Quarterly report pursuant to Section 13 or 15(d)

SEGMENT REPORTING (Narrative) (Details)

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) 5clf_NumberOfMines
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
Asia Pacific Iron Ore [Member]  
Segment Reporting Information [Line Items]  
Number of mines (in number of facilities) 1clf_NumberOfMines
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember