betfred reviews|Welcome_RELATED PARTIES (Summary

Annual report pursuant to Section 13 and 15(d)

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details)

Betfred	12 Months Ended													12 Months Ended					12 Months Ended						12 Months Ended										3 Months Ended	12 Months Ended					12 Months Ended							12 Months Ended
Betfred	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2014 Northern Lands [Member] USD ($)	Dec. 31, 2013 Amapa [Member] USD ($)	Dec. 31, 2012 Amapa [Member] USD ($)	Dec. 31, 2014 U.S. Iron Ore [Member] USD ($) Facility T	Dec. 31, 2013 U.S. Iron Ore [Member] USD ($) T	Dec. 31, 2012 U.S. Iron Ore [Member] USD ($)	Dec. 31, 2014 Asia Pacific [Member] USD ($)	Dec. 31, 2014 Asia Pacific Iron Ore [Member] USD ($) Facility	Dec. 31, 2013 Asia Pacific Iron Ore [Member] USD ($)	Dec. 31, 2012 Asia Pacific Iron Ore [Member] USD ($)	Dec. 31, 2013 Asia Pacific Iron Ore [Member] Cockatoo [Member] USD ($)	Dec. 31, 2013 Asia Pacific Iron Ore [Member] Cockatoo [Member] AUD	Dec. 31, 2013 Other Segment [Member] USD ($)	Dec. 31, 2014 Other Segment [Member] USD ($)	Dec. 31, 2012 Other Segment [Member] USD ($)	Dec. 31, 2014 North American Coal [Member] USD ($)	Dec. 31, 2013 North American Coal [Member] USD ($)	Dec. 31, 2012 North American Coal [Member] USD ($)	Dec. 31, 2014 Eastern Canadian Iron Ore [Member] USD ($) Facility	Dec. 31, 2013 Eastern Canadian Iron Ore [Member] USD ($)	Dec. 31, 2012 Eastern Canadian Iron Ore [Member] USD ($)	Dec. 31, 2013 Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] USD ($)	Dec. 31, 2013 CQIM Reporting Unit [Member] USD ($)	Dec. 31, 2014 Wabush [Member] USD ($)	Dec. 31, 2013 Wabush [Member] USD ($)	Dec. 31, 2013 Sonoma [Member] Asia Pacific Coal [Member] AUD	Jul. 10, 2012 Sonoma [Member] Asia Pacific Coal [Member]	Dec. 31, 2014 Empire [Member]	Dec. 31, 2014 Big Daddy Chromite Deposit [Member]	Dec. 31, 2014 CLCC [Member]	Dec. 31, 2014 Wabush [Member]	Dec. 31, 2013 Bloom Lake [Member] USD ($)	Dec. 31, 2013 Bloom Lake [Member] USD ($)	Dec. 31, 2012 Bloom Lake [Member] USD ($)	Dec. 31, 2011 Bloom Lake [Member] USD ($)	Dec. 31, 2014 Bloom Lake [Member]	Dec. 31, 2013 Investments in Ventures [Member] Amapa [Member]	Dec. 31, 2014 Low Volatile Metallurgical Coal Mines [Member] North American Coal [Member] Facility	Dec. 31, 2014 High volatile metallurgical coal mines [Member] North American Coal [Member] Facility	Dec. 31, 2014 Thermal Coal Mines [Member] North American Coal [Member] Facility	Dec. 31, 2014 Take or Pay Contracts [Member] USD ($)	Dec. 31, 2013 Take or Pay Contracts [Member] USD ($)	Dec. 31, 2014 Customer Supplemental Payments [Member] U.S. Iron Ore [Member] USD ($)	Dec. 31, 2013 Customer Supplemental Payments [Member] U.S. Iron Ore [Member] USD ($)	Dec. 31, 2014 Wisco [Member]	Dec. 31, 2013 Wisco [Member] USD ($)	Dec. 31, 2013 Bloom Lake [Member] USD ($)	Dec. 31, 2014 Minimum [Member] Other Machinery and Equipment [Member]	Dec. 31, 2014 Minimum [Member] Electric Power Facilities [Member]	Dec. 31, 2014 Minimum [Member] Land Improvements [Member]	Dec. 31, 2014 Minimum [Member] Equipment [Member]	Dec. 31, 2014 Maximum [Member] Other Machinery and Equipment [Member]	Dec. 31, 2014 Maximum [Member] Electric Power Facilities [Member]	Dec. 31, 2014 Maximum [Member] Land Improvements [Member]	Dec. 31, 2014 Maximum [Member] Equipment [Member]
Related Party Transaction [Line Items]
Tangible Asset Impairment Charges	$ 8,839,000,000us-gaap_TangibleAssetImpairmentCharges																											$ 145,100,000
Impairment of Long-Lived Assets Held-for-use																											140,100,000	49,900,000
Inventory Valuation Reserves	68,200,000us-gaap_InventoryValuationReserves	63,400,000us-gaap_InventoryValuationReserves
Number Of Mines							5				1											2																			2	2	1
Trading Day Window Determining Number of Common Shares Issuable on Conversion	20
Depositary Share Interest in a Share of 7% Series A Mandatory Convertible Preferred Stock, Class A	0.025
Current Fiscal Year End Date	--12-31
Deferred Revenue																																												29,300,000	13,500,000	102,800,000	115,600,000
Ownership Interest																														45.00%
Increase in Subsidiary or Equity Method Investee Percentage Ownership Acquired																																																	7.80%
Units Issued by CQIM to Bloom Lake for Acquisition of Noncontrolling Interest																																																	457,556
Ownership interest, equity method investment																																								30.00%
Total percentage of Amapa sold																																								100.00%
Equity Method Investment, Other than Temporary Impairment	0	0	(365,400,000)	21,500,000	67,600,000	(365,400,000)
Proceeds from sale of economic interest (in AUD)															4.00														141,000,000
Estimated rehabilitation costs														18,600,000
Goodwill	2,000,000us-gaap_Goodwill	74,500,000us-gaap_Goodwill	167,400,000us-gaap_Goodwill				2,000,000	2,000,000	2,000,000		0	72,500,000	84,500,000			0	0	80,900,000				0	0	0
Reimbursement Revenue	392,900,000us-gaap_ReimbursementRevenue	344,800,000us-gaap_ReimbursementRevenue	351,800,000us-gaap_ReimbursementRevenue				271,000,000	259,500,000	250,800,000	6,900,000									115,000,000	85,800,000	101,000,000
Allowance for Doubtful Accounts Receivable	8,100,000	8,100,000
Provision for Doubtful Accounts	0us-gaap_ProvisionForDoubtfulAccounts	0us-gaap_ProvisionForDoubtfulAccounts	9,000,000us-gaap_ProvisionForDoubtfulAccounts
Quantity Of Finished Goods							1,400,000	1,200,000
Derivative, Policy, Percentage of Amount Permitted to be Hedged	75.00%
Derivative, Policy, Minimum Percentage of Amount Permitted to be Hedged for Derivatives with Periods of up to Twelve Months	40.00%
Derivative, Policy, Minimum Percentage of Amount Permitted to be Hedged for Derivatives with Periods of up to Fifteen Months	10.00%
Deferred Revenue, Current																																														12,800,000	12,800,000
Deferred Revenue, Noncurrent																																														90,000,000	102,800,000
Asset Impairment Charges	9,029,900,000us-gaap_AssetImpairmentCharges	250,800,000us-gaap_AssetImpairmentCharges	1,049,900,000us-gaap_AssetImpairmentCharges																								154,600,000
Noncontrolling Interest, Ownership Percentage by Parent																															79.00%	70.00%	100.00%	100.00%			75.00%		82.80%
Subsidiary Or Equity Method Investee Percentage Ownership Acquired																																																17.152%
Increase/Decrease in Equity for WISCO/Bloom Lake through Acquisition of Noncontrolling Interest																																																	314,800,000
Increase to Cliffs' Shareholders Equity through Acquisition of Noncontrolling Interest																																																		314,800,000
Immaterial Error Adjustment Related to Bloom Lake Purchase Price Acquisition																																				45,100,000
Change in Basic EPS for Immaterial Error Adjustment Related to Bloom Lake Purchase Price Acquisition																																			$ 0.29	$ 0.30	$ 0	$ 0.07
Change in Diluted EPS for Immaterial Error Adjustment Related to Bloom Lake Purchase Price Acquisition																																				$ 0.26	$ 0.25	$ 0.07
Goodwill, Impairment Loss	73,500,000us-gaap_GoodwillImpairmentLoss	80,900,000us-gaap_GoodwillImpairmentLoss					0	0			73,500,000	0				(80,900,000)						0	0		80,900,000	997,300,000
Property, Plant and Equipment, Useful Life																																																			10 years	10 years	20 years	3 years	45 years	45 years	45 years	20 years
Impairment of Intangible Assets (Excluding Goodwill)	$ 15,500,000	$ 14,500,000																										$ 9,500,000