Cleveland-Cliffs (CLF) 10-Q 24 Jul 14 2014 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	6 Months Ended
	Jun. 30, 2014	Jul. 21, 2014
Document and Entity Information [Abstract]	'	'
Entity Registrant Name	'CLIFFS NATURAL RESOURCES INC.	'
Entity Central Index Key	'0000764065	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Document Type	'10-Q	'
Document Period End Date	30-Jun-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q2	'
Amendment Flag	'false	'
Entity Common Stock, Shares Outstanding	'	153,182,488
Trading Symbol	'clf	'

Statements_Of_Condensed_Consol

Statements Of Condensed Consolidated Operations (USD $)	3 Months Ended		6 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
REVENUES FROM PRODUCT SALES AND SERVICES	'	'	'	'
Product	$1,018.60	$1,391.60	$1,879.50	$2,474.20
Freight and venture partners' cost reimbursements	82.2	96.9	161.3	154.8
TOTAL REVENUES	1,100.80	1,488.50	2,040.80	2,629
COST OF GOODS SOLD AND OPERATING EXPENSES	-1,008.80	-1,220.30	-1,885.60	-2,122.90
SALES MARGIN	92	268.2	155.2	506.1
OTHER OPERATING INCOME (EXPENSE)	'	'	'	'
Selling, general and administrative expenses	-52.5	-48.9	-103.6	-97.3
Exploration costs	-3.4	-12.6	-7.6	-35.3
Miscellaneous - net	-47.8	55.3	-106.4	56.8
Other operating expense	-103.7	-6.2	-217.6	-75.8
OPERATING INCOME (EXPENSE)	-11.7	262	-62.4	430.3
OTHER INCOME (EXPENSE)	'	'	'	'
Interest expense, net	-44.8	-40.7	-87.5	-89.8
Other non-operating income	2.2	-2.8	3.4	-1.7
TOTAL OTHER EXPENSE	-42.6	-43.5	-84.1	-91.5
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES AND EQUITY LOSS FROM VENTURES	-54.3	218.5	-146.5	338.8
INCOME TAX BENEFIT (EXPENSE)	69.1	-9.3	90.9	-3.3
EQUITY LOSS FROM VENTURES, net of tax	-0.3	-67.9	-0.6	-73.4
NET INCOME (LOSS)	14.5	141.3	-56.2	262.1
LOSS (INCOME) ATTRIBUTABLE TO NONCONTROLLING INTEREST	-3.6	4.7	-3.2	-9.1
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	10.9	146	-59.4	253
PREFERRED STOCK DIVIDENDS	-12.8	-12.9	-25.6	-22.8
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS	($1.90)	$133.10	($85)	$230.20
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Basic:	($0.01)	$0.87	($0.56)	$1.53
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted:	($0.01)	$0.82	($0.56)	$1.49
AVERAGE NUMBER OF SHARES (IN THOUSANDS)	'	'	'	'
Basic	153,087	153,011	153,064	150,418
Diluted	153,087	178,428	153,064	169,708
CASH DIVIDENDS DECLARED PER DEPOSITARY SHARE	$0.44	$0.44	$0.88	$0.78
CASH DIVIDENDS DECLARED PER COMMON SHARE	$0.15	$0.15	$0.30	$0.30

Statements_Of_Condensed_Consol1

Statements Of Condensed Consolidated Comprehensive Income (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$10.90	$146	($59.40)	$253
OTHER COMPREHENSIVE INCOME (LOSS)	'	'	'	'
Changes in pension and other post-retirement benefits, net of tax	3.2	7.7	6.6	14.2
Unrealized net gain (loss) on marketable securities, net of tax	-3.7	0.6	0.2	3.2
Unrealized net gain (loss) on foreign currency translation	19.7	-151	60.2	-147.7
Unrealized net gain (loss) on derivative financial instruments, net of tax	16.3	-44.4	26.8	-51.4
OTHER COMPREHENSIVE INCOME (LOSS)	35.5	-187.1	93.8	-181.7
OTHER COMPREHENSIVE INCOME ATTRIBUTABLE TO THE NONCONTROLLING INTEREST	-0.6	-1.1	-1.1	-2.3
TOTAL COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$45.80	($42.20)	$33.30	$69

Statements_Of_Condensed_Consol2

Statements Of Condensed Consolidated Financial Position (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
CURRENT ASSETS	'	'
Cash and cash equivalents	$359.90	$335.50
Accounts receivable, net	198.3	270
Inventories	648.8	391.4
Supplies and other inventories	200	216
Income tax receivable	35.4	74.1
Other current assets	221.4	273
TOTAL CURRENT ASSETS	1,663.80	1,560
PROPERTY, PLANT AND EQUIPMENT, NET	11,004.80	11,153.40
OTHER ASSETS	433.8	408.5
TOTAL ASSETS	13,102.40	13,121.90
CURRENT LIABILITIES	'	'
Accounts payable	266	345.5
Accrued expenses	338	392.7
Short-term and current portion of long-term debt	161.1	20.9
Other current liabilities	272.4	326.4
TOTAL CURRENT LIABILITIES	1,037.50	1,085.50
PENSION AND POSTEMPLOYMENT BENEFIT LIABILITIES	276.6	294
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	304.7	309.7
DEFERRED INCOME TAXES	1,034.10	1,146.50
LONG-TERM DEBT	3,293	3,022.60
OTHER LIABILITIES	326.9	379.3
TOTAL LIABILITIES	6,272.80	6,237.60
COMMITMENTS AND CONTINGENCIES (SEE NOTE 18)	'	'
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 14), Issued and Outstanding - 731,233 shares (2013 - 731,250)	731.3	731.3
Common Shares - par value $0.125 per share, Authorized - 400,000,000 shares (2013- 400,000,000 shares); Issued - 159,546,224 shares (2013 - 159,546,224 shares); Outstanding - 153,182,592 shares (2013 - 153,126,291 shares)	19.8	19.8
Capital in excess of par value of shares	2,318	2,329.50
Retained earnings	3,276	3,407.30
Cost of 6,363,632 common shares in treasury (2013 - 6,419,933 shares)	-297.3	-305.5
Accumulated other comprehensive loss	-20.2	-112.9
TOTAL CLIFFS SHAREHOLDERS' EQUITY	6,027.60	6,069.50
NONCONTROLLING INTEREST	802	814.8
TOTAL EQUITY	6,829.60	6,884.30
TOTAL LIABILITIES AND EQUITY	$13,102.40	$13,121.90

Statements_Of_Condensed_Consol3

Statements Of Condensed Consolidated Financial Position (Parenthetical) (USD $)	Jun. 30, 2014	Dec. 31, 2013
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)	159,546,224	159,546,224
Common shares, outstanding	153,182,592	153,126,291
Common shares in treasury	6,363,632	6,419,933
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	731,223	731,250
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 $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
OPERATING ACTIVITIES	'	'
NET INCOME (LOSS)	($56.20)	$262.10
Adjustments to reconcile net income (loss) to net cash provided (used) by operating activities:	'	'
Depreciation, depletion and amortization	286.4	284.9
Deferred income taxes	-139	-121.5
Other	24.8	52.3
Changes in operating assets and liabilities:	'	'
Receivables and other assets	85.5	87.2
Product inventories	-251.7	-105.8
Payables and accrued expenses	-73.7	-70.3
Net cash provided (used) by operating activities	-123.9	388.9
INVESTING ACTIVITIES	'	'
Purchase of property, plant and equipment	-164.3	-501.2
Other investing activities	16	0.9
Net cash used by investing activities	-148.3	-500.3
FINANCING ACTIVITIES	'	'
Net proceeds from issuance of Series A, Mandatory Convertible Preferred Stock, Class A	0	709.4
Net proceeds from issuance of common shares	0	285.3
Repayment of term loan	0	-847.1
Borrowings under credit facilities	730.4	437
Repayment under credit facilities	-315.6	-322
Common stock dividends	-46	-46
Preferred stock dividends	-25.6	-10
Other financing activities	-52.5	-13.3
Net cash provided by financing activities	290.7	193.3
EFFECT OF EXCHANGE RATE CHANGES ON CASH	5.9	-13.8
INCREASE IN CASH AND CASH EQUIVALENTS	24.4	68.1
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	335.5	195.2
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$359.90	$263.30

BASIS_OF_PRESENTATION_AND_SIGN

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2014
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 six months ended June 30, 2014 are not necessarily indicative of results to be expected for the year ending December 31, 2014 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, 2013.
	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	82.80%	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 June 30, 2014 and December 31, 2013. Parentheses indicate a net liability.
					(In Millions)
	Investment	Classification	Accounting	Interest	June 30,		December 31, 2013
			Method	Percentage	2014
	Hibbing	Other non-current assets1	Equity Method	23%	$	9.5	$	(3.9	)
	Other	Other non-current assets	Equity Method	Various	34.1		34.7
					$	43.6	$	30.8
	1 At December 31, 2013, the classification for Hibbing was Other liabilities.
	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, 2013 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.
	Foreign Currency
	Our financial statements are prepared with the U.S. dollar as the reporting currency. The functional currency of the Company’s Australian subsidiaries is the Australian dollar. The functional currency of all other international subsidiaries is the U.S. dollar. The financial statements of international subsidiaries are translated into U.S. dollars using the exchange rate at each balance sheet date for assets and liabilities and a weighted average exchange rate for each period for revenues, expenses, gains and losses. Where the local currency is the functional currency, translation adjustments are recorded as Accumulated other comprehensive loss. Income taxes generally are not provided for foreign currency translation adjustments. To the extent that monetary assets and liabilities, inclusive of intercompany notes, are recorded in a currency other than the functional currency, these amounts are remeasured each reporting period, with the resulting gain or loss being recorded in the Statements of Unaudited Condensed Consolidated Operations. Transaction gains and losses resulting from remeasurement of short-term intercompany loans are included in Miscellaneous - net in our Statements of Unaudited Condensed Consolidated Operations. For the three and six months ended June 30, 2014, net losses of $11.4 million and $18.1 million, respectively, related to the impact of transaction gains and losses resulting from remeasurement. Of these transaction gains and losses, for the three months ended June 30, 2014, losses of $4.2 million and $2.0 million, respectively, and for the six months ended June 30, 2014 losses of $13.0 million and $5.1 million, respectively, resulted from remeasurement of short-term intercompany loans and cash and cash equivalents. For the three and six months ended June 30, 2013, net gains of $47.0 million and $50.5 million, respectively, related to the impact of transaction gains and losses resulting from remeasurement. Of these transaction gains and losses, for the three months ended June 30, 2013 gains of $28.7 million and $12.2 million, respectively, and for the six months ended June 30, 2013 $28.2 million and $11.9 million, respectively, resulted from remeasurement of short-term intercompany loans and cash and cash equivalents.
	Recent Accounting Pronouncements
	In June 2014, the FASB amended the accounting guidance for share-based payments through ASU 2014-12, Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period.  Under the updated guidance, performance targets that affect vesting and that could be achieved after the requisite service period are treated as performance conditions.  A reporting entity should apply existing guidance in Topic 718 as it relates to awards with performance conditions that affect vesting to account for such awards.  As such, the performance target should not be reflected in estimating the grant-date fair value of the award.  Compensation cost should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the period(s) for which the requisite service has already been rendered.  If the performance target becomes probable of being achieved before the end of the requisite service period, the remaining unrecognized compensation cost should be recognized prospectively over the remaining requisite service period.  The total amount of compensation cost recognized during and after the requisite service period should reflect the number of awards that are expected to vest and should be adjusted to reflect those awards that ultimately vest.  The requisite service period ends when the employee can cease rendering service and still be eligible to vest in the award if the performance target is achieved.  As indicated in the definition of vest, the stated vesting period (which includes the period in which the performance target could be achieved) may differ from the requisite service period.  The update is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015 and may be adopted either prospectively or retrospectively.  Earlier adoption is permitted. We are currently evaluating the impact the adoption of the updated guidance will have on the Statements of Unaudited Condensed Consolidated Financial Position, Statements of Unaudited Condensed Consolidated Operations or Statements of Unaudited Condensed Consolidated Cash Flows and do not expect that this guidance will have a material impact on our consolidated financial statements.
	In June 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers.  The new revenue guidance broadly replaces the revenue guidance provided throughout the Codification.  The core principle of the revenue guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.  To achieve that core principle, an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when (or as) the entity satisfies a performance obligation.  The new revenue guidance also requires the capitalization of certain contract acquisition costs.  Reporting entities must provide new disclosures providing qualitative and quantitative information on the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers.  New disclosures also include qualitative and quantitative information on significant judgments, changes in judgments, and contract acquisition assets.  The update is effective for annual periods and interim periods within those annual periods beginning after December 15, 2016 and may be adopted either retrospectively or retrospectively with the cumulative effect.  Earlier adoption is not permitted. We are still evaluating the impact of the updated guidance on the Statements of Unaudited Condensed Consolidated Financial Position, Statements of Unaudited Condensed Consolidated Operations or Statements of Unaudited Condensed Consolidated Cash Flows.

SEGMENT_REPORTING

SEGMENT REPORTING	6 Months Ended
	Jun. 30, 2014
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, 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 were no intersegment revenues in the first half of 2014 or 2013.
	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 Ferroalloys and Global Exploration Group operating segments do not meet reportable segment disclosure requirements and, therefore, are not reported separately. In alignment with our capital allocation strategy, we anticipate decreased levels of exploration spending in our Global Exploration Group and Ferroalloys operation segments throughout 2014.
	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 six months ended June 30, 2014 and 2013, including a reconciliation of segment sales margin to Income (Loss) from Continuing Operations Before Income Taxes and Equity Loss from Ventures:
		(In Millions)
		Three Months Ended										Six Months Ended
		June 30,										June 30,
		2014					2013					2014					2013
	Revenues from product sales and services:
	U.S. Iron Ore	$	514.6		47	%	$	701.7		47	%	$	875.9		43	%	$	1,111.80		42	%
	Eastern Canadian Iron Ore	174			16	%	213.9			14	%	332.3			16	%	459.2			17	%
	Asia Pacific Iron Ore	233.1			21	%	327			22	%	487.3			24	%	597.8			23	%
	North American Coal	179.1			16	%	245.9			17	%	345.3			17	%	460.2			18	%
	Total revenues from product sales and services	$	1,100.80		100	%	$	1,488.50		100	%	$	2,040.80		100	%	$	2,629.00		100	%
	Sales margin:
	U.S. Iron Ore	$	147.2				$	216.3				$	242.2				$	373.6
	Eastern Canadian Iron Ore	(38.5		)			(49.7		)			(88.2		)			(30.3		)
	Asia Pacific Iron Ore	36					95					102.3					156.3
	North American Coal	(52.7		)			6.6					(101.1		)			8.4
	Other	—					—					—					(1.9		)
	Sales margin	92					268.2					155.2					506.1
	Other operating expense	(103.7		)			(6.2		)			(217.6		)			(75.8		)
	Other expense	(42.6		)			(43.5		)			(84.1		)			(91.5		)
	Income (loss) from continuing operations before income taxes and equity loss from ventures	$	(54.3	)			$	218.5				$	(146.5	)			$	338.8
	Depreciation, depletion and amortization:
	U.S. Iron Ore	$	26.6				$	28.4				$	55.3				$	55
	Eastern Canadian Iron Ore	42.4					42.4					83.6					83.5
	Asia Pacific Iron Ore	42.3					41.7					81.4					78.1
	North American Coal	32					28.4					61.9					60.9
	Other	2					3.4					4.2					7.4
	Total depreciation, depletion and amortization	$	145.3				$	144.3				$	286.4				$	284.9
	Capital additions1:
	U.S. Iron Ore	$	14				$	12.2				$	28.9				$	23.9
	Eastern Canadian Iron Ore	23.1					186.8					74.1					353.8
	Asia Pacific Iron Ore	2					2.3					5.2					6.6
	North American Coal	11					15.7					20.2					26.8
	Other	1.9					1.1					2.8					2.7
	Total capital additions	$	52				$	218.1				$	131.2				$	413.8
	1    Includes capital lease additions and non-cash accruals. Refer to NOTE 19 - CASH FLOW INFORMATION.
	A summary of assets by segment is as follows:
		(In Millions)
		June 30,			December 31, 2013
		2014
	Assets:
	U.S. Iron Ore	$	1,825.20		$	1,671.60
	Eastern Canadian Iron Ore	7,740.80			7,915.50
	Asia Pacific Iron Ore	1,046.00			1,078.40
	North American Coal	1,750.60			1,841.80
	Other	513.4			455.6
	Total segment assets	12,876.00			12,962.90
	Corporate	226.4			159
	Total assets	$	13,102.40		$	13,121.90

DERIVATIVE_INSTRUMENTS_AND_HED

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	6 Months Ended
	Jun. 30, 2014
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 June 30, 2014 and December 31, 2013:
		(In Millions)
		Derivative Assets												Derivative Liabilities
		June 30, 2014						December 31, 2013						June 30, 2014					31-Dec-13
	Derivative Instrument	Balance Sheet Location		Fair				Balance		Fair				Balance Sheet		Fair			Balance Sheet	Fair
				Value				Sheet		Value				Location		Value			Location	Value
								Location
	Derivatives designated as hedging instruments under ASC 815:
	Interest Rate Swaps	Other current assets		$	3.6					$	—					$	—		Other current liabilities	$	2.1
	Foreign Exchange Contracts	Other current assets		12.1				Other current assets		0.3				Other current liabilities		0.5			Other current liabilities	25.8
	Total derivatives designated as hedging instruments under ASC 815			$	15.7					$	0.3					$	0.5			$	27.9
	Derivatives not designated as hedging instruments under ASC 815:
	Foreign Exchange Contracts			$	—					$	—					$	—		Other current liabilities	$	1.1
	Customer Supply Agreement	Other current assets		33				Other current assets		55.8						—				—
	Provisional Pricing Arrangements			—				Other current assets		3.1				Other current liabilities		20.2			Other current liabilities	10.3
	Total derivatives not designated as hedging instruments under ASC 815			$	33					$	58.9					$	20.2			$	11.4
	Total derivatives			$	48.7					$	59.2					$	20.7			$	39.3
	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 entities with 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 currency exchange rates 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 June 30, 2014, we had outstanding Australian and Canadian foreign currency exchange contracts with notional amounts of $300.0 million and $259.1 million, respectively, in the form of forward contracts with varying maturity dates ranging from July 2014 to June 2015. This compares with outstanding Australian and Canadian foreign currency exchange contracts with a notional amount of $323.0 million and $285.9 million, respectively, as of December 31, 2013.
	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 June 30, 2014 and 2013, there was no material ineffectiveness recorded for foreign exchange contracts that were classified as cash flow hedges. However, certain Canadian hedge contracts were deemed ineffective during the fourth quarter of 2013 and no longer qualified for hedge accounting treatment. The de-designated hedges are discussed within the Derivatives Not Designated as Hedging Instruments section of this footnote. Amounts recorded as a component of Accumulated other comprehensive loss are reclassified into earnings in the same period the forecasted transactions affect earnings. Of the amounts remaining in Accumulated other comprehensive loss related to Australian hedge contracts and Canadian hedge contracts, we estimate that gains of $6.8 million and gains of $1.4 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 six months ended June 30, 2014 and 2013:
		(In Millions)
	Derivatives in Cash Flow Hedging Relationships	Amount of Gain (Loss)								Location of Gain (Loss)		Amount of Gain (Loss)
		Recognized in OCI on Derivatives								Reclassified		Reclassified
										from Accumulated OCI into Earnings		from Accumulated
												OCI into Earnings
		(Effective Portion)								(Effective Portion)		(Effective Portion)
		Three Months Ended										Three Months Ended
		June 30,										June 30,
		2014				2013						2014				2013
	Australian Dollar Foreign	$	3.7			$	(31.3	)		Product revenues		$	(3.7	)		$	2.6
	Exchange Contracts
	(hedge designation)
	Canadian Dollar Foreign Exchange Contracts (hedge designation)	6				(10.9		)		Cost of goods sold and operating expenses		(2.7		)		(0.4		)
	Canadian Dollar Foreign Exchange Contracts	—				—				Cost of goods sold and operating expenses		(0.2		)		—
	(prior to de-designation)
	Total	$	9.7			$	(42.2	)				$	(6.6	)		$	2.2
		Six Months Ended										Six Months Ended
		June 30,										June 30,
		2014				2013						2014				2013
	Australian Dollar Foreign	$	9.2			$	(28.1	)		Product revenues		$	(12.8	)		$	4.4
	Exchange Contracts
	(hedge designation)
	Canadian Dollar Foreign Exchange Contracts	(1.8		)		(19.1		)		Cost of goods sold and operating expenses		(6.1		)		(0.2		)
	(hedge designation)
	Canadian Dollar Foreign Exchange Contracts	—				—				Cost of goods sold and operating expenses		(0.5		)		—
	(prior to de-designation)
		$	7.4			$	(47.2	)				$	(19.4	)		$	4.2
	Fair Value Hedges
	Interest Rate Hedges
	Our fixed-to-variable interest rate swap derivative instruments, with a notional amount of $250.0 million, are designated and qualify as fair value hedges as of June 30, 2014. The objective of the hedges is to offset changes in the fair value of our debt instruments associated with fluctuations in the benchmark LIBOR interest rate as part of our risk management strategy.
	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 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
	. The net gains recognized in Other non-operating income for the three and six months ended June 30, 2014 were $0.1 million and $0.3 million, respectively. There were no derivative instruments that were designated as fair-value hedges for the period ended June 30, 2013.
	Derivatives Not Designated as Hedging Instruments
	Foreign Exchange Contracts
	During the fourth quarter of 2013, we discontinued hedge accounting for Canadian foreign currency exchange contracts for all outstanding contracts associated with the Wabush operation and the Ferroalloys operating segment as projected future cash flows were no longer considered probable, but we continue to hold these instruments as economic hedges to manage currency risk. Subsequent to de-designation, no further foreign currency exchange contracts were entered into for the Wabush operation or the Ferroalloys operating segment. As of June 30, 2014, there were no outstanding de-designated foreign currency exchange rate contracts as all remaining de-designated foreign exchange contracts matured during the second quarter of 2014. This compares with outstanding de-designated foreign currency exchange contracts with a notional amount of $74.8 million as of December 31, 2013.
	As a result of discontinued hedge accounting, the instruments are prospectively adjusted to fair value each reporting period through Cost of goods sold and operating expenses on the Statements of Unaudited Condensed Consolidated Operations. For the three and six months ended June 30, 2014, the change in fair value of our de-designated foreign currency exchange contracts resulted in net losses of $2.4 million and $3.3 million, respectively. The amounts that were previously recorded as a component of Accumulated other comprehensive loss prior to de-designation will be reclassified to earnings and a corresponding realized gain or loss will be recognized when the forecasted cash flow occurs. For the three and six months ended June 30, 2014, we reclassified losses of $0.2 million and $0.5 million, respectively, from Accumulated other comprehensive loss related to contracts that matured during the period, and recorded the amounts as Cost of goods sold and operating expenses on the Statements of Unaudited Condensed Consolidated Operations. As of June 30, 2014, no gains or losses remain in Accumulated other comprehensive loss related to the effective cash flow hedge contracts prior to de-designation as all de-designated hedges matured by the end of the second quarter of 2014.
	Customer Supply Agreements
Most of our U.S. Iron Ore long-term supply agreements are comprised of a base price with annual price adjustment factors. The base price is the primary component of the purchase price for each contract. The indexed price adjustment factors are integral to the iron ore supply contracts and vary based on the agreement, but typically include adjustments based upon changes in the Platts 62 percent Fe spot rate and/or international pellet prices and changes in specified Producer 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.
A certain supply agreement with one U.S. Iron Ore customer provides for supplemental revenue or refunds to the customer based on the customer’s average annual steel pricing at the time the product is consumed in the customer’s blast furnace. The supplemental pricing is characterized as a freestanding derivative and is required to be accounted for separately once the product is shipped. The derivative instrument, which is finalized based on a future price, is adjusted to fair value as a revenue adjustment each reporting period until the pellets are consumed and the amounts are settled.
We recognized $34.3 million and $62.0 million as Product revenues in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2014, respectively, related to the supplemental payments. This compares with Product revenues of $35.4 million and $59.5 million for the comparable respective periods in 2013. Derivative assets, representing the fair value of the pricing factors, were $33.0 million and $55.8 million in the June 30, 2014 and December 31, 2013 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 period 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 June 30, 2014 we had no Other current assets recorded related to our estimate of the final revenue rate with any of our customers. At December 31, 2013, we recorded $3.1 million as Other current assets in the Statements of Unaudited Condensed Consolidated Financial Position related to our estimate of the final revenue rate with our U.S. Iron Ore, Eastern Canadian Iron Ore and Asia Pacific Iron Ore customers. At June 30, 2014 and December 31, 2013, we recorded $20.2 million and $10.3 million, respectively, as Other current liabilities in the Statements of Unaudited Condensed Consolidated Financial Position related to our estimate of the final revenue rate with our U.S. Iron Ore and Asia Pacific Iron Ore customers and our U.S. Iron Ore, Eastern Canadian Iron Ore and Asia Pacific Iron Ore customers. These amounts represent the difference between the provisional price agreed upon with our customers based on the supply agreement terms and our estimate of the final revenue rate based on the price calculations established in the supply agreements. As a result, we recognized a net $14.1 million decrease and a net $20.2 million decrease in Product revenues in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2014, respectively, related to these arrangements. This compares with a net $28.2 million decrease and a net $31.1 million decrease in Product revenues for the comparable respective periods in 2013.
The following summarizes the effect of our derivatives that are not designated as hedging instruments in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2014 and 2013:
(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								Six Months Ended
		June 30,								June 30,
		2014				2013				2014				2013
Foreign Exchange Contracts	Cost of goods sold and operating expenses	$	(2.4	)		$	—			$	(3.3	)		$	—
Customer Supply Agreement	Product revenues	34.3				35.4				62				59.5
Provisional Pricing Arrangements	Product revenues	(14.1		)		(28.2		)		(20.2		)		(31.1		)
		$	17.8			$	7.2			$	38.5			$	28.4
Refer to NOTE 7 - FAIR VALUE OF FINANCIAL INSTRUMENTS for additional information.

INVENTORIES

INVENTORIES	6 Months Ended
	Jun. 30, 2014
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 June 30, 2014 and December 31, 2013:
		(In Millions)
		30-Jun-14						31-Dec-13
	Segment	Finished Goods		Work-in Process		Total Inventory		Finished Goods		Work-in		Total
										Process		Inventory
	U.S. Iron Ore	$	361.5	$	24.4	$	385.9	$	92.1	$	13	$	105.1
	Eastern Canadian Iron Ore	34.4		51.9		86.3		65.3		48.1		113.4
	Asia Pacific Iron Ore	39.6		75.9		115.5		39.7		50.6		90.3
	North American Coal	45		16.1		61.1		59.4		23.2		82.6
	Total	$	480.5	$	168.3	$	648.8	$	256.5	$	134.9	$	391.4
	We recorded lower-of-cost-or-market inventory charges of $15.0 million and $37.1 million in Cost of goods sold and operating expenses in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2014, respectively, for our North American Coal operations. The charges at North American Coal were a result of market pricing declines during the periods. For the three and six months ended June 30, 2013, we recorded lower-of-cost-or-market inventory charges of $0.7 million and $2.7 million, respectively, for our North American Coal operations. These charges were a result of market declines and costs associated with operational and geological issues.
	We recorded lower-of-cost-or-market inventory charges of $2.6 million and $16.0 million in Cost of goods sold and operating expenses in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2014, respectively, for our Eastern Canadian Iron Ore operations. The $2.6 million charge in the second quarter of 2014 relates to an adjustment of the remaining Wabush mine inventory to estimated net realizable value. The charges in the first quarter of 2014 at Eastern Canadian Iron Ore were a result of declines in Platts pricing and higher inventory costs at both Bloom Lake and Wabush.  Bloom Lake’s higher inventory costs were driven by the timing of maintenance activities and mine development, whereas Wabush’s higher costs were driven by unfavorable production performance up to the idling of the Scully mine operation.
	We recorded a lower-of-cost-or-market inventory charge during the second quarter of 2013 of $11.1 million relating to Wabush pellets that were contractually committed tons. We additionally recorded a lower-of-cost-or-market inventory charge during the second quarter of 2013 of $4.7 million relating to the Wabush sinter feed caused by higher costs as a result of the transition of product being produced and the forest fire that temporarily idled the mine in June. An unsaleable inventory impairment charge was recorded in the second quarter of 2013 relating to Wabush pellets of $10.6 million as a result of our idling of the Wabush pellet plant during the second quarter of 2013. All of these charges recorded during the second quarter were recorded in Cost of goods sold and operating expenses in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2013 for our Eastern Canadian Iron Ore operations.

PROPERTY_PLANT_AND_EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	6 Months Ended
	Jun. 30, 2014
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 June 30, 2014 and December 31, 2013:
		(In Millions)
		June 30,			December 31, 2013
		2014
	Land rights and mineral rights	$	7,854.20		$	7,819.60
	Office and information technology	125.8			125.7
	Buildings	307.1			255.2
	Mining equipment	2,199.30			1,819.30
	Processing equipment	1,943.90			2,148.60
	Electric power facilities	114.6			114.3
	Port facilities	105.1			99.4
	Interest capitalized during construction	23.1			23.8
	Land improvements	54.5			69.3
	Other	89.6			104.4
	Construction in-progress	892.8			991.3
		13,710.00			13,570.90
	Accumulated depreciation and depletion	(2,705.2		)	(2,417.5		)
		$	11,004.80		$	11,153.40
	We recorded depreciation and depletion expense of $142.5 million and $280.9 million in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2014, respectively. This compares with depreciation and depletion expense of $138.9 million and $274.9 million for the three and six months ended June 30, 2013, respectively.
	The accumulated amount of capitalized interest included within construction in-progress at June 30, 2014 is $31.2 million, of which $1.0 million was capitalized during 2014. At December 31, 2013, $31.4 million of capitalized interest was included within construction in-progress, of which $17.4 million was capitalized during 2013.

GOODWILL_AND_OTHER_INTANGIBLE_

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES	6 Months Ended
	Jun. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES	'
	NOTE 6 - 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 six months ended June 30, 2014 and the year ended December 31, 2013:
		(In Millions)
		30-Jun-14																								December 31, 2013
		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			$	—			$	72.5			$	—			$	—			$	74.5			$	2	$	—		$	84.5		$	—		$	80.9		$	167.4
	Arising in business combinations	—				—				—				—				—				—				—		—			—			—			—			—
	Impairment	—				—				—				—				—				—				—		—			—			—			(80.9		)	(80.9		)
	Impact of foreign currency translation	—				—				4.1				—				—				4.1				—		—			(12.0		)	—			—			(12.0		)
	Ending Balance	$	2			$	—			$	76.6			$	—			$	—			$	78.6			$	2	$	—		$	72.5		$	—		$	—		$	74.5
	Accumulated goodwill impairment loss	$	—			$	(1,000.0	)		$	—			$	(27.8	)		$	(80.9	)		$	(1,108.7	)		$	—	$	(1,000.0	)	$	—		$	(27.8	)	$	(80.9	)	$	(1,108.7	)
	Other Intangible Assets and Liabilities
	Following is a summary of intangible assets and liabilities as of June 30, 2014 and December 31, 2013:
				(In Millions)
				30-Jun-14												31-Dec-13
		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		$	130.2			$	(41.6	)		$	88.6			$	127.4			$	(35.9	)		$	91.5
	Utility contracts	Intangible assets, net		54.7				(53.9		)		0.8				54.7				(53.1		)		1.6
	Leases	Intangible assets, net		2.4				(0.2		)		2.2				2.4				(0.1		)		2.3
	Total intangible assets			$	187.3			$	(95.7	)		$	91.6			$	184.5			$	(89.1	)		$	95.4
	Below-market sales contracts	Other current liabilities		$	(23.0	)		$	—			$	(23.0	)		$	(23.0	)		$	—			$	(23.0	)
	Below-market sales contracts	Other liabilities		(205.9		)		167.4				(38.5		)		(205.9		)		159.7				(46.2		)
	Total below-market sales contracts			$	(228.9	)		$	167.4			$	(61.5	)		$	(228.9	)		$	159.7			$	(69.2	)
	Amortization expense relating to intangible assets was $2.8 million and $5.5 million, respectively, for the three and six months ended June 30, 2014 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 $5.3 million and $10.0 million for the comparable respective periods in 2013. The estimated amortization expense relating to intangible assets for the remainder of this year and each of the five succeeding years is as follows:
		(In Millions)
		Amount
	Year Ending December 31,
	2014 (remaining six months)	$	4.6
	2015	7.9
	2016	7
	2017	6.4
	2018	7.4
	2019	7.4
	Total	$	40.7
	The below-market sales contracts are classified as a liability and recognized over the term of the underlying contracts. The outstanding below-market sales contract has a remaining life of approximately three years. For the three and six months ended June 30, 2014 and 2013, we recognized $7.6 million and $14.7 million, respectively, in Product revenues related to below-market sales contracts. 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,
	2014 (remaining six months)	$	15.4
	2015	23
	2016	23
	2017	0.1
	Total	$	61.5

FAIR_VALUE_OF_FINANCIAL_INSTRU

FAIR VALUE OF FINANCIAL INSTRUMENTS	6 Months Ended
	Jun. 30, 2014
Fair Value Disclosures [Abstract]	'
FAIR VALUE OF FINANCIAL INSTRUMENTS	'
	NOTE 7 - FAIR VALUE OF FINANCIAL INSTRUMENTS
	The following represents the assets and liabilities of the Company measured at fair value at June 30, 2014 and December 31, 2013:
		(In Millions)
		June 30, 2014
	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	$	84			$	—			$	—			$	84
	Derivative assets	—				3.6				33				36.6
	Available-for-sale marketable securities	27.1				—				—				27.1
	Foreign exchange contracts	—				12.1				—				12.1
	Total	$	111.1			$	15.7			$	33			$	159.8
	Liabilities:
	Derivative liabilities	$	—			$	—			$	20.2			$	20.2
	Foreign exchange contracts	—				0.5				—				0.5
	Total	$	—			$	0.5			$	20.2			$	20.7
		(In Millions)
		December 31, 2013
	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	$	85			$	—			$	—			$	85
	Derivative assets	—				—				58.9				58.9
	Available-for-sale marketable securities	21.4				—				—				21.4
	Foreign exchange contracts	—				0.3				—				0.3
	Total	$	106.4			$	0.3			$	58.9			$	165.6
	Liabilities:
	Derivative liabilities	$	—			$	2.1			$	10.3			$	12.4
	Foreign exchange contracts	—				26.9				—				26.9
	Total	$	—			$	29			$	10.3			$	39.3
	Financial assets classified in Level 1 at June 30, 2014 and December 31, 2013 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 June 30, 2014 and December 31, 2013, such derivative financial instruments included our existing foreign currency exchange contracts and interest rate swaps. 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 June 30, 2014 and December 31, 2013 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 also consisted of derivatives related to certain provisional pricing arrangements with our U.S. Iron Ore and Asia Pacific Iron Ore customers at June 30, 2014 and to certain provisional pricing arrangements with our U.S. Iron Ore, Eastern Canadian Iron Ore and Asia Pacific Iron Ore customers at December 31, 2013. 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)				Balance Sheet Location		Valuation Technique		Unobservable Input		Range or Point Estimate
			Fair Value at June 30, 2014										(Weighted Average)
	Provisional Pricing Arrangements		$	20.2			Derivative liabilities		Market Approach		Management's		$93
											Estimate of 62% Fe
	Customer Supply Agreement		$	33			Derivative assets		Market Approach		Hot-Rolled Steel Estimate		$635 - $665 ($650)
	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 agreement 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.
	We recognize any transfers between levels as of the beginning of the reporting period. There were no transfers between Level 1 and Level 2 of the fair value hierarchy during the three and six months ended June 30, 2014 or 2013. The following tables represent a reconciliation of the changes in fair value of financial instruments measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the three and six months ended June 30, 2014 and 2013.
		(In Millions)
		Derivative Assets (Level 3)
		Three Months Ended								Six Months Ended
		June 30,								June 30,
		2014				2013				2014				2013
	Beginning balance	$	43.3			$	53.3			$	58.9			$	62.4
	Total gains
	Included in earnings	33				32.4				62				60.4
	Settlements	(43.3		)		(40.6		)		(87.9		)		(77.7		)
	Transfers into Level 3	—				—				—				—
	Transfers out of Level 3	—				—				—				—
	Ending balance - June 30	$	33			$	45.1			$	33			$	45.1
	Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date	$	33			$	32.4			$	62			$	60.4
		(In Millions)
		Derivative Liabilities (Level 3)
		Three Months Ended								Six Months Ended
		June 30,								June 30,
	2014				2013				2014				2013
Beginning balance	$	(7.4	)		$	(6.8	)		$	(10.3	)		$	(11.3	)
Total gains
Included in earnings	(12.8		)		(25.2		)		(20.2		)		(32.0		)
Settlements	—				—				10.3				11.3
Transfers into Level 3	—				—				—				—
Transfers out of Level 3	—				—				—				—
Ending balance - June 30	$	(20.2	)		$	(32.0	)		$	(20.2	)		$	(32.0	)
Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date	$	(12.8	)		$	(25.2	)		$	(20.2	)		$	(32.0	)
Gains and losses included in earnings are reported in Product revenues in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2014 and 2013.
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 June 30, 2014 and December 31, 2013 were as follows:
			(In Millions)
			June 30, 2014								December 31, 2013
	Classification		Carrying				Fair Value				Carrying				Fair Value
			Value								Value
Long-term debt:
Senior notes—$700 million	Level 2		$	699.5			$	756.6			$	699.4			$	718.2
Senior notes—$1.3 billion	Level 2		1,289.80				1,537.40				1,289.60				1,404.90
Senior notes—$400 million	Level 2		398.5				450.2				398.4				432.1
Senior notes—$500 million	Level 2		496.9				532.4				496.5				523.8
Revolving loan	Level 2		275				275				—				—
Equipment loan facilities	Level 2		130				130				140.8				140.8
Fair value adjustment to interest rate hedge	Level 2		3.3				3.3				(2.1		)		(2.1		)
Total long-term debt			$	3,293.00			$	3,684.90			$	3,022.60			$	3,217.70
The fair value of debt is based on the fair market yield curves for the remainder of the term expected to be outstanding. The fair value of long-term debt was determined using quoted market prices or discounted cash flows based upon current borrowing rates. The revolving loan is variable rate interest and approximates fair value. See NOTE 8 - DEBT AND CREDIT FACILITIES for further information.
Items Measured at Fair Value on a Non-Recurring Basis
The following table presents information about the impairment charges on both financial and nonfinancial assets that were measured on a fair value basis at December 31, 2013. The table also indicates the fair value hierarchy of the valuation techniques used to determine such fair value. We had no financial assets and liabilities measured at fair value on a non-recurring basis at June 30, 2014.
		(In Millions)
		December 31, 2013
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:
Goodwill impairment -		$	—			$	—			$	—			$	—			$	80.9
Ferroalloys reporting unit
Other long-lived assets -		—				—				46.3				46.3				155.4
Property, plant and equipment
Other long-lived assets -		—				—				1.6				1.6				14.5
Intangibles and long-term
deposits
Investment in ventures		—				—				—				—				67.6
impairment - Amapá
		$	—			$	—			$	47.9			$	47.9			$	318.4
Financial Assets
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. The sale of Amapá was completed in the fourth quarter of 2013.
Non-Financial Assets
During the fourth quarter of 2013, a goodwill impairment charge of $80.9 million was recorded for our Cliffs Chromite Ontario and Cliffs Chromite Far North reporting units within our Ferroalloys operating segment. The impairment charge was primarily a result of the decision to indefinitely suspend the Chromite Project and to not allocate additional capital for the project given the uncertain timeline and risks associated with the development of necessary infrastructure to bring the project online. Based on our review of the fair value hierarchy, the inputs used in these fair value measurements were considered Level 3 inputs.
We also recorded impairment charges to property, plant and equipment during 2013 related to our Wabush operation within our Eastern Canadian Iron Ore operating segment, our Cliffs Chromite Ontario and Cliffs Chromite Far North reporting units within our Other reportable segments and certain mineral lands at our Asia Pacific Iron Ore operating segment to reduce the related assets to their estimated fair value as we determined that the cash flows associated with these operations were not sufficient to support the recoverability of the carrying value of these assets. Fair value was determined based on management's estimate of liquidation value, which is considered a Level 3 input, and resulted in a charge of $155.4 million.

DEBT_AND_CREDIT_FACILITIES

DEBT AND CREDIT FACILITIES	6 Months Ended
	Jun. 30, 2014
Debt Disclosure [Abstract]	'
DEBT AND CREDIT FACILITIES	'
	NOTE 8 - DEBT AND CREDIT FACILITIES
	The following represents a summary of our long-term debt as of June 30, 2014 and December 31, 2013:
	($ in Millions)
	June 30, 2014
	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	$	699.5		-1
	$1.3 Billion Senior Notes:
	$500 Million 4.80% 2020 Senior Notes		Fixed	4.83%	2020	500		499.3			-2
	$800 Million 6.25% 2040 Senior Notes		Fixed	6.34%	2040	800		790.5			-3
	$400 Million 5.90% 2020 Senior Notes		Fixed	5.98%	2020	400		398.5			-4
	$500 Million 3.95% 2018 Senior Notes		Fixed	4.14%	2018	500		496.9			-5
	$1.75 Billion Credit Facility:
	Revolving Loan		Variable	1.66%	2017	1,750.00		275			-6
	Equipment Loans		Fixed	Various	2020	164.8		151.4
	Short-Term Borrowing Arrangements				2014/2015	139.7		139.7
	Fair Value Adjustment to Interest Rate Hedge							3.3
	Total debt					$	4,954.50	$	3,454.10
	Less: Short-term and current portion of long-term debt							161.1
	Long-term debt							$	3,293.00
	($ in Millions)
	31-Dec-13
	Debt Instrument		Type	Annual Effective Interest Rate	Final Maturity	Total Face Amount		Total Debt
	$700 Million 4.875% 2021 Senior Notes		Fixed	4.88%	2021	700		699.4			-1
	$1.3 Billion Senior Notes:
	$500 Million 4.80% 2020 Senior Notes		Fixed	4.83%	2020	500		499.2			-2
	$800 Million 6.25% 2040 Senior Notes		Fixed	6.34%	2040	800		790.4			-3
	$400 Million 5.90% 2020 Senior Notes		Fixed	5.98%	2020	400		398.4			-4
	$500 Million 3.95% 2018 Senior Notes		Fixed	4.14%	2018	500		496.5			-5
	$1.75 Billion Credit Facility:
	Revolving Loan		Variable	1.64%	2017	1,750.00		—			-6
	Equipment Loans		Fixed	Various	2020	164.8		161.7
	Fair Value Adjustment to Interest Rate Hedge							(2.1		)
	Total debt					$	4,814.80	$	3,043.50
	Less: Short-term and current portion of long-term debt							20.9
	Long-term debt							$	3,022.60
	-1	As of June 30, 2014 and December 31, 2013, the $700 million 4.875 percent senior notes were recorded at a par value of $700 million less unamortized discounts of $0.5 million and $0.6 million, respectively, based on an imputed interest rate of 4.89 percent.
	-2	As of June 30, 2014 and December 31, 2013, the $500 million 4.80 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $0.7 million and $0.8 million, respectively, based on an imputed interest rate of 4.83 percent.
	-3	As of June 30, 2014 and December 31, 2013, the $800 million 6.25 percent senior notes were recorded at a par value of $800 million less unamortized discounts of $9.5 million and $9.6 million, respectively, based on an imputed interest rate of 6.34 percent.
	-4	As of June 30, 2014 and December 31, 2013, the $400 million 5.90 percent senior notes were recorded at a par value of $400 million less unamortized discounts of $1.5 million and $1.6 million, respectively, based on an imputed interest rate of 5.98 percent.
	-5	As of June 30, 2014 and December 31, 2013, the $500 million 3.95 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $3.1 million and $3.5 million, respectively, based on an imputed interest rate of 4.14 percent.
	-6	As of June 30, 2014, $275.0 million of revolving loans were drawn under the credit facility. As of December 31, 2013, no revolving loans were drawn under the credit facility. As of June 30, 2014 and December 31, 2013, the principal amount of letter of credit obligations totaled $5.2 million and $8.4 million, respectively, thereby reducing available borrowing capacity to $1.5 billion and $1.7 billion for each period, respectively.
	Credit Facility
	On June 30, 2014, we amended 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 and Amendment No. 2 as of February 8, 2013), or revolving credit agreement, to effect the following:
	•	Replacing the current maximum leverage covenant ratio of debt to earnings of less than 3.5 times with a maximum balance sheet leverage ratio of debt to capitalization of less than 45 percent.
	•	Resetting the minimum interest coverage ratio from 2.5 to 1.0 to the ratio of 3.5 to 1.0.
	•	Amending the definition of EBITDA to include certain cash charges related to the Company’s Wabush mine and other cash restructuring charges and the definition of net worth to exclude up to $1 billion in non-cash impairment charges.
	•	Modifying the covenants restricting certain investments and acquisitions, the incurrence of certain indebtedness and liens, and the amount of dividends that may be declared or paid and shares that may be repurchased.
	The new amended revolving credit agreement terms are effective June 30, 2014, and remain in effect for the life of the revolving credit agreement. This amended revolving credit agreement allows our borrowing capacity to be less susceptible to the impact of volatile iron ore and metallurgical coal pricing.
	As of June 30, 2014, we were in compliance with these financial covenants. Additionally, as of December 31, 2013, we were in compliance with all applicable financial covenants related to the revolving credit agreement.
	Short-Term Borrowing Arrangements
	As of June 30, 2014, we had outstanding borrowings of $45.0 million on an uncommitted credit facility agreement which was used for general corporate purposes.  Per the uncommitted credit agreement, each loan drawn cannot be outstanding less than 30 days or more than 90 days.  Interest payable under the uncommitted credit facility is at a variable rate based on LIBOR plus an agreed upon margin of approximately one percent.
	On April 22, 2014, we established an accounts receivable securitization facility for certain domestic subsidiaries that provides up to $110 million of funding and expires on April 21, 2015. Availability under this facility is based on eligible receivable balances. At June 30, 2014, the amounts available and utilized under this program totaled $57.3 million. Interest payable under the credit facility is at a variable rate based on LIBOR type rate plus an agreed upon margin of less than one percent.
	As of June 30, 2014, we had outstanding borrowings of $37.4 million on pre-export trade finance loans. Per the agreements, the loans drawn have fixed maturity dates that are short-term in nature. Interest payable under the pre-export trade finance loans are at a fixed rate of less than one percent.
	Letters of Credit
	We issued standby letters of credit with certain financial institutions in order to support general business obligations including, but not limited to, workers compensation and environmental obligations. As of June 30, 2014 and December 31, 2013, these letter of credit obligations totaled $48.0 million, respectively. All of these standby letters of credit are in addition to the letters of credit provided for under the revolving credit agreement.
	Other 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 ($28.3 million) at June 30, 2014 in credit for contingent instruments, such as performance bonds. At December 31, 2013, the facility provided A$30.0 million ($26.8 million) in credit for contingent instruments. As of June 30, 2014, the outstanding bank guarantees under the facility totaled A$23.0 million ($21.7 million), thereby reducing borrowing capacity to A$7.0 million ($6.6 million). As of December 31, 2013, the outstanding bank guarantees under the facility totaled A$23.0 million ($20.5 million), thereby reducing borrowing capacity to A$7.0 million ($6.3 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.
	Debt Maturities
	The following represents a summary of our maturities of debt instruments, excluding borrowings on the revolving credit agreement, based on the principal amounts outstanding at June 30, 2014:
		(In Millions)
		Maturities of Debt
	2014 (July 1 - December 31)	$	150.4
	2015	21.8
2016	22.7
2017	23.6
2018	524.6
2019 and thereafter	2,448.00
Total maturities of debt	$	3,191.10

LEASE_OBLIGATIONS

LEASE OBLIGATIONS	6 Months Ended
	Jun. 30, 2014
Leases [Abstract]	'
LEASE OBLIGATIONS	'
	NOTE 9 - 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 $4.0 million and $11.3 million for the three and six months ended June 30, 2014, respectively, compared with $7.4 million and $14.2 million for the same respective period in 2013.
	Future minimum payments under capital leases and non-cancellable operating leases at June 30, 2014 are as follows:
		(In Millions)
		Capital Leases			Operating Leases
	2014 (July 1 - December 31)	$	33.5		$	9.5
	2015	89			14.2
	2016	38			9.2
	2017	30.5			8.3
	2018	22.4			7.1
	2019 and thereafter	37.8			14.7
	Total minimum lease payments	$	251.2		$	63
	Amounts representing interest	43.4
	Present value of net minimum lease payments	$	207.8	(1)
	(1)	The total is comprised of $82.0 million and $125.7 million classified as Other current liabilities and Other liabilities, respectively, in the Statements of Unaudited Condensed Consolidated Financial Position at June 30, 2014.

ENVIRONMENTAL_AND_MINE_CLOSURE

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	6 Months Ended
	Jun. 30, 2014
Environmental Remediation Obligations [Abstract]	'
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS	'
	NOTE 10 - ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS
	We had environmental and mine closure liabilities of $310.3 million and $321.0 million at June 30, 2014 and December 31, 2013, respectively. The following is a summary of the obligations as of June 30, 2014 and December 31, 2013:
		(In Millions)
		June 30,			December 31, 2013
		2014
	Environmental	$	11		$	8.4
	Mine closure
	LTVSMC	22.4			22
	Operating mines:
	U.S. Iron Ore	137.5			152.2
	Eastern Canadian Iron Ore	76.3			78.2
	Asia Pacific Iron Ore	27.4			25.5
	North American Coal	35.7			34.7
	Total mine closure	299.3			312.6
	Total environmental and mine closure obligations	310.3			321
	Less current portion	5.6			11.3
	Long term environmental and mine closure obligations	$	304.7		$	309.7
	Mine Closure
	The accrued closure obligation for our active mining operations provides for contractual and legal obligations associated with the eventual closure of the mining operations. The accretion of the liability and amortization of the related asset is recognized over the estimated mine lives for each location.
	The following represents a rollforward of our asset retirement obligation liability related to our active mining locations for the six months ended June 30, 2014 and for the year ended December 31, 2013:
		(In Millions)
		June 30,			December 31,
		2014			2013 (1)
	Asset retirement obligation at beginning of period	$	290.6		$	231.1
	Accretion expense	7.2			18.1
	Exchange rate changes	1.2			(3.4		)
	Revision in estimated cash flows	(22.1		)	44.8
	Asset retirement obligation at end of period	$	276.9		$	290.6
	(1)	Represents a 12-month rollforward of our asset retirement obligation at December 31, 2013.
	The revisions in estimated cash flows recorded during the six months ended June 30, 2014 primarily were a result of the announced Empire Mine extension during the first quarter of 2014. As a result of the extension, a portion of the required storm water management systems are now expected to be implemented prior to closure of the mine.

PENSIONS_AND_OTHER_POSTRETIREM

PENSIONS AND OTHER POSTRETIREMENT BENEFITS	6 Months Ended
	Jun. 30, 2014
Postemployment Benefits [Abstract]	'
PENSIONS AND OTHER POSTRETIREMENT BENEFITS	'
	NOTE 11 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS
	The following are the components of defined benefit pension and OPEB expense for the three and six months ended June 30, 2014 and 2013:
	Defined Benefit Pension Expense
		(In Millions)
		Three Months Ended						Six Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
	Service cost	$	7.9		$	9.7		$	15.9		$	19.6
	Interest cost	12.5			11.7			25			23.2
	Expected return on plan assets	(18.0		)	(20.0		)	(36.0		)	(33.1		)
	Amortization:
	Prior service costs	6.5			0.8			7.2			1.5
	Net actuarial (gain) loss	(2.3		)	8.2			1.3			15
	Curtailments/settlements	$	0.9		$	—		1.2			—
	Net periodic benefit cost	$	7.5		$	10.4		$	14.6		$	26.2
	Other Postretirement Benefits Expense
		(In Millions)
		Three Months Ended						Six Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
	Service cost	$	2		$	3.1		$	4		$	6.2
	Interest cost	4.1			4.4			8.1			8.7
	Expected return on plan assets	(4.3		)	(5.0		)	(8.6		)	(10.0		)
	Amortization:
	Prior service costs	(0.9		)	(0.9		)	(1.8		)	(1.8		)
	Net actuarial loss	1.1			3			2.3			5.8
	Net periodic benefit cost	$	2		$	4.6		$	4		$	8.9
	We made pension contributions of $10.4 million and $14.6 million for the three and six months ended June 30, 2014, respectively, compared to pension contributions of $11.4 million and $15.1 million for the three and six months ended June 30, 2013, respectively. OPEB contributions are typically made on an annual basis in the first quarter of each year, but due to plan funding requirements being met, no OPEB contributions were required or made for the six months ended June 30, 2014. OPEB contributions were $14.1 million for the six months ended June 30, 2013.

STOCK_COMPENSATION_PLANS

STOCK COMPENSATION PLANS	6 Months Ended
	Jun. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
STOCK COMPENSATION PLANS	'
	NOTE 12 - STOCK COMPENSATION PLANS
	Employees’ Plans
	The Compensation and Organization Committee (“Committee”) of the board of directors approved grants on February 10, 2014 and May 12, 2014 to certain officers and employees under our shareholder-approved 2012 Equity Plan for the 2014 to 2016 performance period. Shares granted under the awards during 2014 consisted of 0.5 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. No additional grants were issued from the ICE Plan after the date of approval of the 2012 Equity Plan; however, all awards previously granted under the ICE Plan continue in full force and effect in accordance with the terms of the award.
	On February 10, 2014, upon recommendation by the Committee, Cliffs’ Board approved and adopted, subject to the approval of Cliffs' shareholders at the 2014 annual meeting of shareholders, the Cliffs Amended and Restated 2012 Incentive Equity Plan, or Revised Incentive Plan. The principal reason for amending and restating the 2012 Equity Plan is to increase the number of common shares available for issuance by 5.0 million common shares. Upon shareholder approval, additional grants to employees will be made for the 2014 to 2016 performance period.
	For the outstanding ICE Plan and 2012 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 2012 to 2014, 2013 to 2015 and 2014 to 2016 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 2012 to 2014 performance period, the 2013 to 2015 performance period and the 2014 to 2016 performance period will vary from zero to 200 percent of the original grant. The restricted share units are subject to continued employment and 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 prior to October 2013 will vest and become nonforfeitable and will be paid out in cash for awards currently outstanding. For any equity grants awarded after September 2013, if we experience a change in control, then the vesting of all such grants only will accelerate following the employee's termination associated with the change in control and if the common shares are not substituted with a replacement award.
	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 and second quarters of 2014 performance share grants:
	Grant Date	Grant Date Market Price		Average Expected Term (Years)	Expected Volatility	Risk-Free Interest Rate	Dividend Yield	Fair Value		Fair Value (Percent of Grant Date Market Price)
	February 10, 2014	$	20.58	2.89	54.00%	0.54%	2.92%	$	22.21	107.92%
	May 12, 2014	$	17.54	2.61	54.00%	0.54%	2.92%	$	18.93	107.92%
	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	6 Months Ended
	Jun. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	NOTE 13 - INCOME TAXES
	For the six months ended June 30, 2014 we recognized an income tax benefit of $90.9 million. The income tax benefit was primarily driven by the six months ended June 30, 2014 pre-tax loss. The year-to-date benefit was calculated using the year-to-date loss, considering non-taxable and non-deductible items expected to be incurred for the full year unless those items are expected to be ratably incurred based on operating activity or profitability, (e.g. depletion), in which case we only considered year-to-date actual amounts, multiplied by the statutory rate. The tax benefit of the non-taxable interest income is expected to be $48.4 million for the year ending December 31, 2014. This is related to long-term intercompany loans between certain foreign subsidiaries and is a result of the difference in the tax characterization of the instruments in the United States, Australia and Canada. Interest expense is deductible by the debtors in Canada and Australia and interest income is excluded from taxable income by the creditors in the United States and Canada, resulting in an income tax benefit of $48.4 million. The adjustment is based on the terms of the intercompany loans and no significant management judgments or estimates were involved in the computation of the non-taxable interest income. The current year benefit of the intercompany loan between the United States and Canada is $27.8 million and will have no further impact on our financial results subsequent to April 27, 2014 when the terms of the loan were restructured. A benefit of $20.6 million is expected from the intercompany loan between Canada and Australia and will continue to have an impact through the year ending December 31, 2020, of which the impact will vary depending on the fluctuations in currency exchange rates.
	There were discrete items recorded in the first half of 2014 which resulted in a $4.4 million benefit. These adjustments relate primarily to the finalization of certain foreign tax returns and foreign currency remeasurement of current and deferred tax assets and deferred liabilities.

CAPITAL_STOCK

CAPITAL STOCK	6 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
CAPITAL STOCK	'
	NOTE 14 - 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, for total net proceeds of approximately $709.4 million, after underwriter fees and discounts. 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. 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.
	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 Preferred Shareholders of record as of the close of business on April 15, 2013. On May 7, 2013, September 9, 2013 and November 11, 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, November 1, 2013 and February 3, 2014 to our Preferred Shareholders of record as of the close of business on July 15, 2013, October 15, 2013 and January 15, 2014. On February 11, 2014, our board of directors declared the quarterly cash dividend of $17.50 per Preferred Share, which is equivalent to approximately $0.44 per depositary share. The cash dividend was paid on May 1, 2014 to our Preferred Shareholders of record as of the close of business on April 15, 2014. On May 13, 2014, our board of directors declared the quarterly cash dividends of $17.50 per Preferred Share, which is equivalent to approximately $0.44 per depositary share. The cash dividend of $12.8 million will be paid on August 1, 2014 to our shareholders of record as of the close of business on July 15, 2014.
	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, September 3, 2013 and December 2, 2013 to our common shareholders of record as of the close of business on February 22, 2013, May 17, 2013, August 15, 2013 and November 22, 2013, respectively. Additionally, the cash dividend of $0.15 per share was paid on March 3, 2014 and June 3, 2014 to our common shareholders of record as of close of business on February 21, 2014 and May 23, 2014.

SHAREHOLDERS_EQUITY

SHAREHOLDERS' EQUITY	6 Months Ended
	Jun. 30, 2014
Shareholders' Equity [Abstract]	'
SHAREHOLDERS' EQUITY	'
	NOTE 15 - 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 82.8 percent, 85 percent and 79 percent, respectively, for the six months ended June 30, 2014 and June 30, 2013:
		(In Millions)
		Cliffs				Noncontrolling				Total Equity
		Shareholders’				Interest
		Equity
	31-Dec-13	$	6,069.50			$	814.8			$	6,884.30
	Comprehensive income
	Net loss	(59.4		)		3.2				(56.2		)
	Other comprehensive income	92.7				1.1				93.8
	Total comprehensive income	33.3				4.3				37.6
	Stock and other incentive plans	(3.1		)		—				(3.1		)
	Common and preferred share dividends	(72.1		)		—				(72.1		)
	Undistributed losses to noncontrolling interest	—				(17.1		)		(17.1		)
	30-Jun-14	$	6,027.60			$	802			$	6,829.60
		(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	253				9.1				262.1
	Other comprehensive income	(184.0		)		2.3				(181.7		)
	Total comprehensive income	69				11.4				80.4
	Issuance of common shares	263.4				—				263.4
	Issuance of preferred shares	731.3				—				731.3
	Stock and other incentive plans	3.7				—				3.7
	Common and preferred share dividends	(68.9		)		—				(68.9		)
	Capital contribution by noncontrolling interest	—				13				13
	to subsidiary
	30-Jun-13	$	5,631.20			$	1,152.60			$	6,783.80
	The following table reflects the changes in Accumulated other comprehensive income (loss) related to Cliffs shareholders’ equity for June 30, 2014 and June 30, 2013:
		(In Millions)
		Changes in Pension and Other Post-Retirement Benefits, net of tax				Unrealized Net Gain (Loss) on Securities, net of tax				Unrealized Net Gain (Loss) on Foreign Currency Translation				Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax				Accumulated Other Comprehensive Income (Loss)
	Balance December 31, 2013	$	(204.9	)		$	6.2			$	106.7			$	(20.9	)		$	(112.9	)
	Other comprehensive income (loss) before reclassifications	(0.4		)		3.8				40.5				(2.3		)		41.6
	Net loss (gain) reclassified from accumulated other comprehensive income (loss)	3.3				0.1				—				12.8				16.2
	Balance March 31, 2014	$	(202.0	)		$	10.1			$	147.2			$	(10.4	)		$	(55.1	)
	Other comprehensive income (loss) before reclassifications	(1.4		)		(2.4		)		19.7				9.7				25.6
	Net loss (gain) reclassified from accumulated other comprehensive income (loss)	4				(1.3		)		—				6.6				9.3
	Balance June 30, 2014	$	(199.4	)		$	6.4			$	166.9			$	5.9			$	(20.2	)
		(In Millions)
		Changes in Pension and Other Post-Retirement Benefits, net of tax				Unrealized Net Gain (Loss) on Securities, net of tax				Unrealized Net Gain (Loss) on Foreign Currency Translation				Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax				Accumulated Other Comprehensive Income (Loss)
	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 income (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	)
	The following table reflects the details about Accumulated other comprehensive income (loss) components related to Cliffs shareholders’ equity for the three and six months ended June 30, 2014:
			(In Millions)
	Details about Accumulated Other Comprehensive Income (Loss) Components		Amount of (Gain)/Loss Reclassified into Income																Affected Line Item in the Statement of Unaudited Condensed Consolidated Operations
			Three Months Ended								Six Months Ended
			June 30,								June 30,
			2014				2013				2014				2013
	Amortization of Pension and Postretirement Benefit Liability:
	Prior-service costs		$	5.6			$	(0.1	)		$	5.4			$	(0.3	)		-1
	Net actuarial loss		(1.2		)		11.2				3.6				20.8				-1
	Settlements/curtailments		0.9				—				1.2				—				-1
			5.3				11.1				10.2				20.5				Total before taxes
			(1.3		)		(3.0		)		(2.9		)		(6.0		)		Income tax benefit (expense)
			$	4			$	8.1			$	7.3			$	14.5			Net of taxes
Unrealized gain (loss) on marketable securities:
Sale of marketable securities		$	(1.9	)		$	(1.1	)		$	(1.7	)		$	(1.1	)		Other non-operating income
Impairment		—				5.2				—				5.3				Other non-operating income
		(1.9		)		4.1				(1.7		)		4.2				Total before taxes
		0.6				(0.5		)		0.5				(0.5		)		Income tax benefit (expense)
		$	(1.3	)		$	3.6			$	(1.2	)		$	3.7			Net of taxes
Unrealized gain (loss) on derivative financial instruments:
Australian dollar foreign exchange contracts		$	5.3			$	(3.7	)		$	18.3			$	(6.3	)		Product revenues
Canadian dollar foreign exchange contracts		4.4				0.6				9.9				0.3				Cost of goods sold and operating expenses
		9.7				(3.1		)		28.2				(6.0		)		Total before taxes
		(3.1		)		0.9				(8.8		)		1.8				Income tax benefit (expense)
		$	6.6			$	(2.2	)		$	19.4			$	(4.2	)		Net of taxes
Total Reclassifications for the Period		$	9.3			$	9.5			$	25.5			$	14
-1	These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. See NOTE 11 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.

RELATED_PARTIES

RELATED PARTIES	6 Months Ended
	Jun. 30, 2014
Related Party Transactions [Abstract]	'
RELATED PARTIES	'
	NOTE 16 - RELATED PARTIES
	Three of our five U.S. iron ore mines and our Bloom Lake mine in Eastern Canada 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 June 30, 2014:
	Mine		Cliffs Natural Resources		ArcelorMittal			U.S. Steel Corporation			WISCO
	Empire		79	%	21	%		—			—
	Tilden		85	%	—			15	%		—
	Hibbing		23	%	62.3	%		14.7	%		—
	Bloom Lake		82.8	%	—			—			17.2	%
	During the first quarter of 2014, we announced that we entered into a revised commercial agreement with ArcelorMittal to supply iron ore pellets for an additional two years through the end of January 2017, with a mutual option to extend for a third year. In addition, Cliffs and ArcelorMittal also extended the joint partnership for the Empire Mine preventing the impending closure in 2014.
	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							Six Months Ended
		June 30,							June 30,
		2014			2013				2014				2013
	Product revenues from related parties	$	322.1		$	455			$	539			$	756.2
	Total product revenues	1,018.60			1,391.60				1,879.50				2,474.20
	Related party product revenue as a percent of total product revenue	31.6		%	32.7		%		28.7		%		30.6		%
	Amounts due from related parties recorded in Accounts receivable, net and Other current assets, including trade accounts receivable, a customer supply agreement and provisional pricing arrangements, were $69.9 million and $132.0 million at June 30, 2014 and December 31, 2013, respectively. Amounts due to related parties recorded in Accounts payable and Other current liabilities, including provisional pricing arrangements, were $26.3 million at June 30, 2014 and amounts including provisional pricing arrangements and liabilities to related parties were $25.1 million at December 31, 2013.

EARNINGS_PER_SHARE

EARNINGS PER SHARE	6 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
EARNINGS PER SHARE	'
	NOTE 17 - EARNINGS PER SHARE
	The following table summarizes the computation of basic and diluted earnings (loss) per share:
		(In Millions, Except Per Share Amounts)
		Three Months Ended						Six Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
	NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$	10.9		$	146		$	(59.4	)	$	253
	PREFERRED STOCK DIVIDENDS	(12.8		)	(12.9		)	(25.6		)	(22.8		)
	NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS	$	(1.9	)	$	133.1		$	(85.0	)	$	230.2
	Weighted Average Number of Shares:
	Basic	153.1			153			153.1			150.4
	Depositary Shares	—			25.2			—			19.1
	Employee Stock Plans	—			0.2			—			0.2
	Diluted	153.1			178.4			153.1			169.7
	Earnings (Loss) per Common Share Attributable to	$	(0.01	)	$	0.87		$	(0.56	)	$	1.53
	Cliffs Common Shareholders - Basic:
	Earnings (Loss) per Common Share Attributable to	$	(0.01	)	$	0.82		$	(0.56	)	$	1.49
	Cliffs Common Shareholders - Diluted:
	The diluted earnings per share calculation excludes 25.2 million depositary shares that were anti-dilutive for the three and six months ended June 30, 2014. Additionally, the diluted earnings per share calculation excludes 0.8 million shares related to equity plan awards that were anti-dilutive for both the three and six months ended June 30, 2014.

COMMITMENTS_AND_CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
COMMITMENTS AND CONTINGENCIES	'
	NOTE 18 - COMMITMENTS AND CONTINGENCIES
	Contingencies
	Claims and Legal Proceedings
	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, claims and legal proceedings are subject to inherent uncertainties, and unfavorable rulings could occur. An unfavorable ruling could include monetary damages, additional funding requirements or an injunction. If an unfavorable ruling were to occur, there exists the possibility of a material impact on the financial position and results of operations of the period in which the ruling occurs, or future periods. Specifically, our wholly owned subsidiary, CQIM, along with the Bloom Lake General Partner Limited and Bloom Lake, instituted an arbitral claim against Bloom Lake’s former customer, Worldlink, in October 2011 for material and/or fundamental breaches of the parties’ 2007 offtake agreement for the purchase and sale of iron concentrate produced at the Bloom Lake mine.  We filed the arbitration claim with the International Court of Arbitration of the International Chamber of Commerce pursuant to the dispute resolution provisions of the offtake agreement.  Bloom Lake terminated the offtake agreement with Worldlink in August 2011 due to Worldlink’s failure to fulfill its obligations under the agreement and Worldlink’s demand to renegotiate the price of the iron ore concentrate in spite of being party to a long-term offtake agreement.  Our damages for the breach of the offtake agreement are in excess of $85 million and Worldlink has counterclaimed for damages in excess of $100 million.  We strongly disagree with Worldlink’s defenses and counterclaims and intend to vigorously pursue our claim.  The arbitrators heard testimony at a hearing in May 2014 but have not yet issued a decision.  A decision is expected from the arbitrators later in 2014.

CASH_FLOW_INFORMATION

CASH FLOW INFORMATION	6 Months Ended
	Jun. 30, 2014
Supplemental Cash Flow Information [Abstract]	'
Cash Flow Information	'
	NOTE 19 - CASH FLOW INFORMATION
	A reconciliation of capital additions to cash paid for capital expenditures for the six months ended June 30, 2014 and 2013 is as follows:
		(In Millions)
		Six Months Ended
		June 30,
		2014			2013
	Capital additions	$	131.2		$	413.8
	Cash paid for capital expenditures	164.3			501.2
	Difference	$	(33.1	)	$	(87.4	)
	Non-cash accruals	$	(43.0	)	$	(87.4	)
	Capital leases	9.9			—
	Total	$	(33.1	)	$	(87.4	)
	Non-Cash Financing Activities - Declared Dividends
	On May 13, 2014, our board of directors declared the quarterly cash dividend on our Preferred Shares 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 $12.8 million will be payable on August 1, 2014 to our preferred shareholders of record as of the close of business on July 15, 2014.

SUBSEQUENT_EVENTS

SUBSEQUENT EVENTS	6 Months Ended
	Jun. 30, 2014
Subsequent Events [Abstract]	'
SUBSEQUENT EVENTS	'
	NOTE 20 - 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)	6 Months Ended
	Jun. 30, 2014
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	82.80%	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 June 30, 2014 and December 31, 2013. Parentheses indicate a net liability.
					(In Millions)
	Investment	Classification	Accounting	Interest	June 30,		December 31, 2013
			Method	Percentage	2014
	Hibbing	Other non-current assets1	Equity Method	23%	$	9.5	$	(3.9	)
	Other	Other non-current assets	Equity Method	Various	34.1		34.7
					$	43.6	$	30.8
	1 At December 31, 2013, the classification for Hibbing was Other liabilities.
Foreign Currency Transactions and Translations Policy [Policy Text Block]	'
	Foreign Currency
	Our financial statements are prepared with the U.S. dollar as the reporting currency. The functional currency of the Company’s Australian subsidiaries is the Australian dollar. The functional currency of all other international subsidiaries is the U.S. dollar. The financial statements of international subsidiaries are translated into U.S. dollars using the exchange rate at each balance sheet date for assets and liabilities and a weighted average exchange rate for each period for revenues, expenses, gains and losses. Where the local currency is the functional currency, translation adjustments are recorded as Accumulated other comprehensive loss. Income taxes generally are not provided for foreign currency translation adjustments. To the extent that monetary assets and liabilities, inclusive of intercompany notes, are recorded in a currency other than the functional currency, these amounts are remeasured each reporting period, with the resulting gain or loss being recorded in the Statements of Unaudited Condensed Consolidated Operations. Transaction gains and losses resulting from remeasurement of short-term intercompany loans are included in Miscellaneous - net in our Statements of Unaudited Condensed Consolidated Operations. For the three and six months ended June 30, 2014, net losses of $11.4 million and $18.1 million, respectively, related to the impact of transaction gains and losses resulting from remeasurement. Of these transaction gains and losses, for the three months ended June 30, 2014, losses of $4.2 million and $2.0 million, respectively, and for the six months ended June 30, 2014 losses of $13.0 million and $5.1 million, respectively, resulted from remeasurement of short-term intercompany loans and cash and cash equivalents. For the three and six months ended June 30, 2013, net gains of $47.0 million and $50.5 million, respectively, related to the impact of transaction gains and losses resulting from remeasurement. Of these transaction gains and losses, for the three months ended June 30, 2013 gains of $28.7 million and $12.2 million, respectively, and for the six months ended June 30, 2013 $28.2 million and $11.9 million, respectively, resulted from remeasurement of short-term intercompany loans and cash and cash equivalents.
New Accounting Pronouncements, Policy [Policy Text Block]	'
	Recent Accounting Pronouncements
	In June 2014, the FASB amended the accounting guidance for share-based payments through ASU 2014-12, Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period.  Under the updated guidance, performance targets that affect vesting and that could be achieved after the requisite service period are treated as performance conditions.  A reporting entity should apply existing guidance in Topic 718 as it relates to awards with performance conditions that affect vesting to account for such awards.  As such, the performance target should not be reflected in estimating the grant-date fair value of the award.  Compensation cost should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the period(s) for which the requisite service has already been rendered.  If the performance target becomes probable of being achieved before the end of the requisite service period, the remaining unrecognized compensation cost should be recognized prospectively over the remaining requisite service period.  The total amount of compensation cost recognized during and after the requisite service period should reflect the number of awards that are expected to vest and should be adjusted to reflect those awards that ultimately vest.  The requisite service period ends when the employee can cease rendering service and still be eligible to vest in the award if the performance target is achieved.  As indicated in the definition of vest, the stated vesting period (which includes the period in which the performance target could be achieved) may differ from the requisite service period.  The update is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015 and may be adopted either prospectively or retrospectively.  Earlier adoption is permitted. We are currently evaluating the impact the adoption of the updated guidance will have on the Statements of Unaudited Condensed Consolidated Financial Position, Statements of Unaudited Condensed Consolidated Operations or Statements of Unaudited Condensed Consolidated Cash Flows and do not expect that this guidance will have a material impact on our consolidated financial statements.
	In June 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers.  The new revenue guidance broadly replaces the revenue guidance provided throughout the Codification.  The core principle of the revenue guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.  To achieve that core principle, an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when (or as) the entity satisfies a performance obligation.  The new revenue guidance also requires the capitalization of certain contract acquisition costs.  Reporting entities must provide new disclosures providing qualitative and quantitative information on the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers.  New disclosures also include qualitative and quantitative information on significant judgments, changes in judgments, and contract acquisition assets.  The update is effective for annual periods and interim periods within those annual periods beginning after December 15, 2016 and may be adopted either retrospectively or retrospectively with the cumulative effect.  Earlier adoption is not permitted. We are still evaluating the impact of the updated guidance on the Statements of Unaudited Condensed Consolidated Financial Position, Statements of Unaudited Condensed Consolidated Operations or Statements of Unaudited Condensed Consolidated Cash Flows.

BASIS_OF_PRESENTATION_AND_SIGN2

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Tables)	6 Months Ended
	Jun. 30, 2014
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	82.80%	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 June 30, 2014 and December 31, 2013. Parentheses indicate a net liability.
					(In Millions)
	Investment	Classification	Accounting	Interest	June 30,		December 31, 2013
			Method	Percentage	2014
	Hibbing	Other non-current assets1	Equity Method	23%	$	9.5	$	(3.9	)
	Other	Other non-current assets	Equity Method	Various	34.1		34.7
					$	43.6	$	30.8
	1 At December 31, 2013, the classification for Hibbing was Other liabilities.

SEGMENT_REPORTING_Tables

SEGMENT REPORTING (Tables)	6 Months Ended
	Jun. 30, 2014
Segment Reporting [Abstract]	'
Schedule Of Segment Reporting Information, By Segment	'
	The following table presents a summary of our reportable segments for the three and six months ended June 30, 2014 and 2013, including a reconciliation of segment sales margin to Income (Loss) from Continuing Operations Before Income Taxes and Equity Loss from Ventures:
		(In Millions)
		Three Months Ended										Six Months Ended
		June 30,										June 30,
		2014					2013					2014					2013
	Revenues from product sales and services:
	U.S. Iron Ore	$	514.6		47	%	$	701.7		47	%	$	875.9		43	%	$	1,111.80		42	%
	Eastern Canadian Iron Ore	174			16	%	213.9			14	%	332.3			16	%	459.2			17	%
	Asia Pacific Iron Ore	233.1			21	%	327			22	%	487.3			24	%	597.8			23	%
	North American Coal	179.1			16	%	245.9			17	%	345.3			17	%	460.2			18	%
	Total revenues from product sales and services	$	1,100.80		100	%	$	1,488.50		100	%	$	2,040.80		100	%	$	2,629.00		100	%
	Sales margin:
	U.S. Iron Ore	$	147.2				$	216.3				$	242.2				$	373.6
	Eastern Canadian Iron Ore	(38.5		)			(49.7		)			(88.2		)			(30.3		)
	Asia Pacific Iron Ore	36					95					102.3					156.3
	North American Coal	(52.7		)			6.6					(101.1		)			8.4
	Other	—					—					—					(1.9		)
	Sales margin	92					268.2					155.2					506.1
	Other operating expense	(103.7		)			(6.2		)			(217.6		)			(75.8		)
	Other expense	(42.6		)			(43.5		)			(84.1		)			(91.5		)
	Income (loss) from continuing operations before income taxes and equity loss from ventures	$	(54.3	)			$	218.5				$	(146.5	)			$	338.8
	Depreciation, depletion and amortization:
	U.S. Iron Ore	$	26.6				$	28.4				$	55.3				$	55
	Eastern Canadian Iron Ore	42.4					42.4					83.6					83.5
	Asia Pacific Iron Ore	42.3					41.7					81.4					78.1
	North American Coal	32					28.4					61.9					60.9
	Other	2					3.4					4.2					7.4
	Total depreciation, depletion and amortization	$	145.3				$	144.3				$	286.4				$	284.9
	Capital additions1:
	U.S. Iron Ore	$	14				$	12.2				$	28.9				$	23.9
	Eastern Canadian Iron Ore	23.1					186.8					74.1					353.8
	Asia Pacific Iron Ore	2					2.3					5.2					6.6
	North American Coal	11					15.7					20.2					26.8
	Other	1.9					1.1					2.8					2.7
	Total capital additions	$	52				$	218.1				$	131.2				$	413.8
	1    Includes capital lease additions and non-cash accruals. Refer to NOTE 19 - CASH FLOW INFORMATION.
Summary of Assets by Segment	'
	A summary of assets by segment is as follows:
		(In Millions)
		June 30,			December 31, 2013
		2014
	Assets:
	U.S. Iron Ore	$	1,825.20		$	1,671.60
	Eastern Canadian Iron Ore	7,740.80			7,915.50
	Asia Pacific Iron Ore	1,046.00			1,078.40
	North American Coal	1,750.60			1,841.80
	Other	513.4			455.6
	Total segment assets	12,876.00			12,962.90
	Corporate	226.4			159
	Total assets	$	13,102.40		$	13,121.90

DERIVATIVE_INSTRUMENTS_AND_HED1

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Tables)	6 Months Ended
	Jun. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value	'
	The following table presents the fair value of our derivative instruments and the classification of each in the Statements of Unaudited Condensed Consolidated Financial Position as of June 30, 2014 and December 31, 2013:
		(In Millions)
		Derivative Assets												Derivative Liabilities
		June 30, 2014						December 31, 2013						June 30, 2014					31-Dec-13
	Derivative Instrument	Balance Sheet Location		Fair				Balance		Fair				Balance Sheet		Fair			Balance Sheet	Fair
				Value				Sheet		Value				Location		Value			Location	Value
								Location
	Derivatives designated as hedging instruments under ASC 815:
	Interest Rate Swaps	Other current assets		$	3.6					$	—					$	—		Other current liabilities	$	2.1
	Foreign Exchange Contracts	Other current assets		12.1				Other current assets		0.3				Other current liabilities		0.5			Other current liabilities	25.8
	Total derivatives designated as hedging instruments under ASC 815			$	15.7					$	0.3					$	0.5			$	27.9
	Derivatives not designated as hedging instruments under ASC 815:
	Foreign Exchange Contracts			$	—					$	—					$	—		Other current liabilities	$	1.1
	Customer Supply Agreement	Other current assets		33				Other current assets		55.8						—				—
	Provisional Pricing Arrangements			—				Other current assets		3.1				Other current liabilities		20.2			Other current liabilities	10.3
	Total derivatives not designated as hedging instruments under ASC 815			$	33					$	58.9					$	20.2			$	11.4
	Total derivatives			$	48.7					$	59.2					$	20.7			$	39.3
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 six months ended June 30, 2014 and 2013:
		(In Millions)
	Derivatives in Cash Flow Hedging Relationships	Amount of Gain (Loss)								Location of Gain (Loss)		Amount of Gain (Loss)
		Recognized in OCI on Derivatives								Reclassified		Reclassified
										from Accumulated OCI into Earnings		from Accumulated
												OCI into Earnings
		(Effective Portion)								(Effective Portion)		(Effective Portion)
		Three Months Ended										Three Months Ended
		June 30,										June 30,
		2014				2013						2014				2013
	Australian Dollar Foreign	$	3.7			$	(31.3	)		Product revenues		$	(3.7	)		$	2.6
	Exchange Contracts
	(hedge designation)
	Canadian Dollar Foreign Exchange Contracts (hedge designation)	6				(10.9		)		Cost of goods sold and operating expenses		(2.7		)		(0.4		)
	Canadian Dollar Foreign Exchange Contracts	—				—				Cost of goods sold and operating expenses		(0.2		)		—
	(prior to de-designation)
	Total	$	9.7			$	(42.2	)				$	(6.6	)		$	2.2
		Six Months Ended										Six Months Ended
		June 30,										June 30,
		2014				2013						2014				2013
	Australian Dollar Foreign	$	9.2			$	(28.1	)		Product revenues		$	(12.8	)		$	4.4
	Exchange Contracts
	(hedge designation)
	Canadian Dollar Foreign Exchange Contracts	(1.8		)		(19.1		)		Cost of goods sold and operating expenses		(6.1		)		(0.2		)
	(hedge designation)
	Canadian Dollar Foreign Exchange Contracts	—				—				Cost of goods sold and operating expenses		(0.5		)		—
	(prior to de-designation)
		$	7.4			$	(47.2	)				$	(19.4	)		$	4.2
Schedule Of Derivatives Not Designated As Hedging Instruments Statements Of Financial Performance Location Table	'
	The following summarizes the effect of our derivatives that are not designated as hedging instruments in the Statements of Unaudited Condensed Consolidated Operations for the three and six months ended June 30, 2014 and 2013:
	(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								Six Months Ended
			June 30,								June 30,
			2014				2013				2014				2013
	Foreign Exchange Contracts	Cost of goods sold and operating expenses	$	(2.4	)		$	—			$	(3.3	)		$	—
	Customer Supply Agreement	Product revenues	34.3				35.4				62				59.5
	Provisional Pricing Arrangements	Product revenues	(14.1		)		(28.2		)		(20.2		)		(31.1		)
			$	17.8			$	7.2			$	38.5			$	28.4

INVENTORIES_Tables

INVENTORIES (Tables)	6 Months Ended
	Jun. 30, 2014
Inventory Disclosure [Abstract]	'
Schedule Of Inventories	'
	The following table presents the detail of our Inventories in the Statements of Unaudited Condensed Consolidated Financial Position as of June 30, 2014 and December 31, 2013:
		(In Millions)
		30-Jun-14						31-Dec-13
	Segment	Finished Goods		Work-in Process		Total Inventory		Finished Goods		Work-in		Total
										Process		Inventory
	U.S. Iron Ore	$	361.5	$	24.4	$	385.9	$	92.1	$	13	$	105.1
	Eastern Canadian Iron Ore	34.4		51.9		86.3		65.3		48.1		113.4
	Asia Pacific Iron Ore	39.6		75.9		115.5		39.7		50.6		90.3
	North American Coal	45		16.1		61.1		59.4		23.2		82.6
	Total	$	480.5	$	168.3	$	648.8	$	256.5	$	134.9	$	391.4

PROPERTY_PLANT_AND_EQUIPMENT_T

PROPERTY, PLANT AND EQUIPMENT (Tables)	6 Months Ended
	Jun. 30, 2014
Property, Plant and Equipment [Abstract]	'
Value Of Each Of The Major Classes Of Consolidated Depreciable Assets	'
	The following table indicates the value of each of the major classes of our consolidated depreciable assets as of June 30, 2014 and December 31, 2013:
		(In Millions)
		June 30,			December 31, 2013
		2014
	Land rights and mineral rights	$	7,854.20		$	7,819.60
	Office and information technology	125.8			125.7
	Buildings	307.1			255.2
	Mining equipment	2,199.30			1,819.30
	Processing equipment	1,943.90			2,148.60
	Electric power facilities	114.6			114.3
	Port facilities	105.1			99.4
	Interest capitalized during construction	23.1			23.8
	Land improvements	54.5			69.3
	Other	89.6			104.4
	Construction in-progress	892.8			991.3
		13,710.00			13,570.90
	Accumulated depreciation and depletion	(2,705.2		)	(2,417.5		)
		$	11,004.80		$	11,153.40

GOODWILL_AND_OTHER_INTANGIBLE_1

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Tables)	6 Months Ended
	Jun. 30, 2014
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 six months ended June 30, 2014 and the year ended December 31, 2013:
		(In Millions)
		30-Jun-14																								December 31, 2013
		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			$	—			$	72.5			$	—			$	—			$	74.5			$	2	$	—		$	84.5		$	—		$	80.9		$	167.4
	Arising in business combinations	—				—				—				—				—				—				—		—			—			—			—			—
	Impairment	—				—				—				—				—				—				—		—			—			—			(80.9		)	(80.9		)
	Impact of foreign currency translation	—				—				4.1				—				—				4.1				—		—			(12.0		)	—			—			(12.0		)
	Ending Balance	$	2			$	—			$	76.6			$	—			$	—			$	78.6			$	2	$	—		$	72.5		$	—		$	—		$	74.5
	Accumulated goodwill impairment loss	$	—			$	(1,000.0	)		$	—			$	(27.8	)		$	(80.9	)		$	(1,108.7	)		$	—	$	(1,000.0	)	$	—		$	(27.8	)	$	(80.9	)	$	(1,108.7	)
Schedule Of Finite-Lived Intangible Assets By Major Class	'
	Following is a summary of intangible assets and liabilities as of June 30, 2014 and December 31, 2013:
				(In Millions)
				30-Jun-14												31-Dec-13
		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		$	130.2			$	(41.6	)		$	88.6			$	127.4			$	(35.9	)		$	91.5
	Utility contracts	Intangible assets, net		54.7				(53.9		)		0.8				54.7				(53.1		)		1.6
	Leases	Intangible assets, net		2.4				(0.2		)		2.2				2.4				(0.1		)		2.3
	Total intangible assets			$	187.3			$	(95.7	)		$	91.6			$	184.5			$	(89.1	)		$	95.4
	Below-market sales contracts	Other current liabilities		$	(23.0	)		$	—			$	(23.0	)		$	(23.0	)		$	—			$	(23.0	)
	Below-market sales contracts	Other liabilities		(205.9		)		167.4				(38.5		)		(205.9		)		159.7				(46.2		)
	Total below-market sales contracts			$	(228.9	)		$	167.4			$	(61.5	)		$	(228.9	)		$	159.7			$	(69.2	)
Estimated Amortization Expense Relating To Intangible Assets	'
	The estimated amortization expense relating to intangible assets for the remainder of this year and each of the five succeeding years is as follows:
		(In Millions)
		Amount
	Year Ending December 31,
	2014 (remaining six months)	$	4.6
	2015	7.9
	2016	7
	2017	6.4
	2018	7.4
	2019	7.4
	Total	$	40.7
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,
	2014 (remaining six months)	$	15.4
	2015	23
	2016	23
	2017	0.1
	Total	$	61.5

FAIR_VALUE_OF_FINANCIAL_INSTRU1

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 2014
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 June 30, 2014 and December 31, 2013:
		(In Millions)
		June 30, 2014
	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	$	84			$	—			$	—			$	84
	Derivative assets	—				3.6				33				36.6
	Available-for-sale marketable securities	27.1				—				—				27.1
	Foreign exchange contracts	—				12.1				—				12.1
	Total	$	111.1			$	15.7			$	33			$	159.8
	Liabilities:
	Derivative liabilities	$	—			$	—			$	20.2			$	20.2
	Foreign exchange contracts	—				0.5				—				0.5
	Total	$	—			$	0.5			$	20.2			$	20.7
		(In Millions)
		December 31, 2013
	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	$	85			$	—			$	—			$	85
	Derivative assets	—				—				58.9				58.9
	Available-for-sale marketable securities	21.4				—				—				21.4
	Foreign exchange contracts	—				0.3				—				0.3
	Total	$	106.4			$	0.3			$	58.9			$	165.6
	Liabilities:
	Derivative liabilities	$	—			$	2.1			$	10.3			$	12.4
	Foreign exchange contracts	—				26.9				—				26.9
	Total	$	—			$	29			$	10.3			$	39.3
Fair Value, Recurring and Nonrecurring, Valuation Techniques	'
	The following table illustrates information about quantitative inputs and assumptions for the derivative assets and derivative liabilities categorized in Level 3 of the fair value hierarchy:
	Qualitative/Quantitative Information About Level 3 Fair Value Measurements
			($ in millions)				Balance Sheet Location		Valuation Technique		Unobservable Input		Range or Point Estimate
			Fair Value at June 30, 2014										(Weighted Average)
	Provisional Pricing Arrangements		$	20.2			Derivative liabilities		Market Approach		Management's		$93
											Estimate of 62% Fe
	Customer Supply Agreement		$	33			Derivative assets		Market Approach		Hot-Rolled Steel Estimate		$635 - $665 ($650)
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 six months ended June 30, 2014 and 2013.
		(In Millions)
		Derivative Assets (Level 3)
		Three Months Ended								Six Months Ended
		June 30,								June 30,
		2014				2013				2014				2013
	Beginning balance	$	43.3			$	53.3			$	58.9			$	62.4
	Total gains
	Included in earnings	33				32.4				62				60.4
	Settlements	(43.3		)		(40.6		)		(87.9		)		(77.7		)
	Transfers into Level 3	—				—				—				—
	Transfers out of Level 3	—				—				—				—
	Ending balance - June 30	$	33			$	45.1			$	33			$	45.1
	Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date	$	33			$	32.4			$	62			$	60.4
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	'
		(In Millions)
		Derivative Liabilities (Level 3)
		Three Months Ended								Six Months Ended
		June 30,								June 30,
		2014				2013				2014				2013
	Beginning balance	$	(7.4	)		$	(6.8	)		$	(10.3	)		$	(11.3	)
	Total gains
	Included in earnings	(12.8		)		(25.2		)		(20.2		)		(32.0		)
	Settlements	—				—				10.3				11.3
	Transfers into Level 3	—				—				—				—
	Transfers out of Level 3	—				—				—				—
	Ending balance - June 30	$	(20.2	)		$	(32.0	)		$	(20.2	)		$	(32.0	)
	Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date	$	(12.8	)		$	(25.2	)		$	(20.2	)		$	(32.0	)
Schedule Of Carrying Value And Fair Value Of Financial Instruments	'
	A summary of the carrying amount and fair value of other financial instruments at June 30, 2014 and December 31, 2013 were as follows:
				(In Millions)
				June 30, 2014								December 31, 2013
		Classification		Carrying				Fair Value				Carrying				Fair Value
				Value								Value
	Long-term debt:
	Senior notes—$700 million	Level 2		$	699.5			$	756.6			$	699.4			$	718.2
	Senior notes—$1.3 billion	Level 2		1,289.80				1,537.40				1,289.60				1,404.90
	Senior notes—$400 million	Level 2		398.5				450.2				398.4				432.1
	Senior notes—$500 million	Level 2		496.9				532.4				496.5				523.8
	Revolving loan	Level 2		275				275				—				—
	Equipment loan facilities	Level 2		130				130				140.8				140.8
	Fair value adjustment to interest rate hedge	Level 2		3.3				3.3				(2.1		)		(2.1		)
	Total long-term debt			$	3,293.00			$	3,684.90			$	3,022.60			$	3,217.70
Fair Value Measurements, Nonrecurring	'
	The following table presents information about the impairment charges on both financial and nonfinancial assets that were measured on a fair value basis at December 31, 2013. The table also indicates the fair value hierarchy of the valuation techniques used to determine such fair value. We had no financial assets and liabilities measured at fair value on a non-recurring basis at June 30, 2014.
			(In Millions)
			December 31, 2013
	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:
	Goodwill impairment -		$	—			$	—			$	—			$	—			$	80.9
	Ferroalloys reporting unit
	Other long-lived assets -		—				—				46.3				46.3				155.4
	Property, plant and equipment
	Other long-lived assets -		—				—				1.6				1.6				14.5
	Intangibles and long-term
	deposits
	Investment in ventures		—				—				—				—				67.6
	impairment - Amapá
			$	—			$	—			$	47.9			$	47.9			$	318.4

DEBT_AND_CREDIT_FACILITIES_Tab

DEBT AND CREDIT FACILITIES (Tables)	6 Months Ended
	Jun. 30, 2014
Debt Disclosure [Abstract]	'
Schedule Of Long-Term Debt	'
	The following represents a summary of our long-term debt as of June 30, 2014 and December 31, 2013:
	($ in Millions)
	June 30, 2014
	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	$	699.5		-1
	$1.3 Billion Senior Notes:
	$500 Million 4.80% 2020 Senior Notes		Fixed	4.83%	2020	500		499.3			-2
	$800 Million 6.25% 2040 Senior Notes		Fixed	6.34%	2040	800		790.5			-3
	$400 Million 5.90% 2020 Senior Notes		Fixed	5.98%	2020	400		398.5			-4
	$500 Million 3.95% 2018 Senior Notes		Fixed	4.14%	2018	500		496.9			-5
	$1.75 Billion Credit Facility:
	Revolving Loan		Variable	1.66%	2017	1,750.00		275			-6
	Equipment Loans		Fixed	Various	2020	164.8		151.4
	Short-Term Borrowing Arrangements				2014/2015	139.7		139.7
	Fair Value Adjustment to Interest Rate Hedge							3.3
	Total debt					$	4,954.50	$	3,454.10
	Less: Short-term and current portion of long-term debt							161.1
	Long-term debt							$	3,293.00
	($ in Millions)
	31-Dec-13
	Debt Instrument		Type	Annual Effective Interest Rate	Final Maturity	Total Face Amount		Total Debt
	$700 Million 4.875% 2021 Senior Notes		Fixed	4.88%	2021	700		699.4			-1
	$1.3 Billion Senior Notes:
	$500 Million 4.80% 2020 Senior Notes		Fixed	4.83%	2020	500		499.2			-2
	$800 Million 6.25% 2040 Senior Notes		Fixed	6.34%	2040	800		790.4			-3
	$400 Million 5.90% 2020 Senior Notes		Fixed	5.98%	2020	400		398.4			-4
	$500 Million 3.95% 2018 Senior Notes		Fixed	4.14%	2018	500		496.5			-5
	$1.75 Billion Credit Facility:
	Revolving Loan		Variable	1.64%	2017	1,750.00		—			-6
	Equipment Loans		Fixed	Various	2020	164.8		161.7
	Fair Value Adjustment to Interest Rate Hedge							(2.1		)
	Total debt					$	4,814.80	$	3,043.50
	Less: Short-term and current portion of long-term debt							20.9
	Long-term debt							$	3,022.60
	-1	As of June 30, 2014 and December 31, 2013, the $700 million 4.875 percent senior notes were recorded at a par value of $700 million less unamortized discounts of $0.5 million and $0.6 million, respectively, based on an imputed interest rate of 4.89 percent.
	-2	As of June 30, 2014 and December 31, 2013, the $500 million 4.80 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $0.7 million and $0.8 million, respectively, based on an imputed interest rate of 4.83 percent.
	-3	As of June 30, 2014 and December 31, 2013, the $800 million 6.25 percent senior notes were recorded at a par value of $800 million less unamortized discounts of $9.5 million and $9.6 million, respectively, based on an imputed interest rate of 6.34 percent.
	-4	As of June 30, 2014 and December 31, 2013, the $400 million 5.90 percent senior notes were recorded at a par value of $400 million less unamortized discounts of $1.5 million and $1.6 million, respectively, based on an imputed interest rate of 5.98 percent.
	-5	As of June 30, 2014 and December 31, 2013, the $500 million 3.95 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $3.1 million and $3.5 million, respectively, based on an imputed interest rate of 4.14 percent.
	-6	As of June 30, 2014, $275.0 million of revolving loans were drawn under the credit facility. As of December 31, 2013, no revolving loans were drawn under the credit facility. As of June 30, 2014 and December 31, 2013, the principal amount of letter of credit obligations totaled $5.2 million and $8.4 million, respectively, thereby reducing available borrowing capacity to $1.5 billion and $1.7 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 revolving credit agreement, based on the principal amounts outstanding at June 30, 2014:
		(In Millions)
		Maturities of Debt
	2014 (July 1 - December 31)	$	150.4
	2015	21.8
	2016	22.7
	2017	23.6
	2018	524.6
	2019 and thereafter	2,448.00
	Total maturities of debt	$	3,191.10

LEASE_OBLIGATIONS_Tables

LEASE OBLIGATIONS (Tables)	6 Months Ended
	Jun. 30, 2014
Leases [Abstract]	'
Schedule Of Future Minimum Lease Payments For Capital Leases And Operating Leases	'
	Future minimum payments under capital leases and non-cancellable operating leases at June 30, 2014 are as follows:
		(In Millions)
		Capital Leases			Operating Leases
	2014 (July 1 - December 31)	$	33.5		$	9.5
	2015	89			14.2
	2016	38			9.2
	2017	30.5			8.3
	2018	22.4			7.1
	2019 and thereafter	37.8			14.7
	Total minimum lease payments	$	251.2		$	63
	Amounts representing interest	43.4
	Present value of net minimum lease payments	$	207.8	(1)
	(1)	The total is comprised of $82.0 million and $125.7 million classified as Other current liabilities and Other liabilities, respectively, in the Statements of Unaudited Condensed Consolidated Financial Position at June 30, 2014.

ENVIRONMENTAL_AND_MINE_CLOSURE1

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Tables)	6 Months Ended
	Jun. 30, 2014
Environmental Remediation Obligations [Abstract]	'
Summary Of Mine Closure Obligations	'
	The following is a summary of the obligations as of June 30, 2014 and December 31, 2013:
		(In Millions)
		June 30,			December 31, 2013
		2014
	Environmental	$	11		$	8.4
	Mine closure
	LTVSMC	22.4			22
	Operating mines:
	U.S. Iron Ore	137.5			152.2
	Eastern Canadian Iron Ore	76.3			78.2
	Asia Pacific Iron Ore	27.4			25.5
	North American Coal	35.7			34.7
	Total mine closure	299.3			312.6
	Total environmental and mine closure obligations	310.3			321
	Less current portion	5.6			11.3
	Long term environmental and mine closure obligations	$	304.7		$	309.7
Asset Retirement Obligation Disclosure	'
	The following represents a rollforward of our asset retirement obligation liability related to our active mining locations for the six months ended June 30, 2014 and for the year ended December 31, 2013:
		(In Millions)
		June 30,			December 31,
		2014			2013 (1)
	Asset retirement obligation at beginning of period	$	290.6		$	231.1
	Accretion expense	7.2			18.1
	Exchange rate changes	1.2			(3.4		)
	Revision in estimated cash flows	(22.1		)	44.8
	Asset retirement obligation at end of period	$	276.9		$	290.6
	(1)	Represents a 12-month rollforward of our asset retirement obligation at December 31, 2013.

PENSIONS_AND_OTHER_POSTRETIREM1

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Tables)	6 Months Ended
	Jun. 30, 2014
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 six months ended June 30, 2014 and 2013:
	Defined Benefit Pension Expense
		(In Millions)
		Three Months Ended						Six Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
	Service cost	$	7.9		$	9.7		$	15.9		$	19.6
	Interest cost	12.5			11.7			25			23.2
	Expected return on plan assets	(18.0		)	(20.0		)	(36.0		)	(33.1		)
	Amortization:
	Prior service costs	6.5			0.8			7.2			1.5
	Net actuarial (gain) loss	(2.3		)	8.2			1.3			15
	Curtailments/settlements	$	0.9		$	—		1.2			—
	Net periodic benefit cost	$	7.5		$	10.4		$	14.6		$	26.2
	Other Postretirement Benefits Expense
		(In Millions)
		Three Months Ended						Six Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
	Service cost	$	2		$	3.1		$	4		$	6.2
	Interest cost	4.1			4.4			8.1			8.7
	Expected return on plan assets	(4.3		)	(5.0		)	(8.6		)	(10.0		)
	Amortization:
	Prior service costs	(0.9		)	(0.9		)	(1.8		)	(1.8		)
	Net actuarial loss	1.1			3			2.3			5.8
	Net periodic benefit cost	$	2		$	4.6		$	4		$	8.9

STOCK_COMPENSATION_PLANS_Table

STOCK COMPENSATION PLANS (Tables)	6 Months Ended
	Jun. 30, 2014
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 and second quarters of 2014 performance share grants:
	Grant Date	Grant Date Market Price		Average Expected Term (Years)	Expected Volatility	Risk-Free Interest Rate	Dividend Yield	Fair Value		Fair Value (Percent of Grant Date Market Price)
	February 10, 2014	$	20.58	2.89	54.00%	0.54%	2.92%	$	22.21	107.92%
	May 12, 2014	$	17.54	2.61	54.00%	0.54%	2.92%	$	18.93	107.92%

SHAREHOLDERS_EQUITY_Shareholde

SHAREHOLDERS' EQUITY Shareholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2014
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 82.8 percent, 85 percent and 79 percent, respectively, for the six months ended June 30, 2014 and June 30, 2013:
		(In Millions)
		Cliffs				Noncontrolling				Total Equity
		Shareholders’				Interest
		Equity
	31-Dec-13	$	6,069.50			$	814.8			$	6,884.30
	Comprehensive income
	Net loss	(59.4		)		3.2				(56.2		)
	Other comprehensive income	92.7				1.1				93.8
	Total comprehensive income	33.3				4.3				37.6
	Stock and other incentive plans	(3.1		)		—				(3.1		)
	Common and preferred share dividends	(72.1		)		—				(72.1		)
	Undistributed losses to noncontrolling interest	—				(17.1		)		(17.1		)
	30-Jun-14	$	6,027.60			$	802			$	6,829.60
		(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	253				9.1				262.1
	Other comprehensive income	(184.0		)		2.3				(181.7		)
	Total comprehensive income	69				11.4				80.4
	Issuance of common shares	263.4				—				263.4
	Issuance of preferred shares	731.3				—				731.3
	Stock and other incentive plans	3.7				—				3.7
	Common and preferred share dividends	(68.9		)		—				(68.9		)
	Capital contribution by noncontrolling interest	—				13				13
	to subsidiary
	30-Jun-13	$	5,631.20			$	1,152.60			$	6,783.80
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 June 30, 2014 and June 30, 2013:
		(In Millions)
		Changes in Pension and Other Post-Retirement Benefits, net of tax				Unrealized Net Gain (Loss) on Securities, net of tax				Unrealized Net Gain (Loss) on Foreign Currency Translation				Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax				Accumulated Other Comprehensive Income (Loss)
	Balance December 31, 2013	$	(204.9	)		$	6.2			$	106.7			$	(20.9	)		$	(112.9	)
	Other comprehensive income (loss) before reclassifications	(0.4		)		3.8				40.5				(2.3		)		41.6
	Net loss (gain) reclassified from accumulated other comprehensive income (loss)	3.3				0.1				—				12.8				16.2
	Balance March 31, 2014	$	(202.0	)		$	10.1			$	147.2			$	(10.4	)		$	(55.1	)
	Other comprehensive income (loss) before reclassifications	(1.4		)		(2.4		)		19.7				9.7				25.6
	Net loss (gain) reclassified from accumulated other comprehensive income (loss)	4				(1.3		)		—				6.6				9.3
	Balance June 30, 2014	$	(199.4	)		$	6.4			$	166.9			$	5.9			$	(20.2	)
		(In Millions)
		Changes in Pension and Other Post-Retirement Benefits, net of tax				Unrealized Net Gain (Loss) on Securities, net of tax				Unrealized Net Gain (Loss) on Foreign Currency Translation				Net Unrealized Gain (Loss) on Derivative Financial Instruments, net of tax				Accumulated Other Comprehensive Income (Loss)
	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 income (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	)
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 six months ended June 30, 2014:
			(In Millions)
	Details about Accumulated Other Comprehensive Income (Loss) Components		Amount of (Gain)/Loss Reclassified into Income																Affected Line Item in the Statement of Unaudited Condensed Consolidated Operations
			Three Months Ended								Six Months Ended
			June 30,								June 30,
			2014				2013				2014				2013
	Amortization of Pension and Postretirement Benefit Liability:
	Prior-service costs		$	5.6			$	(0.1	)		$	5.4			$	(0.3	)		-1
	Net actuarial loss		(1.2		)		11.2				3.6				20.8				-1
	Settlements/curtailments		0.9				—				1.2				—				-1
			5.3				11.1				10.2				20.5				Total before taxes
			(1.3		)		(3.0		)		(2.9		)		(6.0		)		Income tax benefit (expense)
			$	4			$	8.1			$	7.3			$	14.5			Net of taxes
	Unrealized gain (loss) on marketable securities:
	Sale of marketable securities		$	(1.9	)		$	(1.1	)		$	(1.7	)		$	(1.1	)		Other non-operating income
	Impairment		—				5.2				—				5.3				Other non-operating income
			(1.9		)		4.1				(1.7		)		4.2				Total before taxes
			0.6				(0.5		)		0.5				(0.5		)		Income tax benefit (expense)
			$	(1.3	)		$	3.6			$	(1.2	)		$	3.7			Net of taxes
	Unrealized gain (loss) on derivative financial instruments:
	Australian dollar foreign exchange contracts		$	5.3			$	(3.7	)		$	18.3			$	(6.3	)		Product revenues
	Canadian dollar foreign exchange contracts		4.4				0.6				9.9				0.3				Cost of goods sold and operating expenses
			9.7				(3.1		)		28.2				(6.0		)		Total before taxes
			(3.1		)		0.9				(8.8		)		1.8				Income tax benefit (expense)
			$	6.6			$	(2.2	)		$	19.4			$	(4.2	)		Net of taxes
	Total Reclassifications for the Period		$	9.3			$	9.5			$	25.5			$	14
	-1	These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. See NOTE 11 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.

RELATED_PARTIES_Tables

RELATED PARTIES (Tables)	6 Months Ended
	Jun. 30, 2014
Related Party Transactions [Abstract]	'
Summary Of Other Ownership Interests	'
	The following is a summary of the mine ownership of these iron ore mines at June 30, 2014:
	Mine		Cliffs Natural Resources		ArcelorMittal			U.S. Steel Corporation			WISCO
	Empire		79	%	21	%		—			—
	Tilden		85	%	—			15	%		—
	Hibbing		23	%	62.3	%		14.7	%		—
	Bloom Lake		82.8	%	—			—			17.2	%
Summary Of Related Party Transactions Table Disclosure	'
	Product revenues from related parties were as follows:
		(In Millions)
		Three Months Ended							Six Months Ended
		June 30,							June 30,
		2014			2013				2014				2013
	Product revenues from related parties	$	322.1		$	455			$	539			$	756.2
	Total product revenues	1,018.60			1,391.60				1,879.50				2,474.20
	Related party product revenue as a percent of total product revenue	31.6		%	32.7		%		28.7		%		30.6		%

EARNINGS_PER_SHARE_Tables

EARNINGS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share Computation	'
	The following table summarizes the computation of basic and diluted earnings (loss) per share:
		(In Millions, Except Per Share Amounts)
		Three Months Ended						Six Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
	NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$	10.9		$	146		$	(59.4	)	$	253
	PREFERRED STOCK DIVIDENDS	(12.8		)	(12.9		)	(25.6		)	(22.8		)
	NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS	$	(1.9	)	$	133.1		$	(85.0	)	$	230.2
	Weighted Average Number of Shares:
	Basic	153.1			153			153.1			150.4
	Depositary Shares	—			25.2			—			19.1
	Employee Stock Plans	—			0.2			—			0.2
	Diluted	153.1			178.4			153.1			169.7
	Earnings (Loss) per Common Share Attributable to	$	(0.01	)	$	0.87		$	(0.56	)	$	1.53
	Cliffs Common Shareholders - Basic:
	Earnings (Loss) per Common Share Attributable to	$	(0.01	)	$	0.82		$	(0.56	)	$	1.49
	Cliffs Common Shareholders - Diluted:

CASH_FLOW_INFORMATION_Tables

CASH FLOW INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2014
Supplemental Cash Flow Information [Abstract]	'
Supplemental Cash Flow Disclosures	'
	A reconciliation of capital additions to cash paid for capital expenditures for the six months ended June 30, 2014 and 2013 is as follows:
		(In Millions)
		Six Months Ended
		June 30,
		2014			2013
	Capital additions	$	131.2		$	413.8
	Cash paid for capital expenditures	164.3			501.2
	Difference	$	(33.1	)	$	(87.4	)
	Non-cash accruals	$	(43.0	)	$	(87.4	)
	Capital leases	9.9			—
	Total	$	(33.1	)	$	(87.4	)

BASIS_OF_PRESENTATION_AND_SIGN3

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Related Party Transaction [Line Items]	'	'	'	'
Current Fiscal Year End Date	'	'	'--12-31	'
Black Label And Black Thor Chromite Deposits [Member]	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Ownership Interest	100.00%	'	100.00%	'
Big Daddy Chromite Deposit [Member]	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Ownership Interest	70.00%	'	70.00%	'
Transaction Gains and Losses Resulting from Remeasurement [Member]	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Foreign Currency Transaction Gain (Loss), before Tax	($11.40)	$47	($18.10)	$50.50
Short-term intercompany loan [Member]	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Foreign Currency Transaction Gain (Loss), before Tax	-4.2	28.7	-13	28.2
Cash and Cash Equivalents [Member]	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Foreign Currency Transaction Gain (Loss), before Tax	($2)	$12.20	($5.10)	$11.90

BASIS_OF_PRESENTATION_AND_SIGN4

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)	6 Months Ended
	Jun. 30, 2014
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	82.80%
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 $)	Jun. 30, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Schedule of Equity Method Investments [Line Items]	'		'
Investment	$43.60		$30.80
Other Noncurrent Liabilities [Member] | Hibbing [Member]	'		'
Schedule of Equity Method Investments [Line Items]	'		'
Investment	'		-3.9	[1]
Other Noncurrent Assets [Member] | Hibbing [Member]	'		'
Schedule of Equity Method Investments [Line Items]	'		'
Ownership interest, equity method investment	23.00%	[1]	'
Investment	9.5	[1]	'
Other Noncurrent Assets [Member] | Other Equity Investees [Member]	'		'
Schedule of Equity Method Investments [Line Items]	'		'
Investment	$34.10		$34.70
[1]	At December 31, 2013, the classification for Hibbing was Other liabilities.

SEGMENT_REPORTING_Narrative_De

SEGMENT REPORTING (Narrative) (Details)	6 Months Ended
	Jun. 30, 2014
	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

SEGMENT_REPORTING_Schedule_Of_

SEGMENT REPORTING (Schedule Of Segment Reporting Information, By Segment) (Details) (USD $)	3 Months Ended				6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
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	$1,100.80		$1,488.50		$2,040.80		$2,629
Sales Margin	92		268.2		155.2		506.1
Other operating expense	-103.7		-6.2		-217.6		-75.8
Other expense	-42.6		-43.5		-84.1		-91.5
Income from Continuing Operations before income taxes and equity (loss) from ventures	-54.3		218.5		-146.5		338.8
Depreciation, depletion and amortization	145.3		144.3		286.4		284.9
Capital Additions	52	[1]	218.1	[1]	131.2	[1]	413.8	[1]
U.S. Iron Ore [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues from producet sales and services, percent	47.00%		47.00%		43.00%		42.00%
Revenues from product sales and services	514.6		701.7		875.9		1,111.80
Sales Margin	147.2		216.3		242.2		373.6
Depreciation, depletion and amortization	26.6		28.4		55.3		55
Capital Additions	14	[1]	12.2	[1]	28.9	[1]	23.9	[1]
Eastern Canadian Iron Ore [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues from producet sales and services, percent	16.00%		14.00%		16.00%		17.00%
Revenues from product sales and services	174		213.9		332.3		459.2
Sales Margin	-38.5		-49.7		-88.2		-30.3
Depreciation, depletion and amortization	42.4		42.4		83.6		83.5
Capital Additions	23.1	[1]	186.8	[1]	74.1	[1]	353.8	[1]
Asia Pacific Iron Ore [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues from producet sales and services, percent	21.00%		22.00%		24.00%		23.00%
Revenues from product sales and services	233.1		327		487.3		597.8
Sales Margin	36		95		102.3		156.3
Depreciation, depletion and amortization	42.3		41.7		81.4		78.1
Capital Additions	2	[1]	2.3	[1]	5.2	[1]	6.6	[1]
North American Coal [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues from producet sales and services, percent	16.00%		17.00%		17.00%		18.00%
Revenues from product sales and services	179.1		245.9		345.3		460.2
Sales Margin	-52.7		6.6		-101.1		8.4
Depreciation, depletion and amortization	32		28.4		61.9		60.9
Capital Additions	11	[1]	15.7	[1]	20.2	[1]	26.8	[1]
All Other Segments [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Sales Margin	0		0		0		-1.9
Depreciation, depletion and amortization	2		3.4		4.2		7.4
Capital Additions	$1.90	[1]	$1.10	[1]	$2.80	[1]	$2.70	[1]
[1]	Includes capital lease additions and non-cash accruals. Refer to NOTE 19 - CASH FLOW INFORMATION.

SEGMENT_REPORTING_Segment_Repo

SEGMENT REPORTING Segment Reporting (Summary of Assets by Segment) (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Segment Reporting Information [Line Items]	'	'
Assets	$13,102.40	$13,121.90
U.S. Iron Ore [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	1,825.20	1,671.60
Eastern Canadian Iron Ore [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	7,740.80	7,915.50
Asia Pacific Iron Ore [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	1,046	1,078.40
North American Coal [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	1,750.60	1,841.80
All Other Segments [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	513.4	455.6
Total Segment Assets [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	12,876	12,962.90
Corporate [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Assets	$226.40	$159

DERIVATIVE_INSTRUMENTS_AND_HED2

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

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

In Millions, unless otherwise specified

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2014

Dec. 31, 2013

Dec. 31, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Canadian Dollar Foreign Exchange Contracts Hedge Prior to De Designation [Member]

Canadian Dollar Foreign Exchange Contracts Hedge Prior to De Designation [Member]

Canadian Dollar Foreign Exchange Contracts Hedge Prior to De Designation [Member]

Canadian Dollar Foreign Exchange Contracts Hedge Prior to De Designation [Member]

Australian Dollar Foreign Exchange Contract Hedge Designation [Member]

Australian Dollar Foreign Exchange Contract Hedge Designation [Member]

Australian Dollar Foreign Exchange Contract Hedge Designation [Member]

Australian Dollar Foreign Exchange Contract Hedge Designation [Member]

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]

Canadian Dollar Foreign Exchange Contracts 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]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Canadian Dollar Foreign Exchange Contracts Hedge De Designated [Member] [Member]

Canadian Dollar Foreign Exchange Contracts Hedge De Designated [Member] [Member]

Canadian Dollar Foreign Exchange Contracts Hedge De Designated [Member] [Member]

Foreign Exchange Contract [Member]

Foreign Exchange Contract [Member]

Foreign Exchange Contract [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]

Provisional Pricing Arrangements [Member]

Provisional Pricing Arrangements [Member]

Provisional Pricing Arrangements [Member]

Provisional Pricing Arrangements [Member]

Product Revenues [Member]

Product Revenues [Member]

Product Revenues [Member]

Product Revenues [Member]

Designated as Hedging Instrument [Member]

Designated as Hedging Instrument [Member]

Designated as Hedging Instrument [Member]

Cost of Sales [Member]

Cost of Sales [Member]

Cost of Sales [Member]

Cost of Sales [Member]

Designated as Hedging Instrument [Member]

Designated as Hedging Instrument [Member]

Designated as Hedging Instrument [Member]

Other Nonoperating Income Expense [Member]

Other Nonoperating Income Expense [Member]

Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Cost of Sales [Member]

Cost of Sales [Member]

Cost of Sales [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]

Product Revenues [Member]

Product Revenues [Member]

Product Revenues [Member]

Product Revenues [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]

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 And Asia Pacific Iron Ore [Member]

U S Iron Ore And Asia Pacific Iron Ore [Member]

U S Iron Ore And Asia Pacific Iron Ore [Member]

Product Revenues [Member]

Product Revenues [Member]

Derivative Financial Instruments, Assets [Member]

Derivative Financial Instruments, Assets [Member]

Derivative Financial Instruments, Liabilities [Member]

Product Revenues [Member]

Product Revenues [Member]

Derivative Financial Instruments, Liabilities [Member]

Derivative [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative, Notional Amount

'

'

'

'

'

'

'

'

'

'

'

'

$300

$323

'

'

'

'

'

$259.10

$285.90

'

'

'

$250

$0

$74.80

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gain (Loss) on Fair Value Hedge Ineffectiveness, Net

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.1

0.3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net

17.8

7.2

38.5

28.4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-2.4

-3.3

0

'

'

'

'

'

'

-14.1

-28.2

-20.2

-31.1

'

'

'

'

'

'

'

'

Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net

-6.6

2.2

-19.4

4.2

-0.2

0

-0.5

0

-3.7

2.6

-12.8

4.4

'

'

'

-2.7

-0.4

-6.1

-0.2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6.8

'

'

'

'

'

'

1.4

'

'

'

'

'

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

34.3

35.4

62

59.5

'

'

'

'

'

'

-28.2

-31.1

'

'

'

-14.1

-20.2

'

Derivative assets

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

33

55.8

'

'

'

'

'

'

0

3.1

'

'

'

'

Derivative liabilities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$10.30

'

'

$20.20

DERIVATIVE_INSTRUMENTS_AND_HED3

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value) (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Derivatives, Fair Value [Line Items]	'	'
Derivative asset, fair value	$48.70	$59.20
Derivative liability, fair value	20.7	39.3
Designated as Hedging Instrument [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative asset, fair value	15.7	0.3
Derivative liability, fair value	0.5	27.9
Not Designated as Hedging Instrument [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative asset, fair value	33	58.9
Derivative liability, fair value	20.2	11.4
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	3.6	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	2.1
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	12.1	0.3
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	0.5	25.8
Fair Value, Inputs, Level 2 [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Derivative Financial Instruments, Assets [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative asset, fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Derivative Financial Instruments, Liabilities [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative liability, fair value	0	1.1
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	33	55.8
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	0	3.1
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	$20.20	$10.30

DERIVATIVE_INSTRUMENTS_AND_HED4

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Statements Of Financial Performance Location Table) (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	$9.70	($42.20)	$7.40	($47.20)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	-6.6	2.2	-19.4	4.2
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]	'	'	'	'
Derivative [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	3.7	-31.3	9.2	-28.1
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	-3.7	2.6	-12.8	4.4
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]	'	'	'	'
Derivative [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	6	-10.9	-1.8	-19.1
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	-2.7	-0.4	-6.1	-0.2
Canadian Dollar Foreign Exchange Contracts Hedge Prior to De Designation [Member]	'	'	'	'
Derivative [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	0	0	0	0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	($0.20)	$0	($0.50)	$0

DERIVATIVE_INSTRUMENTS_AND_HED5

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Schedule Of Derivatives Not Designated As Hedging Instruments) (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$17.80	$7.20	$38.50	$28.40
Foreign Exchange Contract [Member] | Cost of Sales [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	-2.4	'	-3.3	0
Foreign Exchange Contract [Member] | Other Income [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	'	0	'	'
Customer Supply Agreements [Member] | Product Revenues [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	34.3	35.4	62	59.5
Provisional Pricing Arrangements [Member] | Product Revenues [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	($14.10)	($28.20)	($20.20)	($31.10)

INVENTORIES_Narrative_Details

INVENTORIES (Narrative) (Details) (Cost of Sales [Member], USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Eastern Canadian Iron Ore [Member]	'	'	'	'
Inventory [Line Items]	'	'	'	'
Inventory Write-down	$2.60	'	$16	'
North American Coal [Member]	'	'	'	'
Inventory [Line Items]	'	'	'	'
Inventory Write-down	15	0.7	37.1	2.7
Pellets [Member] | Wabush [Member]	'	'	'	'
Inventory [Line Items]	'	'	'	'
Inventory Write-down	'	'	'	11.1
Unsaleable Inventory Impairment Charge	'	'	'	10.6
Sinter feed [Member] | Eastern Canadian Iron Ore [Member]	'	'	'	'
Inventory [Line Items]	'	'	'	'
Inventory Write-down	'	'	'	$4.70

INVENTORIES_Schedule_Of_Invent

INVENTORIES (Schedule Of Inventories) (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Inventory, Net [Abstract]	'	'
Finished Goods	$480.50	$256.50
Work-in Process	168.3	134.9
Total Inventory	648.8	391.4
U.S. Iron Ore [Member]	'	'
Inventory, Net [Abstract]	'	'
Finished Goods	361.5	92.1
Work-in Process	24.4	13
Total Inventory	385.9	105.1
Eastern Canadian Iron Ore [Member]	'	'
Inventory, Net [Abstract]	'	'
Finished Goods	34.4	65.3
Work-in Process	51.9	48.1
Total Inventory	86.3	113.4
Asia Pacific Iron Ore [Member]	'	'
Inventory, Net [Abstract]	'	'
Finished Goods	39.6	39.7
Work-in Process	75.9	50.6
Total Inventory	115.5	90.3
North American Coal [Member]	'	'
Inventory, Net [Abstract]	'	'
Finished Goods	45	59.4
Work-in Process	16.1	23.2
Total Inventory	$61.10	$82.60

PROPERTY_PLANT_AND_EQUIPMENT_N

PROPERTY, PLANT AND EQUIPMENT (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended			12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Dec. 31, 2013
					Construction in Progress [Member]	Construction in Progress [Member]
Property, Plant and Equipment [Line Items]	'	'	'	'	'	'
Depreciation And Depletion	$142.50	$138.90	$280.90	$274.90	'	'
Accumulated amount of capitalized interest included within construction in progress	'	'	'	'	31.2	31.4
Interest costs capitalized during the period	'	'	'	'	$1	$17.40

PROPERTY_PLANT_AND_EQUIPMENT_V

PROPERTY, PLANT AND EQUIPMENT (Value Of Each Of The Major Classes Of Consolidated Depreciable Assets) (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	$13,710	$13,570.90
Allowance for depreciation and depletion	-2,705.20	-2,417.50
Property, plant and equipment, net	11,004.80	11,153.40
Land Rights And Mineral Rights [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	7,854.20	7,819.60
Office And Information Technology [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	125.8	125.7
Buildings [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	307.1	255.2
Mining Equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	2,199.30	1,819.30
Processing Equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	1,943.90	2,148.60
Electric Power Facilities [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	114.6	114.3
Port Facilities [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	105.1	99.4
Interest Capitalized During Construction [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	23.1	23.8
Land Improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	54.5	69.3
Other [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	89.6	104.4
Construction in Progress [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	$892.80	$991.30

GOODWILL_AND_OTHER_INTANGIBLE_2

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Goodwill [Line Items]	'	'	'	'
Below Market Sales Contract, Remaining Life	'	'	'3 years	'
Product	$1,018.60	$1,391.60	$1,879.50	$2,474.20
Cost of Sales [Member]	'	'	'	'
Goodwill [Line Items]	'	'	'	'
Amortization expense relating to intangible assets	2.8	5.3	5.5	10
Product Revenues [Member] | Sales Revenue, Goods, Net [Member]	'	'	'	'
Goodwill [Line Items]	'	'	'	'
Product	'	'	$7.60	$14.70

GOODWILL_AND_OTHER_INTANGIBLE_3

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Schedule Of Goodwill) (Details) (USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Goodwill [Roll Forward]	'	'
Beginning Balance	$74.50	$167.40
Arising in business combinations	0	0
Impairment	0	-80.9
Impact of foreign currency translation	4.1	-12
Ending Balance	78.6	74.5
Accumulated goodwill impairment loss	-1,108.70	-1,108.70
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	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	-1,000	-1,000
Asia Pacific Iron Ore [Member]	'	'
Goodwill [Roll Forward]	'	'
Beginning Balance	72.5	84.5
Arising in business combinations	0	0
Impairment	0	0
Impact of foreign currency translation	4.1	-12
Ending Balance	76.6	72.5
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	0	80.9
Arising in business combinations	0	0
Impairment	0	-80.9
Impact of foreign currency translation	0	0
Ending Balance	0	0
Accumulated goodwill impairment loss	($80.90)	($80.90)

GOODWILL_AND_OTHER_INTANGIBLE_4

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Schedule Of Finite-Lived Intangible Assets By Major Class) (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]	'	'
Definite lived intangible assets - Gross Carrying Amount	$187.30	$184.50
Definite lived intangible assets - Accumulated Amortization	-95.7	-89.1
Definite lived intangible assets - Net Carrying Amount	91.6	95.4
Permits [Member] | Intangible Assets, Net [Member]	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Definite lived intangible assets - Gross Carrying Amount	130.2	127.4
Definite lived intangible assets - Accumulated Amortization	-41.6	-35.9
Definite lived intangible assets - Net Carrying Amount	88.6	91.5
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	-53.9	-53.1
Definite lived intangible assets - Net Carrying Amount	0.8	1.6
Leases [Member] | Intangible Assets, Net [Member]	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Definite lived intangible assets - Gross Carrying Amount	2.4	2.4
Definite lived intangible assets - Accumulated Amortization	-0.2	-0.1
Definite lived intangible assets - Net Carrying Amount	2.2	2.3
Below Market Sales Contracts [Member]	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Definite lived intangible assets - Gross Carrying Amount	-228.9	-228.9
Definite lived intangible assets - Accumulated Amortization	167.4	159.7
Definite lived intangible assets - Net Carrying Amount	-61.5	-69.2
Below Market Sales Contracts [Member] | Other Current Liabilities [Member]	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Definite lived intangible assets - Gross Carrying Amount	-23	-23
Definite lived intangible assets - Accumulated Amortization	'	'
Definite lived intangible assets - Net Carrying Amount	-23	-23
Below Market Sales Contracts [Member] | Other Liabilities [Member]	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Definite lived intangible assets - Gross Carrying Amount	-205.9	-205.9
Definite lived intangible assets - Accumulated Amortization	167.4	159.7
Definite lived intangible assets - Net Carrying Amount	($38.50)	($46.20)

GOODWILL_AND_OTHER_INTANGIBLE_5

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Estimated Amortization Expense Relating To Intangible Assets) (Details) (USD $)	Jun. 30, 2014
In Millions, unless otherwise specified
Estimated amortization expense, intangible assets [Abstract]	'
2014 (remaining six months)	$4.60
2015	7.9
2016	7
2017	6.4
2018	7.4
2019	7.4
Total	$40.70

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 $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014
Estimated recognition of product revenues, below-market sales contracts [Abstract]	'
2014 (remaining six months)	$15.40
2015	23
2016	23
2017	0.1
Total	$61.50

FAIR_VALUE_OF_FINANCIAL_INSTRU2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Narrative) (Details) (USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Assets And Liabilities Components [Line Items]	'	'
Management Estimate of 62% Fe	62.00%	'
Goodwill, Impairment Loss	$0	$80.90
Amapa [Member]	'	'
Fair Value, Assets And Liabilities Components [Line Items]	'	'
Equity Method Investments, Fair Value Disclosure	'	0
Equity Method Investment, Other than Temporary Impairment	'	67.6
Wabush and Cliffs Chromite Ontario and Cliffs Chromite Far North [Member]	'	'
Fair Value, Assets And Liabilities Components [Line Items]	'	'
Impairment of Long-Lived Assets Held-for-use	'	155.4
Cliffs Chromite Ontario and Cliffs Chromite Far North [Member]	'	'
Fair Value, Assets And Liabilities Components [Line Items]	'	'
Goodwill, Impairment Loss	'	$80.90

FAIR_VALUE_OF_FINANCIAL_INSTRU3

FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value Of Assets And Liabilities) (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Assets:	'	'
Cash equivalents	$84	$85
Derivative assets	36.6	58.9
Marketable Securities	27.1	21.4
Foreign exchange contracts	12.1	0.3
Total	159.8	165.6
Liabilities:	'	'
Derivative liabilities	20.2	12.4
Foreign exchange contracts	0.5	26.9
Total	20.7	39.3
Fair Value, Inputs, Level 1 [Member]	'	'
Assets:	'	'
Cash equivalents	84	85
Derivative assets	'	'
Marketable Securities	27.1	21.4
Foreign exchange contracts	'	'
Total	111.1	106.4
Liabilities:	'	'
Derivative liabilities	'	'
Foreign exchange contracts	'	'
Total	'	'
Fair Value, Inputs, Level 2 [Member]	'	'
Assets:	'	'
Cash equivalents	'	'
Derivative assets	3.6	'
Marketable Securities	'	'
Foreign exchange contracts	12.1	0.3
Total	15.7	0.3
Liabilities:	'	'
Derivative liabilities	'	2.1
Foreign exchange contracts	0.5	26.9
Total	0.5	29
Fair Value, Inputs, Level 3 [Member]	'	'
Assets:	'	'
Cash equivalents	'	'
Derivative assets	33	58.9
Marketable Securities	'	'
Foreign exchange contracts	'	'
Total	33	58.9
Liabilities:	'	'
Derivative liabilities	20.2	10.3
Foreign exchange contracts	'	'
Total	$20.20	$10.30

FAIR_VALUE_OF_FINANCIAL_INSTRU4

FAIR VALUE OF FINANCIAL INSTRUMENTS (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Details) (USD $)	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Derivative asset, fair value	$48,700,000	$59,200,000
Derivative liability, fair value	20,700,000	39,300,000
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	33,000,000	58,900,000
Derivative liability, fair value	20,200,000	11,400,000
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	93	'
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	650	'
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	635	'
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	665	'
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	0	3,100,000
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	33,000,000	55,800,000
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	20,200,000	10,300,000
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		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation [Roll Forward]	'	'	'	'
Beginning balance - January 1	$43.30	$53.30	$58.90	$62.40
Total gains	'	'	'	'
Included in earnings	33	32.4	62	60.4
Settlements	-43.3	-40.6	-87.9	-77.7
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending balance - June 30	33	45.1	33	45.1
Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date	33	32.4	62	60.4
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]	'	'	'	'
Beginning balance - January 1	-7.4	-6.8	-10.3	-11.3
Total gains	'	'	'	'
Included in earnings	-12.8	-25.2	-20.2	-32
Settlements	0	0	10.3	11.3
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending balance - June 30	-20.2	-32	-20.2	-32
Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date	($12.80)	($25.20)	($20.20)	($32)

FAIR_VALUE_OF_FINANCIAL_INSTRU6

FAIR VALUE OF FINANCIAL INSTRUMENTS (Carrying Value And Fair Value Of Financial Instruments Disclosure) (Details) (USD $)	Jun. 30, 2014		Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Face Amount	$4,954,500,000		$4,814,800,000
Long-term debt:	'		'
Long-term Debt	3,454,100,000		3,043,500,000
Total long-term debt, carrying value	3,293,000,000		3,022,600,000
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:	'		'
Long-term Debt	699,500,000	[1]	699,400,000	[1]
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:	'		'
Long-term Debt	398,500,000	[2]	398,400,000	[2]
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:	'		'
Long-term Debt	496,900,000	[3]	496,500,000	[3]
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	275,000,000	[4]	0	[4]
Equipment Loans [Member]	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Debt Instrument, Face Amount	164,800,000		164,800,000
Long-term debt:	'		'
Long-term Debt	151,400,000		161,700,000
Interest Rate Swap [Member]	'		'
Long-term debt:	'		'
Fair Value Adjustment to Interest Rate Hedge	3,300,000		-2,100,000
Fair Value, Inputs, Level 2 [Member]	'		'
Long-term debt:	'		'
Total long-term debt, fair value	3,684,900,000		3,217,700,000
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	756,600,000		718,200,000
Fair Value, Inputs, Level 2 [Member] | Senior Notes - $1.3 Billion [Member]	'		'
Long-term debt:	'		'
Debt Instrument, Fair Value Disclosure	1,537,400,000		1,404,900,000
Fair Value, Inputs, Level 2 [Member] | Senior Notes - $400 Million [Member]	'		'
Long-term debt:	'		'
Debt Instrument, Fair Value Disclosure	450,200,000		432,100,000
Fair Value, Inputs, Level 2 [Member] | Senior Notes - $500 Million [Member]	'		'
Long-term debt:	'		'
Debt Instrument, Fair Value Disclosure	532,400,000		523,800,000
Fair Value, Inputs, Level 2 [Member] | Revolving Credit Facility [Member]	'		'
Long-term debt:	'		'
Revolving loan, fair value	275,000,000		0
Fair Value, Inputs, Level 2 [Member] | Equipment Loans [Member]	'		'
Long-term debt:	'		'
Debt Instrument, Fair Value Disclosure	130,000,000		140,800,000
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]	'		'
Long-term debt:	'		'
Fair Value Adjustment to Interest Rate Hedge	3,300,000		-2,100,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]	'		'
Long-term debt:	'		'
Total long-term debt, carrying value	3,293,000,000		3,022,600,000
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]	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Senior Notes, Noncurrent	699,500,000		699,400,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Senior Notes - $1.3 Billion [Member]	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Senior Notes, Noncurrent	1,289,800,000		1,289,600,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Senior Notes - $400 Million [Member]	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Senior Notes, Noncurrent	398,500,000		398,400,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Senior Notes - $500 Million [Member]	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Senior Notes, Noncurrent	496,900,000		496,500,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Revolving Credit Facility [Member]	'		'
Long-term debt:	'		'
Revolving loan, carrying value	275,000,000		0
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Equipment Loans [Member]	'		'
Long-term debt:	'		'
Long-term Debt	130,000,000		140,800,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]	'		'
Long-term debt:	'		'
Fair Value Adjustment to Interest Rate Hedge	$3,300,000		($2,100,000)
[1]	As of JuneB 30, 2014 and DecemberB 31, 2013, the $700 million 4.875 percent senior notes were recorded at a par value of $700 million less unamortized discounts of $0.5 million and $0.6 million, respectively, based on an imputed interest rate of 4.89 percent.
[2]	As of JuneB 30, 2014 and DecemberB 31, 2013, the $400 million 5.90 percent senior notes were recorded at a par value of $400 million less unamortized discounts of $1.5 million and $1.6 million, respectively, based on an imputed interest rate of 5.98 percent.
[3]	As of JuneB 30, 2014 and DecemberB 31, 2013, the $500 million 3.95 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $3.1 million and $3.5 million, respectively, based on an imputed interest rate of 4.14 percent.
[4]	As of JuneB 30, 2014, $275.0 million of revolving loans were drawn under the credit facility. As of DecemberB 31, 2013, no revolving loans were drawn under the credit facility. As of JuneB 30, 2014 and DecemberB 31, 2013, the principal amount of letter of credit obligations totaled $5.2 million and $8.4 million, respectively, thereby reducing available borrowing capacity to $1.5 billion and $1.7 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) (USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Goodwill, Impairment Loss	$0	$80.90
ASSETS:	'	'
Assets, Fair Value Disclosure, Nonrecurring	'	47.9
Impairment Charges	'	318.4
Fair Value, Inputs, Level 1 [Member]	'	'
ASSETS:	'	'
Assets, Fair Value Disclosure, Nonrecurring	'	0
Fair Value, Inputs, Level 2 [Member]	'	'
ASSETS:	'	'
Assets, Fair Value Disclosure, Nonrecurring	'	0
Fair Value, Inputs, Level 3 [Member]	'	'
ASSETS:	'	'
Assets, Fair Value Disclosure, Nonrecurring	'	47.9
Amapa [Member]	'	'
ASSETS:	'	'
Equity Method Investments, Fair Value Disclosure	'	0
Equity Method Investment, Other than Temporary Impairment	'	67.6
Amapa [Member] | Fair Value, Inputs, Level 1 [Member]	'	'
ASSETS:	'	'
Equity Method Investments, Fair Value Disclosure	'	0
Amapa [Member] | Fair Value, Inputs, Level 2 [Member]	'	'
ASSETS:	'	'
Equity Method Investments, Fair Value Disclosure	'	0
Amapa [Member] | Fair Value, Inputs, Level 3 [Member]	'	'
ASSETS:	'	'
Equity Method Investments, Fair Value Disclosure	'	0
Cliffs Chromite Ontario and Cliffs Chromite Far North [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Goodwill, Fair Value Disclosure	'	0
Goodwill, Impairment Loss	'	80.9
Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Goodwill, Fair Value Disclosure	'	0
Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Goodwill, Fair Value Disclosure	'	0
Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Goodwill, Fair Value Disclosure	'	0
Wabush and Cliffs Chromite Ontario and Cliffs Chromite Far North [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Property, Plant, and Equipment, Fair Value Disclosure	'	46.3
Impairment of Long-Lived Assets Held-for-use	'	155.4
Wabush and Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Property, Plant, and Equipment, Fair Value Disclosure	'	0
Wabush and Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Property, Plant, and Equipment, Fair Value Disclosure	'	0
Wabush and Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Property, Plant, and Equipment, Fair Value Disclosure	'	46.3
Wabush [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Finite-lived Intangible Assets, Fair Value Disclosure	'	1.6
Other Asset Impairment Charges	'	14.5
Wabush [Member] | Fair Value, Inputs, Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Finite-lived Intangible Assets, Fair Value Disclosure	'	0
Wabush [Member] | Fair Value, Inputs, Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Finite-lived Intangible Assets, Fair Value Disclosure	'	0
Wabush [Member] | Fair Value, Inputs, Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Finite-lived Intangible Assets, Fair Value Disclosure	'	$1.60

DEBT_AND_CREDIT_FACILITIES_Nar

DEBT AND CREDIT FACILITIES (Narrative) (Details)

6 Months Ended

3 Months Ended

6 Months Ended

6 Months Ended

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Mar. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Jun. 30, 2014

Dec. 31, 2013

Dec. 31, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

USD ($)

USD ($)

Revolving Credit Facility [Member]

Revolving Credit Facility [Member]

Revolving Credit Facility [Member]

Revolving Credit Facility [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

Line of Credit [Member]

Accounts Receivable Securitization Facility [Member]

Accounts Receivable Securitization Facility [Member]

Pre-Export Trade Finance Loans [Member]

Line of Credit [Member]

USD ($)

USD ($)

USD ($)

USD ($)

AUD

USD ($)

AUD

USD ($)

Maximum [Member]

USD ($)

USD ($)

USD ($)

Line of Credit Facility [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revolving credit facility, borrowing capacity

'

'

'

'

'

'

$28,300,000

30,000,000

$26,800,000

30,000,000

'

'

'

'

Financial covenant, debt to earnings ratio

'

'

'

3.5

'

'

'

'

'

'

'

'

'

'

Total Funded Debt to Total Capitalization

'

'

0.45

'

'

'

'

'

'

'

'

'

'

'

Financial covenant, interest coverage ratio

'

'

'

2.5

3.5

'

'

'

'

'

'

'

'

'

Maximum Impairment Permitted to be Excluded from Net Worth Calculation for Debt Covenants

1,000,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility, amount outstanding

'

'

275,000,000

[1]

'

275,000,000

[1]

0

[1]

21,700,000

23,000,000

20,500,000

23,000,000

'

'

'

'

Credit facility remaining capacity

'

'

1,500,000,000

'

1,500,000,000

1,700,000,000

6,600,000

7,000,000

6,300,000

7,000,000

'

'

'

'

Short-term Debt

'

'

'

'

'

'

'

'

'

'

57,300,000

110,000,000

37,400,000

45,000,000

Minimum Number of Days Loan Can be Drawn

'

'

'

'

'

'

'

'

'

'

'

'

'

30

Maximum Number of Days Loan can be Drawn

90

'

'

'

'

'

'

'

'

'

'

'

'

'

Letters of credit outstanding

$48,000,000

$48,000,000

$5,200,000

'

$5,200,000

$8,400,000

'

'

'

'

'

'

'

'

[1]

As of JuneB 30, 2014, $275.0 million of revolving loans were drawn under the credit facility. As of DecemberB 31, 2013, no revolving loans were drawn under the credit facility. As of JuneB 30, 2014 and DecemberB 31, 2013, the principal amount of letter of credit obligations totaled $5.2 million and $8.4 million, respectively, thereby reducing available borrowing capacity to $1.5 billion and $1.7 billion for each period, respectively.

DEBT_AND_CREDIT_FACILITIES_Sch

DEBT AND CREDIT FACILITIES (Schedule Of Long-Term Debt) (Details) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Debt Instrument [Line Items]	'		'
Total Face Amount	$4,954,500,000		$4,814,800,000
Letters of credit outstanding	48,000,000		48,000,000
Long-term Debt	3,454,100,000		3,043,500,000
Current portion of long-term debt	161,100,000		20,900,000
Long-term debt noncurrent portion	3,293,000,000		3,022,600,000
Seven Hundred Million Four Point Eight Seven Five Two Thousand Twenty-one Senior Note [Member]	'		'
Debt Instrument [Line Items]	'		'
Stated interest rate	4.88%		'
Type	'Fixed		'Fixed
Final Maturity	'2021		'2021
Total Face Amount	700,000,000		700,000,000
Long-term Debt	699,500,000	[1]	699,400,000	[1]
Debt Instrument, Unamortized Discount	500,000		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%		'
Type	'Fixed		'Fixed
Final Maturity	'2020		'2020
Total Face Amount	500,000,000		500,000,000
Long-term Debt	499,300,000	[2]	499,200,000	[2]
Debt Instrument, Unamortized Discount	700,000		800,000
Imputed interest rate	4.83%		4.83%
$800 Million 6.25% 2040 Senior Notes [Member]	'		'
Debt Instrument [Line Items]	'		'
Stated interest rate	6.25%		'
Type	'Fixed		'Fixed
Final Maturity	'2040		'2040
Total Face Amount	800,000,000		800,000,000
Long-term Debt	790,500,000	[3]	790,400,000	[3]
Debt Instrument, Unamortized Discount	9,500,000		9,600,000
Imputed interest rate	6.34%		6.34%
$400 Million 5.90% 2020 Senior Notes [Member]	'		'
Debt Instrument [Line Items]	'		'
Stated interest rate	5.90%		'
Type	'Fixed		'Fixed
Final Maturity	'2020		'2020
Total Face Amount	400,000,000		400,000,000
Long-term Debt	398,500,000	[4]	398,400,000	[4]
Debt Instrument, Unamortized Discount	1,500,000		1,600,000
Imputed interest rate	5.98%		5.98%
$500 Million 3.95% 2018 Senior Notes [Member]	'		'
Debt Instrument [Line Items]	'		'
Stated interest rate	3.95%		'
Type	'Fixed		'Fixed
Final Maturity	'2018		'2018
Total Face Amount	500,000,000		500,000,000
Long-term Debt	496,900,000	[5]	496,500,000	[5]
Debt Instrument, Unamortized Discount	3,100,000		3,500,000
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	275,000,000	[6]	0	[6]
Letters of credit outstanding	5,200,000		8,400,000
Imputed interest rate	1.66%		1.64%
Credit facility remaining capacity	1,500,000,000		1,700,000,000
Equipment Loans [Member]	'		'
Debt Instrument [Line Items]	'		'
Type	'Fixed		'Fixed
Final Maturity	'2020		'2020
Total Face Amount	164,800,000		164,800,000
Long-term Debt	151,400,000		161,700,000
Short-term Debt [Member]	'		'
Debt Instrument [Line Items]	'		'
Final Maturity	'2014/2015		'
Total Face Amount	139,700,000		'
Interest Rate Swap [Member]	'		'
Debt Instrument [Line Items]	'		'
Fair Value Adjustment to Interest Rate Hedge	$3,300,000		($2,100,000)
[1]	As of JuneB 30, 2014 and DecemberB 31, 2013, the $700 million 4.875 percent senior notes were recorded at a par value of $700 million less unamortized discounts of $0.5 million and $0.6 million, respectively, based on an imputed interest rate of 4.89 percent.
[2]	As of JuneB 30, 2014 and DecemberB 31, 2013, the $500 million 4.80 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $0.7 million and $0.8 million, respectively, based on an imputed interest rate of 4.83 percent.
[3]	As of JuneB 30, 2014 and DecemberB 31, 2013, the $800 million 6.25 percent senior notes were recorded at a par value of $800 million less unamortized discounts of $9.5 million and $9.6 million, respectively, based on an imputed interest rate of 6.34 percent.
[4]	As of JuneB 30, 2014 and DecemberB 31, 2013, the $400 million 5.90 percent senior notes were recorded at a par value of $400 million less unamortized discounts of $1.5 million and $1.6 million, respectively, based on an imputed interest rate of 5.98 percent.
[5]	As of JuneB 30, 2014 and DecemberB 31, 2013, the $500 million 3.95 percent senior notes were recorded at a par value of $500 million less unamortized discounts of $3.1 million and $3.5 million, respectively, based on an imputed interest rate of 4.14 percent.
[6]	As of JuneB 30, 2014, $275.0 million of revolving loans were drawn under the credit facility. As of DecemberB 31, 2013, no revolving loans were drawn under the credit facility. As of JuneB 30, 2014 and DecemberB 31, 2013, the principal amount of letter of credit obligations totaled $5.2 million and $8.4 million, respectively, thereby reducing available borrowing capacity to $1.5 billion and $1.7 billion for each period, respectively.

DEBT_AND_CREDIT_FACILITIES_DEB

DEBT AND CREDIT FACILITIES DEBT AND CREDIT FACILITIES (Schedule of Debt Maturities) (Details) (USD $)	Jun. 30, 2014
In Millions, unless otherwise specified
Debt Disclosure [Abstract]	'
Debt Maturities Remainder 2014	$150.40
Debt Maturities 2015	21.8
Debt Maturities 2016	22.7
Debt Maturities 2017	23.6
Debt Maturities 2018	524.6
Debt Maturities 2019 and After	2,448
Long-term Debt, Maturities, Total	$3,191.10

LEASE_OBLIGATIONS_Narrative_De

LEASE OBLIGATIONS (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Leases [Abstract]	'	'	'	'
Operating lease expense	$4	$7.40	$11.30	$14.20

LEASE_OBLIGATIONS_Future_Minim

LEASE OBLIGATIONS (Future Minimum Lease Payments) (Details) (USD $)	Jun. 30, 2014
In Millions, unless otherwise specified
Capital Leases	'
2014 (April 1 - December 31)	$33.50
2015	89
2016	38
2017	30.5
2018	22.4
2019 and thereafter	37.8
Total minimum lease payments	251.2
Amounts representing interest	43.4
Present value of net minimum lease payments	207.8	[1]
Operating Leases	'
2014 (April 1 - December 31)	9.5
2015	14.2
2016	9.2
2017	8.3
2018	7.1
2019 and thereafter	14.7
Total minimum lease payments	63
Other Current Liabilities [Member]	'
Capital Leases	'
Present value of net minimum lease payments	82
Other Liabilities [Member]	'
Capital Leases	'
Present value of net minimum lease payments	$125.70
[1]	The total is comprised of $82.0 million and $125.7 million classified as Other current liabilities and Other liabilities, respectively, in the Statements of Unaudited Condensed Consolidated Financial Position at JuneB 30, 2014.

ENVIRONMENTAL_AND_MINE_CLOSURE2

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Narrative) (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Environmental Remediation Obligations [Abstract]	'	'
Total environmental and mine closure obligations	$310.30	$321

ENVIRONMENTAL_AND_MINE_CLOSURE3

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Summary Of Mine Closure Obligations) (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Loss Contingencies [Line Items]	'	'
Environmental	$11	$8.40
Mine Reclamation and Closing Liability, current and noncurrent	299.3	312.6
Total environmental and mine closure obligations	310.3	321
Less current portion	5.6	11.3
Long term environmental and mine closure obligations	304.7	309.7
U.S. Iron Ore [Member] | Owned Or Operating Facilities [Member]	'	'
Loss Contingencies [Line Items]	'	'
Mine Reclamation and Closing Liability, current and noncurrent	137.5	152.2
Eastern Canadian Iron Ore [Member] | Owned Or Operating Facilities [Member]	'	'
Loss Contingencies [Line Items]	'	'
Mine Reclamation and Closing Liability, current and noncurrent	76.3	78.2
Asia Pacific Iron Ore [Member] | Owned Or Operating Facilities [Member]	'	'
Loss Contingencies [Line Items]	'	'
Mine Reclamation and Closing Liability, current and noncurrent	27.4	25.5
North American Coal [Member] | Owned Or Operating Facilities [Member]	'	'
Loss Contingencies [Line Items]	'	'
Mine Reclamation and Closing Liability, current and noncurrent	35.7	34.7
LTV Steel Mining Company [Member] | Previously Owned Or Operating Facilities [Member]	'	'
Loss Contingencies [Line Items]	'	'
Mine Reclamation and Closing Liability, current and noncurrent	$22.40	$22

ENVIRONMENTAL_AND_MINE_CLOSURE4

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Asset Retirement Obligation Disclosure) (Details) (USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Asset Retirement Obligation [Roll Forward]	'	'
Asset retirement obligation at beginning of period	$290.60	$231.10
Accretion expense	7.2	18.1
Exchange rate changes	1.2	-3.4
Revision in estimated cash flows	-22.1	44.8
Asset retirement obligation at end of period	$276.90	$290.60

PENSIONS_AND_OTHER_POSTRETIREM2

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension Plans, Defined Benefit [Member]	'	'	'	'
Definted Benefit Plan Disclosure [Line Items]	'	'	'	'
Pension Contributions	$10.40	$11.40	$14.60	$15.10
Other Postretirement Benefit Plans, Defined Benefit [Member]	'	'	'	'
Definted Benefit Plan Disclosure [Line Items]	'	'	'	'
Other Postretirement Benefit Expense	'	'	$0	$14.10

PENSIONS_AND_OTHER_POSTRETIREM3

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Estimated Net Periodic Benefit Cost) (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension Plan, Defined Benefit [Member]	'	'	'	'
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]	'	'	'	'
Defined Benefit Plan, Service Cost	$7.90	$9.70	$15.90	$19.60
Defined Benefit Plan, Interest Cost	12.5	11.7	25	23.2
Defined Benefit Plan, Expected Return on Plan Assets	-18	-20	-36	-33.1
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	6.5	0.8	7.2	1.5
Defined Benefit Plan, Amortization of Gains (Losses)	-2.3	8.2	1.3	15
Defined Benefit Plan, Curtailments	0.9	0	1.2	0
Defined Benefit Plan, Net Periodic Benefit Cost	7.5	10.4	14.6	26.2
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	2	3.1	4	6.2
Defined Benefit Plan, Interest Cost	4.1	4.4	8.1	8.7
Defined Benefit Plan, Expected Return on Plan Assets	-4.3	-5	-8.6	-10
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	-0.9	-0.9	-1.8	-1.8
Defined Benefit Plan, Amortization of Gains (Losses)	1.1	3	2.3	5.8
Defined Benefit Plan, Net Periodic Benefit Cost	$2	$4.60	$4	$8.90

STOCK_COMPENSATION_PLANS_Narra

STOCK COMPENSATION PLANS (Narrative) (Details)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014
	Agreement
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 performance shares granted	0.5
Number of restricted shares granted	0.2
Number of Additional Shares Available for Issuance Proposed to be Added to the Plan	5
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
Two Thousand And Twelve To Two Thousand And Fourteen And The Two Thousand And Thirteen To Two Thousand Fifteen and Two Thousand Fourteen to Two Thousand Sixteen 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 Twelve To Two Thousand And Fourteen And The Two Thousand And Thirteen To Two Thousand Fifteen and Two Thousand Fourteen to Two Thousand Sixteen 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 $)	3 Months Ended	6 Months Ended
	Mar. 31, 2014	Jun. 30, 2014
Performance Shares [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Grant Date Market Price	$20.58	$17.54
Average Expected Term (Years)	'2 years 10 months 21 days	'2 years 7 months 11 days
Expected Volatility	54.00%	54.00%
Risk-Free Interest Rate	0.54%	0.54%
Dividend Yield	2.92%	2.92%
Fair Value	$22.21	$18.93
Fair Value (Percent of Grant Date Market Price)	107.92%	107.92%

INCOME_TAXES_Narrative_Details

INCOME TAXES (Narrative) (Details) (USD $)	3 Months Ended			6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statutory Tax Rate [Line Items]	'	'	'	'	'
Income Tax Expense (Benefit)	($69.10)	'	$9.30	($90.90)	$3.30
Discrete Tax Items Expense (Benefit)	'	'	'	-4.4	'
Tax Benefit of Income Not Subject to Tax	'	-48.4	'	'	'
United States [Member]	'	'	'	'	'
Statutory Tax Rate [Line Items]	'	'	'	'	'
Benefit of Intercompany Loan between U.S. and Canada	'	'	'	27.8	'
Canada	'	'	'	'	'
Statutory Tax Rate [Line Items]	'	'	'	'	'
Expected Benefit from Intercompany Loan between Canada and Australia	'	'	'	$20.60	'

CAPITAL_STOCK_Details

CAPITAL STOCK (Details) (USD $)

3 Months Ended

6 Months Ended

2 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

2 Months Ended

In Millions, except Share data, unless otherwise specified

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Dec. 31, 2013

Feb. 21, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

13-May-14

1-May-14

Feb. 03, 2014

Nov. 01, 2013

Aug. 01, 2013

1-May-13

Feb. 11, 2013

Jun. 30, 2014

Mar. 03, 2014

Dec. 02, 2013

Sep. 03, 2013

Jun. 03, 2013

Mar. 01, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Feb. 21, 2013

Jun. 30, 2014

13-May-14

1-May-14

Feb. 03, 2014

Nov. 01, 2013

Aug. 01, 2013

1-May-13

Preferred Class A [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]

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 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]

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

'

'

$0

$709.40

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Dividends payable, per share

'

'

'

'

'

'

'

'

'

'

$17.50

$17.50

$17.50

$17.50

$17.50

$13.61

'

$0.15

$0.15

$0.15

$0.15

$0.15

$0.15

'

'

'

'

'

$0.44

$0.44

$0.44

$0.44

$0.44

$0.34

Dividends, Preferred Stock

$12.80

$12.90

$25.60

$22.80

'

'

$12.80

$12.90

$25.60

$22.80

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage increase (decrease) in dividends payable

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

76.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Issuance of common shares, public offering (in shares)

'

'

'

'

'

731,250

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

29,250,000

'

'

'

'

'

'

'

Closing price per share (in usd per share)

'

'

'

'

'

'

$25

'

$25

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

SHAREHOLDERS_EQUITY_Schedule_o

SHAREHOLDERS' EQUITY Schedule of Shareholders' Equity (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Stockholders' Equity Attributable to Parent	$6,027.60	'	$6,027.60	'	$6,069.50	'
Stockholders' Equity Attributable to Noncontrolling Interest	802	'	802	'	814.8	'
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	6,829.60	6,783.80	6,829.60	6,783.80	6,884.30	5,760.90
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	10.9	146	-59.4	253	'	'
INCOME (LOSS) ATTRIBUTABLE TO NONCONTROLLING INTEREST	3.6	-4.7	3.2	9.1	'	'
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	14.5	141.3	-56.2	262.1	'	'
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	45.8	-42.2	33.3	69	'	'
Other Comprehensive Income (Loss), Net of Tax	35.5	-187.1	93.8	-181.7	'	'
OTHER COMPREHENSIVE INCOME ATTRIBUTABLE TO THE NONCONTROLLING INTEREST	-0.6	-1.1	-1.1	-2.3	'	'
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	'	'	37.6	80.4	'	'
Stock and Other Incentive Plans	'	'	-3.1	3.7	'	'
Common and preferred share dividends	'	'	-72.1	-68.9	'	'
Undistributed Gains To Noncontrolling Interest	'	'	-17.1	'	'	'
Capital Contribution By Noncontrolling Interest	'	'	'	13	'	'
Cliffs Shareholders Equity [Member]	'	'	'	'	'	'
Stockholders' Equity Attributable to Parent	6,027.60	5,631.20	6,027.60	5,631.20	6,069.50	4,632.70
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	'	'	-59.4	253	'	'
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	'	'	92.7	-184	'	'
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	'	'	33.3	69	'	'
Stock and Other Incentive Plans	'	'	-3.1	3.7	'	'
Common and preferred share dividends	'	'	-72.1	-68.9	'	'
Undistributed Gains To Noncontrolling Interest	'	'	0	'	'	'
Capital Contribution By Noncontrolling Interest	'	'	'	0	'	'
Noncontrolling Interest [Member]	'	'	'	'	'	'
Stockholders' Equity Attributable to Noncontrolling Interest	802	1,152.60	802	1,152.60	814.8	1,128.20
INCOME (LOSS) ATTRIBUTABLE TO NONCONTROLLING INTEREST	'	'	3.2	9.1	'	'
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	'	'	1.1	2.3	'	'
OTHER COMPREHENSIVE INCOME ATTRIBUTABLE TO THE NONCONTROLLING INTEREST	'	'	4.3	11.4	'	'
Stock and Other Incentive Plans	'	'	0	0	'	'
Common and preferred share dividends	'	'	0	0	'	'
Undistributed Gains To Noncontrolling Interest	'	'	-17.1	'	'	'
Capital Contribution By Noncontrolling Interest	'	'	'	13	'	'
Common Stock [Member]	'	'	'	'	'	'
Stock Issued During Period, Value, New Issues	'	'	'	263.4	'	'
Common Stock [Member] | Cliffs Shareholders Equity [Member]	'	'	'	'	'	'
Stock Issued During Period, Value, New Issues	'	'	'	263.4	'	'
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	'	'	'	731.3	'	'
Preferred Class A [Member] | Cliffs Shareholders Equity [Member]	'	'	'	'	'	'
Stock Issued During Period, Value, New Issues	'	'	'	731.3	'	'
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 $)

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Jun. 30, 2014

Mar. 31, 2014

Jun. 30, 2013

Mar. 31, 2013

Jun. 30, 2014

Mar. 31, 2014

Jun. 30, 2013

Mar. 31, 2013

Jun. 30, 2014

Mar. 31, 2014

Jun. 30, 2013

Mar. 31, 2013

Jun. 30, 2014

Mar. 31, 2014

Jun. 30, 2013

Mar. 31, 2013

Jun. 30, 2014

Mar. 31, 2014

Jun. 30, 2013

Mar. 31, 2013

Jun. 30, 2014

Mar. 31, 2014

Jun. 30, 2013

Mar. 31, 2013

Jun. 30, 2014

Mar. 31, 2014

Jun. 30, 2013

Mar. 31, 2013

Jun. 30, 2014

Mar. 31, 2014

Jun. 30, 2013

Mar. 31, 2013

Jun. 30, 2014

Mar. 31, 2014

Jun. 30, 2013

Mar. 31, 2013

In Millions, unless otherwise specified

Accumulated Other Comprehensive Income (Loss) [Member]

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 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 Net Unrealized Investment Gain (Loss) [Member]

Accumulated Translation Adjustment [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 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 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 Net Unrealized Investment Gain (Loss) [Member]

Accumulated Translation Adjustment [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 Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax

($199.40)

($202)

($204.90)

($370.80)

($377.40)

($382.70)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Accumulated other comprehensive loss

-20.2

-55.1

-112.9

-239.6

-51.4

-55.6

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax

6.4

10.1

6.2

6.3

4.7

2.1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax

166.9

147.2

106.7

167.6

319.6

316.3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax

5.9

-10.4

-20.9

-42.7

1.7

8.7

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other Comprehensive Income (Loss), before Reclassifications, before Tax

'

'

'

'

'

'

25.6

41.6

-197.7

-0.3

-1.4

-0.4

-1.5

-1.1

-2.4

3.8

-2

2.5

19.7

40.5

-152

3.3

9.7

-2.3

-42.2

-5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)

'

'

'

'

'

'

$9.30

$16.20

$9.50

$4.50

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$4

$3.30

$8.10

$6.40

($1.30)

$0.10

$3.60

$0.10

$0

$0

$0

$0

$6.60

$12.80

($2.20)

($2)

SHAREHOLDERS_EQUITY_Details_of

SHAREHOLDERS' EQUITY Details of Accumulated Other Comprehensive Income (Loss) Components (Details) (USD $)	3 Months Ended				6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]	'		'		'		'
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	($6.60)		$2.20		($19.40)		$4.20
Total Amount Reclassified from Accumulated Other Comprehensive Income (Loss) During the Period	9.3		9.5		25.5		14
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)	5.6	[1]	-0.1	[1]	5.4	[1]	-0.3	[1]
Defined Benefit Plan, Amortization of Gains (Losses)	-1.2	[1]	11.2	[1]	3.6	[1]	20.8	[1]
Defined Benefit Plan, Curtailments	0.9	[1]	0	[1]	1.2	[1]	0	[1]
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	5.3		11.1		10.2		20.5
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax	-1.3		-3		-2.9		-6
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	4		8.1		7.3		14.5
Realized Gain (Loss) on Marketable Securities [Member]	'		'		'		'
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]	'		'		'		'
Marketable Securities, Realized Gain (Loss)	-1.9		-1.1		-1.7		-1.1
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		5.2		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	-1.9		4.1		-1.7		4.2
Other Comprehensive Income (Loss), Realized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, Tax	0.6		-0.5		0.5		-0.5
Other Comprehensive Income (Loss), Realized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, net of tax	-1.3		3.6		-1.2		3.7
Realized Gain Loss On Derivatives [Member]	'		'		'		'
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]	'		'		'		'
(Gain) Loss on Derivative Instruments, Net, Pretax	9.7		-3.1		28.2		-6
Tax on Derivative Instruments Gain/Loss Reclassified from Accumulated OCI in to Earnings	-3.1		0.9		-8.8		1.8
Amount of (gain)/loss recognized in income on derivative	6.6		-2.2		19.4		-4.2
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	5.3		-3.7		18.3		-6.3
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	$4.40		$0.60		$9.90		$0.30
[1]	These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. See NOTE 11 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.

SHAREHOLDERS_EQUITY_Narrative_

SHAREHOLDERS' EQUITY Narrative (Details)	Jun. 30, 2014
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	82.80%

RELATED_PARTIES_Narrative_Deta

RELATED PARTIES (Narrative) (Details) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]	'	'
Extension of ArcelorMittal Contract	'2 years	'
Due from Related Parties, Current	$69.90	$132
Due to Related Parties, Current	$26.30	$25.10
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	'
Joint Venture Partners [Member] | U.S. Iron Ore [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Number of mines (in number of facilities)	3	'
Joint Venture Partners [Member] | Eastern Canadian Iron Ore [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Number of mines (in number of facilities)	1	'

RELATED_PARTIES_Summary_Of_Oth

RELATED PARTIES (Summary Of Other Ownership Interests) (Details)	Jun. 30, 2014
Hibbing [Member] | Arcelor Mittal [Member]	'
Related Party Transaction [Line Items]	'
Ownership interest, equity method investment	62.30%
Hibbing [Member] | U. S. Steel Canada [Member]	'
Related Party Transaction [Line Items]	'
Ownership interest, equity method investment	14.70%
Hibbing [Member] | WISCO [Member]	'
Related Party Transaction [Line Items]	'
Ownership interest, equity method investment	0.00%
Empire [Member]	'
Related Party Transaction [Line Items]	'
Noncontrolling Interest, Ownership Percentage by Parent	79.00%
Empire [Member] | Arcelor Mittal [Member]	'
Related Party Transaction [Line Items]	'
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	21.00%
Empire [Member] | U. S. Steel Canada [Member]	'
Related Party Transaction [Line Items]	'
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	0.00%
Empire [Member] | WISCO [Member]	'
Related Party Transaction [Line Items]	'
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	0.00%
Tilden [Member]	'
Related Party Transaction [Line Items]	'
Noncontrolling Interest, Ownership Percentage by Parent	85.00%
Tilden [Member] | Arcelor Mittal [Member]	'
Related Party Transaction [Line Items]	'
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	0.00%
Tilden [Member] | U. S. Steel Canada [Member]	'
Related Party Transaction [Line Items]	'
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	15.00%
Tilden [Member] | WISCO [Member]	'
Related Party Transaction [Line Items]	'
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	0.00%
Bloom Lake [Member]	'
Related Party Transaction [Line Items]	'
Noncontrolling Interest, Ownership Percentage by Parent	82.80%
Bloom Lake [Member] | Arcelor Mittal [Member]	'
Related Party Transaction [Line Items]	'
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	0.00%
Bloom Lake [Member] | U. S. Steel Canada [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	17.20%
Other Noncurrent Assets [Member] | Hibbing [Member]	'
Related Party Transaction [Line Items]	'
Ownership interest, equity method investment	23.00%	[1]
[1]	At December 31, 2013, 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		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Related Party Transactions [Abstract]	'	'	'	'
Product revenues from related parties	$322.10	$455	$539	$756.20
Product	$1,018.60	$1,391.60	$1,879.50	$2,474.20
Related party product revenue as a percent of total product revenue	31.60%	32.70%	28.70%	30.60%

EARNINGS_PER_SHARE_EARNINGS_PE

EARNINGS PER SHARE EARNINGS PER SHARE (Narrative) (Details)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	25.2
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements	0.8

Recovered_Sheet1

EARNINGS PER SHARE (Earnings Per Share Computation) (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS	$10.90	$146	($59.40)	$253
PREFERRED STOCK DIVIDENDS	-12.8	-12.9	-25.6	-22.8
NET INCOME ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS	-1.9	133.1	-85	230.2
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Basic:	($0.01)	$0.87	($0.56)	$1.53
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted:	($0.01)	$0.82	($0.56)	$1.49
Weighted Average Number of Shares:	'	'	'	'
Basic	153,087	153,011	153,064	150,418
Depositary Shares	0	25,217	0	19,063
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0	200	0	227
Diluted	153,087	178,428	153,064	169,708
Preferred Class A [Member]	'	'	'	'
PREFERRED STOCK DIVIDENDS	($12.80)	($12.90)	($25.60)	($22.80)

COMMITMENTS_AND_CONTINGENCIES_

COMMITMENTS AND CONTINGENCIES NARRATIVE (Details) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014
Worldlink Arbitration [Member]	'
Loss Contingencies [Line Items]	'
Loss Contingency, Damages Sought, Value	$85
Worldlink Counterclaim [Member]	'
Loss Contingencies [Line Items]	'
Loss Contingency, Damages Sought, Value	$100

CASH_FLOW_INFORMATION_Narrativ

CASH FLOW INFORMATION (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	13-May-14	1-May-14	Feb. 03, 2014	Nov. 01, 2013	Aug. 01, 2013	1-May-13
Dividends Payable [Line Items]	'	'	'	'	'	'	'	'	'	'
Depositary Share Interest in a Share of 7% Series A Mandatory Convertible Preferred Stock, Class A	'	'	0.025	'	'	'	'	'	'	'
Preferred stock cash dividend	$12.80	$12.90	$25.60	$22.80	'	'	'	'	'	'
Preferred Class A [Member]	'	'	'	'	'	'	'	'	'	'
Dividends Payable [Line Items]	'	'	'	'	'	'	'	'	'	'
Dividends payable, per share	'	'	'	'	$17.50	$17.50	$17.50	$17.50	$17.50	$13.61
Preferred stock cash dividend	$12.80	$12.90	$25.60	$22.80	'	'	'	'	'	'
Depositary Share [Member]	'	'	'	'	'	'	'	'	'	'
Dividends Payable [Line Items]	'	'	'	'	'	'	'	'	'	'
Dividends payable, per share	'	'	'	'	$0.44	$0.44	$0.44	$0.44	$0.44	$0.34

CASH_FLOW_INFORMATION_Reconcil

CASH FLOW INFORMATION (Reconciliation Of Capital Additions To Cash Paid For Capital Expenditures) (Details) (USD $)	3 Months Ended				6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Supplemental Cash Flow Information [Abstract]	'		'		'		'
Capital Additions	$52	[1]	$218.10	[1]	$131.20	[1]	$413.80	[1]
Cash Paid for Capital Expenditures	'		'		164.3		501.2
Non-cash accruals	'		'		-43		-87.4
Capital leases	'		'		9.9		0
Total	'		'		($33.10)		($87.40)
[1]	Includes capital lease additions and non-cash accruals. Refer to NOTE 19 - CASH FLOW INFORMATION.