.1
Prior service cost	2.6
Net amount recognized	23.7
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	0	(1.2)
Other Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligations — beginning of year	(266)	(295.8)
Service cost (excluding expenses)	1.7	6.4	1.8
Interest cost	9.1	13.4	11.9
Plan amendments	9.8	0
Actuarial loss	(6)	(6.6)	(4.5)
Defined Benefit Plan, Change in Actuarial (gain) loss	(7.2)	(27)
Benefits paid	(21.3)	(20.6)
Participant contributions	6	4
Federal subsidy on benefits paid	0.5	0.4
Benefit obligations — end of year	(264.6)	(266)	(295.8)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets — beginning of year	250.6	269.3
Actual return on plan assets	16	(3.9)	31.9
Participant contributions	0.5	0.4
Employer contributions	1.7	1.3
Assets Transferred to (from) Plan	0	0
Benefits paid	(15.8)	(16.5)
Fair value of plan assets — end of year	253	250.6	269.3
Funded status at December 31:
Defined Benefit Plan, Fair Value of Plan Assets	250.6	269.3	269.3	253	250.6
Defined Benefit Plan, Benefit Obligation	(266)	(295.8)	$ (295.8)	(264.6)	(266)
Defined Benefit Plan, Funded Status of Plan				(11.6)	(15.4)
Total amount recognized				(11.6)	(15.4)
Amounts recognized in Statements of Financial Position:
Assets, Current					0
Assets, Noncurrent				27.3
Current liabilities				(4.1)	(4.1)
Noncurrent liabilities				(34.8)	(11.3)
Total amount recognized				(11.6)	(15.4)
Amounts recognized in accumulated other comprehensive income:
Prior service cost				(26.9)	(39.5)
Net actuarial loss				87	91.5
Net amount recognized				60.1	52
The estimated amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost:
Net actuarial loss	5
Prior service cost	(3)
Net amount recognized	2
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	0	0
Salaried Employees [Member] | Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligations — beginning of year	(340)
Benefit obligations — end of year	(351.9)	(340)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets — beginning of year	258.3
Fair value of plan assets — end of year	242.9	258.3
Funded status at December 31:
Defined Benefit Plan, Fair Value of Plan Assets	258.3	258.3		242.9	258.3
Defined Benefit Plan, Benefit Obligation	(340)	(340)		(351.9)	(340)
Defined Benefit Plan, Funded Status of Plan				(109)	(81.7)
Salaried Employees [Member] | Other Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligations — beginning of year	(38.2)
Benefit obligations — end of year	(37.6)	(38.2)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets — beginning of year	0
Fair value of plan assets — end of year	0	0
Funded status at December 31:
Defined Benefit Plan, Fair Value of Plan Assets	0	0		0	0
Defined Benefit Plan, Benefit Obligation	(38.2)	(38.2)		(37.6)	(38.2)
Defined Benefit Plan, Funded Status of Plan				(37.6)	(38.2)
Hourly Employees [Member] | Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligations — beginning of year	(558.6)
Benefit obligations — end of year	(565.6)	(558.6)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets — beginning of year	436.7
Fair value of plan assets — end of year	436.9	436.7
Funded status at December 31:
Defined Benefit Plan, Fair Value of Plan Assets	436.7	436.7		436.9	436.7
Defined Benefit Plan, Benefit Obligation	(558.6)	(558.6)		(565.6)	(558.6)
Defined Benefit Plan, Funded Status of Plan				(128.7)	(121.9)
Hourly Employees [Member] | Other Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligations — beginning of year	(227.8)
Benefit obligations — end of year	(227)	(227.8)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets — beginning of year	250.6
Fair value of plan assets — end of year	253	250.6
Funded status at December 31:
Defined Benefit Plan, Fair Value of Plan Assets	250.6	250.6		253	250.6
Defined Benefit Plan, Benefit Obligation	(227.8)	(227.8)		(227)	(227.8)
Defined Benefit Plan, Funded Status of Plan				26	22.8
Mining Employees [Member] | Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligations — beginning of year	(8.6)
Benefit obligations — end of year	(10)	(8.6)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets — beginning of year	5.6
Fair value of plan assets — end of year	6	5.6
Funded status at December 31:
Defined Benefit Plan, Fair Value of Plan Assets	5.6	5.6		6	5.6
Defined Benefit Plan, Benefit Obligation	(8.6)	(8.6)		(10)	(8.6)
Defined Benefit Plan, Funded Status of Plan				(4)	(3)
Supplemental Executive Retirement Plan S E R P [Member] | Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligations — beginning of year	(3.6)
Benefit obligations — end of year	(4.1)	(3.6)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets — beginning of year	0
Fair value of plan assets — end of year	0	0
Funded status at December 31:
Defined Benefit Plan, Fair Value of Plan Assets	0	0		0	0
Defined Benefit Plan, Benefit Obligation	(3.6)	(3.6)		(4.1)	(3.6)
Defined Benefit Plan, Funded Status of Plan				$ (4.1)	$ (3.6)
Pension Costs [Member] | Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost (excluding expenses)	17.6	22.7
Interest cost	30.3	37.7
Pension Costs [Member] | Other Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost (excluding expenses)	1.7	1.9
Interest cost	$ 9.1	$ 11.5

PENSIONS AND OTHER POSTRETIRE80

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amortization:
Relating to assets sold during the period	$ 3.3	$ 2.5
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	17.6	22.7	$ 26.1
Interest cost	(30.3)	(37.7)	(40.3)
Expected return on plan assets	(54.7)	(59.8)	(58.1)
Defined Benefit Plan, Actuarial Gain (Loss)	21.1	20.8	14
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	0	0.2	1.4
Amortization:
Amortization of prior service (cost) credit	(2.2)	(2.3)	(2.5)
Net actuarial loss	21.1	21	15.4
Net periodic benefit cost	16.5	23.9	26.2
Effect of Curtailment	0	(1.2)	0
Current year actuarial (gain)/loss	37.8	(0.7)	109.7
Amortization of net loss	21.1	21	15.4
Current year prior service cost	5.7	0	0
Amortization of prior service (cost) credit	(2.2)	(2.3)	(2.5)
Total recognized in other comprehensive income	20.2	(25.2)	91.8
Total recognized in net periodic cost and other comprehensive income	36.7	(1.3)	118
Defined Benefit Plan, Benefit Obligation	(931.6)	(910.8)	(998)
Defined Benefit Plan, Funded Status of Plan	(245.8)	(210.2)
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.7	6.4	1.8
Interest cost	(9.1)	(13.4)	(11.9)
Expected return on plan assets	(17.1)	(18.3)	(17.1)
Defined Benefit Plan, Actuarial Gain (Loss)	6	6.6	4.5
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	0	0	0
Amortization:
Amortization of prior service (cost) credit	3.7	3.7	3.6
Net actuarial loss	6	6.6	4.5
Net periodic benefit cost	(4)	4.4	(2.5)
Effect of Curtailment	0	0	0
Current year actuarial (gain)/loss	(8.1)	0.2	22.2
Amortization of net loss	6	6.6	4.5
Current year prior service cost	9.8	0	(0.9)
Amortization of prior service (cost) credit	3.7	3.7	3.6
Total recognized in other comprehensive income	(0.6)	(2.7)	20.4
Total recognized in net periodic cost and other comprehensive income	(4.6)	1.7	17.9
Defined Benefit Plan, Benefit Obligation	(264.6)	(266)	$ (295.8)
Defined Benefit Plan, Funded Status of Plan	(11.6)	(15.4)
Salaried Employees [Member] | Pension Benefits [Member]
Amortization:
Defined Benefit Plan, Benefit Obligation	(351.9)	(340)
Defined Benefit Plan, Funded Status of Plan	(109)	(81.7)
Salaried Employees [Member] | Other Benefits [Member]
Amortization:
Defined Benefit Plan, Benefit Obligation	(37.6)	(38.2)
Defined Benefit Plan, Funded Status of Plan	(37.6)	(38.2)
Hourly Employees [Member] | Pension Benefits [Member]
Amortization:
Defined Benefit Plan, Benefit Obligation	(565.6)	(558.6)
Defined Benefit Plan, Funded Status of Plan	(128.7)	(121.9)
Hourly Employees [Member] | Other Benefits [Member]
Amortization:
Defined Benefit Plan, Benefit Obligation	(227)	(227.8)
Defined Benefit Plan, Funded Status of Plan	26	22.8
Mining Employees [Member] | Pension Benefits [Member]
Amortization:
Defined Benefit Plan, Benefit Obligation	(10)	(8.6)
Defined Benefit Plan, Funded Status of Plan	(4)	(3)
Supplemental Executive Retirement Plan S E R P [Member] | Pension Benefits [Member]
Amortization:
Defined Benefit Plan, Benefit Obligation	(4.1)	(3.6)
Defined Benefit Plan, Funded Status of Plan	$ (4.1)	$ (3.6)

PENSIONS AND OTHER POSTRETIRE81

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Additional Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Effect of change in mine ownership & noncontrolling interest	$ 14.2	$ 48.4	$ 51.2
Actual return on plan assets	54.8	(6.4)	59.1
Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Effect of change in mine ownership & noncontrolling interest	5.9	5.5	5.9
Actual return on plan assets	$ 16	$ (3.9)	$ 31.9

PENSIONS AND OTHER POSTRETIRE82

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Weighted-Average Assumptions Used to Determine Benefit Obligations) (Details)	Dec. 31, 2016	Dec. 31, 2015
Salary [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Rate of compensation increase	3.00%	3.00%
Hourly [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Rate of compensation increase	2.00%	2.00%
Iron Hourly [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.02%	4.27%
Salaried [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.92%	4.12%
Salaried [Member] | Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.99%	4.22%
Ore Mining [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.04%	4.28%
Supplemental Executive Retirement Plan S E R P [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.90%	4.22%
Hourly [Member] | Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.02%	4.32%

PENSIONS AND OTHER POSTRETIRE83

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Weighted-Average Assumptions Used to Determine Net Benefit Cost) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	8.25%	8.25%	8.25%
Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	7.00%	7.00%	7.00%
Hourly [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	2.00%	2.50%	3.00%
Hourly [Member] | Pension Benefits [Member] | Obligation [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.27%	3.83%	4.57%
Hourly [Member] | Pension Benefits [Member] | Service Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.66%	3.83%	4.57%
Hourly [Member] | Pension Benefits [Member] | Interest Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.46%	3.83%	4.57%
Hourly [Member] | Other Benefits [Member] | Obligation [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.32%	3.83%	4.57%
Hourly [Member] | Other Benefits [Member] | Service Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.56%	3.83%	4.57%
Hourly [Member] | Other Benefits [Member] | Interest Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.48%	3.83%	4.57%
Salary [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Rate of compensation increase	3.00%	3.00%	4.00%
Salary [Member] | Pension Benefits [Member] | Obligation [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.13%	3.83%	4.57%
Salary [Member] | Pension Benefits [Member] | Service Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.14%	3.83%	4.57%
Salary [Member] | Pension Benefits [Member] | Interest Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.21%	3.83%	4.57%
Salary [Member] | Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Rate of compensation increase	3.00%	3.00%	4.00%
Salary [Member] | Other Benefits [Member] | Obligation [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.22%	3.83%	4.57%
Salary [Member] | Other Benefits [Member] | Service Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.63%	3.83%	4.57%
Salary [Member] | Other Benefits [Member] | Interest Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.31%	3.83%	4.57%
Ore Mining [Domain] | Pension Benefits [Member] | Obligation [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.28%	3.83%	4.57%
Ore Mining [Domain] | Pension Benefits [Member] | Service Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.60%	3.83%	4.57%
Ore Mining [Domain] | Pension Benefits [Member] | Interest Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.48%	3.83%	4.57%
SERP [Domain] | Pension Benefits [Member] | Obligation [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.01%	3.83%	4.57%
SERP [Domain] | Pension Benefits [Member] | Service Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.87%	3.83%	4.57%
SERP [Domain] | Pension Benefits [Member] | Interest Cost [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.30%	3.83%	4.57%

