Cleveland-Cliffs (CLF) 10-Q 25 Oct 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 21, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	CLIFFS NATURAL RESOURCES INC.
Entity Central Index Key	764065
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	30-Sep-13
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding		153,124,101
Trading Symbol	clf

Statements_Of_Condensed_Consol

Statements Of Condensed Consolidated Operations (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
REVENUES FROM PRODUCT SALES AND SERVICES
Product	$1,454.60	$1,447.90	$3,928.80	$4,096.60
Freight and venture partners' cost reimbursements	92	97	246.8	240.2
TOTAL REVENUES	1,546.60	1,544.90	4,175.60	4,336.80
COST OF GOODS SOLD AND OPERATING EXPENSES	-1,197.90	-1,346.60	-3,320.80	-3,403.20
SALES MARGIN	348.7	198.3	854.8	933.6
OTHER OPERATING INCOME (EXPENSE)
Selling, general and administrative expenses	-70.6	-63.9	-167.9	-202.6
Exploration costs	-10.6	-45.6	-45.9	-95.2
Miscellaneous - net	-43.5	-12.5	13.3	25.5
Other operating expense	-124.7	-122	-200.5	-272.3
OPERATING INCOME	224	76.3	654.3	661.3
OTHER INCOME (EXPENSE)
Interest expense, net	-44.7	-45.3	-134.5	-135.7
Other non-operating income (expense)	-1.2	1.4	-2.9	1
TOTAL OTHER INCOME (EXPENSE)	-45.9	-43.9	-137.4	-134.7
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES AND EQUITY LOSS FROM VENTURES	178.1	32.4	516.9	526.6
INCOME TAX BENEFIT (EXPENSE)	-65.7	64	-69	235.2
EQUITY LOSS FROM VENTURES, net of tax	-0.5	-15.3	-73.9	-22.7
INCOME FROM CONTINUING OPERATIONS	111.9	81.1	374	739.1
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, net of tax	2	-2.7	2	5.1
NET INCOME	113.9	78.4	376	744.2
LOSS (INCOME) ATTRIBUTABLE TO NONCONTROLLING INTEREST	3.3	6.7	-5.8	-25.2
NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	117.2	85.1	370.2	719
PREFERRED STOCK DIVIDENDS	-12.9	0	-35.9	0
NET INCOME ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS	$104.30	$85.10	$334.30	$719
EARNINGS PER COMMON SHARE ATTRIBUTABLE TO CLIFFS SHAREHOLDERS - BASIC
Continuing operations	$0.67	$0.62	$2.20	$5.02
Discontinued operations	$0.01	($0.02)	$0.01	$0.04
Earnings per Common Share Attributable to Cliffs Common Shareholders - Basic:	$0.68	$0.60	$2.21	$5.06
EARNINGS PER COMMON SHARE ATTRIBUTABLE TO CLIFFS SHAREHOLDERS - DILUTED
Continuing operations	$0.65	$0.61	$2.13	$5
Discontinued operations	$0.01	($0.02)	$0.01	$0.04
Earnings per Common Share Attributable to Cliffs Common Shareholders - Diluted:	$0.66	$0.59	$2.14	$5.04
AVERAGE NUMBER OF SHARES (IN THOUSANDS)
Basic	153,029	142,396	151,288	142,332
Diluted	178,459	142,895	172,624	142,780
CASH DIVIDENDS DECLARED PER DEPOSITARY SHARE	$0.44	$0	$1.22	$0
CASH DIVIDENDS DECLARED PER COMMON SHARE	$0.15	$0.63	$0.45	$1.54

Statements_Of_Condensed_Consol1

Statements Of Condensed Consolidated Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]
NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$117.20	$85.10	$370.20	$719
OTHER COMPREHENSIVE INCOME (LOSS)
Pension and OPEB liability, net of tax	6.6	7.6	20.8	20.9
Unrealized net gain (loss) on marketable securities, net of tax	4.4	-0.1	7.6	-0.6
Unrealized net gain (loss) on foreign currency translation	22.8	18.6	-124.9	12.2
Unrealized net gain (loss) on derivative financial instruments, net of tax	28.3	14.2	-23.1	13.6
OTHER COMPREHENSIVE INCOME (LOSS)	62.1	40.3	-119.6	46.1
OTHER COMPREHENSIVE INCOME ATTRIBUTABLE TO THE NONCONTROLLING INTEREST	-0.9	-1.5	-3.2	-4.5
TOTAL COMPREHENSIVE INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$178.40	$123.90	$247.40	$760.60

Statements_Of_Condensed_Consol2

Statements Of Condensed Consolidated Financial Position (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
CURRENT ASSETS
Cash and cash equivalents	$298.80	$195.20
Accounts receivable, net	291.7	329
Inventories	438.4	436.5
Supplies and other inventories	257.4	289.1
Derivative assets	72.7	78.6
Other current assets	310.6	321.6
TOTAL CURRENT ASSETS	1,669.60	1,650
PROPERTY, PLANT AND EQUIPMENT, NET	11,354.80	11,207.30
OTHER ASSETS
Investments in ventures	71.5	135.8
Goodwill	158.6	167.4
Intangible assets, net	110.8	129
Deferred income taxes	5.3	91.8
Other non-current assets	196.1	193.6
TOTAL OTHER ASSETS	542.3	717.6
TOTAL ASSETS	13,566.70	13,574.90
CURRENT LIABILITIES
Accounts payable	350.8	555.5
Accrued expenses	404.7	442.6
Income taxes payable	57.3	28.3
Current portion of debt	7.9	94.1
Deferred revenue	15.1	35.9
Derivative liabilities	36.1	13.2
Other current liabilities	188.6	211.9
TOTAL CURRENT LIABILITIES	1,060.50	1,381.50
PENSION AND POSTEMPLOYMENT BENEFIT LIABILITIES	556.1	618.3
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	299.5	252.8
DEFERRED INCOME TAXES	1,000.50	1,108.10
LONG-TERM DEBT	3,319.60	3,960.70
OTHER LIABILITIES	395.9	492.6
TOTAL LIABILITIES	6,632.10	7,814
COMMITMENTS AND CONTINGENCIES (SEE NOTE 19)
CLIFFS SHAREHOLDERS' EQUITY
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 - 731,250 shares (2012 - none)	731.3	0
Common Shares - par value $0.125 per share, Authorized - 400,000,000 shares (2012- 400,000,000 shares); Issued - 159,545,469 shares (2012 - 149,195,469 shares); Outstanding - 153,124,449 shares (2012 - 142,495,902 shares)	19.8	18.5
Capital in excess of par value of shares	2,029.80	1,774.70
Retained earnings	3,483.30	3,217.70
Cost of 6,421,264 common shares in treasury (2012 - 6,699,567 shares)	-306.1	-322.6
Accumulated other comprehensive loss	-178.4	-55.6
TOTAL CLIFFS SHAREHOLDERS' EQUITY	5,779.70	4,632.70
NONCONTROLLING INTEREST	1,154.90	1,128.20
TOTAL EQUITY	6,934.60	5,760.90
TOTAL LIABILITIES AND EQUITY	$13,566.70	$13,574.90

Statements_Of_Condensed_Consol3

Statements Of Condensed Consolidated Financial Position (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Class of Stock [Line Items]
Preferred stock, par value	$0
Cumulative Mandatory Convertible	7.00%
Common shares, par value	$0.13	$0.13
Common shares, authorized (in shares)	400,000,000	400,000,000
Common shares, issued (in shares)	159,545,469	149,195,469
Common shares, outstanding	153,124,449	142,495,902
Common shares in treasury	6,421,264	6,699,567
Preferred Class A [Member]
Class of Stock [Line Items]
Preferred Stock, Liquidation Preference Per Share	$1,000
Preferred stock, shares authorized (in shares)	3,000,000
Preferred Shares, Issued and Outstanding, Shares	731,250	0
Preferred Class B [Member]
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	4,000,000

Statements_Of_Condensed_Consol4

Statements Of Condensed Consolidated Cash Flows (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
OPERATING ACTIVITIES
Net income	$376	$744.20
Adjustments to reconcile net income to net cash provided (used) by operating activities:
Depreciation, depletion and amortization	438	382.3
Derivatives and currency hedges	0.4	12
Equity loss in ventures (net of tax)	73.9	22.7
Deferred income taxes	-39.5	-352.5
Changes in deferred revenue and below-market sales contracts	-52.2	-36.2
Other	-18.3	-55.7
Changes in operating assets and liabilities:
Receivables and other assets	36.2	-118.6
Product inventories	-10.8	-70.4
Payables and accrued expenses	-117.8	-252.3
Net cash provided by operating activities	685.9	275.5
INVESTING ACTIVITIES
Purchase of property, plant and equipment	-742.2	-793.6
Other investing activities	7.8	8.9
Net cash used by investing activities	-734.4	-784.7
FINANCING ACTIVITIES
Net proceeds from issuance of Series A, Mandatory Convertible Preferred Stock, Class A	709.4	0
Net proceeds from issuance of common shares	285.3	0
Repayment of term loan	-847.1	-49.9
Borrowings under credit facilities	567	670
Repayment under credit facilities	-512	-420
Proceeds from equipment loan	62.1	0
Contributions by joint ventures, net	17.7	68.8
Common stock dividends	-68.8	-217.8
Preferred stock dividends	-23	0
Other financing activities	-28.6	-23.9
Net cash provided by financing activities	162	27.2
EFFECT OF EXCHANGE RATE CHANGES ON CASH	-9.9	-0.1
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	103.6	-482.1
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	195.2	521.6
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$298.80	$39.50

BASIS_OF_PRESENTATION_AND_SIGN

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BUSINESS SUMMARY AND SIGNIFICANT ACCOUNTING POLICIES	NOTE 1 - BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES
	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with SEC rules and regulations and, in the opinion of management, include all adjustments (consisting of normal recurring adjustments) necessary to present fairly, the financial position, results of operations, comprehensive income and cash flows for the periods presented. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Management bases its estimates on various assumptions and historical experience, which are believed to be reasonable; however, due to the inherent nature of estimates, actual results may differ significantly due to changed conditions or assumptions. The results of operations for the three and nine months ended September 30, 2013 are not necessarily indicative of results to be expected for the year ended December 31, 2013 or any other future period. These unaudited condensed consolidated financial statements should be read in conjunction with the financial statements and notes included in our Annual Report on Form 10-K for the year ended December 31, 2012.
	Basis of Consolidation
	The unaudited condensed consolidated financial statements include our accounts and the accounts of our wholly owned and majority-owned subsidiaries, including the following operations:
	Name	Location	Ownership Interest	Operation
	Northshore	Minnesota	100.00%	Iron Ore
	United Taconite	Minnesota	100.00%	Iron Ore
	Wabush	Newfoundland and Labrador/ Quebec, Canada	100.00%	Iron Ore
	Bloom Lake	Quebec, Canada	75.00%	Iron Ore
	Tilden	Michigan	85.00%	Iron Ore
	Empire	Michigan	79.00%	Iron Ore
	Koolyanobbing	Western Australia	100.00%	Iron Ore
	Pinnacle	West Virginia	100.00%	Coal
	Oak Grove	Alabama	100.00%	Coal
	CLCC	West Virginia	100.00%	Coal
	Intercompany transactions and balances are eliminated upon consolidation.
	Also included in our consolidated results are Cliffs Chromite Ontario Inc. and Cliffs Chromite Far North Inc. Cliffs Chromite Ontario Inc. holds a 100 percent interest in each of the Black Label and Black Thor chromite deposits and, together with Cliffs Chromite Far North Inc., a 70 percent interest in the Big Daddy chromite deposit, all located in northern Ontario, Canada.
	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. The following table presents the detail of our investments in unconsolidated ventures and where those investments are classified in the Statements of Unaudited Condensed Consolidated Financial Position as of September 30, 2013 and December 31, 2012. Parentheses indicate a net liability.
					(In Millions)
	Investment	Classification	Accounting	Interest	September 30,		December 31, 2012
			Method	Percentage	2013
	Amapá	Investments in ventures	Equity Method	30	$	29.4	$	101.9
	Cockatoo	Other liabilities2	Equity Method	—	N/A		(25.3		)
	Hibbing	Investments in ventures1	Equity Method	23	8.3		(2.1		)
	Other	Investments in ventures	Equity Method	Various	33.8		33.9
					$	71.5	$	108.4
	1 At December 31, 2012 the classification for Hibbing was Other liabilities.
	2 At December 31, 2012 our ownership interest percentage for Cockatoo was 50 percent.
	Amapá
	On December 27, 2012, our board of directors authorized the sale of our 30 percent interest in Amapá. Per this original agreement, together with Anglo American plc, we were to sell our respective interest in a 100 percent sale transaction to a single entity.
	On March 28, 2013, an unknown event caused the Santana port shiploader to collapse into the Amazon River, preventing further ship loading by the mine operator, Anglo American plc. In light of the March 28, 2013 collapse of the Santana port shiploader and subsequent evaluation of the effect that this event had on the carrying value of our investment in Amapá as of June 30, 2013, we recorded an impairment charge of $67.6 million in the second quarter of 2013.
	On August 28, 2013, we entered into an agreement to sell our 30 percent interest in Amapá to Anglo American plc for nominal cash consideration, plus the right to certain contingent deferred consideration upon the two year anniversary of the closing.  The closing is conditional on obtaining certain regulatory approvals.  The transaction is expected to close in the fourth quarter of 2013.
	Cockatoo Island
	On July 31, 2012, we entered into a definitive asset sale agreement with our joint venture partner, HWE Cockatoo Pty Ltd., to sell our beneficial interest in the mining tenements and certain infrastructure of Cockatoo Island to Pluton Resources, which was amended on August 31, 2012. On September 7, 2012, the closing date, Pluton Resources paid a nominal sum of AUD $4.00 and assumed ownership of the assets and responsibility for the environmental rehabilitation obligations and other assumed liabilities not inherently attached to the tenements acquired. The rehabilitation obligations and assumed liabilities that are inherently attached to the tenements were transferred to Pluton Resources upon registration by the Department of Mining and Petroleum denoting Pluton Resources as the tenement holder. Upon final settlement of the sale, which was completed during the second quarter of 2013, we transferred approximately $18.6 million related to the estimated cost of the rehabilitation.
	Discontinued Operations
	On July 10, 2012, we entered into a definitive share and asset sale agreement to sell our 45 percent economic interest in the Sonoma joint venture coal mine located in Queensland, Australia. Upon completion of the transaction on November 12, 2012, we collected approximately AUD $141.0 million in net cash proceeds. The Sonoma operations previously were included in Other within our reportable segments.
	Significant Accounting Policies
	A detailed description of our significant accounting policies can be found in the audited financial statements for the fiscal year ended December 31, 2012 included in our Annual Report on Form 10-K filed with the SEC. The significant accounting policies requiring updates have been included within the disclosures below.
	Other Intangible Assets and Liabilities
	Other intangible assets are subject to periodic amortization on a straight-line basis over their estimated useful lives or on a units of production basis as follows:
	Intangible Assets	Basis	Useful Life (years)
	Permits - Asia Pacific Iron Ore	Units of production	Life of mine
	Permits - All Other	Straight line	15 - 40
	Utility contracts	Straight line	5
	Leases - North American Coal	Units of production	Life of mine
	Leases - All Other	Straight line	4.5 - 17.5
	Earnings Per Share
	We present both basic and diluted earnings per share amounts. Basic earnings per share amounts are calculated by dividing Net Income 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 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. Our outstanding depositary shares are convertible into common shares based on the volume weighted average of closing prices of our common stock over the 20 consecutive trading day period ending on the third day immediately preceding the end of the reporting period. Common share equivalents are excluded from EPS computations in the periods in which they have an anti-dilutive effect. See NOTE 18 - EARNINGS PER SHARE for further information.
	Recent Accounting Pronouncements
	On July 18, 2013, the FASB issued Accounting Standards Update No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. ASU 2013-11 requires the netting of unrecognized tax benefits against a deferred tax asset for a loss or other carryforward that would apply in settlement of the uncertain tax positions. ASU 2013-11 is effective for interim and annual periods beginning after December 15, 2013. We will adopt ASU 2013-11 in the fourth quarter of 2013 on a prospective basis, which will impact the presentation of our non-current Deferred income taxes and unrecognized tax benefits (within non-current Other liabilities) in the Statements of Unaudited Condensed Consolidated Financial Position.
	In February 2013, the FASB amended the guidance on the presentation of comprehensive income in order to improve the reporting of reclassifications out of accumulated other comprehensive income. The amendment does not change the current requirements for reporting net income or other comprehensive income in financial statements. Rather, it requires the entity to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income but only if the amount being reclassified is required under GAAP to be reclassified in its entirety to net income in the same reporting period. For other amounts that are not required under GAAP to be reclassified in their entirety to net income, an entity is required to cross-reference to other disclosures required under GAAP that provide additional detail about those amounts. The new guidance was applied prospectively for reporting periods beginning after December 15, 2012. We adopted the provisions of guidance required for the period beginning January 1, 2013. Refer to NOTE 16 - SHAREHOLDERS' EQUITY for further information.

SEGMENT_REPORTING

SEGMENT REPORTING	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]
SEGMENT REPORTING	NOTE 2 - SEGMENT REPORTING
	Our Company’s primary operations are organized and managed according to product category and geographic location: U.S. Iron Ore, Eastern Canadian Iron Ore, Asia Pacific Iron Ore, North American Coal, Latin American Iron Ore, Ferroalloys and our Global Exploration Group. The U.S. Iron Ore segment is comprised of our interests in five U.S. mines that provide iron ore to the integrated steel industry. The Eastern Canadian Iron Ore segment is comprised of two Eastern Canadian mines that primarily provide iron ore to the seaborne market for Asian steel producers. The Asia Pacific Iron Ore segment is located in Western Australia and provides iron ore to the seaborne market for Asian steel producers. The North American Coal segment is comprised of our four metallurgical coal mines and one thermal coal mine that provide metallurgical coal primarily to the integrated steel industry and thermal coal primarily to the energy industry. There are no intersegment revenues.
	The Latin American Iron Ore operating segment is comprised of our 30 percent Amapá interest in Brazil. The Ferroalloys operating segment is comprised of our interests in chromite deposits held in Northern Ontario, Canada and the Global Exploration Group is focused on early involvement in exploration activities to identify new projects for future development or projects that add significant value to existing operations. The Latin American Iron Ore, Ferroalloys and Global Exploration Group operating segments do not meet reportable segment disclosure requirements and, therefore, are not reported separately.
	We evaluate segment performance based on sales margin, defined as revenues less cost of goods sold, and operating expenses identifiable to each segment. This measure of operating performance is an effective measurement as we focus on reducing production costs throughout the Company.
	The following table presents a summary of our reportable segments for the three and nine months ended September 30, 2013 and 2012, including a reconciliation of segment sales margin to Income from Continuing Operations Before Income Taxes and Equity Loss from Ventures:
		(In Millions)
		Three Months Ended										Nine Months Ended
		September 30,										September 30,
		2013					2012					2013					2012
	Revenues from product sales and services:
	U.S. Iron Ore	$	782.4		51	%	$	796		52	%	$	1,894.20		45	%	$	1,942.70		45	%
	Eastern Canadian Iron Ore	284.2			18	%	253.1			16	%	743.4			18	%	777.8			18	%
	Asia Pacific Iron Ore	301.7			20	%	254.2			16	%	899.5			22	%	975.3			22	%
	North American Coal	178.3			11	%	241.8			16	%	638.5			15	%	640.9			15	%
	Other	—			—	%	(0.2		)	—	%	—			—	%	0.1			—	%
	Total revenues from product sales and services	$	1,546.60		100	%	$	1,544.90		100	%	$	4,175.60		100	%	$	4,336.80		100	%
	Sales margin:
	U.S. Iron Ore	$	273.5				$	255.9				$	647.1				$	708.9
	Eastern Canadian Iron Ore	(22.0		)			(40.5		)			(52.3		)			(43.0		)
	Asia Pacific Iron Ore	99					(15.8		)			255.3					256.1
	North American Coal	(1.8		)			(1.3		)			6.6					3.8
	Other	—					—					(1.9		)			7.8
	Sales margin	348.7					198.3					854.8					933.6
	Other operating expense	(124.7		)			(122.0		)			(200.5		)			(272.3		)
	Other expense	(45.9		)			(43.9		)			(137.4		)			(134.7		)
	Income from continuing operations before income taxes and equity (loss) from ventures	$	178.1				$	32.4				$	516.9				$	526.6
	Depreciation, depletion and amortization:
	U.S. Iron Ore	$	27.3				$	24.9				$	82.3				$	71.9
	Eastern Canadian Iron Ore	46.8					41.7					130.3					118.2
	Asia Pacific Iron Ore	38					40.2					116.1					110
	North American Coal	38.8					25.1					99.7					69.5
	Other	2.2					1					9.6					12.7
	Total depreciation, depletion and amortization	$	153.1				$	132.9				$	438				$	382.3
	Capital additions (1):
	U.S. Iron Ore	$	15.2				$	19.6				$	39.1				$	82.5
	Eastern Canadian Iron Ore	181.5					285.5					535.3					593.4
	Asia Pacific Iron Ore	2					5.8					8.6					132
	North American Coal	10.4					33.3					37.2					105.1
	Other	2.2					10.3					4.9					61
	Total capital additions	$	211.3				$	354.5				$	625.1				$	974
	(1)    Includes capital lease additions and non-cash accruals. Refer to NOTE 20 - CASH FLOW INFORMATION.
	A summary of assets by segment is as follows:
		(In Millions)
		September 30,			December 31, 2012
		2013
	Assets:
	U.S. Iron Ore	$	1,770.60		$	1,735.10
	Eastern Canadian Iron Ore	7,982.70			7,605.10
	Asia Pacific Iron Ore	1,188.70			1,506.30
	North American Coal	1,831.80			1,877.80
	Other	696.5			570.9
	Total segment assets	13,470.30			13,295.20
	Corporate	96.4			279.7
	Total assets	$	13,566.70		$	13,574.90

