Annual report pursuant to Section 13 and 15(d)

GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Schedule Of Goodwill) (Details)

betfred games-free to play_us-gaap_StatementBusinessSegmentsAxis= v2.4.1.9
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12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Goodwill [Roll Forward]    
Beginning Balance $ 74.5us-gaap_Goodwill $ 167.4us-gaap_Goodwill
Arising in business combinations 0us-gaap_GoodwillAcquiredDuringPeriod 0us-gaap_GoodwillAcquiredDuringPeriod
Impairment (73.5)us-gaap_GoodwillImpairmentLoss (80.9)us-gaap_GoodwillImpairmentLoss
Impact of foreign currency translation 1.0us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments (12.0)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments
Ending Balance 2.0us-gaap_Goodwill 74.5us-gaap_Goodwill
Accumulated Goodwill Impairment Loss (1,154.4)us-gaap_GoodwillImpairedAccumulatedImpairmentLoss (1,080.9)us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
U.S. Iron Ore [Member]    
Goodwill [Roll Forward]    
Beginning Balance 2.0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
2.0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
Arising in business combinations 0us-gaap_GoodwillAcquiredDuringPeriod
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
0us-gaap_GoodwillAcquiredDuringPeriod
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
Impairment 0us-gaap_GoodwillImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
0us-gaap_GoodwillImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
Impact of foreign currency translation 0us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
0us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
Ending Balance 2.0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
2.0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
Accumulated Goodwill Impairment Loss 0us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
0us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
Eastern Canadian Iron Ore [Member]    
Goodwill [Roll Forward]    
Beginning Balance 0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
Arising in business combinations 0us-gaap_GoodwillAcquiredDuringPeriod
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
0us-gaap_GoodwillAcquiredDuringPeriod
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
Impairment 0us-gaap_GoodwillImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
0us-gaap_GoodwillImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
Impact of foreign currency translation 0us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
0us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
Ending Balance 0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
Accumulated Goodwill Impairment Loss (1,000.0)us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
(1,000.0)us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
Asia Pacific Iron Ore [Member]    
Goodwill [Roll Forward]    
Beginning Balance 72.5us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
84.5us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
Arising in business combinations 0us-gaap_GoodwillAcquiredDuringPeriod
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
0us-gaap_GoodwillAcquiredDuringPeriod
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
Impairment (73.5)us-gaap_GoodwillImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
0us-gaap_GoodwillImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
Impact of foreign currency translation 1.0us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
(12.0)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
Ending Balance 0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
72.5us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
Accumulated Goodwill Impairment Loss (73.5)us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
0us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
betfred reviewsOther Segment [Member]    
Goodwill [Roll Forward]    
Beginning Balance 0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_OtherSegmentMember
80.9us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_OtherSegmentMember
Arising in business combinations 0us-gaap_GoodwillAcquiredDuringPeriod
/ us-gaap_StatementBusinessSegmentsAxis
= clf_OtherSegmentMember
0us-gaap_GoodwillAcquiredDuringPeriod
/ us-gaap_StatementBusinessSegmentsAxis
= clf_OtherSegmentMember
Impairment   80.9us-gaap_GoodwillImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_OtherSegmentMember
Impact of foreign currency translation 0us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments
/ us-gaap_StatementBusinessSegmentsAxis
= clf_OtherSegmentMember
0us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments
/ us-gaap_StatementBusinessSegmentsAxis
= clf_OtherSegmentMember
Ending Balance 0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_OtherSegmentMember
0us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= clf_OtherSegmentMember
Accumulated Goodwill Impairment Loss (80.9)us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_OtherSegmentMember
(80.9)us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= clf_OtherSegmentMember
betfred reviewsOther Segment [Member]    
Goodwill [Roll Forward]    
Impairment $ 0us-gaap_GoodwillImpairmentLoss
/ clf_ReportingUnitAxis
= clf_OtherSegmentMember