PENSIONS AND OTHER POSTRETIRE84

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Assumed Health Care Cost Trend Rates) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Health care cost trend rate assumed for next year	6.50%	6.75%
Ultimate health care cost trend rate	5.00%	5.00%

PENSIONS AND OTHER POSTRETIRE85

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Change of One Percentage Point in Assumed Health Care Cost Trend Rates) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Effect on total of service and interest cost due to one percentage point increase	$ 1.3
Effect on total of service and interest cost due to one percentage point decrease	(1)
Effect on postretirement benefit obligation due to one percentage point increase	23.4
Effect on postretirement benefit obligation due to one percentage point decrease	$ (19.6)

PENSIONS AND OTHER POSTRETIRE86

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Target Allocation and Actual Asset Allocations for Pension and VEBA Plan Assets) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	100.00%	100.00%
Defined Benefit Plan, Target Plan Asset Allocations	100.00%
Pension Benefits [Member] | Equity Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	43.20%	44.00%
Defined Benefit Plan, Target Plan Asset Allocations	45.00%
Pension Benefits [Member] | Fixed Income Investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	26.40%	27.70%
Defined Benefit Plan, Target Plan Asset Allocations	28.00%
Pension Benefits [Member] | Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	5.90%	5.80%
Defined Benefit Plan, Target Plan Asset Allocations	5.00%
Pension Benefits [Member] | Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	5.30%	4.70%
Defined Benefit Plan, Target Plan Asset Allocations	7.00%
Pension Benefits [Member] | Structured Finance [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	9.30%	8.90%
Defined Benefit Plan, Target Plan Asset Allocations	7.50%
Pension Benefits [Member] | Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	9.00%	8.20%
Defined Benefit Plan, Target Plan Asset Allocations	7.50%
Pension Benefits [Member] | Cash [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	0.90%	0.70%
Defined Benefit Plan, Target Plan Asset Allocations	0.00%
Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	100.00%	100.00%
Defined Benefit Plan, Target Plan Asset Allocations	100.00%
Other Benefits [Member] | Equity Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	8.40%	8.80%
Defined Benefit Plan, Target Plan Asset Allocations	8.00%
Other Benefits [Member] | Fixed Income Investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	78.30%	78.20%
Defined Benefit Plan, Target Plan Asset Allocations	80.10%
Other Benefits [Member] | Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	4.40%	4.50%
Defined Benefit Plan, Target Plan Asset Allocations	4.20%
Other Benefits [Member] | Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	1.70%	2.20%
Defined Benefit Plan, Target Plan Asset Allocations	2.60%
Other Benefits [Member] | Structured Finance [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	2.70%	2.30%
Defined Benefit Plan, Target Plan Asset Allocations	2.10%
Other Benefits [Member] | Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	4.40%	4.00%
Defined Benefit Plan, Target Plan Asset Allocations	3.00%
Other Benefits [Member] | Cash [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average asset allocation	0.10%	0.00%
Defined Benefit Plan, Target Plan Asset Allocations	0.00%

PENSIONS AND OTHER POSTRETIRE87

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Fair Values of Pension Plan Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	$ 202.4	$ 193.4	$ 188.1
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	685.8	700.6	749.8
Equity Securities [Member] | U S Large Cap [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	144.7	150.5
Equity Securities [Member] | U S Small Mid Cap [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	39.9	40.6
Equity Securities [Member] | International [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	111.8	116.8
Fixed Income Investments [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	181.2	194.2
Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	40.6	40.7	41.5
Hedge Funds [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	40.6	40.7
Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	36.1	33.1	31.2
Private Equity Funds [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	36.1	33.1
Structured Finance [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	63.8	62.1	65.4
Structured Finance [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	63.8	62.1
Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	61.9	57.5	$ 50
Real Estate [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	61.9	57.5
Cash [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	5.8	5.1
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	459.7	479.3
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | U S Large Cap [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	144.7	150.5
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | U S Small Mid Cap [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	39.9	40.6
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | International [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	111.8	116.8
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fixed Income Investments [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	157.5	166.3
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Hedge Funds [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Private Equity Funds [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Structured Finance [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Real Estate [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Cash [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	5.8	5.1
Fair Value, Inputs, Level 2 [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	23.7	27.9
Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | U S Large Cap [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | U S Small Mid Cap [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | International [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Fair Value, Inputs, Level 2 [Member] | Fixed Income Investments [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	23.7	27.9
Fair Value, Inputs, Level 2 [Member] | Hedge Funds [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Fair Value, Inputs, Level 2 [Member] | Private Equity Funds [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Fair Value, Inputs, Level 2 [Member] | Structured Finance [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Fair Value, Inputs, Level 2 [Member] | Real Estate [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Fair Value, Inputs, Level 2 [Member] | Cash [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	202.4	193.4
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | U S Large Cap [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | U S Small Mid Cap [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | International [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Investments [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Hedge Funds [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	40.6	40.7
Significant Unobservable Inputs (Level 3) [Member] | Private Equity Funds [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	36.1	33.1
Significant Unobservable Inputs (Level 3) [Member] | Structured Finance [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	63.8	62.1
Significant Unobservable Inputs (Level 3) [Member] | Real Estate [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	61.9	57.5
Significant Unobservable Inputs (Level 3) [Member] | Cash [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	$ 0	$ 0

PENSIONS AND POSTRETIREMENT BEN

PENSIONS AND POSTRETIREMENT BENEFITS (Effect of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) on Changes in Pension Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]
Fair value of plan assets — beginning of year	$ 193.4	$ 188.1
Actual return on plan assets:
Relating to assets still held at the reporting date	12.3	5.5
Purchases	8	5.7
Sales	14.6	8.4
Fair value of plan assets — end of year	202.4	193.4
Hedge Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]
Fair value of plan assets — beginning of year	40.7	41.5
Actual return on plan assets:
Relating to assets still held at the reporting date	(0.1)	(0.8)
Purchases	0	0
Sales	0	0
Fair value of plan assets — end of year	40.6	40.7
Private Equity Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]
Fair value of plan assets — beginning of year	33.1	31.2
Actual return on plan assets:
Relating to assets still held at the reporting date	(2.7)	1.5
Purchases	8	5.7
Sales	6	7.8
Fair value of plan assets — end of year	36.1	33.1
Structured Finance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]
Fair value of plan assets — beginning of year	62.1	65.4
Actual return on plan assets:
Relating to assets still held at the reporting date	10	(3.3)
Purchases	0	0
Sales	8	0
Fair value of plan assets — end of year	63.8	62.1
Real Estate [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]
Fair value of plan assets — beginning of year	57.5	50
Actual return on plan assets:
Relating to assets still held at the reporting date	5.1	8.1
Purchases	0	0
Sales	0.6	0.6
Fair value of plan assets — end of year	$ 61.9	$ 57.5

PENSIONS AND OTHER POSTRETIRE89

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Fair Values of Other Benefit Plan Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 202.4	$ 193.4	$ 188.1
Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	40.6	40.7	41.5
Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	36.1	33.1	31.2
Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	61.9	57.5	50
Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	253	250.6	269.3
Other Benefits [Member] | Equity Securities [Member] | U S Large Cap [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	10.6	11.1
Other Benefits [Member] | Equity Securities [Member] | U S Small Mid Cap [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2.7	2.8
Other Benefits [Member] | Equity Securities [Member] | International [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	8.1	8.2
Other Benefits [Member] | Fixed Income Investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	197.9	196
Other Benefits [Member] | Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.2	11.2
Other Benefits [Member] | Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4.3	5.5
Other Benefits [Member] | Structured Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6.9	5.8
Other Benefits [Member] | Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.1	10
Other Benefits [Member] | Cash [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0.2	0
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	183.6	180.2
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | U S Large Cap [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	10.6	11.1
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | U S Small Mid Cap [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2.7	2.8
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | International [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	8.1	8.2
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fixed Income Investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	162	158.1
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Structured Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Cash [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0.2	0
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	35.9	37.9
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | U S Large Cap [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | U S Small Mid Cap [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | International [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Fixed Income Investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	35.9	37.9
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Structured Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Cash [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	33.5	32.5	32.5
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | U S Large Cap [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | U S Small Mid Cap [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | International [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.2	11.2	11.5
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4.3	5.5	6.2
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Structured Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6.9	5.8	6.1
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.1	10	$ 8.7
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Cash [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 0	$ 0

PENSION AND OTHER POSTRETIREMEN

PENSION AND OTHER POSTRETIREMENT BENEFITS (Effect of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) on Changes in Other Benefit Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	$ 193.4	$ 188.1
Actual return on plan assets:
Relating to assets still held at the reporting date	12.3	5.5
Acquired through business combinations	8	5.7
Sales	14.6	8.4
Fair value of plan assets — end of year	202.4	193.4
Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	40.7	41.5
Actual return on plan assets:
Relating to assets still held at the reporting date	(0.1)	(0.8)
Acquired through business combinations	0	0
Sales	0	0
Fair value of plan assets — end of year	40.6	40.7
Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	33.1	31.2
Actual return on plan assets:
Relating to assets still held at the reporting date	(2.7)	1.5
Acquired through business combinations	8	5.7
Sales	6	7.8
Fair value of plan assets — end of year	36.1	33.1
Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	57.5	50
Actual return on plan assets:
Relating to assets still held at the reporting date	5.1	8.1
Acquired through business combinations	0	0
Sales	0.6	0.6
Fair value of plan assets — end of year	61.9	57.5
Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	250.6	269.3
Actual return on plan assets:
Fair value of plan assets — end of year	253	250.6
Other Benefits [Member] | Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	11.2
Actual return on plan assets:
Fair value of plan assets — end of year	11.2	11.2
Other Benefits [Member] | Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	5.5
Actual return on plan assets:
Fair value of plan assets — end of year	4.3	5.5
Other Benefits [Member] | Structured Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	5.8
Actual return on plan assets:
Fair value of plan assets — end of year	6.9	5.8
Other Benefits [Member] | Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	10
Actual return on plan assets:
Fair value of plan assets — end of year	11.1	10
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	32.5	32.5
Actual return on plan assets:
Relating to assets still held at the reporting date	1.9	1
Acquired through business combinations	0	0.1
Sales	1	1.5
Fair value of plan assets — end of year	33.5	32.5
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	11.2	11.5
Actual return on plan assets:
Relating to assets still held at the reporting date	0	(0.3)
Acquired through business combinations	0	0
Sales	0	0
Fair value of plan assets — end of year	11.2	11.2
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	5.5	6.2
Actual return on plan assets:
Relating to assets still held at the reporting date	(0.3)	0.3
Acquired through business combinations	0	0.1
Sales	1	1.5
Fair value of plan assets — end of year	4.3	5.5
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Structured Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	5.8	6.1
Actual return on plan assets:
Relating to assets still held at the reporting date	1.1	(0.3)
Acquired through business combinations	0	0
Sales	0	0
Fair value of plan assets — end of year	6.9	5.8
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	10	8.7
Actual return on plan assets:
Relating to assets still held at the reporting date	1.1	1.3
Acquired through business combinations	0	0
Sales	0	0
Fair value of plan assets — end of year	$ 11.1	$ 10

PENSIONS AND OTHER POSTRETIRE91

PENSIONS AND OTHER POSTRETIREMENT BENEFITS PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Unobservable Inputs, Level 3) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 202.4	$ 193.4	$ 188.1
Defined Benefit Plan, Actual Return on Plan Assets Still Held	12.3	5.5
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	3.3	2.5
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	8	5.7
Defined Benefit Plan, Divestitures, Plan Assets	(14.6)	(8.4)
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	253	250.6	269.3
Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	36.1	33.1	31.2
Defined Benefit Plan, Actual Return on Plan Assets Still Held	(2.7)	1.5
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	3.7	2.5
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	8	5.7
Defined Benefit Plan, Divestitures, Plan Assets	(6)	(7.8)
Private Equity Funds [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4.3	5.5
Structured Finance [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	63.8	62.1	65.4
Defined Benefit Plan, Actual Return on Plan Assets Still Held	10	(3.3)
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	(0.3)	0
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	0
Defined Benefit Plan, Divestitures, Plan Assets	(8)	0
Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	61.9	57.5	50
Defined Benefit Plan, Actual Return on Plan Assets Still Held	5.1	8.1
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	(0.1)	0
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	0
Defined Benefit Plan, Divestitures, Plan Assets	(0.6)	(0.6)
Real Estate [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.1	10
Structured Credit [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6.9	5.8
Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	40.6	40.7	41.5
Defined Benefit Plan, Actual Return on Plan Assets Still Held	(0.1)	(0.8)
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	0
Defined Benefit Plan, Divestitures, Plan Assets	0	0
Hedge Funds [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.2	11.2
Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	33.5	32.5	32.5
Defined Benefit Plan, Actual Return on Plan Assets Still Held	1.9	1
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0.1	0.4
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	0.1
Defined Benefit Plan, Divestitures, Plan Assets	(1)	(1.5)
Fair Value, Inputs, Level 3 [Member] | Private Equity Funds [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4.3	5.5	6.2
Defined Benefit Plan, Actual Return on Plan Assets Still Held	(0.3)	0.3
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0.1	0.4
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	0.1
Defined Benefit Plan, Divestitures, Plan Assets	(1)	(1.5)
Fair Value, Inputs, Level 3 [Member] | Real Estate [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.1	10	8.7
Defined Benefit Plan, Actual Return on Plan Assets Still Held	1.1	1.3
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	0
Defined Benefit Plan, Divestitures, Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Structured Credit [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6.9	5.8	6.1
Defined Benefit Plan, Actual Return on Plan Assets Still Held	1.1	(0.3)
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	0
Defined Benefit Plan, Divestitures, Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member] | Hedge Funds [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.2	11.2	$ 11.5
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0	(0.3)
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	0
Defined Benefit Plan, Divestitures, Plan Assets	$ 0	$ 0

PENSIONS AND OTHER POSTRETIRE92

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Annual Contributions To The Pension Plans) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Funded Percentage	70.00%
Company contributions	$ 1.1	$ 3.5
Expected company contributions, next fiscal year	$ 4.1
Value of VEBA Trust Assets as a Percentage of the Funding Obligation	0.9
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Company contributions	$ 1.2	35.7
Expected company contributions, next fiscal year	24.5
Direct Payments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Company contributions	1.1	3.5
Expected company contributions, next fiscal year	4.1
Veba Trust [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Company contributions	0	$ 0
Expected company contributions, next fiscal year	$ 0

PENSIONS AND OTHER POSTRETIRE93

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Estimated Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated net periodic benefit cost	$ 13.3
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Contributions by Plan Participants	0	$ 0
Estimated net periodic benefit cost	18.6
Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Contributions by Plan Participants	6	$ 4
Estimated net periodic benefit cost	$ (5.3)

PENSION AND OTHER POSTRETIREM94

PENSION AND OTHER POSTRETIREMENT BENEFITS (Estimated Future Benefit Payments) (Details) $ in Millions	Dec. 31, 2016USD ($)
Net Company Payments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,017	$ 19.1
2,018	19.3
2,019	18.3
2,020	17.5
2,021	16.7
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	76.6
Less Medicare Subsidy [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,017	0.6
2,018	0.7
2,019	0.8
2,020	0.9
2,021	0.9
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	5.2
Gross Company Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,017	19.7
2,018	20
2,019	19.1
2,020	18.4
2,021	17.6
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	81.8
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,017	77.3
2,018	64.8
2,019	63.3
2,020	63
2,021	62.4
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	$ 308

PENSIONS AND OTHER POSTRETIRE95

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Other Potential Benefit Obligations) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 202.4	$ 193.4	$ 188.1
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	685.8	700.6	749.8
Defined Benefit Plan, Benefit Obligation	(931.6)	(910.8)	(998)
Defined Benefit Plan, Funded Status of Plan	(245.8)	(210.2)
Additional shutdown and early retirement benefits	22.1
Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	253	250.6	269.3
Defined Benefit Plan, Benefit Obligation	(264.6)	(266)	$ (295.8)
Defined Benefit Plan, Funded Status of Plan	(11.6)	$ (15.4)
Additional shutdown and early retirement benefits	$ 2.2

PENSIONS AND OTHER POSTRETIRE96

PENSIONS AND OTHER POSTRETIREMENT BENEFITS PENSIONS AND OTHER POSTRETIREMENT BENEFITS ( Fair Value of Recurring) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 202.4	$ 193.4	$ 188.1
Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	40.6	40.7	41.5
Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	36.1	33.1	31.2
Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	61.9	57.5	50
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	253	250.6	269.3
Other Postretirement Benefit Plan, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	35.9	37.9
Other Postretirement Benefit Plan, Defined Benefit [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	33.5	32.5	32.5
Other Postretirement Benefit Plan, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	183.6	180.2
Other Postretirement Benefit Plan, Defined Benefit [Member] | Fixed Income Investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	197.9	196
Other Postretirement Benefit Plan, Defined Benefit [Member] | Fixed Income Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	35.9	37.9
Other Postretirement Benefit Plan, Defined Benefit [Member] | Fixed Income Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Fixed Income Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	162	158.1
Other Postretirement Benefit Plan, Defined Benefit [Member] | Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.2	11.2
Other Postretirement Benefit Plan, Defined Benefit [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.2	11.2	11.5
Other Postretirement Benefit Plan, Defined Benefit [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4.3	5.5
Other Postretirement Benefit Plan, Defined Benefit [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4.3	5.5	6.2
Other Postretirement Benefit Plan, Defined Benefit [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Structured Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6.9	5.8
Other Postretirement Benefit Plan, Defined Benefit [Member] | Structured Credit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Structured Credit [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6.9	5.8	6.1
Other Postretirement Benefit Plan, Defined Benefit [Member] | Structured Credit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.1	10
Other Postretirement Benefit Plan, Defined Benefit [Member] | Real Estate [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Real Estate [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.1	10	$ 8.7
Other Postretirement Benefit Plan, Defined Benefit [Member] | Real Estate [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Cash [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0.2	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Cash [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Cash [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0.2	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | U S Small Mid Cap [Member] | Equity Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2.7	2.8
Other Postretirement Benefit Plan, Defined Benefit [Member] | U S Small Mid Cap [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | U S Small Mid Cap [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | U S Small Mid Cap [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2.7	2.8
Other Postretirement Benefit Plan, Defined Benefit [Member] | International [Member] | Equity Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	8.1	8.2
Other Postretirement Benefit Plan, Defined Benefit [Member] | International [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | International [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | International [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	8.1	8.2
Other Postretirement Benefit Plan, Defined Benefit [Member] | U S Large Cap [Member] | Equity Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	10.6	11.1
Other Postretirement Benefit Plan, Defined Benefit [Member] | U S Large Cap [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | U S Large Cap [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | U S Large Cap [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 10.6	$ 11.1

STOCK COMPENSATION PLANS (Narra

STOCK COMPENSATION PLANS (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016USD ($)AgreementPlanshares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Plans | Plan	2
Allocated Share-based Compensation Expense | $	$ 14,200,000	$ 13,900,000	$ 21,500,000
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense | $	$ 0	$ 0	$ 7,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Plan Year Agreements | Agreement	3
Number of performance shares granted	3,571,337
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized | $	$ 14,700,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 9 months 15 days
Option Indexed to Issuer's Equity, Strike Price | $ / shares		$ 13.83
Common Stock, Shares Authorized	400,000,000	400,000,000
2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance/vesting period	27 months
2015 Equity Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares that may be issued (in shares)	12,900,000
Two Thousand Twelve Equity Plan and Amended Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Available for Issuance Proposed to be added to the Plan	5,000,000
Directors Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Arrangement with Individual, Fair Value of Shares Issued | $	$ 85,000
2012 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance/vesting period	3 years
Number of shares granted under the award	900,000
Number of performance shares granted	900,000
Number of restricted shares granted	400,000
Change in Control [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense | $		$ 11,700,000
2015 to 2017 Performance Period [Member] | 2012 Equity Plan [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout rate, as a percentage of the original grant	0.00%
2015 to 2017 Performance Period [Member] | 2012 Equity Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout rate, as a percentage of the original grant	200.00%
Restricted Stock Units (RSUs) [Member] | 2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance/vesting period	3 years
Number of restricted shares granted	3,400,000	1,500,000
Cliffs Natural Resource Inc. 2015 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Shares Authorized	10,000,000

STOCK COMPENSATION PLANS STOCK

STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Incentive Plan Details) (Details) - shares	Feb. 09, 2015	Dec. 31, 2016	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance shares granted						3,571,337
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance shares granted	410,105	464,470	188,510	80,560	230,265	0	874,575	1,233,685
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Estimated Forfeitures		82,636	188,510	80,560	230,265	157,979
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Expected to Vest		381,834	0	0	0	252,126

STOCK COMPENSATION PLANS STOC99

STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Nonemployee Directors) (Details)	12 Months Ended
	Dec. 31, 2016USD ($)
Directors Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Arrangement with Individual, Fair Value of Shares Issued	$ 85,000

STOCK COMPENSATION PLANS STO100

STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Incentive Compensation and Other Benefit Plans for Employees and Directors) (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restricted Equity Grant Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period Shares Director Stock Award	135,038	109,408	73,635
Deferred Equity Grant Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period Shares Director Stock Award	29,583	25,248	0