DERIVATIVE_INSTRUMENTS_AND_HED

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	9 Months Ended
	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	NOTE 3 - 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 Unaudited Condensed Consolidated Financial Position as of September 30, 2013 and December 31, 2012:
		(In Millions)
		Derivative Assets												Derivative Liabilities
		September 30, 2013						December 31, 2012						September 30, 2013				31-Dec-12
	Derivative	Balance Sheet Location		Fair				Balance		Fair				Balance Sheet		Fair		Balance Sheet	Fair
	Instrument			Value				Sheet		Value				Location		Value		Location	Value
								Location
	Derivatives designated as hedging instruments under ASC 815:
	Interest-rate Swaps	Derivative assets		$	1.7					$	—					$	—		$	—
	Foreign Exchange Contracts	Derivative assets		4.3				Derivative assets		16.2				Derivative liabilities		22		Derivative liabilities	1.9
	Total derivatives designated as hedging instruments under ASC 815			$	6					$	16.2					$	22		$	1.9
	Derivatives not designated as hedging instruments under ASC 815:
	Commodity Contracts			$	—					$	—			Derivative liabilities		$	2.7		$	—
	Customer Supply Agreements	Derivative assets		62.1				Derivative assets		58.9						—			—
	Provisional Pricing Arrangements	Derivative assets		4.6				Derivative assets		3.5				Derivative liabilities		11.4		Derivative liabilities	11.3
	Total derivatives not designated as hedging instruments under ASC 815			$	66.7					$	62.4					$	14.1		$	11.3
	Total derivatives			$	72.7					$	78.6					$	36.1		$	13.2
	Derivatives Designated as Hedging Instruments
	Cash Flow Hedges
	Australian and Canadian Dollar Foreign Exchange Contracts
	We are subject to changes in foreign currency exchange rates as a result of our operations in Australia and Canada. With respect to Australia, foreign exchange risk arises from our exposure to fluctuations in foreign currency exchange rates because the functional currency of our Asia Pacific operations is the Australian dollar. Our Asia Pacific operations receive funds in U.S. currency for their iron ore sales. The functional currency of our Canadian operations is the U.S. dollar; however, the production costs for these operations primarily are incurred in the Canadian dollar.
	We use foreign currency exchange contracts to hedge our foreign currency exposure for a portion of our U.S. dollar sales receipts in our Australian functional currency entities and our Canadian dollar operating costs. For our Australian operations, U.S. dollars are converted to Australian dollars at the currency exchange rate in effect during the period the transaction occurred. For our Canadian operations, U.S. dollars are converted to Canadian dollars at the exchange rate in effect for the period the operating costs are incurred. The primary objective for the use of these instruments is to reduce exposure to changes in Australian and U.S. currency exchange rates and U.S. and Canadian currency exchange rates, respectively, and to protect against undue adverse movement in these exchange rates. These instruments qualify for hedge accounting treatment, and are tested for effectiveness at inception and at least once each reporting period. If and when any of our hedge contracts are determined not to be highly effective as hedges, the underlying hedged transaction is no longer likely to occur, or the derivative is terminated, hedge accounting is discontinued.
	As of September 30, 2013, we had outstanding Australian and Canadian foreign currency exchange contracts with notional amounts of $333.0 million and $453.5 million, respectively, in the form of forward contracts with varying maturity dates ranging from October 2013 to September 2014. This compares with outstanding Australian and Canadian foreign currency exchange contracts with a notional amount of $400.0 million and $630.4 million, respectively, as of December 31, 2012.
	Changes in fair value of highly effective hedges are recorded as a component of Accumulated other comprehensive loss in the Statements of Unaudited Condensed Consolidated Financial Position. Any ineffectiveness is recognized immediately in income and, as of September 30, 2013 and 2012, there was no material ineffectiveness recorded for these foreign exchange contracts. Amounts recorded as a component of Accumulated other comprehensive loss are reclassified into earnings in the same period the forecasted transaction affects earnings. Of the amounts remaining in Accumulated other comprehensive loss related to Australian hedge contracts and Canadian hedge contracts, we estimate that losses of $13.4 million and gains of $1.0 million (net of tax), respectively, will be reclassified into earnings within the next 12 months.
	The following summarizes the effect of our derivatives designated as cash flow hedging instruments, net of tax in Accumulated other comprehensive loss in the Statements of Unaudited Condensed Consolidated Operations for the three and nine months ended September 30, 2013 and 2012:
		(In Millions)
	Derivatives in Cash Flow	Amount of Gain (Loss)								Location of Gain (Loss)		Amount of Gain (Loss)
		Recognized in OCI on Derivative								Reclassified		Reclassified
										from Accumulated OCI into Earnings		from Accumulated
												OCI into Earnings
	Hedging Relationships	(Effective Portion)								(Effective Portion)		(Effective Portion)
		Three Months Ended										Three Months Ended
		September 30,										September 30,
		2013				2012						2013				2012
	Australian Dollar Foreign	$	2.9			$	1.4			Product revenues		$	(8.9	)		$	5.1
	Exchange Contracts
	(hedge designation)
	Canadian Dollar Foreign Exchange Contracts (hedge designation)	9.2				11.3				Cost of goods sold and operating expenses		(7.3		)		1.3
	Total	$	12.1			$	12.7					$	(16.2	)		$	6.4
		Nine Months Ended										Nine Months Ended
		September 30,										September 30,
		2013				2012						2013				2012
	Australian Dollar Foreign	$	(25.2	)		$	7.5			Product revenues		$	(4.5	)		$	7.8
	Exchange Contracts
	(hedge designation)
	Canadian Dollar Foreign Exchange Contracts (hedge designation)	(9.9		)		6.2				Cost of goods sold and operating expenses		(7.5		)		1.6
		$	(35.1	)		$	13.7					$	(12.0	)		$	9.4
	Fair Value Hedges
	Interest Rate Hedges
	Interest rate risk is managed using a portfolio of variable- and fixed-rate debt composed of short- and long-term instruments, such as U.S. treasury lock agreements and interest rate swaps. From time to time, these instruments, which are derivative instruments, are entered into to facilitate the maintenance of the desired ratio of variable- to fixed-rate debt. These derivative instruments, with a notional amount of $250.0 million, are designated and qualify as fair value hedges as of September 30, 2013. These instruments did not have a material impact on our financial statements for the year ended December 31, 2012.
	For derivative instruments that are designated and qualify as fair-value hedges, the gain or loss on the hedge instrument as well as the offsetting loss or gain on the hedged item attributable to the hedged risk are recognized in current net income. We include the gain or loss on the derivative instrument and the offsetting loss or gain on the hedged item in Other non-operating income (expense). The net gain or loss recognized in Other non-operating income (expense) for the three and nine months ended September 30, 2013 and 2012 were as follows:
	(In Millions)
	Derivatives in Fair Value Hedging Relationships	Location of Gain Recognized in	Net Gain Recognized in Income on Derivative
		Income on Derivative
			Three Months Ended								Nine Months Ended
			September 30,								September 30,
			2013				2012				2013				2012
	Interest Rate Swaps	Other non-operating income (expense)	$	0.1			$	—			$	0.1			$	—
	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, some of which are subject to annual price collars in order to limit the percentage increase or decrease in prices for our iron ore pellets during any given year. The base price is the primary component of the purchase price for each contract. The inflation-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 percent Fe market rate and/or international pellet prices and changes in specified Producers Price Indices, including those for all commodities, 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.
	Certain supply agreements with one U.S. Iron Ore customer provide for supplemental revenue or refunds to the customer based on the customer’s average annual steel pricing 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 $53.9 million and $113.4 million as Product revenues in the Statements of Unaudited Condensed Consolidated Operations for the three and nine months ended September 30, 2013, respectively, related to the supplemental payments. This compares with Product revenues of $49.8 million and $131.8 million for the comparable respective periods in 2012. Derivative assets, representing the fair value of the pricing factors, were $62.1 million and $58.9 million in the September 30, 2013 and December 31, 2012 Statements of Unaudited Condensed Consolidated Financial Position, respectively.
	Provisional Pricing Arrangements
Certain of our U.S. Iron Ore, Eastern Canadian 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 point in time in the future, per the terms of the supply agreements. The difference between the provisionally agreed-upon price and the estimated final revenue rate is characterized as a freestanding derivative and is required to be accounted for separately once the provisional 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. At September 30, 2013 and December 31, 2012, we recorded $4.6 million and $3.5 million, respectively, as Derivative assets and $11.4 million and $11.3 million, respectively, as Derivative liabilities in the Statements of Unaudited Condensed Consolidated Financial Position related to our estimate of final revenue rate with our U.S. Iron Ore, Eastern Canadian Iron Ore and Asia Pacific Iron Ore customers at September 30, 2013 and related to our U.S. Iron Ore and Eastern Canadian Iron Ore customers at December 31, 2012. These amounts represent the difference between the provisional price agreed upon with our customers based on the supply agreement terms and our estimate of the final revenue rate based on the price calculations established in the supply agreements. As a result, we recognized a net $24.3 million increase and a net $6.8 million decrease in Product revenues in the Statements of Unaudited Condensed Consolidated Operations for the three and nine months ended September 30, 2013, respectively, related to these arrangements. This compares with a net $8.1 million decrease and a net $10.3 million decrease in Product revenues for the comparable respective periods in 2012.
The following summarizes the effect of our derivatives that are not designated as hedging instruments in the Statements of Unaudited Condensed Consolidated Operations for the three and nine months ended September 30, 2013 and 2012:
(In Millions)
Derivatives Not Designated as Hedging Instruments	Location of Gain (Loss) Recognized in	Amount of Gain/(Loss) Recognized in Income on Derivative
	Income on Derivative
		Three Months Ended								Nine Months Ended
		September 30,								September 30,
		2013				2012				2013				2012
Foreign Exchange Contracts	Other income (expense)	$	—			$	—			$	—			$	0.3
Foreign Exchange Contracts	Income (Loss) from Discontinued Operations, net of tax	—				1.1				—				1.1
Commodity Contracts	Other non-operating income (expense)	(2.7		)		—				(2.7		)		—
Customer Supply Agreements	Product revenues	53.9				49.8				113.4				131.8
Provisional Pricing Arrangements	Product revenues	24.3				(10.3		)		(6.8		)		(10.3		)
Total		$	75.5			$	40.6			$	103.9			$	122.9
Refer to NOTE 8 - FAIR VALUE OF FINANCIAL INSTRUMENTS for additional information.

INVENTORIES

INVENTORIES	9 Months Ended
	Sep. 30, 2013
Inventory Disclosure [Abstract]
Inventories	NOTE 4 - INVENTORIES
	The following table presents the detail of our Inventories in the Statements of Unaudited Condensed Consolidated Financial Position as of September 30, 2013 and December 31, 2012:
		(In Millions)
		30-Sep-13						31-Dec-12
	Segment	Finished Goods		Work-in Process		Total Inventory		Finished Goods		Work-in		Total
										Process		Inventory
	U.S. Iron Ore	$	160.4	$	20.3	$	180.7	$	147.2	$	22.9	$	170.1
	Eastern Canadian Iron Ore	54.2		36.2		90.4		62.6		44.2		106.8
	Asia Pacific Iron Ore	54		34.7		88.7		36.7		37.2		73.9
	North American Coal	55.6		23		78.6		36.7		49		85.7
	Total	$	324.2	$	114.2	$	438.4	$	283.2	$	153.3	$	436.5
	We recorded a lower-of-cost-or-market inventory charge during the third quarter of 2013 of $5.9 million relating to concentrate inventory primarily driven by extended maintenance shutdowns that resulted in higher costs and reduced fixed-cost leverage. We recorded these charges in Cost of goods sold and operating expenses in the Statements of Unaudited Condensed Consolidated Operations for our Eastern Canadian Iron Ore operations. For the nine months ended September 30, 2013, the lower-of-cost-or-market inventory charge recorded was $10.6 million concentrate inventory. During the first half of 2013, the Wabush concentrate inventory charge was caused by higher costs as a result of transitioning into concentrate-only production and the forest fire that temporarily idled the mine in June.
	Additionally, as a result of the idling of our Wabush pellet plant during the second quarter of 2013, we recorded a lower-of-cost-or-market inventory charge of $11.1 million relating to Wabush pellets that are contractually committed tons, and we recorded an unsaleable inventory impairment charge of $10.6 million relating to Wabush pellets. Both of these charges were recorded in Cost of goods sold and operating expenses in the second quarter of 2013 and included in the Statements of Unaudited Condensed Consolidated Operations for the nine months ended September 30, 2013 for our Eastern Canadian Iron Ore operations. No lower-of-cost-or-market inventory adjustments were recorded for the three and nine months ended September 30, 2012 within the Eastern Canadian Iron Ore operating segment results.
	We recorded lower-of-cost-or-market inventory charges of $2.6 million and $5.3 million in Cost of goods sold and operating expenses in the Statements of Unaudited Condensed Consolidated Operations for the three and nine months ended September 30, 2013, respectively, for our North American Coal operations. These charges were a result of market declines and costs associated with operational and geological issues. For the three and nine months ended September 30, 2012, we recorded lower-of-cost-or-market inventory charges of $8.0 million and $17.9 million, respectively, for our North American Coal operations due to market prices for coal.

PROPERTY_PLANT_AND_EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	9 Months Ended
	Sep. 30, 2013
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	NOTE 5 - PROPERTY, PLANT AND EQUIPMENT
	The following table indicates the value of each of the major classes of our consolidated depreciable assets as of September 30, 2013 and December 31, 2012:
		(In Millions)
		September 30,			December 31, 2012
		2013
	Land rights and mineral rights	$	7,826.50		$	7,920.80
	Office and information technology	119.3			92.4
	Buildings	214			162
	Mining equipment	1,554.70			1,290.70
	Processing equipment	2,172.80			1,937.40
	Railroad equipment	222.3			240.8
	Electric power facilities	82.9			58.7
	Port facilities	103.8			114.3
	Interest capitalized during construction	25.5			20.8
	Land improvements	63			43.9
	Other	91.8			39
	Construction in progress	1,049.20			1,123.90
		13,525.80			13,044.70
	Allowance for depreciation and depletion	(2,171.0		)	(1,837.4		)
		$	11,354.80		$	11,207.30
	We recorded depreciation and depletion expense of $148.3 million and $423.1 million in the Statements of Unaudited Condensed Consolidated Operations for the three and nine months ended September 30, 2013, respectively. This compares with depreciation and depletion expense of $127.7 million and $364.9 million for the three and nine months ended September 30, 2012, respectively.
	The accumulated amount of capitalized interest included within construction in progress at September 30, 2013 is $30.1 million, of which $15.3 million was capitalized during 2013. At December 31, 2012, $17.1 million of capitalized interest was included within construction in progress, of which $15.4 million was capitalized during 2012.

DISCONTINUED_OPERATIONS

DISCONTINUED OPERATIONS	9 Months Ended
	Sep. 30, 2013
Discontinued Operations and Disposal Groups [Abstract]
DISCONTINUED OPERATIONS	NOTE 6 - DISCONTINUED OPERATIONS
	The table below sets forth selected financial information related to operating results of our business classified as discontinued operations. While the reclassification of revenues and expenses related to discontinued operations for prior periods has no impact upon previously reported net income, the Statements of Unaudited Condensed Consolidated Operations present the revenues and expenses that were reclassified from the specified line items to discontinued operations. During the fourth quarter of 2012, we sold our 45 percent economic interest in Sonoma. The Sonoma operations previously were included in Other within our reportable segments.
	The following table presents detail of our operations related to our Sonoma operations in the Statements of Unaudited Condensed Consolidated Operations:
		(In Millions)
		Three Months Ended September 30,					Nine Months Ended September 30,
		2013		2012			2013		2012
	REVENUES FROM PRODUCT SALES AND SERVICES
	Product	$	—	$	42.6		$	—	$	141.6
	INCOME (LOSS) FROM DISCONTINUED OPERATIONS, net of tax	$	2	$	(2.7	)	$	2	$	5.2
	Income (Loss) from Discontinued Operations, net of tax during the three and nine months ended September 30, 2013 relates to additional income tax benefit resulting from the actual tax gain from the sale of Sonoma as included on the 2012 tax return, which was filed during the three months ended September 30, 2013.
	We recorded a loss from discontinued operations of $2.7 million, net of $1.2 million in income tax credits, and income from discontinued operations of $5.2 million, net of $2.1 million in tax expense in Income (Loss) from Discontinued Operations, net of tax for the three and nine months ended September 30, 2012, respectively, related to our previously owned interest in the Sonoma operations.

GOODWILL_AND_OTHER_INTANGIBLE_

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES	9 Months Ended
	Sep. 30, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES	NOTE 7 - GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES
	Goodwill
	The following table summarizes changes in the carrying amount of goodwill allocated by operating segment for the nine months ended September 30, 2013 and the year ended December 31, 2012:
		(In Millions)
		30-Sep-13																								December 31, 2012
		U.S. Iron Ore				Eastern Canadian Iron Ore				Asia Pacific				North American Coal				Other				Total				U.S. Iron Ore		Eastern			Asia Pacific Iron Ore		North American Coal			Other		Total
										Iron Ore																		Canadian Iron Ore
	Beginning Balance	$	2			$	—			$	84.5			$	—			$	80.9			$	167.4			$	2	$	986.2		$	83	$	—		$	80.9	$	1,152.10
	Arising in business combinations	—				—				—				—				—				—				—		13.8			—		—			—		13.8
	Impairment	—				—				—				—				—				—				—		(1,000.0		)	—		—			—		(1,000.0		)
	Impact of foreign currency translation	—				—				(8.8		)		—				—				(8.8		)		—		—			1.5		—			—		1.5
	Ending Balance	$	2			$	—			$	75.7			$	—			$	80.9			$	158.6			$	2	$	—		$	84.5	$	—		$	80.9	$	167.4
	Accumulated Goodwill Impairment Loss	$	—			$	(1,000.0	)		$	—			$	(27.8	)		$	—			$	(1,027.8	)		$	—	$	(1,000.0	)	$	—	$	(27.8	)	$	—	$	(1,027.8	)
	Other Intangible Assets and Liabilities
	Following is a summary of intangible assets and liabilities as of September 30, 2013 and December 31, 2012:
				(In Millions)
				30-Sep-13												31-Dec-12
		Classification		Gross				Accumulated				Net				Gross				Accumulated				Net
				Carrying				Amortization				Carrying				Carrying				Amortization				Carrying
				Amount								Amount				Amount								Amount
	Definite-lived intangible assets:
	Permits	Intangible assets, net		$	130.3			$	(35.7	)		$	94.6			$	136.1			$	(31.7	)		$	104.4
	Utility contracts	Intangible assets, net		54.7				(40.8		)		13.9				54.7				(32.4		)		22.3
	Leases	Intangible assets, net		5.7				(3.4		)		2.3				5.7				(3.4		)		2.3
	Total intangible assets			$	190.7			$	(79.9	)		$	110.8			$	196.5			$	(67.5	)		$	129
	Below-market sales contracts	Other current liabilities		$	(46.0	)		$	13.3			$	(32.7	)		$	(46.0	)		$	—			$	(46.0	)
	Below-market sales contracts	Other liabilities		(250.7		)		199.6				(51.1		)		(250.7		)		181.6				(69.1		)
	Total below-market sales contracts			$	(296.7	)		$	212.9			$	(83.8	)		$	(296.7	)		$	181.6			$	(115.1	)
	Amortization expense relating to intangible assets was $4.8 million and $14.9 million for the three and nine months ended September 30, 2013, respectively, and is recognized in Cost of goods sold and operating expenses in the Statements of Unaudited Condensed Consolidated Operations. Amortization expense relating to intangible assets was $4.8 million and $14.1 million for the comparable respective periods in 2012. 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
	2013 (remaining three months)	$	6.1
	2014	19.3
	2015	8.5
	2016	8.4
	2017	8.4
	2018	7.8
	Total	$	58.5
	The below-market sales contracts are classified as a liability and recognized over the term of the underlying contracts, which have remaining lives ranging from one to four years. For the three and nine months ended September 30, 2013, we recognized $14.7 million and $31.3 million, respectively, in Product revenues related to the below-market sales contracts, compared with $14.7 million and $31.3 million for the three and nine months ended September 30, 2012, respectively. The following amounts are estimated to be recognized in Product revenues for the remainder of this year and each of the three succeeding fiscal years:
		(In Millions)
		Amount
	Year Ending December 31
	2013 (remaining three months)	$	14.7
	2014	23
	2015	23
	2016	23.1
	Total	$	83.8

FAIR_VALUE_OF_FINANCIAL_INSTRU

FAIR VALUE OF FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	NOTE 8 - FAIR VALUE OF FINANCIAL INSTRUMENTS
	The following represents the assets and liabilities of the Company measured at fair value at September 30, 2013 and December 31, 2012:
		(In Millions)
		September 30, 2013
	Description	Quoted Prices in Active				Significant Other Observable Inputs				Significant Unobservable Inputs				Total
		Markets for Identical Assets/Liabilities				(Level 2)				(Level 3)
		(Level 1)
	Assets:
	Cash equivalents	$	192			$	—			$	—			$	192
	Derivative assets	—				1.7				66.7				68.4
	Marketable securities	26.7				—				—				26.7
	Foreign exchange contracts	—				4.3				—				4.3
	Total	$	218.7			$	6			$	66.7			$	291.4
	Liabilities:
	Derivative liabilities	$	—			$	2.7			$	11.4			$	14.1
	Foreign exchange contracts	—				22				—				22
	Total	$	—			$	24.7			$	11.4			$	36.1
		(In Millions)
		December 31, 2012
	Description	Quoted Prices in Active				Significant Other Observable Inputs				Significant Unobservable Inputs				Total
		Markets for Identical				(Level 2)				(Level 3)
		Assets/Liabilities (Level 1)
	Assets:
	Cash equivalents	$	100			$	—			$	—			$	100
	Derivative assets	—				—				62.4				62.4
	Marketable securities	27				—				—				27
	Foreign exchange contracts	—				16.2				—				16.2
	Total	$	127			$	16.2			$	62.4			$	205.6
	Liabilities:
	Derivative liabilities	$	—			$	—			$	11.3			$	11.3
	Foreign exchange contracts	—				1.9				—				1.9
	Total	$	—			$	1.9			$	11.3			$	13.2
	Financial assets classified in Level 1 at September 30, 2013 and December 31, 2012 include money market funds and available-for-sale marketable securities. The valuation of these instruments is based upon unadjusted quoted prices for identical assets in active markets.
	The valuation of financial assets and liabilities classified in Level 2 is determined using a market approach based upon quoted prices for similar assets and liabilities in active markets, or other inputs that are observable. Level 2 securities primarily include derivative financial instruments valued using financial models that use as their basis readily observable market parameters. At September 30, 2013, such derivative financial instruments included our existing foreign currency exchange contracts, commodity contracts, and interest rate swaps. At December 31, 2012, such derivative financial instruments included our existing foreign currency exchange contracts. The fair value of the foreign currency exchange contracts is based on forward market prices and represents the estimated amount we would receive or pay to terminate these agreements at the reporting date, taking into account creditworthiness, nonperformance risk and liquidity risks associated with current market conditions.
	The derivative financial assets classified within Level 3 at September 30, 2013 and December 31, 2012 included 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 steel at the steelmaker’s facilities, and takes into consideration current market conditions and nonperformance risk.
	The Level 3 derivative assets and liabilities at September 30, 2013 and December 31, 2012, also consisted of derivatives related to certain provisional pricing arrangements with our U.S. Iron Ore, Eastern Canadian Iron Ore and Asia Pacific Iron Ore customers at September 30, 2013 and our U.S. Iron Ore and Eastern Canadian Iron Ore customers at December 31, 2012. 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 provisionally agreed-upon price 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				Balance Sheet Location		Valuation Technique		Unobservable Input		Range or Point Estimate
			9/30/13										(Weighted Average)
	Provisional Pricing Arrangements		$	4.6			Derivative assets		Market Approach		Management's		$131
											Estimate of 62% Fe
			$	11.4			Derivative liabilities
	Customer Supply Agreement		$	62.1			Derivative assets		Market Approach		Hot-Rolled Steel Estimate		$590 - $660 ($630)
	The significant unobservable input used in the fair value measurement of the reporting entity’s provisional pricing arrangements is management’s estimate of 62 percent Fe price based upon current market data, including historical seasonality 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.
	The significant unobservable input used in the fair value measurement of the reporting entity’s customer supply agreements is the future hot-rolled steel price that is estimated based on current market data, analysts' projections, projections provided by the customer and forward-looking estimates determined by management. Significant increases or decreases in this input would result in a significantly higher or lower fair value measurement, respectively.
	Substantially all of the financial assets and liabilities are carried at fair value or contracted amounts that approximate fair value.
	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 nine months of 2013 or 2012. The following tables represent a reconciliation of the changes in fair value of financial instruments measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the three and nine months ended September 30, 2013 and 2012.
		(In Millions)
		Derivative Assets (Level 3)
		Three Months Ended								Nine Months Ended
		September 30,								September 30,
		2013				2012				2013				2012
	Beginning balance	$	45.1			$	83.9			$	62.4			$	157.9
	Total gains
	Included in earnings	57.6				24.9				118				129.6
	Settlements	(36.0		)		(52.9		)		(113.7		)		(231.6		)
	Transfers into Level 3	—				—				—				—
	Transfers out of Level 3	—				—				—				—
	Ending balance - September 30	$	66.7			$	55.9			$	66.7			$	55.9
	Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date	$	57.6			$	24.9			$	118			$	129.6
		(In Millions)
		Derivative Liabilities (Level 3)
		Three Months Ended								Nine Months Ended
September 30,							September 30,
	2013				2012				2013				2012
Beginning balance	$	(32.0	)		$	(15.8	)		$	(11.3	)		$	(19.5	)
Total gains
Included in earnings	20.6				4.1				(11.4		)		(11.7		)
Settlements	—				—				11.3				19.5
Transfers into Level 3	—				—				—				—
Transfers out of Level 3	—				—				—				—
Ending balance - September 30	$	(11.4	)		$	(11.7	)		$	(11.4	)		$	(11.7	)
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	$	20.6			$	4.1			$	(11.4	)		$	(11.7	)
Gains and losses included in earnings are reported in Product revenues in the Statements of Unaudited Condensed Consolidated Operations for the three and nine months ended September 30, 2013 and 2012.
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 September 30, 2013 and December 31, 2012 were as follows:
			(In Millions)
			September 30, 2013								December 31, 2012
	Classification		Carrying				Fair Value				Carrying				Fair Value
			Value								Value
Other receivables:
Customer supplemental payments	Level 2		$	—			$	—			$	22.3			$	21.3
ArcelorMittal USA—Receivable	Level 2		13.4				14.3				19.3				21.3
Other	Level 2		10.1				10.1				10.9				10.9
Total receivables			$	23.5			$	24.4			$	52.5			$	53.5
Long-term debt:
Term loan—$1.25 billion	Level 2		$	—			$	—			$	753			$	753
Senior notes—$700 million	Level 2		699.4				719.2				699.4				759.4
Senior notes—$1.3 billion	Level 2		1,289.60				1,442.20				1,289.40				1,524.70
Senior notes—$400 million	Level 2		398.4				439.7				398.2				464.3
Senior notes—$500 million	Level 2		496.3				528.4				495.7				528.4
Revolving loan	Level 2		380				380				325				325
Equipment Loan Facilities	Level 2		54.2				54.2				—				—
Fair Value Adjustment to Interest Rate Hedge	Level 2		1.7				1.7				—				—
Total long-term debt			$	3,319.60			$	3,565.40			$	3,960.70			$	4,354.80
The fair value of the receivables and debt are based on the fair market yield curves for the remainder of the term expected to be outstanding.
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 up to $22.3 million in exchange for interest payments until the deferred amount was repaid in 2013. Interest was payable by the customer quarterly and began in September 2009 at the higher of 9 percent or the prime rate plus 350 basis points. During the first half of 2013, payments totaling $22.3 million on the outstanding amount due were made by the customer and the receivable was fully repaid by the end of June 2013. As of December 31, 2012, the receivable of $22.3 million was classified as current and recorded in Other current assets in the Statements of Unaudited Condensed Consolidated Financial Position as all supplemental payments to be paid by the customer were due by the end of 2013. The fair value of the receivable of $21.3 million at December 31, 2012 is based on a discount rate of 2.81 percent, which represented the estimated credit-adjusted risk-free interest rate for the period the receivable was outstanding.
In 2002, we entered into an agreement with Ispat that restructured the ownership of the Empire mine and increased our ownership from 46.7 percent to 79.0 percent in exchange for the assumption of all mine liabilities. Under the terms of the agreement, we indemnified Ispat from obligations of Empire in exchange for certain future payments to Empire and to us by Ispat of $120.0 million, recorded at a present value of $13.4 million and $19.3 million at September 30, 2013 and December 31, 2012, respectively, of which $10.0 million was recorded in Other current assets at September 30, 2013 and December 31, 2012. The fair value of the receivable of $14.3 million and $21.3 million at September 30, 2013 and December 31, 2012, respectively, is based on a discount rate of 1.98 percent and 2.85 percent, respectively, which represents the estimated credit-adjusted risk-free interest rate for the period the receivable is outstanding.
The fair value of long-term debt was determined using quoted market prices or discounted cash flows based upon current borrowing rates. The term loan and revolving loan are variable rate interest and approximate fair value. See NOTE 9 - DEBT AND CREDIT FACILITIES for further information.
Items Measured at Fair Value on a Non-Recurring Basis
The following tables present information about the impairment charges on both financial and nonfinancial assets that were measured on a fair value basis at September 30, 2013 and December 31, 2012. The table also indicates the fair value hierarchy of the valuation techniques used to determine such fair value.
		(In Millions)
		30-Sep-13
Description		Quoted Prices in Active		Significant Other Observable Inputs		Significant Unobservable Inputs		Total				Total Losses
		Markets for Identical Assets/		(Level 2)		(Level 3)
		Liabilities
		(Level 1)
Assets:
Investment in ventures impairment -		—		—		—		$	—			$	67.6
Amapá
In light of the March 28, 2013 collapse of the Santana port shiploader and subsequent evaluation of the effect that this event had on the carrying value of our investment in Amapá as of June 30, 2013, we recorded an impairment charge of $67.6 million in the second quarter of 2013.
		(In Millions)
		December 31, 2012
Description		Quoted Prices in Active				Significant Other Observable Inputs				Significant Unobservable Inputs				Total
		Markets for Identical Assets/				(Level 2)				(Level 3)
		Liabilities
		(Level 1)
Assets:
Investment in ventures impairment -		$	—			$	—			$	72.5			$	72.5
Amapá
On December 27, 2012, the board of directors approved the sale of our 30 percent investment in Amapá, which is recorded as an equity method investment in the Statements of Unaudited Condensed Consolidated Operations. The carrying value of the investment was reduced to fair value of $72.5 million as of December 31, 2012, resulting in an impairment charge of $365.4 million, which was recorded in the fourth quarter of 2012. We believe the sum of the sale proceeds approximates fair value. The fair value of the proceeds (and therefore the portion of the equity method investment measured at fair value) was determined using a probability-weighted cash flow approach.

DEBT_AND_CREDIT_FACILITIES

DEBT AND CREDIT FACILITIES	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]
DEBT AND CREDIT FACILITIES	NOTE 9 - DEBT AND CREDIT FACILITIES
	The following represents a summary of our long-term debt as of September 30, 2013 and December 31, 2012:
	($ in Millions)
	September 30, 2013
	Debt Instrument		Type	Annual Effective Interest Rate	Final Maturity	Total Face Amount			Total Debt
	$700 Million 4.875% 2021 Senior Notes		Fixed	4.89%	2021	$	700		$	699.4	-2
	$1.3 Billion Senior Notes:
	$500 Million 4.80% 2020 Senior Notes		Fixed	4.83%	2020	500			499.2		-3
	$800 Million 6.25% 2040 Senior Notes		Fixed	6.34%	2040	800			790.4		-4
	$400 Million 5.90% 2020 Senior Notes		Fixed	5.98%	2020	400			398.4		-5
	$500 Million 3.95% 2018 Senior Notes		Fixed	4.14%	2018	500			496.3		-6
	$1.75 Billion Credit Facility:
	Revolving Loan		Variable	2.08%	2017	1,750.00			380		-7
	Equipment Loans		Fixed	Various	2020	62.1			62.1
	Fair Value Adjustment to Interest Rate Hedge								1.7
	Total debt					$	4,712.10		$	3,327.50
	Less current portion								7.9
	Long-term debt								$	3,319.60
	($ in Millions)
	31-Dec-12
	Debt Instrument		Type	Annual Effective Interest Rate	Final Maturity	Total Face Amount			Total Debt
	$1.25 Billion Term Loan		Variable	1.83%	2016	$	847.1	-1	$	847.1	-1
	$700 Million 4.875% 2021 Senior Notes		Fixed	4.88%	2021	700			699.4		-2
	$1.3 Billion Senior Notes:
	$500 Million 4.80% 2020 Senior Notes		Fixed	4.80%	2020	500			499.2		-3
	$800 Million 6.25% 2040 Senior Notes		Fixed	6.25%	2040	800			790.2		-4
	$400 Million 5.90% 2020 Senior Notes		Fixed	5.90%	2020	400			398.2		-5
	$500 Million 3.95% 2018 Senior Notes		Fixed	4.14%	2018	500			495.7		-6
	$1.75 Billion Credit Facility:
	Revolving Loan		Variable	2.02%	2017	1,750.00			325		-7
	Total debt					$	5,497.10		$	4,054.80
	Less current portion								94.1
	Long-term debt								$	3,960.70
	-1	During the first quarter of 2013, the term loan was repaid in full through repayments totaling $847.1 million. As of December 31, 2012, $402.8 million had been paid on the original $1.25 billion term loan and, of the remaining term loan, $94.1 million was classified as Current portion of debt. The current classification was based upon the principal payment terms of the arrangement requiring principal payments on each three-month anniversary following the funding of the term loan.
	-2	As of September 30, 2013 and December 31, 2012, the $700 million 4.875 percent senior notes were recorded at a par value of $700 million less unamortized discounts of $0.6 million for each period, based on an imputed interest rate of 4.89 percent.
	-3	As of September 30, 2013 and December 31, 2012, the $500 million 4.80 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $0.8 million for each period, based on an imputed interest rate of 4.83 percent.
	-4	As of September 30, 2013 and December 31, 2012, the $800 million 6.25 percent senior notes were recorded at par value of $800 million less unamortized discounts of $9.6 million and $9.8 million, respectively, based on an imputed interest rate of 6.34 percent.
	-5	As of September 30, 2013 and December 31, 2012, the $400 million 5.90 percent senior notes were recorded at a par value of $400 million less unamortized discounts of $1.6 million and $1.8 million, respectively, based on an imputed interest rate of 5.98 percent.
	-6	As of September 30, 2013 and December 31, 2012, the $500 million 3.95 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $3.7 million and $4.3 million, respectively, based on an imputed interest rate of 4.14 percent.
	-7	As of September 30, 2013 and December 31, 2012, $380.0 million and $325.0 million revolving loans were drawn under the credit facility, respectively, and the principal amount of letter of credit obligations totaled $27.7 million for each period, thereby reducing available borrowing capacity to $1.3 billion and $1.4 billion for each period, respectively.
	Credit Facility and Term Loan
	On February 8, 2013, we amended the Term Loan Agreement among Cliffs Natural Resources Inc. and various lenders dated March 4, 2011, as amended, or term loan, and the Amended and Restated Multicurrency Credit Agreement among Cliffs Natural Resources Inc. and various lenders dated August 11, 2011 (as further amended by Amendment No. 1 as of October 16, 2012), or amended credit agreement, to effect the following:
	•	Suspend the current Funded Debt to EBITDA ratio requirement for all quarterly measurement periods in 2013, after which point it will revert back to the period ending March 31, 2014 until maturity.
	•	Require a Minimum Tangible Net Worth of approximately $4.6 billion as of each of the three-month periods ended March 31, 2013, June 30, 2013, September 30, 2013 and December 31, 2013. Minimum Tangible Net Worth, in accordance with the amended credit agreement and term loan, is defined as total equity less goodwill and intangible assets.
	•	Maintain a Maximum Total Funded Debt to Capitalization of 52.5 percent from the amendments' effective date through the period ending December 31, 2013.
	•	The amended agreements retain the Minimum Interest Coverage Ratio requirement of 2.5 to 1.0.
	During February 2013, we repaid the $847.1 million outstanding balance under the term loan through the use of proceeds from the 2013 public equity offerings. Additionally, as a result of the term loan repayment, the remaining deferred financing costs associated with the issuance of the term loan of $7.1 million were expensed. Upon the repayment of the term loan, the financial covenants associated with the term loan no longer were applicable.
	Per the terms of the amended credit agreement, we are subject to higher borrowing costs. The applicable interest rate is determined by reference to the former Funded Debt to EBITDA ratio. Based on the amended terms, borrowing costs could increase as much as 0.5 percent relative to the outstanding borrowings, as well as 0.1 percent on unborrowed amounts. Furthermore, the amended credit agreement places certain restrictions upon our declaration and payment of dividends, our ability to consummate acquisitions and the debt levels of our subsidiaries.
	As of September 30, 2013, we were in compliance with all applicable financial covenants related to the amended credit agreement.
	At December 31, 2012, prior to the amendments made on February 8, 2013 that are discussed above, the terms of the term loan and amended credit agreement each contained customary covenants that require compliance with certain financial covenants based on: (1) debt to earnings ratio (Total Funded Debt to EBITDA, as those terms are defined in the amended credit agreement), as of the last day of each fiscal quarter cannot exceed (i) 3.5 to 1.0, if none of the $270.0 million private placement senior notes due 2013 remain outstanding, or otherwise (ii) the then applicable maximum multiple under the $270.0 million private placement senior notes due 2013 and (2) interest coverage ratio (Consolidated EBITDA to Interest Expense, as those terms are defined in the amended credit agreement), for the preceding four quarters must not be less than 2.5 to 1.0 on the last day of any fiscal quarter. As the $270.0 million private placement senior notes due 2013 were repaid on December 28, 2012 with proceeds from the 2012 public debt offering, the financial covenant relating to the outstanding notes no longer was applicable. As of December 31, 2012, we were in compliance with the financial covenants related to both the term loan and the amended credit agreement.
	Equipment Loans
	During September 2013, we entered into $62.1 million of seven-year installment equipment loans with various interest rates.  The loans are secured by equipment from our Eastern Canadian Iron Ore operations.  Proceeds from the borrowings were used for general corporate purposes.
	Short-Term Facilities
	Asia Pacific Iron Ore maintains a bank contingent instrument and cash advance facility. The facility, which is renewable annually at the bank’s discretion, provides A$30.0 million ($27.9 million) at September 30, 2013 in credit for contingent instruments, such as performance bonds, and the ability to request a cash advance facility to be provided at the discretion of the bank. The facility limit was reduced from A$40.0 million to A$30.0 million during the third quarter of 2013. At December 31, 2012, the facility provided A$40.0 million ($41.6 million) in credit for contingent instruments. As of September 30, 2013, the outstanding bank guarantees under the facility totaled A$27.5 million ($25.6 million), thereby reducing borrowing capacity to A$2.5 million ($2.3 million). As of December 31, 2012, the outstanding bank guarantees under the facility totaled A$25.0 million ($26.0 million), thereby reducing borrowing capacity to A$15.0 million ($15.6 million). We have provided a guarantee of the facility, along with certain of our Australian subsidiaries. The terms of the short-term facility contain certain customary covenants; however, there are no financial covenants.
	Letters of Credit
	We issued standby letters of credit with certain financial institutions in order to support Bloom Lake’s general business obligations. In addition, we issued standby letters of credit with certain financial institutions during the third quarter of 2011 in order to support Wabush’s obligations. As of September 30, 2013 and December 31, 2012, these letter of credit obligations totaled $43.3 million and $96.9 million, respectively. All of these standby letters of credit are in addition to the letters of credit provided for under the amended credit agreement.
	Debt Maturities
	The following represents a summary of our maturities of debt instruments, excluding borrowings on the amended credit agreement, based on the principal amounts outstanding at September 30, 2013:
		(In Millions)
		Maturities of Debt
	2013 (October 1 - December 31)	$	1.9
	2014	7.9
	2015	8.3
	2016	8.6
2017	8.9
2018 and thereafter	2,926.50
Total maturities of debt	$	2,962.10

LEASE_OBLIGATIONS

LEASE OBLIGATIONS	9 Months Ended
	Sep. 30, 2013
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 $5.3 million and $19.5 million for the three and nine months ended September 30, 2013, respectively, compared with $6.7 million and $19.2 million for the same respective periods in 2012.
	Future minimum payments under capital leases and non-cancellable operating leases at September 30, 2013 are as follows:
		(In Millions)
		Capital Leases			Operating Leases
	2013 (October 1 - December 31)	$	18.2		$	8.2
	2014	65.5			20
	2015	87			13.5
	2016	36.1			8.3
	2017	28.6			7.5
	2018 and thereafter	54.2			21.5
	Total minimum lease payments	$	289.6		$	79
	Amounts representing interest	54.4
	Present value of net minimum lease payments	$	235.2	-1
	-1	The total is comprised of $51.3 million and $183.9 million classified as Other current liabilities and Other liabilities, respectively, in the Statements of Unaudited Condensed Consolidated Financial Position at September 30, 2013.

ENVIRONMENTAL_AND_MINE_CLOSURE

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	9 Months Ended
	Sep. 30, 2013
Environmental Remediation Obligations [Abstract]
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	NOTE 11 - ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS
	We had environmental and mine closure liabilities of $310.2 million and $265.1 million at September 30, 2013 and December 31, 2012, respectively. The following is a summary of the obligations as of September 30, 2013 and as of the year ended December 31, 2012:
		(In Millions)
		September 30,			December 31, 2012
		2013
	Environmental	$	8.4		$	15.7
	Mine closure
	LTVSMC	19.4			18.3
	Operating mines:
	U.S. Iron Ore	139.6			81.2
	Eastern Canadian Iron Ore	76.6			88.9
	Asia Pacific Iron Ore	26.2			22.4
	North American Coal	40			38.6
	Total mine closure	301.8			249.4
	Total environmental and mine closure obligations	310.2			265.1
	Less current portion	10.7			12.3
	Long term environmental and mine closure obligations	$	299.5		$	252.8
	Mine Closure
	Our mine closure obligations are for our four consolidated U.S. operating iron ore mines, our two Eastern Canadian operating iron ore mines, our Asia Pacific operating iron ore mine, our five operating North American coal mines and a closed operation formerly operating as LTVSMC.
	The accrued closure obligation for our active mining operations provides for contractual and legal obligations associated with the eventual closure of the mining operations. The accretion of the liability and amortization of the related asset is recognized over the estimated mine lives for each location.
	The following represents a rollforward of our asset retirement obligation liability related to our active mining locations for the nine months ended September 30, 2013 and the year ended December 31, 2012:
		(In Millions)
		September 30,			December 31, 2012 (1)
		2013
	Asset retirement obligation at beginning of period	$	231.1		$	194.9
	Accretion expense	13.6			17.6
	Exchange rate changes	2.8			0.3
	Revision in estimated cash flows	35.2			18.2
	Payments	(0.3		)	0.1
	Asset retirement obligation at end of period	$	282.4		$	231.1
	-1	Represents a 12-month rollforward of our asset retirement obligation at December 31, 2012.
	The revisions in estimated cash flows recorded during the nine months ended September 30, 2013 primarily include estimated asset retirement costs for one of our U.S. Iron Ore mines associated with required storm water management systems expected to be implemented subsequent to the closure of the mine.

PENSIONS_AND_OTHER_POSTRETIREM

PENSIONS AND OTHER POSTRETIREMENT BENEFITS	9 Months Ended
	Sep. 30, 2013
Postemployment Benefits [Abstract]
PENSIONS AND OTHER POSTRETIREMENT BENEFITS	NOTE 12 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS
	The following are the components of defined benefit pension and OPEB expense for the three and nine months ended September 30, 2013 and 2012:
	Defined Benefit Pension Expense
		(In Millions)
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2013			2012			2013			2012
	Service cost	$	9.6		$	8		$	29.2		$	24
	Interest cost	11.2			12.1			34.4			36.4
	Expected return on plan assets	(16.2		)	(14.9		)	(49.3		)	(44.7		)
	Amortization:
	Prior service costs	0.8			1.1			2.3			3
	Net actuarial loss	7.5			7.4			22.5			22.4
	Settlements	—			0.4			—			0.4
	Net periodic benefit cost	$	12.9		$	14.1		$	39.1		$	41.5
	Other Postretirement Benefits Expense
		(In Millions)
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2013			2012			2013			2012
	Service cost	$	3		$	3.7		$	9.2		$	11.2
	Interest cost	4.3			5.3			13			15.9
	Expected return on plan assets	(5.0		)	(4.3		)	(15.0		)	(12.9		)
	Amortization:
	Prior service costs	(0.9		)	0.7			(2.7		)	2.2
	Net actuarial loss	2.9			2.8			8.7			8.4
	Net periodic benefit cost	$	4.3		$	8.2		$	13.2		$	24.8
	We made pension contributions of $36.1 million and $51.2 million for the three and nine months ended September 30, 2013, respectively, compared to pension contributions of $7.6 million and $32.5 million for the three and nine months ended September 30, 2012, respectively. The OPEB contributions, made annually in the first quarter, were $14.1 million and $21.9 million for the nine months ended September 30, 2013 and 2012, respectively.

STOCK_COMPENSATION_PLANS

STOCK COMPENSATION PLANS	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK COMPENSATION PLANS	NOTE 13 - STOCK COMPENSATION PLANS
	Employees’ Plans
	On March 11, 2013, the Compensation and Organization Committee (“Committee”) of the board of directors approved a grant under our shareholder-approved 2012 Equity Plan for the 2013 to 2015 performance period. A total of 1.0 million shares were granted under the award, consisting of 0.8 million performance shares and 0.2 million restricted share units.
	The 2012 Equity Plan was approved by our board of directors on March 13, 2012 and our shareholders approved it on May 8, 2012, effective as of March 13, 2012. The 2012 Equity Plan replaced the ICE Plan. The maximum number of shares that may be issued under the 2012 Equity Plan is 6.0 million common shares. During 2012, a total of 23.6 thousand and 426.6 thousand shares were granted under the 2012 Equity Plan and the ICE Plan, respectively.
	The ICE Plan was terminated on May 8, 2012 and no additional grants will be issued from the ICE Plan after this date; however, all awards previously granted under the ICE Plan continue in full force and effect in accordance with the terms of the award.
	For the outstanding ICE Plan and Equity Plan awards, each performance share, if earned, entitles the holder to receive common shares or cash within a range between a threshold and maximum number of our common shares, with the actual number of common shares earned dependent upon whether the Company achieves certain objectives and performance goals as established by the Committee. The 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 for the 2011 to 2013 performance period is measured on the basis of two factors: 1) relative TSR for the period and 2) three-year cumulative free cash flow. The relative TSR for the 2011 to 2013 performance period is measured against the constituents of the S&P Metals and Mining ETF Index on the last day of trading of the performance period. Performance for the 2012 to 2014 and for the 2013 to 2015 performance periods are measured only on the basis of relative TSR for the period and measured against the constituents of the S&P Metals and Mining ETF Index on the last day of trading of the performance period. The final payouts for the 2011 to 2013 performance period, the 2012 to 2014 performance period and the 2013 to 2015 performance period will vary from zero to 200 percent of the original grant. The restricted share units are subject to continued employment, are retention based, will vest at the end of the respective performance period, and are payable in common shares or cash in certain circumstances at a time determined by the Committee at its discretion.
	Upon the occurrence of a change in control, all performance shares, restricted share units, restricted stock, performance units and retention units granted to a participant will vest and become nonforfeitable and will be paid out in cash.
	Determination of Fair Value
	The fair value of each grant is estimated on the date of grant using a Monte Carlo simulation to forecast relative TSR performance. A correlation matrix of historic and projected stock prices was developed for both the Company and our predetermined peer group of mining and metals companies. The fair value assumes that performance goals will be achieved.
	The expected term of the grant represents the time from the grant date to the end of the service period for each of the three plan-year agreements. We estimate the volatility of our common shares and that of the peer group of mining and metals companies using daily price intervals for all companies. The risk-free interest rate is the rate at the grant date on zero-coupon government bonds, with a term commensurate with the remaining life of the performance plans.
	The following assumptions were utilized to estimate the fair value for the first quarter of 2013 performance share grants:
	Grant Date	Grant Date Market Price		Average Expected Term (Years)	Expected Volatility	Risk-Free Interest Rate	Dividend Yield	Fair Value		Fair Value (Percent of Grant Date Market Price)
	March 11, 2013	$	23.83	2.81	52.90%	0.40%	2.52%	$	17.01	71.38%
	The fair value of the restricted share units is determined based on the closing price of the Company’s common shares on the grant date. The restricted share units granted under either the ICE Plan or 2012 Equity Plan vest over a period of three years.

INCOME_TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 14 - INCOME TAXES
	Our 2013 estimated annual effective tax rate before discrete items is approximately 16.2 percent. This estimated annual effective tax rate differs from the U.S. statutory rate of 35 percent primarily due to deductions for percentage depletion in excess of cost depletion related to U.S. operations, income not subject to tax and foreign taxes and benefits derived from operations outside the United States, which are taxed at rates lower than the U.S. statutory rate of 35 percent. There were discrete items booked in the first nine months of 2013 of approximately $14.7 million benefit. These adjustments relate primarily to deferred tax balances, which include the amendments of prior year income tax returns and the reversal of a previously recorded valuation allowance for which it was determined the benefit of the associated deferred tax asset is realizable.

CAPITAL_STOCK

CAPITAL STOCK	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]
CAPITAL STOCK	NOTE 15 - CAPITAL STOCK
	Depositary Shares
	On February 21, 2013, we issued 29.25 million depositary shares, equivalent to 731,250 preferred shares, comprised of the 27.0 million depositary share offering and the exercise of an underwriters' over-allotment option to purchase an additional 2.25 million depositary shares. Each depositary share represents a 1/40th interest in a share of our 7.00 percent Series A Mandatory Convertible Preferred Stock, Class A, without par value, or Preferred Share, at a price of $25 per depositary share for total net proceeds of approximately $709.4 million, after underwriter fees and discounts. Each Preferred Share has an initial liquidation preference of $1,000 per share (equivalent to a $25 liquidation preference per depositary share). When and if declared by our board of directors, we will pay cumulative dividends on each Preferred Share at an annual rate of 7.00 percent on the liquidation preference. We will pay declared dividends in cash on February 1, May 1, August 1 and November 1 of each year, commencing on May 1, 2013 and to, and including February 1, 2016. Holders of the depositary shares are entitled to a proportional fractional interest in the rights and preferences of the Preferred Shares, including conversion, dividend, liquidation and voting rights, subject to the provisions of the deposit agreement.
	The Preferred Shares may be converted, 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 Preferred Share will convert 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 issuable on conversion will be determined based on the average VWAP per share of our common shares during the 20 trading day period beginning on, and including, the 23rd scheduled trading day prior to February 1, 2016, subject to customary anti-dilution adjustments. Upon conversion, a minimum of 20.6 million common shares and a maximum of 25.2 million common shares will be issued.
	If certain fundamental changes involving the Company occur, holders of the Preferred Shares may convert their shares into a number of common shares at the conversion rate that will be adjusted under certain circumstances, and such holders also will be entitled to a fundamental change dividend make-whole amount. The Preferred Shares are not redeemable.
	Common Share Public Offering
	On February 21, 2013, we issued 10.35 million common shares, comprised of the 9.0 million common share offering and the exercise of an underwriters' over-allotment option to purchase an additional 1.35 million common shares. We received net proceeds of approximately $285.3 million at a closing price of $29.00 per common share.
	Dividends
	On March 20, 2013, our board of directors declared a cash dividend of $13.6111 per Preferred Share, which is equivalent to approximately $0.34 per depositary share. The cash dividend was paid on May 1, 2013 to our shareholders of record as of the close of business on April 15, 2013. On May 7, 2013, 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 August 1, 2013 to our shareholders of record as of the close of business on July 15, 2013. On September 9, 2013, 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 of $12.9 million will be paid on November 1, 2013 to our shareholders of record as of the close of business on October 15, 2013.
	A $0.28 per common share cash dividend was paid on March 1, 2012 to our shareholders of record as of the close of business on February 15, 2012. On March 13, 2012, our board of directors increased the quarterly common share dividend by 123 percent to $0.625 per share. The increased cash dividend of $0.625 per share was paid on June 1, 2012, August 31, 2012 and December 3, 2012 to our common shareholders of record as of the close of business on April 27, 2012, August 15, 2012 and November 23, 2012, respectively. On February 11, 2013, our board of directors approved a reduction to our quarterly cash dividend rate by 76 percent to $0.15 per share. Our board of directors took this step in order to improve the future cash flows available for investment in the Phase II expansion at Bloom Lake, as well as to preserve our investment-grade credit ratings. The decreased dividend of $0.15 per share was paid on March 1, 2013, June 3, 2013 and September 3, 2013 to our common shareholders of record as of the close of business on February 22, 2013, May 17, 2013 and August 15, 2013, respectively.

SHAREHOLDERS_EQUITY

SHAREHOLDERS' EQUITY	9 Months Ended
	Sep. 30, 2013
Shareholders' Equity [Abstract]
SHAREHOLDERS' EQUITY	NOTE 16 - SHAREHOLDERS' EQUITY
	The following table reflects the changes in shareholders' equity attributable to both Cliffs and the noncontrolling interests primarily related to Bloom Lake, Tilden and Empire of which Cliffs owns 75 percent, 85 percent and 79 percent, respectively, for the nine months ended September 30, 2013 and September 30, 2012:
		(In Millions)
		Cliffs				Noncontrolling				Total Equity
		Shareholders’				Interest
		Equity
	31-Dec-12	$	4,632.70			$	1,128.20			$	5,760.90
	Comprehensive income
	Net income	370.2				5.8				376
	Other comprehensive income (loss)	(122.8		)		3.2				(119.6		)
	Total comprehensive income	247.4				9				256.4
	Issuance of common shares	285.3				—				285.3
	Issuance of Preferred Shares	709.4				—				709.4
	Stock and other incentive plans	9.6				—				9.6
	Common and Preferred Shares dividends	(104.7		)		—				(104.7		)
	Capital contribution by noncontrolling	—				17.7				17.7
	interest to subsidiary
	30-Sep-13	$	5,779.70			$	1,154.90			$	6,934.60
		(In Millions)
		Cliffs				Noncontrolling				Total Equity
		Shareholders’				Interest
		Equity
	31-Dec-11	$	5,785.00			$	1,254.70			$	7,039.70
	Comprehensive income
	Net income	719				25.2				744.2
	Other comprehensive income	41.6				4.5				46.1
	Total comprehensive income	760.6				29.7				790.3
	Stock and other incentive plans	9				—				9
	Common shares dividends	(217.8		)		—				(217.8		)
	Undistributed gains to noncontrolling interest	—				11.3				11.3
	Capital contribution by noncontrolling interest	—				64.7				64.7
	to subsidiary
	Acquisition of controlling interest	—				(8.0		)		(8.0		)
	30-Sep-12	$	6,336.80			$	1,352.40			$	7,689.20
	The following table reflects the changes in Accumulated other comprehensive income (loss) related to Cliffs shareholders’ equity for September 30, 2013 and September 30, 2012:
		(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, 2012	$	(382.7	)		$	2.1			$	316.3		$	8.7		$	(55.6	)
	Other comprehensive income (loss) before reclassifications	(1.1		)		2.5				3.3			(5.0		)	(0.3		)
	Net loss (gain) reclassified from accumulated other comprehensive income (loss)	6.4				0.1				—			(2.0		)	4.5
	Balance March 31, 2013	$	(377.4	)		$	4.7			$	319.6		$	1.7		$	(51.4	)
	Other comprehensive loss before reclassifications	(1.5		)		(2.0		)		(152.0		)	(42.2		)	(197.7		)
	Net loss (gain) reclassified from accumulated other comprehensive income (loss)	8.1				3.6				—			(2.2		)	9.5
	Balance June 30, 2013	$	(370.8	)		$	6.3			$	167.6		$	(42.7	)	$	(239.6	)
	Other comprehensive income (loss) before reclassifications	(0.6		)		3.5				22.8			12.1			37.8
	Net loss (gain) reclassified from accumulated other comprehensive income (loss)	6.3				0.9				—			16.2			23.4
	Balance September 30, 2013	$	(365.1	)		$	10.7			$	190.4		$	(14.4	)	$	(178.4	)
		(In Millions)
		Postretirement Benefit Liability, net of tax				Unrealized Net Gain (Loss) on Securities, net of tax				Unrealized Net Gain on Foreign Currency Translation			Net Unrealized Gain on Derivative Financial Instruments, net of tax			Accumulated Other Comprehensive Income (Loss)
	Balance December 31, 2011	$	(408.9	)		$	2.6			$	312.5		$	1.2		$	(92.6	)
	Change during 2012	16.4				(0.6		)		12.2			13.6			41.6
	Balance September 30, 2012	$	(392.5	)		$	2			$	324.7		$	14.8		$	(51.0	)
	The following table reflects the details about Accumulated other comprehensive income (loss) components related to Cliffs shareholders’ equity for the three and nine months ended September 30, 2013:
			(In Millions)
	Details about Accumulated Other Comprehensive Income (Loss) Components		Amount of (Gain)/Loss Reclassified into Income								Affected Line Item in the Statement of Unaudited Condensed Consolidated Operations
			Three Months Ended				Nine Months Ended
			30-Sep-13				30-Sep-13
	Amortization of Pension and Postretirement Benefit Liability:
	Prior-service costs		$	(0.1	)		$	(0.4	)		-1
	Net actuarial loss		10.4				31.2				-1
			10.3				30.8				Total before taxes
			(4.0		)		(10.0		)		Income tax benefit (expense)
			$	6.3			$	20.8			Net of taxes
	Unrealized gain (loss) on marketable securities:
Sale of marketable securities		$	0.6			$	(0.5	)		Other non-operating income (expense)
Impairment		—				5.3				Other non-operating income (expense)
		0.6				4.8				Total before taxes
		0.3				(0.2		)		Income tax benefit (expense)
		$	0.9			$	4.6			Net of taxes
Unrealized gain (loss) on derivative financial instruments:
Australian dollar foreign exchange contracts		$	12.7			$	6.4			Product revenues
Canadian dollar foreign exchange contracts		11				11.3				Cost of goods sold and operating expenses
		23.7				17.7				Total before taxes
		(7.5		)		(5.7		)		Income tax benefit (expense)
		$	16.2			$	12			Net of taxes
Total Reclassifications for the Period		$	23.4			$	37.4
-1	These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. See NOTE 12 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.

RELATED_PARTIES

RELATED PARTIES	9 Months Ended
	Sep. 30, 2013
Related Party Transactions [Abstract]
RELATED PARTIES	NOTE 17 - RELATED PARTIES
	Three of our five U.S. iron ore mines and one of our two Eastern Canadian iron ore mines 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 and concentrate that we produce. The joint venture partners are also our customers. The following is a summary of the mine ownership of these iron ore mines at September 30, 2013:
	Mine		Cliffs Natural Resources		ArcelorMittal			U.S. Steel Canada			WISCO
	Empire		79	%	21	%		—			—
	Tilden		85	%	—			15	%		—
	Hibbing		23	%	62.3	%		14.7	%		—
	Bloom Lake		75	%	—			—			25	%
	ArcelorMittal has a unilateral right to put its interest in the Empire mine to us, but has not exercised this right to date.
	Product revenues from related parties were as follows:
		(In Millions)
		Three Months Ended							Nine Months Ended
		September 30,							September 30,
		2013			2012				2013				2012
	Product revenues from related parties	$	455.5		$	476.1			$	1,211.60			$	1,279.60
	Total product revenues	1,454.60			1,447.90				3,928.80				4,096.60
	Related party product revenue as a percent of total product revenue	31.3		%	32.9		%		30.8		%		31.2		%
	Amounts due from related parties recorded in Accounts receivable, net and Derivative assets, including customer supply agreements and provisional pricing arrangements, were $124.2 million and $149.8 million at September 30, 2013 and December 31, 2012, respectively. Amounts due to related parties recorded in Other current liabilities, including provisional pricing arrangements and liabilities to related parties, were $38.5 million and $20.2 million at September 30, 2013 and December 31, 2012, respectively.

EARNINGS_PER_SHARE

EARNINGS PER SHARE	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
EARNINGS PER SHARE	NOTE 18 - EARNINGS PER SHARE
	The following table summarizes the computation of basic and diluted earnings per share:
		(In Millions, Except Per Share Amounts)
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2013			2012			2013			2012
	Net Income from Continuing Operations	$	115.2		$	87.8		$	368.2		$	713.9
	attributable to Cliffs shareholders
	Income from Discontinued Operations,	2			(2.7		)	2			5.1
	net of tax
	NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$	117.2		$	85.1		$	370.2		$	719
	PREFERRED STOCK DIVIDENDS	(12.9		)	—			(35.9		)	—
	NET INCOME ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS	$	104.3		$	85.1		$	334.3		$	719
	Weighted Average Number of Shares:
	Basic	153			142.4			151.3			142.3
	Depositary Shares	25.2			—			21.1			—
	Employee Stock Plans	0.2			0.5			0.2			0.5
	Diluted	178.4			142.9			172.6			142.8
	Earnings per Common Share Attributable to
	Cliffs Common Shareholders - Basic:
	Continuing operations	$	0.67		$	0.62		$	2.2		$	5.02
	Discontinued operations	0.01			(0.02		)	0.01			0.04
		$	0.68		$	0.6		$	2.21		$	5.06
	Earnings per Common Share Attributable to
	Cliffs Common Shareholders - Diluted:
	Continuing operations	$	0.65		$	0.61		$	2.13		$	5
	Discontinued operations	0.01			(0.02		)	0.01			0.04
		$	0.66		$	0.59		$	2.14		$	5.04

COMMITMENTS_AND_CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	NOTE 19 - COMMITMENTS AND CONTINGENCIES
	Purchase Commitments
	In 2011, we began to incur capital commitments related to the expansion of the Bloom Lake mine. The Phase II expansion project includes expansion of the mine and the mine’s processing capabilities. The capital investment also includes common infrastructure necessary to sustain current operations and support the expansion. As previously announced, we are continuing to delay certain components of the Phase II expansion at the Bloom Lake mine, including the completion of the concentrator and load-out facility. Common infrastructure projects necessary to sustain current operations and support the expansion are continuing as planned. Through September 30, 2013, approximately $1.3 billion of the total capital investment for the Bloom Lake expansion project had been committed, of which a total of approximately $1.2 billion had been expended. Of the remaining committed capital, expenditures of approximately $104 million are expected to be made during the remainder of 2013.
	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 believe that any pending litigation will not result in a material liability in relation to our unaudited condensed consolidated financial statements.

CASH_FLOW_INFORMATION

CASH FLOW INFORMATION	9 Months Ended
	Sep. 30, 2013
Supplemental Cash Flow Information [Abstract]
Cash Flow Information	NOTE 20 - CASH FLOW INFORMATION
	A reconciliation of capital additions to cash paid for capital expenditures for the nine months ended September 30, 2013 and 2012 is as follows:
		(In Millions)
		Nine Months Ended
		September 30,
		2013			2012
	Capital additions	$	625.1		$	974
	Cash paid for capital expenditures	742.2			793.6
	Difference	$	(117.1	)	$	180.4
	Non-cash accruals	$	(117.1	)	$	125.1
	Capital leases	—			55.3
	Total	$	(117.1	)	$	180.4
	Non-Cash Financing Activities - Declared Dividends
	On September 9, 2013, our board of directors declared the quarterly cash dividend on our 7.00 percent Series A Mandatory Convertible Preferred Stock, Class A, of $17.50 per share, which is equivalent to approximately $0.44 per depositary share, each representing 1/40th of a share of Series A preferred stock. The cash dividend of $12.9 million will be payable on November 1, 2013 to our shareholders of record as of the close of business on October 15, 2013.

SUBSEQUENT_EVENTS

SUBSEQUENT EVENTS	9 Months Ended
	Sep. 30, 2013
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	NOTE 21 - SUBSEQUENT EVENTS
	We have evaluated subsequent events through the date of financial statement issuance.

BASIS_OF_PRESENTATION_AND_SIGN1

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis Of Consolidation	Basis of Consolidation
	The unaudited condensed consolidated financial statements include our accounts and the accounts of our wholly owned and majority-owned subsidiaries, including the following operations:
	Name	Location	Ownership Interest	Operation
	Northshore	Minnesota	100.00%	Iron Ore
	United Taconite	Minnesota	100.00%	Iron Ore
	Wabush	Newfoundland and Labrador/ Quebec, Canada	100.00%	Iron Ore
	Bloom Lake	Quebec, Canada	75.00%	Iron Ore
	Tilden	Michigan	85.00%	Iron Ore
	Empire	Michigan	79.00%	Iron Ore
	Koolyanobbing	Western Australia	100.00%	Iron Ore
	Pinnacle	West Virginia	100.00%	Coal
	Oak Grove	Alabama	100.00%	Coal
	CLCC	West Virginia	100.00%	Coal
	Intercompany transactions and balances are eliminated upon consolidation.
	Also included in our consolidated results are Cliffs Chromite Ontario Inc. and Cliffs Chromite Far North Inc. Cliffs Chromite Ontario Inc. holds a 100 percent interest in each of the Black Label and Black Thor chromite deposits and, together with Cliffs Chromite Far North Inc., a 70 percent interest in the Big Daddy chromite deposit, all located in northern Ontario, Canada.
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. The following table presents the detail of our investments in unconsolidated ventures and where those investments are classified in the Statements of Unaudited Condensed Consolidated Financial Position as of September 30, 2013 and December 31, 2012. Parentheses indicate a net liability.
					(In Millions)
	Investment	Classification	Accounting	Interest	September 30,		December 31, 2012
			Method	Percentage	2013
	Amapá	Investments in ventures	Equity Method	30	$	29.4	$	101.9
	Cockatoo	Other liabilities2	Equity Method	—	N/A		(25.3		)
	Hibbing	Investments in ventures1	Equity Method	23	8.3		(2.1		)
	Other	Investments in ventures	Equity Method	Various	33.8		33.9
					$	71.5	$	108.4
	1 At December 31, 2012 the classification for Hibbing was Other liabilities.
	2 At December 31, 2012 our ownership interest percentage for Cockatoo was 50 percent.
	Amapá
	On December 27, 2012, our board of directors authorized the sale of our 30 percent interest in Amapá. Per this original agreement, together with Anglo American plc, we were to sell our respective interest in a 100 percent sale transaction to a single entity.
	On March 28, 2013, an unknown event caused the Santana port shiploader to collapse into the Amazon River, preventing further ship loading by the mine operator, Anglo American plc. In light of the March 28, 2013 collapse of the Santana port shiploader and subsequent evaluation of the effect that this event had on the carrying value of our investment in Amapá as of June 30, 2013, we recorded an impairment charge of $67.6 million in the second quarter of 2013.
	On August 28, 2013, we entered into an agreement to sell our 30 percent interest in Amapá to Anglo American plc for nominal cash consideration, plus the right to certain contingent deferred consideration upon the two year anniversary of the closing.  The closing is conditional on obtaining certain regulatory approvals.  The transaction is expected to close in the fourth quarter of 2013.
	Cockatoo Island
	On July 31, 2012, we entered into a definitive asset sale agreement with our joint venture partner, HWE Cockatoo Pty Ltd., to sell our beneficial interest in the mining tenements and certain infrastructure of Cockatoo Island to Pluton Resources, which was amended on August 31, 2012. On September 7, 2012, the closing date, Pluton Resources paid a nominal sum of AUD $4.00 and assumed ownership of the assets and responsibility for the environmental rehabilitation obligations and other assumed liabilities not inherently attached to the tenements acquired. The rehabilitation obligations and assumed liabilities that are inherently attached to the tenements were transferred to Pluton Resources upon registration by the Department of Mining and Petroleum denoting Pluton Resources as the tenement holder. Upon final settlement of the sale, which was completed during the second quarter of 2013, we transferred approximately $18.6 million related to the estimated cost of the rehabilitation
Discontinued Operations	Discontinued Operations
	On July 10, 2012, we entered into a definitive share and asset sale agreement to sell our 45 percent economic interest in the Sonoma joint venture coal mine located in Queensland, Australia. Upon completion of the transaction on November 12, 2012, we collected approximately AUD $141.0 million in net cash proceeds. The Sonoma operations previously were included in Other within our reportable segments.
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 or on a units of production basis as follows:
	Intangible Assets	Basis	Useful Life (years)
	Permits - Asia Pacific Iron Ore	Units of production	Life of mine
	Permits - All Other	Straight line	15 - 40
	Utility contracts	Straight line	5
	Leases - North American Coal	Units of production	Life of mine
	Leases - All Other	Straight line	4.5 - 17.5
Earnings Per Share	Earnings Per Share
	We present both basic and diluted earnings per share amounts. Basic earnings per share amounts are calculated by dividing Net Income 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 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. Our outstanding depositary shares are convertible into common shares based on the volume weighted average of closing prices of our common stock over the 20 consecutive trading day period ending on the third day immediately preceding the end of the reporting period. Common share equivalents are excluded from EPS computations in the periods in which they have an anti-dilutive effect. See NOTE 18 - EARNINGS PER SHARE for further information.
Recent Accounting Pronouncements	Recent Accounting Pronouncements
	On July 18, 2013, the FASB issued Accounting Standards Update No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. ASU 2013-11 requires the netting of unrecognized tax benefits against a deferred tax asset for a loss or other carryforward that would apply in settlement of the uncertain tax positions. ASU 2013-11 is effective for interim and annual periods beginning after December 15, 2013. We will adopt ASU 2013-11 in the fourth quarter of 2013 on a prospective basis, which will impact the presentation of our non-current Deferred income taxes and unrecognized tax benefits (within non-current Other liabilities) in the Statements of Unaudited Condensed Consolidated Financial Position.
	In February 2013, the FASB amended the guidance on the presentation of comprehensive income in order to improve the reporting of reclassifications out of accumulated other comprehensive income. The amendment does not change the current requirements for reporting net income or other comprehensive income in financial statements. Rather, it requires the entity to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income but only if the amount being reclassified is required under GAAP to be reclassified in its entirety to net income in the same reporting period. For other amounts that are not required under GAAP to be reclassified in their entirety to net income, an entity is required to cross-reference to other disclosures required under GAAP that provide additional detail about those amounts. The new guidance was applied prospectively for reporting periods beginning after December 15, 2012. We adopted the provisions of guidance required for the period beginning January 1, 2013. Refer to NOTE 16 - SHAREHOLDERS' EQUITY for further information.

BASIS_OF_PRESENTATION_AND_SIGN2

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Tables)	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule Of Subsidiaries	The unaudited condensed consolidated financial statements include our accounts and the accounts of our wholly owned and majority-owned subsidiaries, including the following operations:
	Name	Location	Ownership Interest	Operation
	Northshore	Minnesota	100.00%	Iron Ore
	United Taconite	Minnesota	100.00%	Iron Ore
	Wabush	Newfoundland and Labrador/ Quebec, Canada	100.00%	Iron Ore
	Bloom Lake	Quebec, Canada	75.00%	Iron Ore
	Tilden	Michigan	85.00%	Iron Ore
	Empire	Michigan	79.00%	Iron Ore
	Koolyanobbing	Western Australia	100.00%	Iron Ore
	Pinnacle	West Virginia	100.00%	Coal
	Oak Grove	Alabama	100.00%	Coal
	CLCC	West Virginia	100.00%	Coal
Schedule of Equity Method Investments	The following table presents the detail of our investments in unconsolidated ventures and where those investments are classified in the Statements of Unaudited Condensed Consolidated Financial Position as of September 30, 2013 and December 31, 2012. Parentheses indicate a net liability.
					(In Millions)
	Investment	Classification	Accounting	Interest	September 30,		December 31, 2012
			Method	Percentage	2013
	Amapá	Investments in ventures	Equity Method	30	$	29.4	$	101.9
	Cockatoo	Other liabilities2	Equity Method	—	N/A		(25.3		)
	Hibbing	Investments in ventures1	Equity Method	23	8.3		(2.1		)
	Other	Investments in ventures	Equity Method	Various	33.8		33.9
					$	71.5	$	108.4
	1 At December 31, 2012 the classification for Hibbing was Other liabilities.
	2 At December 31, 2012 our ownership interest percentage for Cockatoo was 50 percent.
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 or on a units of production basis as follows:
	Intangible Assets	Basis	Useful Life (years)
	Permits - Asia Pacific Iron Ore	Units of production	Life of mine
	Permits - All Other	Straight line	15 - 40
	Utility contracts	Straight line	5
	Leases - North American Coal	Units of production	Life of mine
	Leases - All Other	Straight line	4.5 - 17.5

SEGMENT_REPORTING_Tables

SEGMENT REPORTING (Tables)	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]
Schedule Of Segment Reporting Information, By Segment	The following table presents a summary of our reportable segments for the three and nine months ended September 30, 2013 and 2012, including a reconciliation of segment sales margin to Income from Continuing Operations Before Income Taxes and Equity Loss from Ventures:
		(In Millions)
		Three Months Ended										Nine Months Ended
		September 30,										September 30,
		2013					2012					2013					2012
	Revenues from product sales and services:
	U.S. Iron Ore	$	782.4		51	%	$	796		52	%	$	1,894.20		45	%	$	1,942.70		45	%
	Eastern Canadian Iron Ore	284.2			18	%	253.1			16	%	743.4			18	%	777.8			18	%
	Asia Pacific Iron Ore	301.7			20	%	254.2			16	%	899.5			22	%	975.3			22	%
	North American Coal	178.3			11	%	241.8			16	%	638.5			15	%	640.9			15	%
	Other	—			—	%	(0.2		)	—	%	—			—	%	0.1			—	%
	Total revenues from product sales and services	$	1,546.60		100	%	$	1,544.90		100	%	$	4,175.60		100	%	$	4,336.80		100	%
	Sales margin:
	U.S. Iron Ore	$	273.5				$	255.9				$	647.1				$	708.9
	Eastern Canadian Iron Ore	(22.0		)			(40.5		)			(52.3		)			(43.0		)
	Asia Pacific Iron Ore	99					(15.8		)			255.3					256.1
	North American Coal	(1.8		)			(1.3		)			6.6					3.8
	Other	—					—					(1.9		)			7.8
	Sales margin	348.7					198.3					854.8					933.6
	Other operating expense	(124.7		)			(122.0		)			(200.5		)			(272.3		)
	Other expense	(45.9		)			(43.9		)			(137.4		)			(134.7		)
	Income from continuing operations before income taxes and equity (loss) from ventures	$	178.1				$	32.4				$	516.9				$	526.6
	Depreciation, depletion and amortization:
	U.S. Iron Ore	$	27.3				$	24.9				$	82.3				$	71.9
	Eastern Canadian Iron Ore	46.8					41.7					130.3					118.2
	Asia Pacific Iron Ore	38					40.2					116.1					110
	North American Coal	38.8					25.1					99.7					69.5
	Other	2.2					1					9.6					12.7
	Total depreciation, depletion and amortization	$	153.1				$	132.9				$	438				$	382.3
	Capital additions (1):
	U.S. Iron Ore	$	15.2				$	19.6				$	39.1				$	82.5
	Eastern Canadian Iron Ore	181.5					285.5					535.3					593.4
	Asia Pacific Iron Ore	2					5.8					8.6					132
	North American Coal	10.4					33.3					37.2					105.1
	Other	2.2					10.3					4.9					61
	Total capital additions	$	211.3				$	354.5				$	625.1				$	974
	(1)    Includes capital lease additions and non-cash accruals. Refer to NOTE 20 - CASH FLOW INFORMATION.
Summary of Assets by Segment	A summary of assets by segment is as follows:
		(In Millions)
		September 30,			December 31, 2012
		2013
	Assets:
	U.S. Iron Ore	$	1,770.60		$	1,735.10
	Eastern Canadian Iron Ore	7,982.70			7,605.10
	Asia Pacific Iron Ore	1,188.70			1,506.30
	North American Coal	1,831.80			1,877.80
	Other	696.5			570.9
	Total segment assets	13,470.30			13,295.20
	Corporate	96.4			279.7
	Total assets	$	13,566.70		$	13,574.90

DERIVATIVE_INSTRUMENTS_AND_HED1

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Tables)	9 Months Ended
	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value	The following table presents the fair value of our derivative instruments and the classification of each in the Statements of Unaudited Condensed Consolidated Financial Position as of September 30, 2013 and December 31, 2012:
		(In Millions)
		Derivative Assets												Derivative Liabilities
		September 30, 2013						December 31, 2012						September 30, 2013				31-Dec-12
	Derivative	Balance Sheet Location		Fair				Balance		Fair				Balance Sheet		Fair		Balance Sheet	Fair
	Instrument			Value				Sheet		Value				Location		Value		Location	Value
								Location
	Derivatives designated as hedging instruments under ASC 815:
	Interest-rate Swaps	Derivative assets		$	1.7					$	—					$	—		$	—
	Foreign Exchange Contracts	Derivative assets		4.3				Derivative assets		16.2				Derivative liabilities		22		Derivative liabilities	1.9
	Total derivatives designated as hedging instruments under ASC 815			$	6					$	16.2					$	22		$	1.9
	Derivatives not designated as hedging instruments under ASC 815:
	Commodity Contracts			$	—					$	—			Derivative liabilities		$	2.7		$	—
	Customer Supply Agreements	Derivative assets		62.1				Derivative assets		58.9						—			—
	Provisional Pricing Arrangements	Derivative assets		4.6				Derivative assets		3.5				Derivative liabilities		11.4		Derivative liabilities	11.3
	Total derivatives not designated as hedging instruments under ASC 815			$	66.7					$	62.4					$	14.1		$	11.3
	Total derivatives			$	72.7					$	78.6					$	36.1		$	13.2
Schedule Of Derivative Gains (Losses) Recognized In Accumulated Other Comprehensive Income	The following summarizes the effect of our derivatives designated as cash flow hedging instruments, net of tax in Accumulated other comprehensive loss in the Statements of Unaudited Condensed Consolidated Operations for the three and nine months ended September 30, 2013 and 2012:
		(In Millions)
	Derivatives in Cash Flow	Amount of Gain (Loss)								Location of Gain (Loss)		Amount of Gain (Loss)
		Recognized in OCI on Derivative								Reclassified		Reclassified
										from Accumulated OCI into Earnings		from Accumulated
												OCI into Earnings
	Hedging Relationships	(Effective Portion)								(Effective Portion)		(Effective Portion)
		Three Months Ended										Three Months Ended
		September 30,										September 30,
		2013				2012						2013				2012
	Australian Dollar Foreign	$	2.9			$	1.4			Product revenues		$	(8.9	)		$	5.1
	Exchange Contracts
	(hedge designation)
	Canadian Dollar Foreign Exchange Contracts (hedge designation)	9.2				11.3				Cost of goods sold and operating expenses		(7.3		)		1.3
	Total	$	12.1			$	12.7					$	(16.2	)		$	6.4
		Nine Months Ended										Nine Months Ended
		September 30,										September 30,
		2013				2012						2013				2012
	Australian Dollar Foreign	$	(25.2	)		$	7.5			Product revenues		$	(4.5	)		$	7.8
	Exchange Contracts
	(hedge designation)
	Canadian Dollar Foreign Exchange Contracts (hedge designation)	(9.9		)		6.2				Cost of goods sold and operating expenses		(7.5		)		1.6
		$	(35.1	)		$	13.7					$	(12.0	)		$	9.4
Schedule of Derivatives in Fair Value Hedging Relationships, Statements of Financial Performance and Financial Position, Location	The net gain or loss recognized in Other non-operating income (expense) for the three and nine months ended September 30, 2013 and 2012 were as follows:
	(In Millions)
	Derivatives in Fair Value Hedging Relationships	Location of Gain Recognized in	Net Gain Recognized in Income on Derivative
		Income on Derivative
			Three Months Ended								Nine Months Ended
			September 30,								September 30,
			2013				2012				2013				2012
	Interest Rate Swaps	Other non-operating income (expense)	$	0.1			$	—			$	0.1			$	—
Schedule Of Derivatives Not Designated As Hedging Instruments Statements Of Financial Performance Location Table	The following summarizes the effect of our derivatives that are not designated as hedging instruments in the Statements of Unaudited Condensed Consolidated Operations for the three and nine months ended September 30, 2013 and 2012:
	(In Millions)
	Derivatives Not Designated as Hedging Instruments	Location of Gain (Loss) Recognized in	Amount of Gain/(Loss) Recognized in Income on Derivative
		Income on Derivative
			Three Months Ended								Nine Months Ended
			September 30,								September 30,
			2013				2012				2013				2012
	Foreign Exchange Contracts	Other income (expense)	$	—			$	—			$	—			$	0.3
	Foreign Exchange Contracts	Income (Loss) from Discontinued Operations, net of tax	—				1.1				—				1.1
	Commodity Contracts	Other non-operating income (expense)	(2.7		)		—				(2.7		)		—
	Customer Supply Agreements	Product revenues	53.9				49.8				113.4				131.8
	Provisional Pricing Arrangements	Product revenues	24.3				(10.3		)		(6.8		)		(10.3		)
	Total		$	75.5			$	40.6			$	103.9			$	122.9

INVENTORIES_Tables

INVENTORIES (Tables)	9 Months Ended
	Sep. 30, 2013
Inventory Disclosure [Abstract]
Schedule Of Inventories	The following table presents the detail of our Inventories in the Statements of Unaudited Condensed Consolidated Financial Position as of September 30, 2013 and December 31, 2012:
		(In Millions)
		30-Sep-13						31-Dec-12
	Segment	Finished Goods		Work-in Process		Total Inventory		Finished Goods		Work-in		Total
										Process		Inventory
	U.S. Iron Ore	$	160.4	$	20.3	$	180.7	$	147.2	$	22.9	$	170.1
	Eastern Canadian Iron Ore	54.2		36.2		90.4		62.6		44.2		106.8
	Asia Pacific Iron Ore	54		34.7		88.7		36.7		37.2		73.9
	North American Coal	55.6		23		78.6		36.7		49		85.7
	Total	$	324.2	$	114.2	$	438.4	$	283.2	$	153.3	$	436.5

PROPERTY_PLANT_AND_EQUIPMENT_T

PROPERTY, PLANT AND EQUIPMENT (Tables)	9 Months Ended
	Sep. 30, 2013
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 September 30, 2013 and December 31, 2012:
		(In Millions)
		September 30,			December 31, 2012
		2013
	Land rights and mineral rights	$	7,826.50		$	7,920.80
	Office and information technology	119.3			92.4
	Buildings	214			162
	Mining equipment	1,554.70			1,290.70
	Processing equipment	2,172.80			1,937.40
	Railroad equipment	222.3			240.8
	Electric power facilities	82.9			58.7
	Port facilities	103.8			114.3
	Interest capitalized during construction	25.5			20.8
	Land improvements	63			43.9
	Other	91.8			39
	Construction in progress	1,049.20			1,123.90
		13,525.80			13,044.70
	Allowance for depreciation and depletion	(2,171.0		)	(1,837.4		)
		$	11,354.80		$	11,207.30

DISCONTINUED_OPERATIONS_Tables

DISCONTINUED OPERATIONS (Tables)	9 Months Ended
	Sep. 30, 2013
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations, Statements of Consolidated Financial Position and Statements of Consolidated Operations Information	The following table presents detail of our operations related to our Sonoma operations in the Statements of Unaudited Condensed Consolidated Operations:
		(In Millions)
		Three Months Ended September 30,					Nine Months Ended September 30,
		2013		2012			2013		2012
	REVENUES FROM PRODUCT SALES AND SERVICES
	Product	$	—	$	42.6		$	—	$	141.6
	INCOME (LOSS) FROM DISCONTINUED OPERATIONS, net of tax	$	2	$	(2.7	)	$	2	$	5.2

GOODWILL_AND_OTHER_INTANGIBLE_1

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Tables)	9 Months Ended
	Sep. 30, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule Of Goodwill	The following table summarizes changes in the carrying amount of goodwill allocated by operating segment for the nine months ended September 30, 2013 and the year ended December 31, 2012:
		(In Millions)
		30-Sep-13																								December 31, 2012
		U.S. Iron Ore				Eastern Canadian Iron Ore				Asia Pacific				North American Coal				Other				Total				U.S. Iron Ore		Eastern			Asia Pacific Iron Ore		North American Coal			Other		Total
										Iron Ore																		Canadian Iron Ore
	Beginning Balance	$	2			$	—			$	84.5			$	—			$	80.9			$	167.4			$	2	$	986.2		$	83	$	—		$	80.9	$	1,152.10
	Arising in business combinations	—				—				—				—				—				—				—		13.8			—		—			—		13.8
	Impairment	—				—				—				—				—				—				—		(1,000.0		)	—		—			—		(1,000.0		)
	Impact of foreign currency translation	—				—				(8.8		)		—				—				(8.8		)		—		—			1.5		—			—		1.5
	Ending Balance	$	2			$	—			$	75.7			$	—			$	80.9			$	158.6			$	2	$	—		$	84.5	$	—		$	80.9	$	167.4
	Accumulated Goodwill Impairment Loss	$	—			$	(1,000.0	)		$	—			$	(27.8	)		$	—			$	(1,027.8	)		$	—	$	(1,000.0	)	$	—	$	(27.8	)	$	—	$	(1,027.8	)
Schedule Of Finite-Lived Intangible Assets By Major Class	Following is a summary of intangible assets and liabilities as of September 30, 2013 and December 31, 2012:
				(In Millions)
				30-Sep-13												31-Dec-12
		Classification		Gross				Accumulated				Net				Gross				Accumulated				Net
				Carrying				Amortization				Carrying				Carrying				Amortization				Carrying
				Amount								Amount				Amount								Amount
	Definite-lived intangible assets:
	Permits	Intangible assets, net		$	130.3			$	(35.7	)		$	94.6			$	136.1			$	(31.7	)		$	104.4
	Utility contracts	Intangible assets, net		54.7				(40.8		)		13.9				54.7				(32.4		)		22.3
	Leases	Intangible assets, net		5.7				(3.4		)		2.3				5.7				(3.4		)		2.3
	Total intangible assets			$	190.7			$	(79.9	)		$	110.8			$	196.5			$	(67.5	)		$	129
	Below-market sales contracts	Other current liabilities		$	(46.0	)		$	13.3			$	(32.7	)		$	(46.0	)		$	—			$	(46.0	)
	Below-market sales contracts	Other liabilities		(250.7		)		199.6				(51.1		)		(250.7		)		181.6				(69.1		)
	Total below-market sales contracts			$	(296.7	)		$	212.9			$	(83.8	)		$	(296.7	)		$	181.6			$	(115.1	)
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
	2013 (remaining three months)	$	6.1
	2014	19.3
	2015	8.5
	2016	8.4
	2017	8.4
	2018	7.8
	Total	$	58.5
Schedule Of Earnings To Be Recognized On Below-Market Sales Contract	The following amounts are estimated to be recognized in Product revenues for the remainder of this year and each of the three succeeding fiscal years:
		(In Millions)
		Amount
	Year Ending December 31
	2013 (remaining three months)	$	14.7
	2014	23
	2015	23
	2016	23.1
	Total	$	83.8

FAIR_VALUE_OF_FINANCIAL_INSTRU1

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]
Fair Value Of Assets And Liabilities	The following represents the assets and liabilities of the Company measured at fair value at September 30, 2013 and December 31, 2012:
		(In Millions)
		September 30, 2013
	Description	Quoted Prices in Active				Significant Other Observable Inputs				Significant Unobservable Inputs				Total
		Markets for Identical Assets/Liabilities				(Level 2)				(Level 3)
		(Level 1)
	Assets:
	Cash equivalents	$	192			$	—			$	—			$	192
	Derivative assets	—				1.7				66.7				68.4
	Marketable securities	26.7				—				—				26.7
	Foreign exchange contracts	—				4.3				—				4.3
	Total	$	218.7			$	6			$	66.7			$	291.4
	Liabilities:
	Derivative liabilities	$	—			$	2.7			$	11.4			$	14.1
	Foreign exchange contracts	—				22				—				22
	Total	$	—			$	24.7			$	11.4			$	36.1
		(In Millions)
		December 31, 2012
	Description	Quoted Prices in Active				Significant Other Observable Inputs				Significant Unobservable Inputs				Total
		Markets for Identical				(Level 2)				(Level 3)
		Assets/Liabilities (Level 1)
	Assets:
	Cash equivalents	$	100			$	—			$	—			$	100
	Derivative assets	—				—				62.4				62.4
	Marketable securities	27				—				—				27
	Foreign exchange contracts	—				16.2				—				16.2
	Total	$	127			$	16.2			$	62.4			$	205.6
	Liabilities:
	Derivative liabilities	$	—			$	—			$	11.3			$	11.3
	Foreign exchange contracts	—				1.9				—				1.9
	Total	$	—			$	1.9			$	11.3			$	13.2
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				Balance Sheet Location		Valuation Technique		Unobservable Input		Range or Point Estimate
			9/30/13										(Weighted Average)
	Provisional Pricing Arrangements		$	4.6			Derivative assets		Market Approach		Management's		$131
											Estimate of 62% Fe
			$	11.4			Derivative liabilities
	Customer Supply Agreement		$	62.1			Derivative assets		Market Approach		Hot-Rolled Steel Estimate		$590 - $660 ($630)
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 three and nine months ended September 30, 2013 and 2012.
		(In Millions)
		Derivative Assets (Level 3)
		Three Months Ended								Nine Months Ended
		September 30,								September 30,
		2013				2012				2013				2012
	Beginning balance	$	45.1			$	83.9			$	62.4			$	157.9
	Total gains
	Included in earnings	57.6				24.9				118				129.6
	Settlements	(36.0		)		(52.9		)		(113.7		)		(231.6		)
	Transfers into Level 3	—				—				—				—
	Transfers out of Level 3	—				—				—				—
	Ending balance - September 30	$	66.7			$	55.9			$	66.7			$	55.9
	Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date	$	57.6			$	24.9			$	118			$	129.6
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
		(In Millions)
		Derivative Liabilities (Level 3)
		Three Months Ended								Nine Months Ended
		September 30,								September 30,
		2013				2012				2013				2012
	Beginning balance	$	(32.0	)		$	(15.8	)		$	(11.3	)		$	(19.5	)
	Total gains
	Included in earnings	20.6				4.1				(11.4		)		(11.7		)
	Settlements	—				—				11.3				19.5
	Transfers into Level 3	—				—				—				—
	Transfers out of Level 3	—				—				—				—
	Ending balance - September 30	$	(11.4	)		$	(11.7	)		$	(11.4	)		$	(11.7	)
	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	$	20.6			$	4.1			$	(11.4	)		$	(11.7	)
Schedule Of Carrying Value And Fair Value Of Financial Instruments	A summary of the carrying amount and fair value of other financial instruments at September 30, 2013 and December 31, 2012 were as follows:
				(In Millions)
				September 30, 2013								December 31, 2012
		Classification		Carrying				Fair Value				Carrying				Fair Value
				Value								Value
	Other receivables:
	Customer supplemental payments	Level 2		$	—			$	—			$	22.3			$	21.3
	ArcelorMittal USA—Receivable	Level 2		13.4				14.3				19.3				21.3
	Other	Level 2		10.1				10.1				10.9				10.9
	Total receivables			$	23.5			$	24.4			$	52.5			$	53.5
	Long-term debt:
	Term loan—$1.25 billion	Level 2		$	—			$	—			$	753			$	753
	Senior notes—$700 million	Level 2		699.4				719.2				699.4				759.4
	Senior notes—$1.3 billion	Level 2		1,289.60				1,442.20				1,289.40				1,524.70
	Senior notes—$400 million	Level 2		398.4				439.7				398.2				464.3
	Senior notes—$500 million	Level 2		496.3				528.4				495.7				528.4
	Revolving loan	Level 2		380				380				325				325
	Equipment Loan Facilities	Level 2		54.2				54.2				—				—
	Fair Value Adjustment to Interest Rate Hedge	Level 2		1.7				1.7				—				—
	Total long-term debt			$	3,319.60			$	3,565.40			$	3,960.70			$	4,354.80
Fair Value Measurements, Nonrecurring	The following tables present information about the impairment charges on both financial and nonfinancial assets that were measured on a fair value basis at September 30, 2013 and December 31, 2012. The table also indicates the fair value hierarchy of the valuation techniques used to determine such fair value.
			(In Millions)
			30-Sep-13
	Description		Quoted Prices in Active		Significant Other Observable Inputs		Significant Unobservable Inputs		Total				Total Losses
			Markets for Identical Assets/		(Level 2)		(Level 3)
			Liabilities
			(Level 1)
	Assets:
	Investment in ventures impairment -		—		—		—		$	—			$	67.6
	Amapá
	In light of the March 28, 2013 collapse of the Santana port shiploader and subsequent evaluation of the effect that this event had on the carrying value of our investment in Amapá as of June 30, 2013, we recorded an impairment charge of $67.6 million in the second quarter of 2013.
			(In Millions)
			December 31, 2012
	Description		Quoted Prices in Active				Significant Other Observable Inputs				Significant Unobservable Inputs				Total
			Markets for Identical Assets/				(Level 2)				(Level 3)
			Liabilities
			(Level 1)
	Assets:
	Investment in ventures impairment -		$	—			$	—			$	72.5			$	72.5
	Amapá

DEBT_AND_CREDIT_FACILITIES_Tab

DEBT AND CREDIT FACILITIES (Tables)	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]
Schedule Of Long-Term Debt	The following represents a summary of our long-term debt as of September 30, 2013 and December 31, 2012:
	($ in Millions)
	September 30, 2013
	Debt Instrument		Type	Annual Effective Interest Rate	Final Maturity	Total Face Amount			Total Debt
	$700 Million 4.875% 2021 Senior Notes		Fixed	4.89%	2021	$	700		$	699.4	-2
	$1.3 Billion Senior Notes:
	$500 Million 4.80% 2020 Senior Notes		Fixed	4.83%	2020	500			499.2		-3
	$800 Million 6.25% 2040 Senior Notes		Fixed	6.34%	2040	800			790.4		-4
	$400 Million 5.90% 2020 Senior Notes		Fixed	5.98%	2020	400			398.4		-5
	$500 Million 3.95% 2018 Senior Notes		Fixed	4.14%	2018	500			496.3		-6
	$1.75 Billion Credit Facility:
	Revolving Loan		Variable	2.08%	2017	1,750.00			380		-7
	Equipment Loans		Fixed	Various	2020	62.1			62.1
	Fair Value Adjustment to Interest Rate Hedge								1.7
	Total debt					$	4,712.10		$	3,327.50
	Less current portion								7.9
	Long-term debt								$	3,319.60
	($ in Millions)
	31-Dec-12
	Debt Instrument		Type	Annual Effective Interest Rate	Final Maturity	Total Face Amount			Total Debt
	$1.25 Billion Term Loan		Variable	1.83%	2016	$	847.1	-1	$	847.1	-1
	$700 Million 4.875% 2021 Senior Notes		Fixed	4.88%	2021	700			699.4		-2
	$1.3 Billion Senior Notes:
	$500 Million 4.80% 2020 Senior Notes		Fixed	4.80%	2020	500			499.2		-3
	$800 Million 6.25% 2040 Senior Notes		Fixed	6.25%	2040	800			790.2		-4
	$400 Million 5.90% 2020 Senior Notes		Fixed	5.90%	2020	400			398.2		-5
	$500 Million 3.95% 2018 Senior Notes		Fixed	4.14%	2018	500			495.7		-6
	$1.75 Billion Credit Facility:
	Revolving Loan		Variable	2.02%	2017	1,750.00			325		-7
	Total debt					$	5,497.10		$	4,054.80
	Less current portion								94.1
	Long-term debt								$	3,960.70
	-1	During the first quarter of 2013, the term loan was repaid in full through repayments totaling $847.1 million. As of December 31, 2012, $402.8 million had been paid on the original $1.25 billion term loan and, of the remaining term loan, $94.1 million was classified as Current portion of debt. The current classification was based upon the principal payment terms of the arrangement requiring principal payments on each three-month anniversary following the funding of the term loan.
	-2	As of September 30, 2013 and December 31, 2012, the $700 million 4.875 percent senior notes were recorded at a par value of $700 million less unamortized discounts of $0.6 million for each period, based on an imputed interest rate of 4.89 percent.
	-3	As of September 30, 2013 and December 31, 2012, the $500 million 4.80 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $0.8 million for each period, based on an imputed interest rate of 4.83 percent.
	-4	As of September 30, 2013 and December 31, 2012, the $800 million 6.25 percent senior notes were recorded at par value of $800 million less unamortized discounts of $9.6 million and $9.8 million, respectively, based on an imputed interest rate of 6.34 percent.
	-5	As of September 30, 2013 and December 31, 2012, the $400 million 5.90 percent senior notes were recorded at a par value of $400 million less unamortized discounts of $1.6 million and $1.8 million, respectively, based on an imputed interest rate of 5.98 percent.
	-6	As of September 30, 2013 and December 31, 2012, the $500 million 3.95 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $3.7 million and $4.3 million, respectively, based on an imputed interest rate of 4.14 percent.
	-7	As of September 30, 2013 and December 31, 2012, $380.0 million and $325.0 million revolving loans were drawn under the credit facility, respectively, and the principal amount of letter of credit obligations totaled $27.7 million for each period, thereby reducing available borrowing capacity to $1.3 billion and $1.4 billion for each period, respectively.
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 amended credit agreement, based on the principal amounts outstanding at September 30, 2013:
		(In Millions)
		Maturities of Debt
	2013 (October 1 - December 31)	$	1.9
	2014	7.9
	2015	8.3
	2016	8.6
	2017	8.9
	2018 and thereafter	2,926.50
	Total maturities of debt	$	2,962.10

LEASE_OBLIGATIONS_Tables

LEASE OBLIGATIONS (Tables)	9 Months Ended
	Sep. 30, 2013
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 September 30, 2013 are as follows:
		(In Millions)
		Capital Leases			Operating Leases
	2013 (October 1 - December 31)	$	18.2		$	8.2
	2014	65.5			20
	2015	87			13.5
	2016	36.1			8.3
	2017	28.6			7.5
	2018 and thereafter	54.2			21.5
	Total minimum lease payments	$	289.6		$	79
	Amounts representing interest	54.4
	Present value of net minimum lease payments	$	235.2	-1
	-1	The total is comprised of $51.3 million and $183.9 million classified as Other current liabilities and Other liabilities, respectively, in the Statements of Unaudited Condensed Consolidated Financial Position at September 30, 2013.

ENVIRONMENTAL_AND_MINE_CLOSURE1

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Tables)	9 Months Ended
	Sep. 30, 2013
Environmental Remediation Obligations [Abstract]
Summary Of Mine Closure Obligations	The following is a summary of the obligations as of September 30, 2013 and as of the year ended December 31, 2012:
		(In Millions)
		September 30,			December 31, 2012
		2013
	Environmental	$	8.4		$	15.7
	Mine closure
	LTVSMC	19.4			18.3
	Operating mines:
	U.S. Iron Ore	139.6			81.2
	Eastern Canadian Iron Ore	76.6			88.9
	Asia Pacific Iron Ore	26.2			22.4
	North American Coal	40			38.6
	Total mine closure	301.8			249.4
	Total environmental and mine closure obligations	310.2			265.1
	Less current portion	10.7			12.3
	Long term environmental and mine closure obligations	$	299.5		$	252.8
Asset Retirement Obligation Disclosure	The following represents a rollforward of our asset retirement obligation liability related to our active mining locations for the nine months ended September 30, 2013 and the year ended December 31, 2012:
		(In Millions)
		September 30,			December 31, 2012 (1)
		2013
	Asset retirement obligation at beginning of period	$	231.1		$	194.9
	Accretion expense	13.6			17.6
	Exchange rate changes	2.8			0.3
	Revision in estimated cash flows	35.2			18.2
	Payments	(0.3		)	0.1
	Asset retirement obligation at end of period	$	282.4		$	231.1
	-1	Represents a 12-month rollforward of our asset retirement obligation at December 31, 2012.

PENSIONS_AND_OTHER_POSTRETIREM1

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Tables)	9 Months Ended
	Sep. 30, 2013
Postemployment Benefits [Abstract]
Schedule of Net Benefit Costs [Table Text Block]	The following are the components of defined benefit pension and OPEB expense for the three and nine months ended September 30, 2013 and 2012:
	Defined Benefit Pension Expense
		(In Millions)
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2013			2012			2013			2012
	Service cost	$	9.6		$	8		$	29.2		$	24
	Interest cost	11.2			12.1			34.4			36.4
	Expected return on plan assets	(16.2		)	(14.9		)	(49.3		)	(44.7		)
	Amortization:
	Prior service costs	0.8			1.1			2.3			3
	Net actuarial loss	7.5			7.4			22.5			22.4
	Settlements	—			0.4			—			0.4
	Net periodic benefit cost	$	12.9		$	14.1		$	39.1		$	41.5
	Other Postretirement Benefits Expense
		(In Millions)
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2013			2012			2013			2012
	Service cost	$	3		$	3.7		$	9.2		$	11.2
	Interest cost	4.3			5.3			13			15.9
	Expected return on plan assets	(5.0		)	(4.3		)	(15.0		)	(12.9		)
	Amortization:
	Prior service costs	(0.9		)	0.7			(2.7		)	2.2
	Net actuarial loss	2.9			2.8			8.7			8.4
	Net periodic benefit cost	$	4.3		$	8.2		$	13.2		$	24.8

STOCK_COMPENSATION_PLANS_Table

STOCK COMPENSATION PLANS (Tables)	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule Of Share-Based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions	The following assumptions were utilized to estimate the fair value for the first quarter of 2013 performance share grants:
	Grant Date	Grant Date Market Price		Average Expected Term (Years)	Expected Volatility	Risk-Free Interest Rate	Dividend Yield	Fair Value		Fair Value (Percent of Grant Date Market Price)
	March 11, 2013	$	23.83	2.81	52.90%	0.40%	2.52%	$	17.01	71.38%

SHAREHOLDERS_EQUITY_Shareholde

SHAREHOLDERS' EQUITY Shareholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2013
Changes in Accumulated Othe Comprehensive Income [Abstract]
Schedule of Stockholders Equity [Table Text Block]	The following table reflects the changes in shareholders' equity attributable to both Cliffs and the noncontrolling interests primarily related to Bloom Lake, Tilden and Empire of which Cliffs owns 75 percent, 85 percent and 79 percent, respectively, for the nine months ended September 30, 2013 and September 30, 2012:
		(In Millions)
		Cliffs				Noncontrolling				Total Equity
		Shareholders’				Interest
		Equity
	31-Dec-12	$	4,632.70			$	1,128.20			$	5,760.90
	Comprehensive income
	Net income	370.2				5.8				376
	Other comprehensive income (loss)	(122.8		)		3.2				(119.6		)
	Total comprehensive income	247.4				9				256.4
	Issuance of common shares	285.3				—				285.3
	Issuance of Preferred Shares	709.4				—				709.4
	Stock and other incentive plans	9.6				—				9.6
	Common and Preferred Shares dividends	(104.7		)		—				(104.7		)
	Capital contribution by noncontrolling	—				17.7				17.7
	interest to subsidiary
	30-Sep-13	$	5,779.70			$	1,154.90			$	6,934.60
		(In Millions)
		Cliffs				Noncontrolling				Total Equity
		Shareholders’				Interest
		Equity
	31-Dec-11	$	5,785.00			$	1,254.70			$	7,039.70
	Comprehensive income
	Net income	719				25.2				744.2
	Other comprehensive income	41.6				4.5				46.1
	Total comprehensive income	760.6				29.7				790.3
	Stock and other incentive plans	9				—				9
	Common shares dividends	(217.8		)		—				(217.8		)
	Undistributed gains to noncontrolling interest	—				11.3				11.3
	Capital contribution by noncontrolling interest	—				64.7				64.7
	to subsidiary
	Acquisition of controlling interest	—				(8.0		)		(8.0		)
	30-Sep-12	$	6,336.80			$	1,352.40			$	7,689.20
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following table reflects the changes in Accumulated other comprehensive income (loss) related to Cliffs shareholders’ equity for September 30, 2013 and September 30, 2012:
		(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, 2012	$	(382.7	)		$	2.1			$	316.3		$	8.7		$	(55.6	)
	Other comprehensive income (loss) before reclassifications	(1.1		)		2.5				3.3			(5.0		)	(0.3		)
	Net loss (gain) reclassified from accumulated other comprehensive income (loss)	6.4				0.1				—			(2.0		)	4.5
	Balance March 31, 2013	$	(377.4	)		$	4.7			$	319.6		$	1.7		$	(51.4	)
	Other comprehensive loss before reclassifications	(1.5		)		(2.0		)		(152.0		)	(42.2		)	(197.7		)
	Net loss (gain) reclassified from accumulated other comprehensive income (loss)	8.1				3.6				—			(2.2		)	9.5
	Balance June 30, 2013	$	(370.8	)		$	6.3			$	167.6		$	(42.7	)	$	(239.6	)
	Other comprehensive income (loss) before reclassifications	(0.6		)		3.5				22.8			12.1			37.8
	Net loss (gain) reclassified from accumulated other comprehensive income (loss)	6.3				0.9				—			16.2			23.4
	Balance September 30, 2013	$	(365.1	)		$	10.7			$	190.4		$	(14.4	)	$	(178.4	)
		(In Millions)
		Postretirement Benefit Liability, net of tax				Unrealized Net Gain (Loss) on Securities, net of tax				Unrealized Net Gain on Foreign Currency Translation			Net Unrealized Gain on Derivative Financial Instruments, net of tax			Accumulated Other Comprehensive Income (Loss)
	Balance December 31, 2011	$	(408.9	)		$	2.6			$	312.5		$	1.2		$	(92.6	)
	Change during 2012	16.4				(0.6		)		12.2			13.6			41.6
	Balance September 30, 2012	$	(392.5	)		$	2			$	324.7		$	14.8		$	(51.0	)
Details of Accumulated Other Comprehensive Income (Loss) Components [Table Text Block]	The following table reflects the details about Accumulated other comprehensive income (loss) components related to Cliffs shareholders’ equity for the three and nine months ended September 30, 2013:
			(In Millions)
	Details about Accumulated Other Comprehensive Income (Loss) Components		Amount of (Gain)/Loss Reclassified into Income								Affected Line Item in the Statement of Unaudited Condensed Consolidated Operations
			Three Months Ended				Nine Months Ended
			30-Sep-13				30-Sep-13
	Amortization of Pension and Postretirement Benefit Liability:
	Prior-service costs		$	(0.1	)		$	(0.4	)		-1
	Net actuarial loss		10.4				31.2				-1
			10.3				30.8				Total before taxes
			(4.0		)		(10.0		)		Income tax benefit (expense)
			$	6.3			$	20.8			Net of taxes
	Unrealized gain (loss) on marketable securities:
	Sale of marketable securities		$	0.6			$	(0.5	)		Other non-operating income (expense)
	Impairment		—				5.3				Other non-operating income (expense)
			0.6				4.8				Total before taxes
			0.3				(0.2		)		Income tax benefit (expense)
			$	0.9			$	4.6			Net of taxes
	Unrealized gain (loss) on derivative financial instruments:
	Australian dollar foreign exchange contracts		$	12.7			$	6.4			Product revenues
	Canadian dollar foreign exchange contracts		11				11.3				Cost of goods sold and operating expenses
			23.7				17.7				Total before taxes
			(7.5		)		(5.7		)		Income tax benefit (expense)
			$	16.2			$	12			Net of taxes
	Total Reclassifications for the Period		$	23.4			$	37.4
	-1	These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. See NOTE 12 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.

RELATED_PARTIES_Tables

RELATED PARTIES (Tables)	9 Months Ended
	Sep. 30, 2013
Related Party Transactions [Abstract]
Summary Of Other Ownership Interests	The following is a summary of the mine ownership of these iron ore mines at September 30, 2013:
	Mine		Cliffs Natural Resources		ArcelorMittal			U.S. Steel Canada			WISCO
	Empire		79	%	21	%		—			—
	Tilden		85	%	—			15	%		—
	Hibbing		23	%	62.3	%		14.7	%		—
	Bloom Lake		75	%	—			—			25	%
Summary Of Related Party Transactions Table Disclosure	Product revenues from related parties were as follows:
		(In Millions)
		Three Months Ended							Nine Months Ended
		September 30,							September 30,
		2013			2012				2013				2012
	Product revenues from related parties	$	455.5		$	476.1			$	1,211.60			$	1,279.60
	Total product revenues	1,454.60			1,447.90				3,928.80				4,096.60
	Related party product revenue as a percent of total product revenue	31.3		%	32.9		%		30.8		%		31.2		%

EARNINGS_PER_SHARE_Tables

EARNINGS PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Earnings Per Share Computation	The following table summarizes the computation of basic and diluted earnings per share:
		(In Millions, Except Per Share Amounts)
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2013			2012			2013			2012
	Net Income from Continuing Operations	$	115.2		$	87.8		$	368.2		$	713.9
	attributable to Cliffs shareholders
	Income from Discontinued Operations,	2			(2.7		)	2			5.1
	net of tax
	NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$	117.2		$	85.1		$	370.2		$	719
	PREFERRED STOCK DIVIDENDS	(12.9		)	—			(35.9		)	—
	NET INCOME ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS	$	104.3		$	85.1		$	334.3		$	719
	Weighted Average Number of Shares:
	Basic	153			142.4			151.3			142.3
	Depositary Shares	25.2			—			21.1			—
	Employee Stock Plans	0.2			0.5			0.2			0.5
	Diluted	178.4			142.9			172.6			142.8
	Earnings per Common Share Attributable to
	Cliffs Common Shareholders - Basic:
	Continuing operations	$	0.67		$	0.62		$	2.2		$	5.02
	Discontinued operations	0.01			(0.02		)	0.01			0.04
		$	0.68		$	0.6		$	2.21		$	5.06
	Earnings per Common Share Attributable to
	Cliffs Common Shareholders - Diluted:
	Continuing operations	$	0.65		$	0.61		$	2.13		$	5
	Discontinued operations	0.01			(0.02		)	0.01			0.04
		$	0.66		$	0.59		$	2.14		$	5.04

CASH_FLOW_INFORMATION_Tables

CASH FLOW INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2013
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Disclosures	A reconciliation of capital additions to cash paid for capital expenditures for the nine months ended September 30, 2013 and 2012 is as follows:
		(In Millions)
		Nine Months Ended
		September 30,
		2013			2012
	Capital additions	$	625.1		$	974
	Cash paid for capital expenditures	742.2			793.6
	Difference	$	(117.1	)	$	180.4
	Non-cash accruals	$	(117.1	)	$	125.1
	Capital leases	—			55.3
	Total	$	(117.1	)	$	180.4

BASIS_OF_PRESENTATION_AND_SIGN3

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details)	9 Months Ended		12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2012	Jul. 10, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
		Amapa [Member]	Amapa [Member]	Asia Pacific Iron Ore [Member]	Asia Pacific Iron Ore [Member]	Sonoma [Member]	Sonoma [Member]	Black Label And Black Thor Chromite Deposits [Member]	Big Daddy Chromite Deposit [Member]	Investments in Ventures [Member]
		USD ($)	USD ($)	Cockatoo [Member]	Cockatoo [Member]	Asia Pacific Coal [Member]	Asia Pacific Coal [Member]			Amapa [Member]
				USD ($)	AUD	AUD
Related Party Transaction [Line Items]
Trading Day Window Determining Number of Common Shares Issuable on Conversion	20
Depositary Share Interest in a Share of 7% Series A Mandatory Convertible Preferred Stock, Class A	0.025
Current Fiscal Year End Date	-19
Ownership Interest							45.00%	100.00%	70.00%
Ownership interest, equity method investment										30.00%
Total percentage of Amapa sold										100.00%
Equity Method Investment, Other than Temporary Impairment		$67,600,000	$365,400,000
Proceeds from sale of economic interest (in AUD)					4	141,000,000
Estimated rehabilitation costs				$18,600,000

BASIS_OF_PRESENTATION_AND_SIGN4

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)	9 Months Ended
	Sep. 30, 2013
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
Wabush [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Newfoundland and Labrador/ Quebec, Canada
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Segment Reporting Information, Description of Products and Services	Iron Ore
Bloom Lake [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Quebec, Canada
Noncontrolling Interest, Ownership Percentage by Parent	75.00%
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
Pinnacle [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	West Virginia
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Segment Reporting Information, Description of Products and Services	Coal
Oak Grove [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Alabama
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Segment Reporting Information, Description of Products and Services	Coal
CLCC [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	West Virginia
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Segment Reporting Information, Description of Products and Services	Coal

BASIS_OF_PRESENTATION_AND_SIGN5

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Investments In Unconsolidated Ventures) (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Millions, unless otherwise specified
Schedule of Equity Method Investments [Line Items]
Investment	$71.50		$108.40
Investments in Ventures [Member] | Amapa [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest, equity method investment	30.00%
Total percentage of Amapa sold	100.00%
Investment	29.4		101.9
Investments in Ventures [Member] | Hibbing [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest, equity method investment	23.00%	[1]
Investment	8.3	[1]
Investments in Ventures [Member] | Other Equity Investees [Member]
Schedule of Equity Method Investments [Line Items]
Investment	33.8		33.9
Other Noncurrent Liabilities [Member] | Cockatoo [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest, equity method investment	0.00%	[2]	50.00%	[2]
Investment			-25.3	[2]
Other Noncurrent Liabilities [Member] | Hibbing [Member]
Schedule of Equity Method Investments [Line Items]
Investment			($2.10)	[1]
[1]	At December 31, 2012 the classification for Hibbing was Other liabilities.
[2]	At December 31, 2012 our ownership interest percentage for Cockatoo was 50 percent.

BASIS_OF_PRESENTATION_AND_SIGN6

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES Schedule of Intangible Asset Lives (Details) (All Other Segments [Member])	9 Months Ended
	Sep. 30, 2013
Permits [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Permits [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	40 years
Utility Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Leases [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	4 years 6 months
Leases [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	17 years 6 months

SEGMENT_REPORTING_Narrative_De

SEGMENT REPORTING (Narrative) (Details)	9 Months Ended
	Sep. 30, 2013
	Facility
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Number of mines (in number of facilities)	5
Eastern Canadian Iron Ore [Member]
Segment Reporting Information [Line Items]
Number of mines (in number of facilities)	2
Asia Pacific Iron Ore [Member]
Segment Reporting Information [Line Items]
Number of mines (in number of facilities)	1
North American Coal [Member] | Metallurgical Coal Mines [Member]
Segment Reporting Information [Line Items]
Number of mines (in number of facilities)	4
North American Coal [Member] | Thermal Coal Mines [Member]
Segment Reporting Information [Line Items]
Number of mines (in number of facilities)	1
Latin American Iron Ore [Member] | Amapa [Member]
Segment Reporting Information [Line Items]
Interest Percentage	30.00%

SEGMENT_REPORTING_Schedule_Of_

SEGMENT REPORTING (Schedule Of Segment Reporting Information, By Segment) (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	100.00%		100.00%		100.00%		100.00%
Revenues from product sales and services	$1,546.60		$1,544.90		$4,175.60		$4,336.80
Sales Margin	348.7		198.3		854.8		933.6
Other operating expense	-124.7		-122		-200.5		-272.3
Other expense	-45.9		-43.9		-137.4		-134.7
Income from Continuing Operations before income taxes and equity (loss) from ventures	178.1		32.4		516.9		526.6
Depreciation, depletion and amortization	153.1		132.9		438		382.3
Capital Additions	211.3	[1]	354.5	[1]	625.1	[1]	974	[1]
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	51.00%		52.00%		45.00%		45.00%
Revenues from product sales and services	782.4		796		1,894.20		1,942.70
Sales Margin	273.5		255.9		647.1		708.9
Depreciation, depletion and amortization	27.3		24.9		82.3		71.9
Capital Additions	15.2	[1]	19.6	[1]	39.1	[1]	82.5	[1]
Eastern Canadian Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	18.00%		16.00%		18.00%		18.00%
Revenues from product sales and services	284.2		253.1		743.4		777.8
Sales Margin	-22		-40.5		-52.3		-43
Depreciation, depletion and amortization	46.8		41.7		130.3		118.2
Capital Additions	181.5	[1]	285.5	[1]	535.3	[1]	593.4	[1]
Asia Pacific Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	20.00%		16.00%		22.00%		22.00%
Revenues from product sales and services	301.7		254.2		899.5		975.3
Sales Margin	99		-15.8		255.3		256.1
Depreciation, depletion and amortization	38		40.2		116.1		110
Capital Additions	2	[1]	5.8	[1]	8.6	[1]	132	[1]
North American Coal [Member]
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	11.00%		16.00%		15.00%		15.00%
Revenues from product sales and services	178.3		241.8		638.5		640.9
Sales Margin	-1.8		-1.3		6.6		3.8
Depreciation, depletion and amortization	38.8		25.1		99.7		69.5
Capital Additions	10.4	[1]	33.3	[1]	37.2	[1]	105.1	[1]
All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues from producet sales and services, percent	0.00%		0.00%		0.00%		0.00%
Revenues from product sales and services	0		-0.2		0		0.1
Sales Margin	0		0		-1.9		7.8
Depreciation, depletion and amortization	2.2		1		9.6		12.7
Capital Additions	$2.20	[1]	$10.30	[1]	$4.90	[1]	$61	[1]
[1]	Includes capital lease additions and non-cash accruals. Refer to NOTE 20 - CASH FLOW INFORMATION.

SEGMENT_REPORTING_Segment_Repo

SEGMENT REPORTING Segment Reporting (Summary of Assets by Segment) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Segment Reporting Information [Line Items]
Assets	$13,566.70	$13,574.90
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Assets	1,770.60	1,735.10
Eastern Canadian Iron Ore [Member]
Segment Reporting Information [Line Items]
Assets	7,982.70	7,605.10
Asia Pacific Iron Ore [Member]
Segment Reporting Information [Line Items]
Assets	1,188.70	1,506.30
North American Coal [Member]
Segment Reporting Information [Line Items]
Assets	1,831.80	1,877.80
All Other Segments [Member]
Segment Reporting Information [Line Items]
Assets	696.5	570.9
Total Segment Assets [Member]
Segment Reporting Information [Line Items]
Assets	13,470.30	13,295.20
Corporate [Member]
Segment Reporting Information [Line Items]
Assets	$96.40	$279.70

DERIVATIVE_INSTRUMENTS_AND_HED2

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details) (USD $)

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Dec. 31, 2012

In Millions, unless otherwise specified

Australian Dollar Foreign Exchange Contract Hedge Designation [Member]

Australian Dollar Foreign Exchange Contract Hedge Designation [Member]

Australian Dollar Foreign Exchange Contract Hedge Designation [Member]

Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]

Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]

Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]

Interest Rate Swap [Member]

Customer Supply Agreement [Member]

Customer Supply Agreement [Member]

Customer Supply Agreement [Member]

Customer Supply Agreement [Member]

Customer Supply Agreement [Member]

Customer Supply Agreement [Member]

Provisional Pricing Arrangements [Member]

Provisional Pricing Arrangements [Member]

Provisional Pricing Arrangements [Member]

Provisional Pricing Arrangements [Member]

Provisional Pricing Arrangements [Member]

Provisional Pricing Arrangements [Member]

Provisional Pricing Arrangements [Member]

Provisional Pricing Arrangements [Member]

Designated as Hedging Instrument [Member]

Designated as Hedging Instrument [Member]

Designated as Hedging Instrument [Member]

Designated as Hedging Instrument [Member]

Designated as Hedging Instrument [Member]

Designated as Hedging Instrument [Member]

Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Product Revenues [Member]

Product Revenues [Member]

Product Revenues [Member]

Product Revenues [Member]

Derivative Financial Instruments, Assets [Member]

Derivative Financial Instruments, Assets [Member]

U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]

U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]

U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]

U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]

U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]

U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]

U.S. Iron Ore and Eastern Canadian Iron Ore [Member]

U.S. Iron Ore and Eastern Canadian Iron Ore [Member]

Product Revenues [Member]

Product Revenues [Member]

Product Revenues [Member]

Product Revenues [Member]

Derivative Financial Instruments, Assets [Member]

Derivative Financial Instruments, Liabilities [Member]

Derivative Financial Instruments, Assets [Member]

Derivative Financial Instruments, Liabilities [Member]

Derivative [Line Items]

Derivative, Notional Amount

$333

$400

$453.50

$630.40

$250

Amount that will be reclassified to product revenues in the next 12 months upon settlement of the related contracts

-13.4

1

Amount of gain/(loss) recognized in income on derivative

53.9

49.8

113.4

131.8

24.3

-8.1

-6.8

-10.3

Derivative assets

72.7

78.6

62.1

58.9

4.6

3.5

Derivative liabilities

$36.10

$13.20

$11.40

$11.30

DERIVATIVE_INSTRUMENTS_AND_HED3

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	$72.70	$78.60
Derivative liability, fair value	36.1	13.2
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	6	16.2
Derivative liability, fair value	22	1.9
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	66.7	62.4
Derivative liability, fair value	14.1	11.3
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	1.7	0
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Derivative Financial Instruments, Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	4.3	16.2
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Derivative Financial Instruments, Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	22	1.9
Fair Value, Inputs, Level 2 [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Derivative Financial Instruments, Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value
Fair Value, Inputs, Level 2 [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Derivative Financial Instruments, Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	2.7
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Customer Supply Agreement [Member] | Derivative Financial Instruments, Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	62.1	58.9
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Customer Supply Agreement [Member] | Derivative Financial Instruments, Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member] | Derivative Financial Instruments, Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	4.6	3.5
Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member] | Derivative Financial Instruments, Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	$11.40	$11.30

DERIVATIVE_INSTRUMENTS_AND_HED4

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Statements Of Financial Performance Location Table) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative [Line Items]
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	$12.10	$12.70	($35.10)	$13.70
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	-16.2	6.4	-12	9.4
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	2.9	1.4	-25.2	7.5
Australian Dollar Foreign Exchange Contract Hedge Designation [Member] | Product Revenues [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	-8.9	5.1	-4.5	7.8
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	9.2	11.3	-9.9	6.2
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member] | Cost of Sales [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	($7.30)	$1.30	($7.50)	$1.60

DERIVATIVE_INSTRUMENTS_AND_HED5

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Schedule of Derivative Instruments Designated as Fair Value Hedges) (Details) (Other Nonoperating Income Expense [Member], Interest Rate Swap [Member], USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Other Nonoperating Income Expense [Member] | Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net	$0.10	$0	$0.10	$0

DERIVATIVE_INSTRUMENTS_AND_HED6

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Schedule Of Derivatives Not Designated As Hedging Instruments) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$75.50	$40.60	$103.90	$122.90
Foreign Exchange Contract [Member] | Other Income (Expense) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	0	0	0.3
Foreign Exchange Contract [Member] | Discontinued Operations [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	1.1	0	1.1
Commodity Contract [Member] | Other Nonoperating Income Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	-2.7	0	-2.7	0
Customer Supply Agreements [Member] | Product Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	53.9	49.8	113.4	131.8
Provisional Pricing Arrangements [Member] | Product Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$24.30	($10.30)	($6.80)	($10.30)

INVENTORIES_Narrative_Details

INVENTORIES (Narrative) (Details) (Cost of Sales [Member], USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
North American Coal [Member]
Inventory [Line Items]
Inventory Write-down	$2.60	$8	$5.30	$17.90
Pellets [Member] | Wabush [Member]
Inventory [Line Items]
Inventory Write-down			11.1
Unsaleable Inventory Impairment Charge			10.6
Concentrate [Member] | Eastern Canadian Iron Ore [Member]
Inventory [Line Items]
Inventory Write-down	$5.90		$10.60

INVENTORIES_Schedule_Of_Invent

INVENTORIES (Schedule Of Inventories) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Inventory, Net [Abstract]
Finished Goods	$324.20	$283.20
Work-in Process	114.2	153.3
Total Inventory	438.4	436.5
U.S. Iron Ore [Member]
Inventory, Net [Abstract]
Finished Goods	160.4	147.2
Work-in Process	20.3	22.9
Total Inventory	180.7	170.1
Eastern Canadian Iron Ore [Member]
Inventory, Net [Abstract]
Finished Goods	54.2	62.6
Work-in Process	36.2	44.2
Total Inventory	90.4	106.8
Asia Pacific Iron Ore [Member]
Inventory, Net [Abstract]
Finished Goods	54	36.7
Work-in Process	34.7	37.2
Total Inventory	88.7	73.9
North American Coal [Member]
Inventory, Net [Abstract]
Finished Goods	55.6	36.7
Work-in Process	23	49
Total Inventory	$78.60	$85.70

PROPERTY_PLANT_AND_EQUIPMENT_N

PROPERTY, PLANT AND EQUIPMENT (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended			12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012
					Construction in Progress [Member]	Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Depreciation And Depletion	$148.30	$127.70	$423.10	$364.90
Accumulated amount of capitalized interest included within construction in progress					30.1	17.1
Interest costs capitalized during the period					$15.30	$15.40

PROPERTY_PLANT_AND_EQUIPMENT_V

PROPERTY, PLANT AND EQUIPMENT (Value Of Each Of The Major Classes Of Consolidated Depreciable Assets) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$13,525.80	$13,044.70
Allowance for depreciation and depletion	-2,171	-1,837.40
Property, plant and equipment, net	11,354.80	11,207.30
Land Rights And Mineral Rights [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,826.50	7,920.80
Office And Information Technology [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	119.3	92.4
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	214	162
Mining Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,554.70	1,290.70
Processing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,172.80	1,937.40
Railroad Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	222.3	240.8
Electric Power Facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	82.9	58.7
Port Facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	103.8	114.3
Capitalized Interest Charges [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	25.5	20.8
Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	63	43.9
Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	91.8	39
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$1,049.20	$1,123.90

DISCONTINUED_OPERATIONS_Detail

DISCONTINUED OPERATIONS (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jul. 10, 2012
					Sonoma [Member]	Sonoma [Member]	Sonoma [Member]	Sonoma [Member]	Sonoma [Member]
									Asia Pacific Coal [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage Of Ownership Interests									45.00%
Statements of Consolidated Operations
Disposal Group, Including Discontinued Operation, Revenue					$0	$42.60	$0	$141.60
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, net of tax	2	-2.7	2	5.1	2	-2.7	2	5.2
Tax effect of discontinued operation, tax expense (benefit)						($1.20)		$2.10

GOODWILL_AND_OTHER_INTANGIBLE_2

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Goodwill [Line Items]
Product	$1,454.60	$1,447.90	$3,928.80	$4,096.60
Minimum [Member]
Goodwill [Line Items]
Below-market sales contracts, remaining contract life	1 year		1 year
Maximum [Member]
Goodwill [Line Items]
Below-market sales contracts, remaining contract life	4 years		4 years
Cost of Sales [Member]
Goodwill [Line Items]
Amortization expense relating to intangible assets	4.8	4.8	14.9	14.1
Product Revenues [Member] | Sales Revenue, Goods, Net [Member]
Goodwill [Line Items]
Product	$14.70	$14.70	$31.30	$31.30

GOODWILL_AND_OTHER_INTANGIBLE_3

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Schedule Of Goodwill) (Details) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Goodwill [Roll Forward]
Beginning Balance	$167.40	$1,152.10
Arising in business combinations	0	13.8
Impairment	0	-1,000
Impact of foreign currency translation	-8.8	1.5
Ending Balance	158.6	167.4
Accumulated Goodwill Impairment Loss	-1,027.80	-1,027.80
U.S. Iron Ore [Member]
Goodwill [Roll Forward]
Beginning Balance	2	2
Arising in business combinations	0	0
Impairment	0	0
Impact of foreign currency translation	0	0
Ending Balance	2	2
Accumulated Goodwill Impairment Loss	0	0
Eastern Canadian Iron Ore [Member]
Goodwill [Roll Forward]
Beginning Balance	0	986.2
Arising in business combinations	0	13.8
Impairment	0	-1,000
Impact of foreign currency translation	0	0
Ending Balance	0	0
Accumulated Goodwill Impairment Loss	-1,000	-1,000
Asia Pacific Iron Ore [Member]
Goodwill [Roll Forward]
Beginning Balance	84.5	83
Arising in business combinations	0	0
Impairment	0	0
Impact of foreign currency translation	-8.8	1.5
Ending Balance	75.7	84.5
Accumulated Goodwill Impairment Loss	0	0
North American Coal [Member]
Goodwill [Roll Forward]
Beginning Balance	0	0
Arising in business combinations	0	0
Impairment	0	0
Impact of foreign currency translation	0	0
Ending Balance	0	0
Accumulated Goodwill Impairment Loss	-27.8	-27.8
Other Segment [Member]
Goodwill [Roll Forward]
Beginning Balance	80.9	80.9
Arising in business combinations	0	0
Impairment	0	0
Impact of foreign currency translation	0	0
Ending Balance	80.9	80.9
Accumulated Goodwill Impairment Loss	$0	$0

GOODWILL_AND_OTHER_INTANGIBLE_4

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Schedule Of Finite-Lived Intangible Assets By Major Class) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	$190.70	$196.50
Definite lived intangible assets - Accumulated Amortization	-79.9	-67.5
Definite lived intangible assets - Net Carrying Amount	110.8	129
Permits [Member] | Intangible Assets, Net [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	130.3	136.1
Definite lived intangible assets - Accumulated Amortization	-35.7	-31.7
Definite lived intangible assets - Net Carrying Amount	94.6	104.4
Utility Contracts [Member] | Intangible Assets, Net [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	54.7	54.7
Definite lived intangible assets - Accumulated Amortization	-40.8	-32.4
Definite lived intangible assets - Net Carrying Amount	13.9	22.3
Leases [Member] | Intangible Assets, Net [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	5.7	5.7
Definite lived intangible assets - Accumulated Amortization	-3.4	-3.4
Definite lived intangible assets - Net Carrying Amount	2.3	2.3
Below Market Sales Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	-296.7	-296.7
Definite lived intangible assets - Accumulated Amortization	212.9	181.6
Definite lived intangible assets - Net Carrying Amount	-83.8	-115.1
Below Market Sales Contracts [Member] | Other Current Liabilities [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	-46	-46
Definite lived intangible assets - Accumulated Amortization	13.3
Definite lived intangible assets - Net Carrying Amount	-32.7	-46
Below Market Sales Contracts [Member] | Other Liabilities [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lived intangible assets - Gross Carrying Amount	-250.7	-250.7
Definite lived intangible assets - Accumulated Amortization	199.6	181.6
Definite lived intangible assets - Net Carrying Amount	($51.10)	($69.10)

GOODWILL_AND_OTHER_INTANGIBLE_5

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Estimated Amortization Expense Relating To Intangible Assets) (Details) (USD $)	Sep. 30, 2013
In Millions, unless otherwise specified
Estimated amortization expense, intangible assets [Abstract]
2013 (remaining three months)	$6.10
2014	19.3
2015	8.5
2016	8.4
2017	8.4
2018	7.8
Total	$58.50

GOODWILL_AND_OTHER_INTANGIBLE_6

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Schedule Of Earnings To Be Recognized On Below Market Sales Contract) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Estimated recognition of product revenues, below-market sales contracts [Abstract]
2013 (remaining three months)	$14.70
2014	23
2015	23
2016	23.1
Total	$83.80

FAIR_VALUE_OF_FINANCIAL_INSTRU2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Narrative) (Details) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2002
Fair Value, Assets And Liabilities Components [Line Items]
Management Estimate of 62% Fe	62.00%
Supply agreement, customer receivable, basis spread on variable rate	3.50%
Empire [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Loans Receivable, Fair Value Disclosure	$14.30	$21.30
Estimated credit-adjusted risk-free interest rate	1.98%	2.85%
Accounts, Notes, Loans and Financing Receivable, Net, Noncurrent	13.4	19.3	120
Prior [Member] | Empire [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners			46.70%
Current [Member] | Empire [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Percent ownership interest after transaction			79.00%
Other Current Assets [Member] | Empire [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Other current assets	10	10
Customer Supplemental Payments [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Maximum deferred portion of supplemental payments	22.3
Supply agreement, customer receivable, stated interest rate	9.00%
Supply agreement, customer receivable, description of variable rate basis	prime rate
Payments for (Proceeds from) Loans Receivable	22.3
Loans Receivable, Fair Value Disclosure		21.3
Estimated credit-adjusted risk-free interest rate		2.81%
Customer Supplemental Payments [Member] | Other Current Assets [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Other current assets		22.3
Amapa [Member]
Fair Value, Assets And Liabilities Components [Line Items]
Equity Method Investments, Fair Value Disclosure	0	72.5
Equity Method Investment, Other than Temporary Impairment	$67.60	$365.40

FAIR_VALUE_OF_FINANCIAL_INSTRU3

FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value Of Assets And Liabilities) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Assets:
Cash equivalents	$192	$100
Derivative assets	68.4	62.4
Marketable Securities	26.7	27
Foreign exchange contracts	4.3	16.2
Total	291.4	205.6
Liabilities:
Derivative liabilities	14.1	11.3
Foreign exchange contracts	22	1.9
Total	36.1	13.2
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents	192	100
Derivative assets
Marketable Securities	26.7	27
Foreign exchange contracts
Total	218.7	127
Liabilities:
Derivative liabilities
Foreign exchange contracts
Total
Fair Value, Inputs, Level 2 [Member]
Assets:
Cash equivalents
Derivative assets	1.7
Marketable Securities
Foreign exchange contracts	4.3	16.2
Total	6	16.2
Liabilities:
Derivative liabilities	2.7
Foreign exchange contracts	22	1.9
Total	24.7	1.9
Fair Value, Inputs, Level 3 [Member]
Assets:
Cash equivalents
Derivative assets	66.7	62.4
Marketable Securities
Foreign exchange contracts
Total	66.7	62.4
Liabilities:
Derivative liabilities	11.4	11.3
Foreign exchange contracts
Total	$11.40	$11.30

FAIR_VALUE_OF_FINANCIAL_INSTRU4

FAIR VALUE OF FINANCIAL INSTRUMENTS (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, fair value	$72,700,000	$78,600,000
Derivative liability, fair value	36,100,000	13,200,000
Management Estimate of 62% Fe	62.00%
Not Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, fair value	66,700,000	62,400,000
Derivative liability, fair value	14,100,000	11,300,000
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Managements Estimate Of 62% Fee [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Management Estimate of 62% Fe	62.00%
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member] | Managements Estimate Of 62% Fee [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	131
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	630
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	590
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Hot-Rolled Steel Estimate [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement with unobservable inputs derivative asset range	660
Derivative Financial Instruments, 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	4,600,000	3,500,000
Derivative Financial Instruments, 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	62,100,000	58,900,000
Derivative Financial Instruments, 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	11,400,000	11,300,000
Derivative Financial Instruments, Liabilities [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 liability, fair value

FAIR_VALUE_OF_FINANCIAL_INSTRU5

FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value, Assets and Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance - January 1	$45.10	$83.90	$62.40	$157.90
Total gains
Included in earnings	57.6	24.9	118	129.6
Settlements	-36	-52.9	-113.7	-231.6
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending balance - September 30	66.7	55.9	66.7	55.9
Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date	57.6	24.9	118	129.6
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance - January 1	-32	-15.8	-11.3	-19.5
Total gains
Included in earnings	20.6	4.1	-11.4	-11.7
Settlements	0	0	11.3	19.5
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending balance - September 30	-11.4	-11.7	-11.4	-11.7
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	$20.60	$4.10	($11.40)	($11.70)

FAIR_VALUE_OF_FINANCIAL_INSTRU6

FAIR VALUE OF FINANCIAL INSTRUMENTS (Carrying Value And Fair Value Of Financial Instruments Disclosure) (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	$4,712,100,000		$5,497,100,000
Long-term debt:
Term loan, carrying value	3,327,500,000		4,054,800,000
Total long-term debt, carrying value	3,319,600,000		3,960,700,000
Term Loan - $1.25 Billion [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount			847,100,000
Term Loan Original Amount	0		1,250,000,000
Long-term debt:
Term loan, carrying value			847,100,000	[1]
Seven Hundred Million Four Point Eight Seven Five Two Thousand Twenty-one Senior Note [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	700,000,000		700,000,000
Long-term debt:
Term loan, carrying value	699,400,000	[2]	699,400,000	[2]
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
Senior Notes - $400 Million [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	400,000,000		400,000,000
Long-term debt:
Term loan, carrying value	398,400,000	[3]	398,200,000	[3]
Senior Notes - $500 Million [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	500,000,000		500,000,000
Long-term debt:
Term loan, carrying value	496,300,000	[4]	495,700,000	[4]
Revolving Credit Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	1,750,000,000		1,750,000,000
Long-term debt:
Revolving loan, carrying value	380,000,000	[5]	325,000,000	[5]
Equipment Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	62,100,000
Long-term debt:
Term loan, carrying value	62,100,000
Interest Rate Swap [Member]
Long-term debt:
Fair Value Adjustment to Interest Rate Hedge	1,700,000
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accounts Receivable, Fair Value Disclosure	24,400,000		53,500,000
Long-term debt:
Total long-term debt, fair value	3,565,400,000		4,354,800,000
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Customer Supplemental Payments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accounts Receivable, Fair Value Disclosure	0		21,300,000
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | ArcelorMittal USA - Receivable [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accounts Receivable, Fair Value Disclosure	14,300,000		21,300,000
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Other Credit Receivable [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accounts Receivable, Fair Value Disclosure	10,100,000		10,900,000
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Term Loan - $1.25 Billion [Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	0		753,000,000
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Seven Hundred Million Four Point Eight Seven Five Two Thousand Twenty-one Senior Note [Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	719,200,000		759,400,000
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Senior Notes - $1.3 Billion [Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	1,442,200,000		1,524,700,000
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Senior Notes - $400 Million [Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	439,700,000		464,300,000
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Senior Notes - $500 Million [Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	528,400,000		528,400,000
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Revolving Credit Facility [Member]
Long-term debt:
Revolving loan, fair value	380,000,000		325,000,000
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Equipment Loans [Member]
Long-term debt:
Debt Instrument, Fair Value Disclosure	54,200,000		0
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Long-term debt:
Fair Value Adjustment to Interest Rate Hedge	1,700,000		0
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accounts, Notes, Loans and Financing Receivable, Net, Noncurrent	23,500,000		52,500,000
Long-term debt:
Total long-term debt, carrying value	3,319,600,000		3,960,700,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Customer Supplemental Payments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accounts, Notes, Loans and Financing Receivable, Net, Noncurrent	0		22,300,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | ArcelorMittal USA - Receivable [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accounts, Notes, Loans and Financing Receivable, Net, Noncurrent	13,400,000		19,300,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Other Credit Receivable [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accounts, Notes, Loans and Financing Receivable, Net, Noncurrent	10,100,000		10,900,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Term Loan - $1.25 Billion [Member]
Long-term debt:
Term loan, carrying value	0		753,000,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Seven Hundred Million Four Point Eight Seven Five Two Thousand Twenty-one Senior Note [Member]
Long-term debt:
Senior notes, carrying value	699,400,000		699,400,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Senior Notes - $1.3 Billion [Member]
Long-term debt:
Senior notes, carrying value	1,289,600,000		1,289,400,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Senior Notes - $400 Million [Member]
Long-term debt:
Senior notes, carrying value	398,400,000		398,200,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Senior Notes - $500 Million [Member]
Long-term debt:
Senior notes, carrying value	496,300,000		495,700,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Revolving Credit Facility [Member]
Long-term debt:
Revolving loan, carrying value	380,000,000		325,000,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Equipment Loans [Member]
Long-term debt:
Term loan, carrying value	54,200,000		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	$1,700,000		$0
[1]	During the first quarter of 2013, the term loan was repaid in full through repayments totaling $847.1 million. As of DecemberB 31, 2012, $402.8 million had been paid on the original $1.25 billion term loan and, of the remaining term loan, $94.1 million was classified as Current portion of debt. The current classification was based upon the principal payment terms of the arrangement requiring principal payments on each three-month anniversary following the funding of the term loan.
[2]	As of SeptemberB 30, 2013 and DecemberB 31, 2012, the $700 million 4.875 percent senior notes were recorded at a par value of $700 million less unamortized discounts of $0.6 million for each period, based on an imputed interest rate of 4.89 percent.
[3]	As of SeptemberB 30, 2013 and DecemberB 31, 2012, the $400 million 5.90 percent senior notes were recorded at a par value of $400 million less unamortized discounts of $1.6 million and $1.8 million, respectively, based on an imputed interest rate of 5.98 percent.
[4]	As of SeptemberB 30, 2013 and DecemberB 31, 2012, the $500 million 3.95 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $3.7 million and $4.3 million, respectively, based on an imputed interest rate of 4.14 percent.
[5]	As of SeptemberB 30, 2013 and DecemberB 31, 2012, $380.0 million and $325.0 million revolving loans were drawn under the credit facility, respectively, and the principal amount of letter of credit obligations totaled $27.7 million for each period, thereby reducing available borrowing capacity to $1.3 billion and $1.4 billion for each period, respectively.

FAIR_VALUE_OF_FINANCIAL_INSTRU7

FAIR VALUE OF FINANCIAL INSTRUMENTS FAIR VALUE OF FINANCIAL INSTRUMENTS (Impairment Charges on Financial and Nonfinancial Assets) (Details) (Amapa [Member], USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
ASSETS:
Equity Method Investments, Fair Value Disclosure	$0	$72.50
Equity Method Investment, Other than Temporary Impairment	67.6	365.4
Fair Value, Inputs, Level 1 [Member]
ASSETS:
Equity Method Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member]
ASSETS:
Equity Method Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member]
ASSETS:
Equity Method Investments, Fair Value Disclosure	$0	$72.50

DEBT_AND_CREDIT_FACILITIES_Nar

DEBT AND CREDIT FACILITIES (Narrative) (Details)

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 28, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Dec. 31, 2012

USD ($)

USD ($)

Term Loan - $1.25 Billion [Member]

Term Loan - $1.25 Billion [Member]

Seven Hundred Million Four Point Eight Seven Five Two Thousand Twenty-one Senior Note [Member]

Seven Hundred Million Four Point Eight Seven Five Two Thousand Twenty-one Senior Note [Member]

Revolving Credit Facility [Member]

Revolving Credit Facility [Member]

Revolving Credit Facility [Member]

$270 Million Senior Notes [Member]

Equipment Loans [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Maximum [Member]

USD ($)

USD ($)

USD ($)

AUD

USD ($)

AUD

Quarter

Line of Credit Facility [Line Items]

Revolving credit facility, borrowing capacity

$27,900,000

30,000,000

$41,600,000

40,000,000

Financial covenant, debt to earnings ratio

3.5

Debt Instrument, Face Amount

4,712,100,000

5,497,100,000

847,100,000

700,000,000

700,000,000

1,750,000,000

1,750,000,000

270,000,000

62,100,000

Number of preceding quarters to calculate financial covenant

4

Financial covenant, interest coverage ratio

2.5

2.5

Extinguishment of Debt, Amount

847,100,000

Deferred Finance Costs, Net

7,100,000

Credit facility, amount outstanding

380,000,000

[1]

325,000,000

[1]

25,600,000

27,500,000

26,000,000

25,000,000

Credit facility remaining capacity

1,300,000,000

1,400,000,000

2,300,000

2,500,000

15,600,000

15,000,000

Letters of credit outstanding

43,300,000

96,900,000

Debt Instrument, Minimum Tangible Net Worth Required Under Agreement, as of the End of Each Fiscal Quarter in the Next Fiscal Year

$4,600,000,000

Debt Instrument, Maximum Total Funded Debt to Capitalization Required Until the End of the Next Fiscal Year End

52.50%

Potential Increase in Borrowing Costs on Outstanding Borrowings

0.50%

Potential Increase in Borrowing Costs on Unused Borrowing Capacity

0.10%

[1]

As of SeptemberB 30, 2013 and DecemberB 31, 2012, $380.0 million and $325.0 million revolving loans were drawn under the credit facility, respectively, and the principal amount of letter of credit obligations totaled $27.7 million for each period, thereby reducing available borrowing capacity to $1.3 billion and $1.4 billion for each period, respectively.

DEBT_AND_CREDIT_FACILITIES_Sch

DEBT AND CREDIT FACILITIES (Schedule Of Long-Term Debt) (Details) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Total Face Amount	$4,712,100,000		$5,497,100,000
Long-term Debt	3,327,500,000		4,054,800,000
Current portion of long-term debt	7,900,000		94,100,000
Long-term debt noncurrent portion	3,319,600,000		3,960,700,000
Term Loan - $1.25 Billion [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount	847,100,000
Type			Variable
Final Maturity			2016
Total Face Amount			847,100,000
Long-term Debt			847,100,000	[1]
Total amounts paid down on original loan			402,800,000
Term Loan Original Amount	0		1,250,000,000
Current portion of long-term debt			94,100,000
Imputed interest rate			1.83%
Seven Hundred Million Four Point Eight Seven Five Two Thousand Twenty-one Senior Note [Member]
Debt Instrument [Line Items]
Stated interest rate	4.88%		4.88%
Type	Fixed		Fixed
Final Maturity	2021		2021
Total Face Amount	700,000,000		700,000,000
Long-term Debt	699,400,000	[2]	699,400,000	[2]
Debt Instrument, Unamortized Discount	600,000		600,000
Imputed interest rate	4.89%		4.88%
$500 million 4.80% 2020 Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	4.80%		4.80%
Type	Fixed		Fixed
Final Maturity	2020		2020
Total Face Amount	500,000,000		500,000,000
Long-term Debt	499,200,000	[3]	499,200,000	[3]
Debt Instrument, Unamortized Discount	800,000		800,000
Imputed interest rate	4.83%		4.80%
$800 Million 6.25% 2040 Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	6.25%		6.25%
Type	Fixed		Fixed
Final Maturity	2040		2040
Total Face Amount	800,000,000		800,000,000
Long-term Debt	790,400,000	[4]	790,200,000	[4]
Debt Instrument, Unamortized Discount	9,600,000		9,800,000
Imputed interest rate	6.34%		6.25%
$400 Million 5.90% 2020 Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	5.90%		5.90%
Type	Fixed		Fixed
Final Maturity	2020		2020
Total Face Amount	400,000,000		400,000,000
Long-term Debt	398,400,000	[5]	398,200,000	[5]
Debt Instrument, Unamortized Discount	1,600,000		1,800,000
Imputed interest rate	5.98%		5.90%
$500 Million 3.95% 2018 Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	3.95%		3.95%
Type	Fixed		Fixed
Final Maturity	2018		2018
Total Face Amount	500,000,000		500,000,000
Long-term Debt	496,300,000	[6]	495,700,000	[6]
Debt Instrument, Unamortized Discount	3,700,000		4,300,000
Imputed interest rate	4.14%		4.14%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Type	Variable		Variable
Final Maturity	2017		2017
Total Face Amount	1,750,000,000		1,750,000,000
Credit facility, amount outstanding	380,000,000	[7]	325,000,000	[7]
Imputed interest rate	2.08%		2.02%
Credit facility remaining capacity	1,300,000,000		1,400,000,000
Letter of Credit [Member]
Debt Instrument [Line Items]
Credit facility, amount outstanding	27,700,000		27,700,000
Equipment Loans [Member]
Debt Instrument [Line Items]
Total Face Amount	62,100,000
Long-term Debt	62,100,000
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Fair Value Adjustment to Interest Rate Hedge	$1,700,000
[1]	During the first quarter of 2013, the term loan was repaid in full through repayments totaling $847.1 million. As of DecemberB 31, 2012, $402.8 million had been paid on the original $1.25 billion term loan and, of the remaining term loan, $94.1 million was classified as Current portion of debt. The current classification was based upon the principal payment terms of the arrangement requiring principal payments on each three-month anniversary following the funding of the term loan.
[2]	As of SeptemberB 30, 2013 and DecemberB 31, 2012, the $700 million 4.875 percent senior notes were recorded at a par value of $700 million less unamortized discounts of $0.6 million for each period, based on an imputed interest rate of 4.89 percent.
[3]	As of SeptemberB 30, 2013 and DecemberB 31, 2012, the $500 million 4.80 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $0.8 million for each period, based on an imputed interest rate of 4.83 percent.
[4]	As of SeptemberB 30, 2013 and DecemberB 31, 2012, the $800 million 6.25 percent senior notes were recorded at par value of $800 million less unamortized discounts of $9.6 million and $9.8 million, respectively, based on an imputed interest rate of 6.34 percent.
[5]	As of SeptemberB 30, 2013 and DecemberB 31, 2012, the $400 million 5.90 percent senior notes were recorded at a par value of $400 million less unamortized discounts of $1.6 million and $1.8 million, respectively, based on an imputed interest rate of 5.98 percent.
[6]	As of SeptemberB 30, 2013 and DecemberB 31, 2012, the $500 million 3.95 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $3.7 million and $4.3 million, respectively, based on an imputed interest rate of 4.14 percent.
[7]	As of SeptemberB 30, 2013 and DecemberB 31, 2012, $380.0 million and $325.0 million revolving loans were drawn under the credit facility, respectively, and the principal amount of letter of credit obligations totaled $27.7 million for each period, thereby reducing available borrowing capacity to $1.3 billion and $1.4 billion for each period, respectively.

DEBT_AND_CREDIT_FACILITIES_DEB

DEBT AND CREDIT FACILITIES DEBT AND CREDIT FACILITIES (Schedule of Debt Maturities) (Details) (USD $)	Sep. 30, 2013
In Millions, unless otherwise specified
Debt Disclosure [Abstract]
Debt Maturities Remainder 2013	$1.90
Debt Maturities 2014	7.9
Debt Maturities 2015	8.3
Debt Maturities 2016	8.6
Debt Maturities 2017	8.9
Debt Maturities 2018 and After	2,926.50
Long-term Debt, Maturities, Total	$2,962.10

LEASE_OBLIGATIONS_Narrative_De

LEASE OBLIGATIONS (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Leases [Abstract]
Operating lease expense	$5.30	$6.70	$19.50	$19.20

LEASE_OBLIGATIONS_Future_Minim

LEASE OBLIGATIONS (Future Minimum Lease Payments) (Details) (USD $)	Sep. 30, 2013
In Millions, unless otherwise specified
Capital Leases
2013 (October 1 - December 31)	$18.20
2014	65.5
2015	87
2016	36.1
2017	28.6
2018 and thereafter	54.2
Total minimum lease payments	289.6
Amounts representing interest	54.4
Present value of net minimum lease payments	235.2	[1]
Operating Leases
2013 (October 1 - December 31)	8.2
2014	20
2015	13.5
2016	8.3
2017	7.5
2018 and thereafter	21.5
Total minimum lease payments	79
Other Current Liabilities [Member]
Capital Leases
Present value of net minimum lease payments	51.3
Other Liabilities [Member]
Capital Leases
Present value of net minimum lease payments	$183.90
[1]	The total is comprised of $51.3 million and $183.9 million classified as Other current liabilities and Other liabilities, respectively, in the Statements of Unaudited Condensed Consolidated Financial Position at SeptemberB 30, 2013.

ENVIRONMENTAL_AND_MINE_CLOSURE2

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Narrative) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
In Millions, unless otherwise specified			U.S. Iron Ore [Member]	Eastern Canadian Iron Ore [Member]	Asia Pacific Iron Ore [Member]	North American Coal [Member]	LTV Steel Mining Company [Member]
			Facility	Facility	Facility	Facility	Facility
Loss Contingencies [Line Items]
Total environmental and mine closure obligations	$310.20	$265.10
Mine closure obligation, number of mines (in number of facilities)			4	2	1	5	1

ENVIRONMENTAL_AND_MINE_CLOSURE3

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Summary Of Mine Closure Obligations) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Loss Contingencies [Line Items]
Environmental	$8.40	$15.70
Mine Reclamation and Closing Liability, current and noncurrent	301.8	249.4
Total environmental and mine closure obligations	310.2	265.1
Less current portion	10.7	12.3
Long term environmental and mine closure obligations	299.5	252.8
U.S. Iron Ore [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	139.6	81.2
Eastern Canadian Iron Ore [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	76.6	88.9
Asia Pacific Iron Ore [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	26.2	22.4
North American Coal [Member] | Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	40	38.6
LTV Steel Mining Company [Member] | Previously Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	$19.40	$18.30

ENVIRONMENTAL_AND_MINE_CLOSURE4

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Asset Retirement Obligation Disclosure) (Details) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Asset Retirement Obligation [Roll Forward]
Asset retirement obligation at beginning of period	$231.10	$194.90
Accretion expense	13.6	17.6
Exchange rate changes	2.8	0.3
Revision in estimated cash flows	35.2	18.2
Payments	-0.3	0.1
Asset retirement obligation at end of period	$282.40	$231.10

PENSIONS_AND_OTHER_POSTRETIREM2

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Plans, Defined Benefit [Member]
Definted Benefit Plan Disclosure [Line Items]
Pension Contributions	$36.10	$7.60	$51.20	$32.50
Other Postretirement Benefit Plans, Defined Benefit [Member]
Definted Benefit Plan Disclosure [Line Items]
Other Postretirement Benefit Expense			$14.10	$21.90

PENSIONS_AND_OTHER_POSTRETIREM3

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Estimated Net Periodic Benefit Cost) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Service Cost	$9.60	$8	$29.20	$24
Defined Benefit Plan, Interest Cost	11.2	12.1	34.4	36.4
Defined Benefit Plan, Expected Return on Plan Assets	-16.2	-14.9	-49.3	-44.7
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0.8	1.1	2.3	3
Defined Benefit Plan, Amortization of Gains (Losses)	7.5	7.4	22.5	22.4
Defined Benefit Plan, Settlements, Benefit Obligation	0	0.4	0	0.4
Defined Benefit Plan, Net Periodic Benefit Cost	12.9	14.1	39.1	41.5
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Service Cost	3	3.7	9.2	11.2
Defined Benefit Plan, Interest Cost	4.3	5.3	13	15.9
Defined Benefit Plan, Expected Return on Plan Assets	-5	-4.3	-15	-12.9
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	-0.9	0.7	-2.7	2.2
Defined Benefit Plan, Amortization of Gains (Losses)	2.9	2.8	8.7	8.4
Defined Benefit Plan, Net Periodic Benefit Cost	$4.30	$8.20	$13.20	$24.80

STOCK_COMPENSATION_PLANS_Narra

STOCK COMPENSATION PLANS (Narrative) (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Plan Year Agreements	3
ICE Plan and 2012 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance/vesting period	3 years
2012 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted under the award	1,000,000
Number of performance shares granted	800,000
Number of restricted shares granted	200,000
Number of shares granted		23,600
2012 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)	6,000,000
Ice Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted		426,600
Two Thousand And Eleven To Two Thousand And Thirteen And The Two Thousand And Twelve To Two Thousand Fourteen and Two Thousand Thirteen to Two Thousand Fifteen Performance Periods [Member] | ICE Plan and 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%
Two Thousand And Eleven To Two Thousand And Thirteen And The Two Thousand And Twelve To Two Thousand Fourteen and Two Thousand Thirteen to Two Thousand Fifteen Performance Periods [Member] | ICE Plan and 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%

STOCK_COMPENSATION_PLANS_Assum

STOCK COMPENSATION PLANS (Assumptions Utilized To Estimate Fair Value For Performance Share Grants) (Details) (Performance Shares [Member], USD $)	9 Months Ended
	Sep. 30, 2013
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Date Market Price	$23.83
Average Expected Term (Years)	2 years 9 months 21 days
Expected Volatility	52.90%
Risk-Free Interest Rate	0.40%
Dividend Yield	2.52%
Fair Value	$17.01
Fair Value (Percent of Grant Date Market Price)	71.38%

INCOME_TAXES_Narrative_Details

INCOME TAXES (Narrative) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Statutory Tax Rate [Line Items]
Document Fiscal Year Focus	2013
Effective Income Tax Rate, Continuing Operations	16.20%
Discrete Tax Items	$14.70
United States [Member]
Statutory Tax Rate [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	35.00%

CAPITAL_STOCK_Details

CAPITAL STOCK (Details) (USD $)

3 Months Ended

9 Months Ended

2 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

2 Months Ended

3 Months Ended

2 Months Ended

In Millions, except Share data, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Feb. 21, 2013

Feb. 21, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 09, 2013

7-May-13

Mar. 20, 2013

Mar. 13, 2012

Feb. 21, 2013

Feb. 11, 2013

Sep. 03, 2013

Jun. 03, 2013

Mar. 01, 2013

Dec. 03, 2012

Aug. 31, 2012

Jun. 01, 2012

Mar. 01, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Feb. 21, 2013

Sep. 30, 2013

Sep. 09, 2013

7-May-13

Mar. 20, 2013

Over Allotment Option [Member]

Preferred Class A [Member]

Preferred Class A [Member]

Preferred Class A [Member]

Preferred Class A [Member]

Preferred Class A [Member]

Preferred Class A [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock from when Mandatory Convertible Preferred Stock Converts on February 1, 2016 [Member]

Depositary Share [Member]

Depositary Share [Member]

Depositary Share [Member]

Depositary Share [Member]

Depositary Share [Member]

Minimum [Member]

Maximum [Member]

Class of Stock [Line Items]

Depositary Share Offering included in Depositary Share Issuance

27,000,000

Number of Shares included in Depositary Share Issuance due to Exercise of

2,250,000

Depositary Share Interest in a Share of 7% Series A Mandatory Convertible Preferred Stock, Class A

0.025

Series A Mandatory Convertible Preferred Stock, Class A, Percentage

7.00%

Convertible Preferred Stock, Shares Issued upon Conversion

28.148

34.484

Convertible Preferred Stock, Shares Issued Upon Conversion per Depositary Share

0.7037

Preferred Stock, Liquidation Preference Per Share

$1,000

$1,000

$25

Common Stock, Par or Stated Value Per Share

$0.13

$0.13

$0.13

$0.13

Trading Day Window Determining Number of Common Shares Issuable on Conversion

20

Number of Common Shares Mandatory Convertible Stock Converts to on February 1, 2016

20,600,000

25,200,000

Net proceeds from issuance of Series A, Mandatory Convertible Preferred Stock, Class A

$709.40

$0

Dividends payable, per share

$17.50

$17.50

$13.61

$0.15

$0.15

$0.15

$0.63

$0.63

$0.63

$0.28

$0.44

$0.44

$0.34

Dividends, Preferred Stock

12.9

0

35.9

0

12.9

35.9

Percentage increase (decrease) in dividends payable

123.00%

76.00%

Issuance of common shares, public offering (in shares)

731,250

10,350,000

29,250,000

Common shares, issued (in shares)

159,545,469

159,545,469

149,195,469

1,350,000

9,000,000

Net proceeds from issuance of common shares

$285.30

$0

Closing price per share (in usd per share)

$25

$29

SHAREHOLDERS_EQUITY_Schedule_o

SHAREHOLDERS' EQUITY Schedule of Shareholders' Equity (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Stockholders' Equity Attributable to Parent	$5,779.70		$5,779.70		$4,632.70
Stockholders' Equity Attributable to Noncontrolling Interest	1,154.90		1,154.90		1,128.20
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	6,934.60	7,689.20	6,934.60	7,689.20	5,760.90	7,039.70
NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	117.2	85.1	370.2	719
INCOME (LOSS) ATTRIBUTABLE TO NONCONTROLLING INTEREST	-3.3	-6.7	5.8	25.2
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	113.9	78.4	376	744.2
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	178.4	123.9	247.4	760.6
Other Comprehensive Income (Loss), Net of Tax	62.1	40.3	-119.6	46.1
OTHER COMPREHENSIVE INCOME ATTRIBUTABLE TO THE NONCONTROLLING INTEREST	-0.9	-1.5	-3.2	-4.5
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest			256.4	790.3
Stock and Other Incentive Plans			9.6	9
Common and Preferred Shares dividends			-104.7
Common shares dividends				-217.8
Undistributed Gains To Noncontrolling Interest				11.3
Capital Contribution By Noncontrolling Interest			17.7	64.7
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests				-8
Cliffs Shareholders Equity [Member]
Stockholders' Equity Attributable to Parent	5,779.70	6,336.80	5,779.70	6,336.80	4,632.70	5,785
NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS			370.2	719
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent			-122.8	41.6
Other Comprehensive Income (Loss), Net of Tax				41.6
Comprehensive Income (Loss), Net of Tax, Attributable to Parent			247.4	760.6
Stock and Other Incentive Plans			9.6	9
Common and Preferred Shares dividends			-104.7
Undistributed Gains To Noncontrolling Interest				0
Capital Contribution By Noncontrolling Interest			0	0
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests				0
Noncontrolling Interest [Member]
Stockholders' Equity Attributable to Noncontrolling Interest	1,154.90	1,352.40	1,154.90	1,352.40	1,128.20	1,254.70
INCOME (LOSS) ATTRIBUTABLE TO NONCONTROLLING INTEREST			5.8	25.2
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest			3.2	4.5
OTHER COMPREHENSIVE INCOME ATTRIBUTABLE TO THE NONCONTROLLING INTEREST			9	29.7
Stock and Other Incentive Plans			0	0
Common and Preferred Shares dividends			0
Common shares dividends				0
Undistributed Gains To Noncontrolling Interest				11.3
Capital Contribution By Noncontrolling Interest			17.7	64.7
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests				-8
Common Stock [Member]
Stock Issued During Period, Value, New Issues			285.3
Common Stock [Member] | Cliffs Shareholders Equity [Member]
Stock Issued During Period, Value, New Issues			285.3
Common shares dividends				-217.8
Common Stock [Member] | Noncontrolling Interest [Member]
Stock Issued During Period, Value, New Issues			0
Preferred Class A [Member]
Stock Issued During Period, Value, New Issues			709.4
Preferred Class A [Member] | Cliffs Shareholders Equity [Member]
Stock Issued During Period, Value, New Issues			709.4
Preferred Class A [Member] | Noncontrolling Interest [Member]
Stock Issued During Period, Value, New Issues			$0

SHAREHOLDERS_EQUITY_Accumulate

SHAREHOLDERS' EQUITY Accumulate Other Comprehensive Income (Loss) (Details) (USD $)	3 Months Ended		9 Months Ended						3 Months Ended																											9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2012
									Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Accumulated Net Unrealized Investment Gain (Loss) [Member]	Accumulated Net Unrealized Investment Gain (Loss) [Member]	Accumulated Net Unrealized Investment Gain (Loss) [Member]	Accumulated Translation Adjustment [Member]	Accumulated Translation Adjustment [Member]	Accumulated Translation Adjustment [Member]	Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Accumulated Net Unrealized Investment Gain (Loss) [Member]	Accumulated Net Unrealized Investment Gain (Loss) [Member]	Accumulated Net Unrealized Investment Gain (Loss) [Member]	Accumulated Translation Adjustment [Member]	Accumulated Translation Adjustment [Member]	Accumulated Translation Adjustment [Member]	Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Cliffs Shareholders Equity [Member]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	($365.10)	($392.50)	($365.10)	($392.50)	($370.80)	($377.40)	($382.70)	($408.90)
Accumulated other comprehensive loss	-178.4	-51	-178.4	-51	-239.6	-51.4	-55.6	-92.6
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	10.7	2	10.7	2	6.3	4.7	2.1	2.6
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	190.4	324.7	190.4	324.7	167.6	319.6	316.3	312.5
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	-14.4	14.8	-14.4	14.8	-42.7	1.7	8.7	1.2
Other Comprehensive Income (Loss), before Reclassifications, before Tax									37.8	-197.7	-0.3	-0.6	-1.5	-1.1	3.5	-2	2.5	22.8	-152	3.3	12.1	-42.2	-5
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)									23.4	9.5	4.5													6.3	8.1	6.4	0.9	3.6	0.1	0	0	0	16.2	-2.2	-2
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	-6.6	-7.6	-20.8	-20.9																																16.4
Unrealized net gain (loss) on marketable securities, net of tax	4.4	-0.1	7.6	-0.6																																-0.6
Unrealized net gain (loss) on foreign currency translation	22.8	18.6	-124.9	12.2																																12.2
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	28.3	14.2	-23.1	13.6																																13.6
Other Comprehensive Income (Loss), Net of Tax	$62.10	$40.30	($119.60)	$46.10																																$41.60

SHAREHOLDERS_EQUITY_Details_of

SHAREHOLDERS' EQUITY Details of Accumulated Other Comprehensive Income (Loss) Components (Details) (USD $)	3 Months Ended			9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	($16.20)		$6.40	($12)		$9.40
Total Amount Reclassified from Accumulated Other Comprehensive Income (Loss) During the Period	23.4			37.4
Accumulated Defined Benefit Plans Adjustment [Member]
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	-0.1	[1]		-0.4	[1]
Defined Benefit Plan, Amortization of Gains (Losses)	10.4	[1]		31.2	[1]
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	10.3			30.8
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax	-4			-10
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	6.3			20.8
Realized Gain (Loss) on Marketable Securities [Member]
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]
Marketable Securities, Realized Gain (Loss)	0.6			-0.5
Accumulated Other-than-Temporary Impairment [Member]
Details of Accumulated Other Comprehensive Income (Loss) Components [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			5.3
Realized Gain (Loss) on Marketable Securities and Other than Temporary Impairment [Member]
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, before tax	0.6			4.8
Other Comprehensive Income (Loss), Realized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, Tax	0.3			-0.2
Other Comprehensive Income (Loss), Realized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, net of tax	0.9			4.6
Realized Gain Loss On Derivatives [Member]
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]
(Gain) Loss on Derivative Instruments, Net, Pretax	23.7			17.7
Tax on Derivative Instruments Gain/Loss Reclassified from Accumulated OCI in to Earnings	-7.5			-5.7
Amount of (gain)/loss recognized in income on derivative	16.2			12
Realized Gain Loss On Derivatives [Member] | Australian Hedge Contracts [Member]
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	12.7			6.4
Realized Gain Loss On Derivatives [Member] | Canadian Hedge Contracts [Member]
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	$11			$11.30
[1]	These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. See NOTE 12 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.

SHAREHOLDERS_EQUITY_Narrative_

SHAREHOLDERS' EQUITY Narrative (Details)	Sep. 30, 2013
Empire [Member]
Noncontrolling Interest, Ownership Percentage by Parent	79.00%
Tilden [Member]
Noncontrolling Interest, Ownership Percentage by Parent	85.00%
Bloom Lake [Member]
Noncontrolling Interest, Ownership Percentage by Parent	75.00%

RELATED_PARTIES_Narrative_Deta

RELATED PARTIES (Narrative) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
In Millions, unless otherwise specified			U.S. Iron Ore [Member]	Eastern Canadian Iron Ore [Member]	Joint Venture Partners [Member]	Joint Venture Partners [Member]
			Facility	Facility	U.S. Iron Ore [Member]	Eastern Canadian Iron Ore [Member]
					Facility	Facility
Segment Reporting Information [Line Items]
Due from Related Parties, Current	$124.20	$149.80
Number of mines (in number of facilities)			5	2	3	1
Due to Related Parties, Current	$38.50	$20.20

RELATED_PARTIES_Summary_Of_Oth

RELATED PARTIES (Summary Of Other Ownership Interests) (Details)	Sep. 30, 2013
Hibbing [Member] | Arcelor Mittal [Member]
Related Party Transaction [Line Items]
Ownership interest, equity method investment	62.30%
Hibbing [Member] | WISCO [Member]
Related Party Transaction [Line Items]
Ownership interest, equity method investment	0.00%
Hibbing [Member] | U. S. Steel Canada [Member]
Related Party Transaction [Line Items]
Ownership interest, equity method investment	14.70%
Empire [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent	79.00%
Empire [Member] | Arcelor Mittal [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	21.00%
Empire [Member] | WISCO [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	0.00%
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] | WISCO [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%
Bloom Lake [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent	75.00%
Bloom Lake [Member] | Arcelor Mittal [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	0.00%
Bloom Lake [Member] | WISCO [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	25.00%
Bloom Lake [Member] | U. S. Steel Canada [Member]
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	0.00%
Investments in Ventures [Member] | Hibbing [Member]
Related Party Transaction [Line Items]
Ownership interest, equity method investment	23.00%	[1]
[1]	At December 31, 2012 the classification for Hibbing was Other liabilities.

RELATED_PARTIES_Summary_Of_Rel

RELATED PARTIES (Summary Of Related Party Transactions Table Disclosure) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Related Party Transactions [Abstract]
Product revenues from related parties	$455.50	$476.10	$1,211.60	$1,279.60
Product	$1,454.60	$1,447.90	$3,928.80	$4,096.60
Related party product revenue as a percent of total product revenue	31.30%	32.90%	30.80%	31.20%

EARNINGS_PER_SHARE_Earnings_Pe

EARNINGS PER SHARE (Earnings Per Share Computation) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income from Continuing Operations Attributable to Parent	$115.20	$87.80	$368.20	$713.90
Income from Discontinued Operations, net of tax	2	-2.7	2	5.1
NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	117.2	85.1	370.2	719
PREFERRED STOCK DIVIDENDS	-12.9	0	-35.9	0
NET INCOME ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS	104.3	85.1	334.3	719
Weighted Average Number of Shares:
Basic	153,029	142,396	151,288	142,332
Depositary Shares	25,216	0	21,114	0
Employee Stock Plans	214	499	222	448
Diluted	178,459	142,895	172,624	142,780
Earnings per Common Share Attributable to Cliffs Common Shareholders - Basic:
Continuing operations	$0.67	$0.62	$2.20	$5.02
Discontinued operations	$0.01	($0.02)	$0.01	$0.04
Earnings per Common Share Attributable to Cliffs Common Shareholders - Basic:	$0.68	$0.60	$2.21	$5.06
Earnings per Common Share Attributable to Cliffs Common Shareholders - Diluted:
Continuing operations	$0.65	$0.61	$2.13	$5
Discontinued operations	$0.01	($0.02)	$0.01	$0.04
Earnings per Common Share Attributable to Cliffs Common Shareholders - Diluted:	$0.66	$0.59	$2.14	$5.04
Preferred Class A [Member]
PREFERRED STOCK DIVIDENDS	($12.90)		($35.90)

COMMITMENTS_AND_CONTINGENCIES_

COMMITMENTS AND CONTINGENCIES (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Other Commitments [Line Items]
Capital investment, future payments	($117,100,000)	$125,100,000
Bloom Lake [Member]
Other Commitments [Line Items]
Capital investment committed	1,300,000,000
Capital expenditures related to commitment	1,200,000,000
Capital investment, future payments	$104,000,000

CASH_FLOW_INFORMATION_Narrativ

CASH FLOW INFORMATION (Narrative) (Details) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

In Millions, except Per Share data, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 09, 2013

7-May-13

Mar. 20, 2013

Sep. 09, 2013

7-May-13

Mar. 20, 2013

Preferred Class A [Member]

Preferred Class A [Member]

Preferred Class A [Member]

Preferred Class A [Member]

Preferred Class A [Member]

Depositary Share [Member]

Depositary Share [Member]

Depositary Share [Member]

Dividends Payable [Line Items]

Series A Mandatory Convertible Preferred Stock, Class A, Percentage

7.00%

Depositary Share Interest in a Share of 7% Series A Mandatory Convertible Preferred Stock, Class A

0.025

Dividends payable, per share

$17.50

$17.50

$13.61

$0.44

$0.44

$0.34

Preferred stock cash dividend

$12.90

$0

$35.90

$0

$12.90

$35.90

CASH_FLOW_INFORMATION_Reconcil

CASH FLOW INFORMATION (Reconciliation Of Capital Additions To Cash Paid For Capital Expenditures) (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Supplemental Cash Flow Information [Abstract]
Property, Plant and Equipment, Additions	$211.30	[1]	$354.50	[1]	$625.10	[1]	$974	[1]
Payments to Acquire Property, Plant, and Equipment					742.2		793.6
Non-cash accruals					-117.1		125.1
Capital leases					0		55.3
Total					($117.10)		$180.40
[1]	Includes capital lease additions and non-cash accruals. Refer to NOTE 20 - CASH FLOW INFORMATION.