AGÕæÈËƽ̨AGÕæÈËÊÔÍæ

Quarterly report pursuant to Section 13 or 15(d)

SEGMENT REPORTING Segment Reporting (Summary of Assets by Segment) (Details)

v2.4.1.9
SEGMENT REPORTING Segment Reporting (Summary of Assets by Segment) (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Segment Reporting Information [Line Items] Ìý Ìý
Assets $ 2,702.6us-gaap_Assets $ 3,164.0us-gaap_Assets
U.S. Iron Ore [Member] Ìý Ìý
Segment Reporting Information [Line Items] Ìý Ìý
Assets 1,550.1us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember 		1,464.9us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
Asia Pacific Iron Ore [Member] Ìý Ìý
Segment Reporting Information [Line Items] Ìý Ìý
Assets 250.6us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember 		274.6us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
All Other Segments [Member] Ìý Ìý
Segment Reporting Information [Line Items] Ìý Ìý
Assets 31.2us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember 		147.0us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember
Total Segment Assets [Member] Ìý Ìý
Segment Reporting Information [Line Items] Ìý Ìý
Assets 1,831.9us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_OperatingSegmentsMember 		1,886.5us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_OperatingSegmentsMember
Corporate [Member] Ìý Ìý
Segment Reporting Information [Line Items] Ìý Ìý
Assets 673.5us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateMember 		546.8us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateMember
Discontinued Operations [Member] Ìý Ìý
Segment Reporting Information [Line Items] Ìý Ìý
Disposal Group, Including Discontinued Operation, Assets $ 197.2us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_SegmentDiscontinuedOperationsMember 		$ 730.7us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_SegmentDiscontinuedOperationsMember