STOCK COMPENSATION PLANS STO101

STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Schedule of Compensation Costs) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Selling, General and Administrative Expense										$ 117.8	$ 110	$ 154.7
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest										207	313.1	(19.7)
Income Tax Expense (Benefit)										(12.2)	169.3	(86)
Net Income (Loss) Attributable to Parent						$ 10.6	$ 60.2	$ (759.8)	$ (60.3)	$ 174.1	$ (749.3)	$ (7,224.2)
Earnings Per Share, Basic	$ 0.35	$ (0.12)	$ 0.07	$ 0.62	$ (0.39)	$ (0.10)	$ 0.39	$ (5.04)		$ 0.88	$ (5.14)	$ (47.52)
Earnings Per Share, Diluted	$ 0.34	$ (0.12)	$ 0.07	$ 0.62	$ (0.39)	$ (0.10)	$ 0.39	$ (4.26)		$ 0.87	$ (5.13)	$ (47.52)
Deferred Compensation, Share-based Payments [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Costs and Expenses										$ 2.1	$ 4	$ 5.6
Selling, General and Administrative Expense										12.1	9.9	15.9
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest										14.2	13.9	21.5
Income Tax Expense (Benefit)										0	0	(7.5)
Net Income (Loss) Attributable to Parent										$ 14.2	$ 13.9	$ 14
Earnings Per Share, Basic										$ 0.07	$ 0.09	$ 0.09
Earnings Per Share, Diluted										$ 0.07	$ 0.09	$ 0.09

STOCK COMPENSATION PLANS STO102

STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Outstanding Employee Awards) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	7,430,122	4,442,048
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 5.55	$ 8.93
Number of performance shares granted	3,571,337
Fair Value	$ 1.93
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	(331,248)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$ 11.25
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(252,015)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 5.90

STOCK COMPENSATION PLANS STO103

STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Share Based Compensation Arrangement by Share-based Payment Award) (Details) - USD ($)	Feb. 09, 2015	Dec. 31, 2016	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price		417,914				417,914
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price		$ 8.88				$ 8.88
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value		$ 239,640				$ 239,640
Option Indexed to Issuer's Equity, Strike Price							$ 13.83
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number		7,430,122				7,430,122	4,442,048
Number of performance shares granted						3,571,337
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period						(331,248)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period						(252,015)
Common Stock, Capital Shares Reserved for Future Issuance		7,190,716				7,190,716
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term						7 years 5 months 4 days
Fair Value						$ 1.93
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options		166,667				166,667
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price		$ 13.83				$ 13.83
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value		$ 0				$ 0
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Remaining Contractual Term						4 years 10 months 16 days
Restricted Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number		599,870				599,870	607,489	250,000	0
Number of performance shares granted						0	412,710	250,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period						(7,619)	(55,221)	0
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number		5,461,783				5,461,783	2,338,070	523,176	586,084
Number of performance shares granted						3,571,337	2,482,415	531,030
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period						(271,988)	(477,157)	(423,822)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period						(175,636)	(190,364)	(170,116)
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number		1,368,469				1,368,469	1,496,489	1,072,376	1,040,453
Number of performance shares granted	410,105	464,470	188,510	80,560	230,265	0	874,575	1,233,685
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period						(59,260)	(242,920)	(796,624)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period						(68,760)	(207,542)	(405,138)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested or Expected to Vest, Outstanding, Number		6,716,979				6,716,979
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Estimated Forfeitures		82,636	188,510	80,560	230,265	157,979
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Expected to Vest		381,834	0	0	0	252,126
Directors Retainer and Voluntary Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number		0				0	0	0	7,329
Number of performance shares granted						0	0	2,281
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period						0	0	(9,610)
January 12, 2015 [Member] | Restricted Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Date Market Price						$ 7.70
Employee Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance		6,514,038				6,514,038
Directors Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance		676,678				676,678

INCOME TAXES (Narrative) (Detai

INCOME TAXES (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 30.7	$ 156.2	$ 72.6	$ 71.8
Undistributed Earnings of Foreign Subsidiaries	0	0
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	3,700	3,900
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	6,900	11,100
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	5.8	5.8
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	251.2	218.7
Valuation Allowance, Deferred Tax Asset, Change in Amount	0
Impact Of Tax Law Change	$ 149.1	$ 0	$ 13
Effective Income Tax Rate, Continuing Operations	35.00%	35.00%	35.00%
Current Fiscal Year End Date	--12-31
Reversal of Valuation Allowance on MRRT credits [Member]
Income Tax Contingency [Line Items]
Valuation Allowance, Deferred Tax Asset, Change in Amount	$ 33.1
Close of Audits [Domain]
Income Tax Contingency [Line Items]
Valuation Allowance, Deferred Tax Asset, Change in Amount	39.6
Tax Asset, Current Year Activity [Domain]
Income Tax Contingency [Line Items]
Valuation Allowance, Deferred Tax Asset, Change in Amount	104.9
Other Noncurrent Assets [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	22.4	$ 134.7
Other Liabilities [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	8.3	21.5
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	0.8	$ 2.1
Deferred Tax Asset, Alternative Minimum Tax Credit Not Utilized [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	$ 1,400

INCOME TAXES INCOME TAXES (SCHE

INCOME TAXES INCOME TAXES (SCHEDULE OF INCOME BEFORE INCOME TAXES) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Domestic	$ 124.9	$ 314.2	$ (447.5)
Income (Loss) from Continuing Operations before Income Taxes, Foreign	82.1	(1.1)	427.8
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	$ 207	$ 313.1	$ (19.7)

INCOME TAXES INCOME TAXES (S106

INCOME TAXES INCOME TAXES (Schedule of Components of Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Current Federal Tax Expense (Benefit)	$ (11.1)	$ 8.2	$ (125.2)
Current State and Local Tax Expense (Benefit)	(0.5)	0.3	(0.6)
Current Foreign Tax Expense (Benefit)	(0.1)	0.9	11.7
Current Income Tax Expense (Benefit)	(11.7)	9.4	(114.1)
Deferred Federal Income Tax Expense (Benefit)	(0.5)	165.8	20.4
Deferred State and Local Income Tax Expense (Benefit)	0	0	(24.9)
Deferred Foreign Income Tax Expense (Benefit)	0	(5.9)	32.6
Deferred Income Tax Expense (Benefit)	0	159.8	(1,153.9)
Income Tax Expense (Benefit)	(12.2)	169.3	(86)
Deferred Provision (Benefit) [Member]
Income Tax Contingency [Line Items]
Deferred Income Tax Expense (Benefit)	$ (0.5)	$ 159.9	$ 28.1

INCOME TAXES INCOME TAXES (S107

INCOME TAXES INCOME TAXES (Schedule of Effective Rate Reconciliation) (Details) - USD ($) AUD / $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2014
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ 72.5			$ 109.6			$ (6.9)
Effective Income Tax Rate Reconciliation, Percent		35.00%			35.00%			35.00%
Non-taxable loss (income) related to noncontrolling interests	(8.8)			(3)			(9.4)
Non-taxable loss (income) related to noncontrolling interests percent		(4.20%)			(1.00%)			47.70%
Impact Of Tax Law Change	149.1			0			13
Impact Of Tax Law Change Percent		72.00%			0.00%			(66.00%)
Income Tax Reconciliation Tax Deduction for percentage depletion in excess of cost depletion	(36.1)			(34.9)			(87.9)
Income Tax Reconciliation Tax Deduction for percentage depletion in excess of cost depletion percent		(17.40%)			(11.10%)			446.20%
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	(42.7)			(53.9)			51.4
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent		(20.60%)			(17.20%)			(260.90%)
Income not subject to tax	0			0			(27.7)
Income not subject to tax percent		0.00%			0.00%			140.60%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Amount	0			0			22.7
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Percent		0.00%			0.00%			(115.20%)
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	0.4			0.2			(25.4)
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent		0.20%			0.10%			128.90%
Effective Income Tax Rate Reconciliation, Tax Settlement, Amount	0			0			(347.1)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		0.00%			0.00%			1761.90%
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	93.9			(104.6)			318.3
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent		45.40%			(33.40%)			(1615.70%)
Effective Income Tax Reconciliation, Valuation Allowance Prior Year	(142.6)			165.8			15.2
Effective Income Tax Reconciliation, Valuation Allowance Prior Year, Percent		(68.90%)			52.90%			(77.20%)
Tax Adjustments, Settlements, and Unusual Provisions	(11.3)			84.1			0
Tax Adjustments Settlements And Unusual Provisions Percent		(5.50%)			26.90%			0.00%
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Percent		(5.70%)	(1180.00%)		1.90%	590.00%		32.10%	(630.00%)
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	(1.4)			0.1			4.1
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent		(0.70%)			0.00%			(20.90%)
Income Tax Expense (Benefit)	(12.2)			169.3			(86)
Income Tax Expense Benefit Percent		(5.90%)			54.10%			436.50%
Worthless Stock Deduction, Amount	$ (73.4)			$ 0			$ 0
Worthless Stock Deduction, Percent		(35.50%)			0.00%			0.00%

INCOME TAXES INCOME TAXES (Inco

INCOME TAXES INCOME TAXES (Income Taxes for Other than Continuing Operations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax	$ 0	$ 0	$ 37.1
Other Comprehensive Income Unrealized Gain Loss On Mark To Market Adjustments Arising During Period Tax	0	0.3	3.6
Other Comprehensive Income (Loss), Other Tax	0.5	5.9	0.2
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	0.5	6.2	40.9
Income Tax Effects Allocated Directly to Equity, Equity Transactions	0	0	(4.8)
Discontinued Operation, Tax Effect of Discontinued Operation	$ 0	$ (6)	$ (1,216)

INCOME TAXES INCOME TAXES (S109

INCOME TAXES INCOME TAXES (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Pensions	$ 114.6	$ 106.6
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Postretirement Benefits	35.2	36.5
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	251.2	218.7
Deferred Tax Assets, Deferred Income	44.5	57.2
Deferred Tax Assets, Amortization	71.3	0
Deferred Tax Assets Development Costs	0	4.9
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Asset Retirement Obligations	22.3	5.3
Deferred Tax Assets, Operating Loss Carryforwards	2,699.7	2,791.6
Deferred Tax Assets, Property, Plant and Equipment	181.2	189.8
Deferred Tax Assets, State Taxes	59.2	59.9
Deferred Tax Assets Leasing Arrangements	12.9	18.3
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Other	108.3	148.9
Deferred Tax Assets, Gross	3,600.4	3,637.7
Deferred Tax Assets, Valuation Allowance	(3,334.8)	(3,372.5)
Deferred Tax Assets, Net of Valuation Allowance	265.6	265.2
Deferred Tax Liabilities, Property, Plant and Equipment	(34)	(35.5)
Deferred Tax Liabilities Investment In Ventures	(203.1)	(206.6)
Deferred Tax Liabilities, Intangible Assets	(1)	(1.5)
Deferred Tax Liabilities, Tax Deferred Income	(3.4)	(2.5)
Deferred Tax Liabilities Other Assets	(24.1)	(19.1)
Deferred Tax Liabilities, Net	(265.6)	(265.2)
Deferred Tax Assets, Net	$ 0	$ 0

