Quarterly report pursuant to Section 13 or 15(d)

SEGMENT REPORTING (Schedule Of Segment Reporting Information, By Segment) (Details)

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SEGMENT REPORTING (Schedule Of Segment Reporting Information, By Segment) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Segment Reporting Information [Line Items]    
Revenues from product sales and services $ 1,140.5 $ 1,212.4
Revenues from product sales and services, percent 100.00% 100.00%
Sales margin 237.9 291.8
Other operating expense (69.6) (68.9)
Other income (expense) (48.0) (43.3)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES AND EQUITY LOSS FROM VENTURES 120.3 179.6
Depreciation, depletion and amortization 140.6 117.3
Capital additions 195.7 [1] 353.4 [1]
U.S. Iron Ore [Member]
   
Segment Reporting Information [Line Items]    
Revenues from product sales and services 410.1 441.7
Revenues from product sales and services, percent 36.00% 36.00%
Sales margin 157.3 166.9
Depreciation, depletion and amortization 26.6 23.2
Capital additions 11.7 [1] 34.8 [1]
Eastern Canadian Iron Ore [Member]
   
Segment Reporting Information [Line Items]    
Revenues from product sales and services 245.3 220.7
Revenues from product sales and services, percent 22.00% 18.00%
Sales margin 19.4 (14.3)
Depreciation, depletion and amortization 41.1 37.9
Capital additions 167.0 [1] 130.6 [1]
Asia Pacific Iron Ore [Member]
   
Segment Reporting Information [Line Items]    
Revenues from product sales and services 270.8 359.8
Revenues from product sales and services, percent 24.00% 30.00%
Sales margin 61.3 125.0
Depreciation, depletion and amortization 36.4 30.0
Capital additions 4.3 [1] 109.3 [1]
North American Coal [Member]
   
Segment Reporting Information [Line Items]    
Revenues from product sales and services 214.3 189.9
Revenues from product sales and services, percent 18.00% 16.00%
Sales margin 1.8 14.5
Depreciation, depletion and amortization 32.5 20.1
Capital additions 11.1 [1] 39.1 [1]
All Other Segments [Member]
   
Segment Reporting Information [Line Items]    
Revenues from product sales and services 0 0.3
Revenues from product sales and services, percent 0.00% 0.00%
Sales margin (1.9) (0.3)
Depreciation, depletion and amortization 4.0 6.1
Capital additions $ 1.6 [1] $ 39.6 [1]
[1] Includes capital lease additions and non-cash accruals. Refer to NOTE 20 - CASH FLOW INFORMATION.