Annual report pursuant to Section 13 and 15(d)

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

v2.4.0.8
SEGMENT REPORTING Segment Reporting (Summary of Assets by Segment) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Segment Reporting Information [Line Items]      
Assets $ 13,121.9 $ 13,574.9 $ 14,541.7
U.S. Iron Ore [Member]
     
Segment Reporting Information [Line Items]      
Assets 1,671.6 1,735.1 1,691.8
Eastern Canadian Iron Ore [Member]
     
Segment Reporting Information [Line Items]      
Assets 7,915.5 7,605.1 7,973.1
Asia Pacific Iron Ore [Member]
     
Segment Reporting Information [Line Items]      
Assets 1,078.4 1,506.3 1,814.4
North American Coal [Member]
     
Segment Reporting Information [Line Items]      
Assets 1,841.8 1,877.8 1,511.2
All Other Segments [Member]
     
Segment Reporting Information [Line Items]      
Assets 455.6 570.9 1,017.6
Total Segment Assets [Member]
     
Segment Reporting Information [Line Items]      
Assets 12,962.9 13,295.2 14,008.1
Corporate [Member]
     
Segment Reporting Information [Line Items]      
Assets $ 159.0 $ 279.7 $ 533.6