INCOME TAXES INCOME TAXES (S110

INCOME TAXES INCOME TAXES (Schedule of Deferred Tax Assets and Liabilities by Location) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Deferred Tax Assets, Net	$ 0	$ 0

INCOME TAXES INCOME TAXES (S111

INCOME TAXES INCOME TAXES (Schedule of Unrecognized Tax Benefits Rollforward) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 30.7	$ 156.2	$ 72.6	$ 71.8
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions	(61)
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions		6.7	0
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	0.2	78.5	5.9
Unrecognized Tax Benefits Increases Decreases Resulting From Currency Translation	0	0	(0.2)
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	(64.7)	(1.1)	0
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	(0.5)	(3.7)
Other Increases decreases to unrecognized tax benefits	$ 0	$ 0	$ (1.2)

LEASE OBLIGATIONS (Narrative) (

LEASE OBLIGATIONS (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Leased Assets [Line Items]
Capital Leased Assets, Gross	$ 29.3	$ 32.5
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	13.1	8.7
Operating lease expense	$ 7.6	$ 12	$ 17.8

LEASE OBLIGATIONS (Future Minim

LEASE OBLIGATIONS (Future Minimum Lease Payments) (Details) $ in Millions	Dec. 31, 2016USD ($)
Capital Leases
2,016	$ 22
2,017	17.9
2,018	9.9
2,019	9
2,020	8.3
2021 and thereafter	0.7
Total minimum lease payments	67.8
Amounts representing interest	12
Present value of net minimum lease payments	55.8
Operating Leases
2,016	6.9
2,017	5.6
2,018	3
2,019	2.9
2,020	3
2021 and thereafter	0
Total minimum lease payments	21.4
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	$ 38.4

ENVIRONMENTAL AND MINE CLOSU114

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)T	Dec. 31, 2015USD ($)
Site Contingency [Line Items]
Accrual for Environmental Loss Contingencies, Period Increase (Decrease)	$ 9.2	$ (45.2)
Proved Developed and Undeveloped Reserves, Net, Period Increase (Decrease) | T	115,000,000
Environmental Loss Contingency And Mine Reclamation And Closing Liability Current And Noncurrent	$ 206.8	234
Payments for Environmental Liabilities	2.4	2.6
Accrual for Environmental Loss Contingencies	2.8	3.6
Mine Reclamation and Closing Liability, current and noncurrent	204	230.4
Previously Owned Or Operating Facilities [Member] | LTV Steel Mining Company [Member]
Site Contingency [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	25.5	$ 24.1
Selenium [Domain]
Site Contingency [Line Items]
Accrual for Environmental Loss Contingencies, Period Increase (Decrease)	$ 29.6

ENVIRONMENTAL AND MINE CLOSU115

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Summary Of Mine Closure Obligations) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Environmental	$ 2.8	$ 3.6
Mine Reclamation and Closing Liability, current and noncurrent	204	230.4
Environmental Loss Contingency And Mine Reclamation And Closing Liability Current And Noncurrent	206.8	234
Environmental Loss Contingency And Mine Reclamation And Closing Liability Current	12.9	2.8
Environmental Loss Contingency And Mine Reclamation And Closing Liability Noncurrent	193.9	231.2
U.S. Iron Ore [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	187.8	214
Asia Pacific Iron Ore [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	16.2	16.4
LTV Steel Mining Company [Member] | Previously Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	$ 25.5	$ 24.1

ENVIRONMENTAL AND MINE CLOSU116

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Asset Retirement Obligation Disclosure) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accrual for Environmental Loss Contingencies	$ 2.8	$ 3.6
Mine Reclamation and Closing Liability, current and noncurrent	204	230.4
Environmental Loss Contingency And Mine Reclamation And Closing Liability Current And Noncurrent	206.8	234
Environmental Loss Contingency And Mine Reclamation And Closing Liability Current	12.9	2.8
Environmental Loss Contingency And Mine Reclamation And Closing Liability Noncurrent	193.9	231.2
Asset Retirement Obligation	204	230.4	$ 165.3
Asset Retirement Obligation, Accretion Expense	14	7.7
Asset Retirement Obligation, Foreign Currency Translation Gain (Loss)	(0.2)	(1.1)
Asset Retirement Obligation, Liabilities Settled	(2.2)	0
Asset Retirement Obligation, Revision of Estimate	(38)	58.5
Previously Owned Or Operating Facilities [Member] | LTV Steel Mining Company [Member]
Mine Reclamation and Closing Liability, current and noncurrent	25.5	24.1
U.S. Iron Ore [Member] | Owned Or Operating Facilities [Member]
Mine Reclamation and Closing Liability, current and noncurrent	187.8	214
Asia Pacific Iron Ore [Member] | Owned Or Operating Facilities [Member]
Mine Reclamation and Closing Liability, current and noncurrent	$ 16.2	$ 16.4

GOODWILL AND OTHER INTANGIBL117

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Line Items]
Goodwill, Impairment Loss	$ 0	$ 0
Product	1,913,500,000	1,832,400,000	$ 3,095,200,000
Cost of Sales [Member]
Goodwill [Line Items]
Amortization expense relating to intangible assets	4,800,000	4,200,000	8,400,000
Sales Revenue, Goods, Net [Member] | Sales Revenue, Goods, Net [Member]
Goodwill [Line Items]
Product	23,100,000	$ 23,100,000	23,100,000
Permits [Member]
Goodwill [Line Items]
Impairment of Intangible Assets, Finite-lived	0		13,800,000
Asia Pacific Iron Ore [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss			$ 73,500,000
U.S. Iron Ore [Member]
Goodwill [Line Items]
Goodwill	$ 2,000,000

GOODWILL AND OTHER INTANGIBL118

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Schedule Of Finite-Lived Intangible Assets By Major Class) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	$ 78.4	$ 78.4
Definite lived intangible assets - Accumulated Amortization	(24.6)	(20.2)
Definite lived intangible assets - Net Carrying Amount	53.8	58.2
Below-market sales contracts, gross		(228.9)
Below-market sales contracts, accumulated amortization		205.8
Below-market sales contracts, net		(23.1)
Other Current Liabilities [Member]
Finite-Lived Intangible Assets [Line Items]
Below-market sales contracts, gross		(23.1)
Below-market sales contracts, net	0	(23.1)
Other Liabilities [Member]
Finite-Lived Intangible Assets [Line Items]
Below-market sales contracts, gross		(205.8)
Below-market sales contracts, accumulated amortization		205.8
Below-market sales contracts, net	0
Permits [Member] | Other Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	78.4	78.4
Definite lived intangible assets - Accumulated Amortization	(24.6)	(20.2)
Definite lived intangible assets - Net Carrying Amount	$ 53.8	$ 58.2

GOODWILL AND OTHER INTANGIBL119

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Estimated Amortization Expense Relating To Intangible Assets) (Details) $ in Millions	Dec. 31, 2016USD ($)
Estimated amortization expense, intangible assets [Abstract]
2,016	$ 1.9
2,017	1.9
2,018	2
2,019	1.6
2,020	1
Total	$ 8.4

DERIVATIVE INSTRUMENTS AND H120

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Current Fiscal Year End Date	--12-31
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 92,600,000	$ 5,500,000	$ 178,300,000
Accounts receivable, net	128,700,000	40,200,000
Foreign Exchange Contract [Member] | Other Nonoperating Income (Expense) [Member]
Derivative [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments			0
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	(3,600,000)
Foreign Exchange Contract [Member] | Product Revenues [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	(12,600,000)	0
Customer Supply Agreement [Member] | Not Designated as Hedging Instrument [Member] | Product Revenues [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	41,700,000	27,100,000	187,800,000
Customer Supply Agreement [Member] | Not Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative assets	21,300,000	5,800,000
Provisional Pricing Arrangements [Member] | Product Revenues [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	49,000,000	(1,400,000)	(9,500,000)
Provisional Pricing Arrangements [Member] | Not Designated as Hedging Instrument [Member] | U S Iron Ore And Asia Pacific Iron Ore [Member] | Product Revenues [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	49,000,000	(1,400,000)	$ (9,500,000)
Provisional Pricing Arrangements [Member] | Not Designated as Hedging Instrument [Member] | U S Iron Ore And Asia Pacific Iron Ore [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative assets	10,300,000	2,000,000
Provisional Pricing Arrangements [Member] | Not Designated as Hedging Instrument [Member] | U S Iron Ore And Asia Pacific Iron Ore [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative liabilities	500,000	3,400,000
$500 Million 3.95% 2018 Senior Notes [Member]
Derivative [Line Items]
Debt Instrument, Face Amount	$ 500,000,000	$ 500,000,000

DERIVATIVE INSTRUMENTS AND H121

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	$ 33.1	$ 7.8
Derivative liability, fair value	0.5	4
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Commodity Contract [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	1.5	0
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	0	0.6
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Customer Supply Agreement [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	21.3	5.8
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Provisional Pricing Arrangements [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	10.3	2
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	$ 0.5	$ 3.4

DERIVATIVE INSTRUMENTS AND H122

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Schedule Of Derivatives Not Designated As Hedging Instruments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 92.6	$ 5.5	$ 178.3
Foreign Exchange Contract [Member] | Product Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	(12.6)	0
Foreign Exchange Contract [Member] | Other Nonoperating Income (Expense) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	(3.6)
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments			0
Commodity Contract [Member] | Other Nonoperating Income (Expense) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	1.9	(4)	0
Customer Supply Agreements [Member] | Product Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	41.7	27.1	187.8
Provisional Pricing Arrangements [Member] | Product Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 49	$ (1.4)	$ (9.5)

DISCONTINUED OPERATIONS (Narrat

DISCONTINUED OPERATIONS (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Tax Effect of Discontinued Operation		$ 0	$ (6,000,000)	$ (1,216,000,000)
Tangible Asset Impairment Charges		0	0	537,800,000
Deconsolidation, Gain (Loss), Amount			(528,200,000)
LOSS FROM DISCONTINUED OPERATIONS, net of tax		(19,900,000)	(892,100,000)	(8,368,000,000)
Potential Earn Out from North American Coal sale		50,000,000
Canadian Entities [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue		0	11,300,000	563,500,000
Discontinued Operation, Tax Effect of Discontinued Operation		0	5,800,000	913,700,000
Deconsolidation, Gain (Loss), Amount		(17,500,000)	(710,900,000)	0
Disposal Group, including discontinued operations, Impairment of long-lived assets		0	0	(7,536,800,000)
Cost Method Investments		0	0
Disposal Group, Including Discontinued Operation, Costs of Goods Sold		0	(11,100,000)	(808,400,000)
Eliminations with Continuing Operations		0	0	(53,600,000)
Disposal Group, Including Discontinued Operation, Gross Profit (Loss)		0	200,000	(298,500,000)
Disposal Group, Including Discontinued Operation, Operating Expense		0	(33,800,000)	(306,300,000)
Disposal Group, Including Discontinued Operation, Other Expense		0	(1,000,000)	(5,600,000)
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax		0	(34,600,000)	(610,400,000)
LOSS FROM DISCONTINUED OPERATIONS, net of tax		(17,500,000)	(739,700,000)	(7,233,500,000)
North American Coal [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amounts released from escrow		10,300,000
Disposal Group, Including Discontinued Operation, Revenue		0	392,900,000	687,100,000
Discontinued Operations, Amounts Held in Escrow		0	14,900,000
Discontinued Operation, Tax Effect of Discontinued Operation		0	200,000	302,200,000
Tangible Asset Impairment Charges	$ 73,400,000
Disposal Group, Including Discontinued Operation, Costs of Goods Sold		0	(449,200,000)	(822,900,000)
Disposal Group, Including Discontinued Operation, Gross Profit (Loss)		0	(56,300,000)	(135,800,000)
Disposal Group, Including Discontinued Operation, Operating Expense		(4,500,000)	(30,400,000)	(20,800,000)
Disposal Group, Including Discontinued Operation, Other Expense		0	(1,800,000)	(3,000,000)
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax		(2,400,000)	(79,200,000)	(579,200,000)
LOSS FROM DISCONTINUED OPERATIONS, net of tax		(2,400,000)	(152,400,000)	$ (1,134,500,000)
Bloom Lake Group [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deconsolidation, Gain (Loss), Amount	$ 818,700,000
Contingent Liabilities of Deconsolidated Entities		0	(203,100,000)
Wabush Group [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deconsolidation, Gain (Loss), Amount			134,700,000
Other Current Assets [Member] | Canadian Entities [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Pre-Petition Financing		7,200,000
DIP Financing		6,800,000
Guarantees [Member] | Bloom Lake Group [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent Liabilities recognized in Consolidated Financials		200,000	96,500,000
Other Current Liabilities [Member] | Bloom Lake Group [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent Liabilities recognized in Consolidated Financials		37,000,000	35,900,000
Fair Value, Inputs, Level 3 [Member] | Other Current Assets [Member] | Canadian Entities [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans, Associated Interest and Accounts Receivable recognized in Consolidated Financials at Fair Value		48,600,000	$ 72,900,000
Maximum [Member] | Other Current Assets [Member] | Canadian Entities [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
DIP Financing		$ 10,000,000

DISCONTINUED OPERATIONS PreTax

DISCONTINUED OPERATIONS PreTax Exit Costs (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
PreTax Exit Costs [Line Items]
Deconsolidation, Gain (Loss), Amount			$ (528.2)
Canadian Entities [Member]
PreTax Exit Costs [Line Items]
Investment Impairment of Deconsolidation		$ (17.5)	(507.8)
Deconsolidation, Gain (Loss), Amount		(17.5)	(710.9)	$ 0
Bloom Lake Group [Member]
PreTax Exit Costs [Line Items]
Contingent Liabilities of Deconsolidated Entities		$ 0	$ (203.1)
Deconsolidation, Gain (Loss), Amount	$ 818.7

DISCONTINUED OPERATIONS Schedul

DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Assets and Liabilities - Canadian Entities (Details) CAD in Thousands, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2015USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Jun. 30, 2016CAD	Mar. 31, 2016CAD
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Deconsolidation, Gain (Loss), Amount			$ (528.2)
Sale amount for Pointe Noire port and rail assets | CAD						CAD 66,750
Sale Amount of the Bloom Lake Mine and Labrador Trough South mineral claims | CAD					CAD 10,500
Canadian Entities [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Deconsolidation, Gain (Loss), Amount		$ (17.5)	(710.9)	$ 0
Wabush [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Debtor-in-Possession Financing, Borrowings Outstanding		0
Bloom Lake Group [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Deconsolidation, Gain (Loss), Amount	$ 818.7
Other Current Assets [Member] | Canadian Entities [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Debtor-in-Possession Financing, Borrowings Outstanding		1.5
Debtor-in-possession,Repayment		8.3
Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Canadian Entities [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Loans, Associated Interest and Accounts Receivable recognized in Consolidated Financials at Fair Value		48.6	72.9
Other Current Liabilities [Member] | Bloom Lake Group [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Contingent Liabilities recognized in Consolidated Financials		37	35.9
Guarantees [Member] | Bloom Lake Group [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Contingent Liabilities recognized in Consolidated Financials		$ 0.2	$ 96.5

DISCONTINUED OPERATIONS Sche126

DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Assets and Liabilities - North American Coal (Details) CAD in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Jun. 30, 2016CAD	Mar. 31, 2016CAD
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Discontinued Operation, Tax Effect of Discontinued Operation	$ 0	$ (6,000,000)	$ (1,216,000,000)
Sale amount for Pointe Noire port and rail assets | CAD					CAD 66,750
Sale Amount of the Bloom Lake Mine and Labrador Trough South mineral claims | CAD				CAD 10,500
North American Coal [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Loss Contingency Accrual	2,100,000	7,800,000
Disposal Group, Including Discontinued Operation, Other Assets, Current	0	14,900,000
Disposal Group, Including Discontinued Operation, Assets	0	14,900,000
Disposal Group, Including Discontinued Operation, Accrued Liabilities	1,100,000	0
Disposal Group, Including Discontinued Operation, Other Liabilities, Current	4,900,000	6,900,000
Disposal Group, Including Discontinued Operation, Liabilities	6,000,000	6,900,000
Discontinued Operation, Tax Effect of Discontinued Operation	0	200,000	302,200,000
Canadian Entities [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Cost Method Investments	0	0
Discontinued Operation, Tax Effect of Discontinued Operation	$ 0	$ 5,800,000	$ 913,700,000

DISCONTINUED OPERATIONS Sche127

DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Income Statement - Canadian Entities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Disposal Groups, including Discontinued Operations, Income Statement [Line Items]
Deconsolidation, Gain (Loss), Amount		$ (528.2)
Discontinued Operation, Tax Effect of Discontinued Operation	$ 0	(6)	$ (1,216)
LOSS FROM DISCONTINUED OPERATIONS, net of tax	(19.9)	(892.1)	(8,368)
Canadian Entities [Member]
Schedule of Disposal Groups, including Discontinued Operations, Income Statement [Line Items]
Disposal Group, Including Discontinued Operation, Revenue	0	11.3	563.5
Disposal Group, Including Discontinued Operation, Costs of Goods Sold	0	11.1	808.4
Eliminations with Continuing Operations	0	0	(53.6)
Disposal Group, Including Discontinued Operation, Gross Profit (Loss)	0	0.2	(298.5)
Disposal Group, Including Discontinued Operation, Operating Expense	0	33.8	306.3
Disposal Group, Including Discontinued Operation, Other Expense	0	1	5.6
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax	0	(34.6)	(610.4)
Deconsolidation, Gain (Loss), Amount	(17.5)	(710.9)	0
Disposal Group, including discontinued operations, Impairment of long-lived assets	0	0	(7,536.8)
Discontinued Operation, Tax Effect of Discontinued Operation	0	5.8	913.7
LOSS FROM DISCONTINUED OPERATIONS, net of tax	$ (17.5)	$ (739.7)	$ (7,233.5)

DISCONTINUED OPERATIONS Sche128

DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Income Statement - North American Coal (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Discontinued Operation, Tax Effect of Discontinued Operation	$ 0	$ (6)	$ (1,216)
LOSS FROM DISCONTINUED OPERATIONS, net of tax	(19.9)	(892.1)	(8,368)
North American Coal [Member]
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]
Disposal Group, Including Discontinued Operation, Revenue	0	392.9	687.1
Disposal Group, Including Discontinued Operation, Costs of Goods Sold	0	(449.2)	(822.9)
Disposal Group, Including Discontinued Operation, Gross Profit (Loss)	0	(56.3)	(135.8)
Disposal Group, Including Discontinued Operation, Operating Expense	(4.5)	(30.4)	(20.8)
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax	2.1	9.3	(419.6)
Disposal Group, Including Discontinued Operation, Other Expense	0	(1.8)	(3)
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax	(2.4)	(79.2)	(579.2)
Impairment of Long-Lived Assets to be Disposed of	0	(73.4)	(857.5)
Discontinued Operation, Tax Effect of Discontinued Operation	0	0.2	302.2
LOSS FROM DISCONTINUED OPERATIONS, net of tax	$ (2.4)	$ (152.4)	$ (1,134.5)

DISCONTINUED OPERATIONS Sche129

DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Income Statement, Balance Sheet and Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
LOSS FROM DISCONTINUED OPERATIONS, net of tax	$ (19.9)	$ (892.1)	$ (8,368)
Income (Loss) from Discontinued Operations, net of tax, including portion attributable to Noncontrolling interest, Canadian Entities and North American Coal			(8,368)
Short-term assets of discontinued operations		14.9
Short-term liabilities of discontinued operations	6	6.9
Depreciation, depletion and amortization	115.4	134	504
Payments to Acquire Property, Plant, and Equipment	69.1	80.8	284.1
Impairment of goodwill and other long-lived assets	0	76.6	9,029.9
North American Coal [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
LOSS FROM DISCONTINUED OPERATIONS, net of tax	(2.4)	(152.4)	(1,134.5)
Short-term assets of discontinued operations		14.9
Short-term liabilities of discontinued operations	6	6.9
Depreciation, depletion and amortization		3.2	106.9
Payments to Acquire Property, Plant, and Equipment		15.9	29.9
Impairment of goodwill and other long-lived assets		73.4	857.5
Eastern Canadian Iron Ore [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
LOSS FROM DISCONTINUED OPERATIONS, net of tax	(17.5)	(638.7)	(6,952.9)
Short-term assets of discontinued operations		0
Short-term liabilities of discontinued operations	0	0
Depreciation, depletion and amortization		0	135.6
Payments to Acquire Property, Plant, and Equipment		0	190.3
Impairment of goodwill and other long-lived assets		0	7,269.2
Other Canadian Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
LOSS FROM DISCONTINUED OPERATIONS, net of tax	0	(101)	(280.6)
Short-term assets of discontinued operations		0
Short-term liabilities of discontinued operations	0	0
Depreciation, depletion and amortization		0	0.5
Payments to Acquire Property, Plant, and Equipment		0	0
Impairment of goodwill and other long-lived assets		0	267.6
Canadian Entities [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
LOSS FROM DISCONTINUED OPERATIONS, net of tax	(17.5)	(739.7)	(7,233.5)
Short-term assets of discontinued operations		0
Short-term liabilities of discontinued operations	$ 0	0
Depreciation, depletion and amortization		0	136.1
Payments to Acquire Property, Plant, and Equipment		0	190.3
Impairment of goodwill and other long-lived assets		0	7,536.8
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation, depletion and amortization		3.2	243
Payments to Acquire Property, Plant, and Equipment		15.9	220.2
Impairment of goodwill and other long-lived assets		$ 73.4	$ 8,394.3

DISCONTINUED OPERATIONS Discont

DISCONTINUED OPERATIONS Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis - Canadian Entities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Canadian Entities [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Loans to and Accounts Receivables from Bloom Lake Group, Fair Value Disclosure	$ 48.6	$ 72.9
Losses on Loans to and Accounts Receivables from the Bloom Lake Group	17.5	507.8
Bloom Lake Group [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Contingent Liabilities and Joint and Several Liabilities, Fair Value Disclosure	37.2	132.4
Contingent Liabilities of Deconsolidated Entities	0	(203.1)
Losses on Contingent Liabilities	0	203.1
Fair Value, Inputs, Level 1 [Member] | Canadian Entities [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Loans to and Accounts Receivables from Bloom Lake Group, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Bloom Lake Group [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Contingent Liabilities and Joint and Several Liabilities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Canadian Entities [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Loans to and Accounts Receivables from Bloom Lake Group, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Bloom Lake Group [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Contingent Liabilities and Joint and Several Liabilities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Bloom Lake Group [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Contingent Liabilities and Joint and Several Liabilities, Fair Value Disclosure	37.2	132.4
Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Canadian Entities [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Loans, Associated Interest and Accounts Receivable recognized in Consolidated Financials at Fair Value	$ 48.6	$ 72.9

DISCONTINUED OPERATIONS Disc131

DISCONTINUED OPERATIONS Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis - North American Coal (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Tangible Asset Impairment Charges			$ 0	$ 0	$ 537,800,000
North American Coal [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure		$ 20,400,000
Tangible Asset Impairment Charges		73,400,000
Assets, Fair Value Disclosure, Nonrecurring		20,400,000
Impairment Charges	$ 73,400,000
Fair Value, Inputs, Level 1 [Member] | North American Coal [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure		0
Assets, Fair Value Disclosure, Nonrecurring		0
Fair Value, Inputs, Level 2 [Member] | North American Coal [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure		0
Assets, Fair Value Disclosure, Nonrecurring		0
Fair Value, Inputs, Level 3 [Member] | North American Coal [Member]
Discontinued Operations, Items Measured at Fair Value on a Non-Recurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure		20,400,000
Assets, Fair Value Disclosure, Nonrecurring		$ 20,400,000

CAPITAL STOCK (Details)

CAPITAL STOCK (Details) $ / shares in Units, $ in Millions	3 Months Ended							9 Months Ended	12 Months Ended
	Dec. 31, 2016USD ($)$ / sharesshares	Sep. 30, 2016USD ($)	Dec. 31, 2015USD ($)$ / sharesshares	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Feb. 11, 2013	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)	Aug. 10, 2016$ / shares	Mar. 31, 2016USD ($)	Nov. 02, 2015$ / shares	Aug. 03, 2015$ / shares	May 01, 2015$ / shares	Feb. 02, 2015$ / shares	Jan. 26, 2015$ / shares	Dec. 03, 2014$ / shares	Nov. 03, 2014$ / shares	Sep. 02, 2014$ / shares	Aug. 01, 2014$ / shares	Jun. 03, 2014$ / shares	Mar. 03, 2014$ / shares
Class of Stock [Line Items]
Gain on extinguishment/restructuring of debt									$ 166.3	$ 392.9	$ 16.2
Common Stock, New Shares, Issued | shares									44,400,000
Depositary Share Interest in a Share of 7% Series A Mandatory Convertible Preferred Stock, Class A									0.025
Common Stock, Par or Stated Value Per Share | $ / shares	$ 0.125		$ 0.125						$ 0.125	$ 0.125
Trading Day Window Determining Number of Common Shares Issuable on Conversion									20
Dividends, Preferred Stock									$ 0	$ 38.4	51.2
Common shares, issued (in shares) | shares	238,636,794		159,546,224						238,636,794	159,546,224
Net proceeds from issuance of common shares								$ 287.6	$ 287.4	$ 0	0
Elimination of Dividend | $ / shares																		$ 0.15
Current Fiscal Year End Date									--12-31
Common Shares Issued in Debt to Equity Exchange | shares	8,200,000								8,200,000
Debt Instrument, Face Amount Exchanged						$ 674.6							$ 512.2
Shares Issued, Price Per Share | $ / shares												$ 6.75
Preferred Class A [Member]
Class of Stock [Line Items]
Preferred Stock, Liquidation Preference Per Share | $ / shares	$ 1,000		$ 1,000						$ 1,000	$ 1,000
Dividends payable, per share | $ / shares														$ 17.5000	$ 0.44	$ 17.50	$ 0.44			$ 17.5000		$ 0.44
Dividends, Preferred Stock			$ 0	$ 25.6	$ 0	12.8			$ 0	$ 38.4	$ 51.2
Common Stock [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Common Shares Issued Upon Conversion in Lieu of Dividend | shares	1,300,000								1,300,000
Convertible Preferred Stock, Shares Issued upon Conversion | shares	0.7037								0.7037
Convertible Preferred Stock, Shares Issued Upon Conversion per Depositary Share | shares	0.9052								0.9052
Dividends payable, per share | $ / shares																			$ 0.150		$ 0.150		$ 0.150	$ 0.150
Increase Decrease In Dividends Payable Percentage							76.00%
Common shares, issued (in shares) | shares	26,500,000								26,500,000
Convertible Preferred Stock, Common Shares Issued Upon Conversion | shares	25,200,000								25,200,000
Common Stock [Member] | Minimum [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion | shares	28.1480								28.1480
Convertible Preferred Stock, Shares Issued Upon Conversion per Depositary Share | shares	0.8621								0.8621
Common Stock [Member] | Maximum [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion | shares	34.4840								34.4840
Depositary Shares [Member]
Class of Stock [Line Items]
Dividends payable, per share | $ / shares														$ 0.44	$ 17.5000	$ 0.44	$ 17.5000			$ 0.44		$ 17.5000
Exchange of Debt for Equity [Member]
Class of Stock [Line Items]
Gain on extinguishment/restructuring of debt	$ 11.3
$500 Million 3.95% 2018 Senior Notes [Member]
Class of Stock [Line Items]
Gain on extinguishment/restructuring of debt		$ (19.9)
Debt Instrument, Face Amount Exchanged													17.6
$500 Million 3.95% 2018 Senior Notes [Member] | Exchange of Debt for Equity [Member]
Class of Stock [Line Items]
Debt Instrument, Face Amount Exchanged	10								$ 10
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member]
Class of Stock [Line Items]
Debt Instrument, Face Amount Received in Debt Exchange of $500M 3.95% Notes													11.4
Debt Instrument, Face Amount Received in Debt Exchange of $500M 4.80% Notes													17.9
Debt instrument, Face Amount Received in Debt Exchange of $700M 4.875% Notes													30.5
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member] | Exchange of Debt for Equity [Member]
Class of Stock [Line Items]
Debt Instrument, Face Amount Exchanged	20.1								20.1
$700 Million 4.875% 2021 Senior Notes[Member]
Class of Stock [Line Items]
Debt Instrument, Face Amount Exchanged						$ 208.5							$ 76.3
$700 Million 4.875% 2021 Senior Notes[Member] | Exchange of Debt for Equity [Member]
Class of Stock [Line Items]
Debt Instrument, Face Amount Exchanged	$ 26.8								$ 26.8

ACCUMULATED OTHER COMPREHENS133

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Accumulated Other Comprehensive Income (Loss) and Related Tax Effects (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Before Taxes	$ (144.7)	$ (141.8)	$ (388.1)
Accumulated Other Comprehensive Income (Loss), Tax	123.4	123.8	142.3
Accumulated other comprehensive loss	(21.3)	(18)	(245.8)	$ (112.9)
Postretirement Benefit Liability [Member]
Accumulated Other Comprehensive Income (Loss), Before Taxes	(384)	(364.8)	(425.3)
Accumulated Other Comprehensive Income (Loss), Tax	123.4	123.4	134.2
Accumulated other comprehensive loss	(260.6)	(241.4)	(291.1)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Before Taxes	239.3	220.7	64.4
Accumulated Other Comprehensive Income (Loss), Tax	0	0	0
Accumulated other comprehensive loss	$ 239.3	220.7	64.4
Unrealized Gain Loss On Derivatives [Member]
Accumulated Other Comprehensive Income (Loss), Before Taxes		2.2	(25.9)
Accumulated Other Comprehensive Income (Loss), Tax		0.4	7.8
Accumulated other comprehensive loss		2.6	(18.1)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Before Taxes		0.1	(1.3)
Accumulated Other Comprehensive Income (Loss), Tax		0	0.3
Accumulated other comprehensive loss		$ 0.1	$ (1)

ACCUMULATED OTHER COMPREHENS134

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	$ (260.6)	$ (241.4)	$ (291.1)	$ (204.9)
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	0	0.1	(1)	6.2
Accumulated other comprehensive loss	(21.3)	(18)	(245.8)	(112.9)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	239.3	220.7	64.4	106.7
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	0	2.6	(18.1)	$ (20.9)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	19.8	(45.2)	91
Unrealized net gain (loss) on marketable securities, net of tax	0	1.7	(7.2)
Unrealized net gain (loss) on foreign currency translation	18.6	155.6	(42.3)
Other Comprehensive Income (Loss), Net of Tax	(3.8)	223.2	(137.7)
Accumulated Other Comprehensive Income (Loss) [Member]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(29.8)	(10)	(166.2)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	26.5	237.8	33.3
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(3.3)	1.9	(28.2)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.7	18.8	31
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	18.4	(26.4)	(42.3)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.2	182.7	0
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(44.8)	9.1	(97)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	25.6	40.6	10.8
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(0.1)	5.4	1.3
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 0	$ (4.3)	$ (8.5)

ACCUMULATED OTHER COMPREHENS135

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Details of Accumulated Other Comprehensive Income (Loss) Components (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other Comprehensive Income (Loss), Foreign Currency Translation, Dissolution of Entity	$ 0.2	$ 0	$ 0
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Marketable Securities, Unrealized Gain (Loss)	0	(2.6)	(11.4)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	1.2	26.9	45.6
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	0	4.3	(8.5)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	0	(4.6)	(11.9)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	26.5	237.8	35.5
Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(29.8)	(10)	(166.2)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	26.5	237.8	33.3
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(3.3)	1.9	(28.2)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.7	18.8	31
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	18.4	(26.4)	(42.3)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.2	182.7	0
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(44.8)	9.1	(97)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	25.6	40.6	10.8
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Amortization of prior service (cost) credit	1.5	1.4	1.1
Defined Benefit Plan, Amortization of Gains (Losses)	27.1	27.4	18.5
Defined Benefit Plan, Curtailments	0	0.2	1.4
Defined Benefit Plan, Effect of Deconsolidation	0	15.1	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax	25.6	41.3	18.8
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax	0	(0.7)	(5.8)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), Net of Tax	25.6	40.6	13
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(0.1)	5.4	1.3
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	(4.3)	(8.5)
Accumulated Other-than-Temporary Impairment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	0	(2)	(0.5)
Foreign Currency Translation Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	0.2	182.7	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax	0	182.7	0
Realized Gain (Loss) on Marketable Securities and Other than Temporary Impairment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other Comprehensive Income (Loss), Realized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, Tax	0	0.3	3.4
Realized Gain Loss On Derivatives [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
TaxOnDerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoEarnings	(0.5)	(8.1)	(14.6)
Derivative, Gain (Loss) on Derivative, Net	0.7	18.8	31
T-Lock Amortization [Member] | Realized Gain Loss On Derivatives [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	1.2	0	0
Australian Hedge Contracts [Member] | Realized Gain Loss On Derivatives [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	26.9	18.9
Canadian Hedge Contracts [Member] | Realized Gain Loss On Derivatives [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 0	$ 0	$ 26.7

CASH FLOW INFORMATION (Narrativ

CASH FLOW INFORMATION (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Dividends Payable [Line Items]
Income Tax Refunds, Discontinued Operations		$ 47.8
Interest Paid, Discontinued Operations	$ 1.4	4.8	$ 6.1
Property, Plant and Equipment, Additions	$ 68.5	72.2	65.5
Capital Expenditure, Discontinued Operations		$ 24.5	$ 170

CASH FLOW INFORMATION (Reconcil

CASH FLOW INFORMATION (Reconciliation Of Capital Additions To Cash Paid For Capital Expenditures) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment, Additions, Including Discontinued Operations	$ 68.5	$ 96.7	$ 235.5
Payments To Acquire Property Plant And Equipment Net	69.1	80.8	284.1
Non-cash accruals	(0.6)	14.4	(58.5)
Capital leases	0	1.5	9.9
Total	$ (0.6)	$ 15.9	$ (48.6)

CASH FLOW INFORMATION CASH FLOW

CASH FLOW INFORMATION CASH FLOW INFORMATION (Cash Paid for Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Income Taxes Paid	$ 6	$ 5	$ 47.3
Proceeds from Income Tax Refunds	5.4	211.4	54.7
Interest Paid	$ 184	$ 185.6	$ 176.5

RELATED PARTIES (Narrative) (De

RELATED PARTIES (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)Facility	Dec. 31, 2015USD ($)
Segment Reporting Information [Line Items]
Due from Related Parties, Current	$ 73.8	$ 15.8
Due to Related Parties, Current	$ 8.7	14.5
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Number Of Mines | Facility	4
Joint Venture Partners [Member] | U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Number Of Mines | Facility	2
Empire [Member] | Arcelor Mittal [Member]
Segment Reporting Information [Line Items]
Recorded Distributions of Partners' Equity Amounts	$ 57.5	51.7
Paid Distributions of Partners' Equity Amounts	$ 48.8	$ 40.6

RELATED PARTIES (Summary Of Oth

RELATED PARTIES (Summary Of Other Ownership Interests) (Details)	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%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	21.00%
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%
Investments in Ventures [Member] | Hibbing [Member]
Related Party Transaction [Line Items]
Ownership interest, equity method investment	23.00%

RELATED PARTIES (Summary Of Rel

RELATED PARTIES (Summary Of Related Party Transactions Table Disclosure) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Product revenues from related parties	$ 830.1	$ 671.1	$ 1,011.4
Product	$ 1,913.5	$ 1,832.4	$ 3,095.2
Related party product revenue as a percent of total product revenue	43.40%	36.60%	32.70%

EARNINGS PER SHARE (Earnings Pe

EARNINGS PER SHARE (Earnings Per Share Computation) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount											25,300	25,200
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	$ 100.1	$ (25.1)	$ 29.9	$ 114.3	$ (34.8)	$ 49.9	$ (38.2)	$ 166.8		$ 219.2	$ 143.7	$ 56.4
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest	(1.7)	2	(16.7)	(8.8)	(2.4)	4.6	(5)	1.9		(25.2)	(8.6)	(25.9)
Income (Loss) from Continuing Operations Attributable to Parent	98.4	(23.1)	13.2	105.5		54.5	(43.2)	168.7	$ (37.2)	194	135.1	30.5
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(19.3)	(2.7)	(0.4)	2.5	$ (23.1)	(43.9)	103.4	(928.5)		(19.9)	(884.4)	(7,254.7)
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS						10.6	60.2	(759.8)	(60.3)	174.1	(749.3)	(7,224.2)
PREFERRED STOCK DIVIDENDS										0	(38.4)	(51.2)
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS	$ 79.1	$ (25.8)	$ 12.8	$ 108		$ (15)	$ 60.2	$ (772.6)	$ (60.3)	$ 174.1	$ (787.7)	$ (7,275.4)
Weighted Average Number of Shares:
Basic										197,659	153,230	153,098
Employee Stock Plans										2,386	375	0
Diluted										200,145	153,605	153,098
Earnings (loss) per Common Share Attributable to Cliffs Common Shareholders - Basic:
Continuing operations	$ 0.43	$ (0.11)	$ 0.07	$ 0.61	$ (0.24)	$ 0.19	$ (0.28)	$ 1.02		$ 0.98	$ 0.63	$ (0.14)
Discontinued operations	(0.08)	(0.01)	0	0.01	(0.15)	(0.29)	0.67	(6.06)		(0.10)	(5.77)	(47.38)
Earnings (loss) per Common Share Attributable to Cliffs Common Shareholders - Basic:	0.35	(0.12)	0.07	0.62	(0.39)	(0.10)	0.39	(5.04)		0.88	(5.14)	(47.52)
Earnings (loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted:
Continuing operations	0.42	(0.11)	0.07	0.61	(0.24)	0.19	(0.28)	0.94		0.97	0.63	(0.14)
Discontinued operations	(0.08)	(0.01)	0	0.01	(0.15)	(0.29)	0.67	(5.20)		(0.10)	(5.76)	(47.38)
Earnings (loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted:	$ 0.34	$ (0.12)	$ 0.07	$ 0.62	$ (0.39)	$ (0.10)	$ 0.39	$ (4.26)		$ 0.87	$ (5.13)	$ (47.52)
Preferred Class A [Member]
PREFERRED STOCK DIVIDENDS					$ 0	$ (25.6)	$ 0	$ (12.8)		$ 0	$ (38.4)	$ (51.2)

EARNINGS PER SHARE EARNINGS PER

EARNINGS PER SHARE EARNINGS PER SHARE (Narrative Details) (Details) - shares shares in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			25.3	25.2
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements	0	3		0.7

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	$ 2.8	$ 3.6
Michigan Electricity Matters [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual	$ 13.6

SUBSEQUENT EVENTS Narrative (De

SUBSEQUENT EVENTS Narrative (Details) - shares	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Common shares, issued (in shares)	238,636,794	159,546,224
Common Stock [Member]
Subsequent Event [Line Items]
Convertible Preferred Stock, Common Shares Issued Upon Conversion in Lieu of Dividend	1,300,000
Convertible Preferred Stock, Shares Issued upon Conversion	0.7037
Common shares, issued (in shares)	26,500,000
Convertible Preferred Stock, Common Shares Issued Upon Conversion	25,200,000
Maximum [Member] | Common Stock [Member]
Subsequent Event [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion	34.4840
Minimum [Member] | Common Stock [Member]
Subsequent Event [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion	28.1480

QUARTERLY RESULTS OF OPERATI146

QUARTERLY RESULTS OF OPERATIONS (Schedule of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount											25.3	25.2
Revenues	$ 754	$ 553.3	$ 496.2	$ 305.5	$ 476	$ 593.2	$ 498.1	$ 446		$ 2,109	$ 2,013.3	$ 3,373.2
SALES MARGIN	181.5	85.4	91.5	30.9	43.3	55.1	57.3	80.8		389.3	236.5	885.7
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	100.1	(25.1)	29.9	114.3	(34.8)	49.9	(38.2)	166.8		219.2	143.7	56.4
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest	(1.7)	2	(16.7)	(8.8)	(2.4)	4.6	(5)	1.9		(25.2)	(8.6)	(25.9)
Income (Loss) from Continuing Operations Attributable to Parent	98.4	(23.1)	13.2	105.5		54.5	(43.2)	168.7	$ (37.2)	194	135.1	30.5
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(19.3)	(2.7)	(0.4)	2.5	$ (23.1)	(43.9)	103.4	(928.5)		(19.9)	(884.4)	(7,254.7)
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS						10.6	60.2	(759.8)	(60.3)	174.1	(749.3)	(7,224.2)
Dividends, Preferred Stock										0	38.4	51.2
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS	$ 79.1	$ (25.8)	$ 12.8	$ 108		$ (15)	$ 60.2	$ (772.6)	$ (60.3)	$ 174.1	$ (787.7)	$ (7,275.4)
Continuing operations	$ 0.43	$ (0.11)	$ 0.07	$ 0.61	$ (0.24)	$ 0.19	$ (0.28)	$ 1.02		$ 0.98	$ 0.63	$ (0.14)
Discontinued operations	(0.08)	(0.01)	0	0.01	(0.15)	(0.29)	0.67	(6.06)		(0.10)	(5.77)	(47.38)
Earnings Per Share, Basic	0.35	(0.12)	0.07	0.62	(0.39)	(0.10)	0.39	(5.04)		0.88	(5.14)	(47.52)
Continuing operations	0.42	(0.11)	0.07	0.61	(0.24)	0.19	(0.28)	0.94		0.97	0.63	(0.14)
Discontinued operations	(0.08)	(0.01)	0	0.01	(0.15)	(0.29)	0.67	(5.20)		(0.10)	(5.76)	(47.38)
Earnings Per Share, Diluted	$ 0.34	$ (0.12)	$ 0.07	$ 0.62	$ (0.39)	$ (0.10)	$ 0.39	$ (4.26)		$ 0.87	$ (5.13)	$ (47.52)
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements	0	3										0.7
Preferred Class A [Member]
Dividends, Preferred Stock					$ 0	$ 25.6	$ 0	$ 12.8		$ 0	$ 38.4	$ 51.2
Maximum [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount											25.6
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements											0.3

QUARTERLY RESULTS OF OPERATI147

QUARTERLY RESULTS OF OPERATIONS (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount						25.3	25.2
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements	0	3					0.7
Loss (gain) on sale of North American Coal mines				$ 155
Sale Price of CLCC Assets				$ 174
Income Tax Expense (Benefit)					$ (12.2)	$ 169.3	$ (86)
Asset Impairment Charges					$ 0	$ 3.3	$ 635.5
Minimum [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			25.2
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements			0.1
Maximum [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount						25.6
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements						0.3

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation Allowance of Deferred Tax Assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Balance	$ 3,334.8	$ 3,372.5	$ 1,152.3	$ 849.6
Valuation Allowances and Reserves, Charged to Cost and Expense	(40.6)	54.3	634.9
Valuation Allowances and Reserves, Charged to Other Accounts	5.1	2,165.9	(12.6)
Valuation Allowances and Reserves, Reserves of Businesses Acquired	0	0	0
Valuation Allowances and Reserves, Deductions	2.2	0	319.6
Allowance for Trade Receivables [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Balance	0	7.1	0	$ 0
Valuation Allowances and Reserves, Charged to Cost and Expense	0	7.1	0
Valuation Allowances and Reserves, Charged to Other Accounts	(7.1)	0	0
Valuation Allowances and Reserves, Reserves of Businesses Acquired	0	0	0
Valuation Allowances and Reserves, Deductions	$ 0	$ 0	$ 0