XML 117 R49.htm IDEA: XBRL DOCUMENT
v2.4.1.9

SEGMENT REPORTING (Narrative) (Details) | 3 Months Ended
--- | ---
Mar. 31, 2015 Facility
U.S. Iron Ore [Member] |
Segment Reporting Information [Line Items] |
Number of mines (in number of facilities) | 5 clf_NumberOfMines / us-gaap_StatementBusinessSegmentsAxis = clf_USIronOreMember
Asia Pacific Iron Ore [Member] |
Segment Reporting Information [Line Items] |
Number of mines (in number of facilities) | 1 clf_NumberOfMines / us-gaap_StatementBusinessSegmentsAxis = clf_AsiaPacificIronOreMember

X
- Definition Number of mines + References No definition available. + Details
Name: | clf_NumberOfMines
Namespace Prefix: | clf_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=clf_AsiaPacificIronOreMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=clf_USIronOreMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |