Quarterly report pursuant to Section 13 or 15(d)

Environmental And Mine Closure Obligations (Narrative) (Detail)

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Environmental And Mine Closure Obligations (Narrative) (Detail) (USD $)
In Millions, unless otherwise specified
 6 Months Ended
Jun. 30, 2012
Dec. 31, 2011
Jun. 30, 2012
LTV Steel Mining Company [Member]
Jun. 30, 2012
U.S. Iron Ore [Member]
Jun. 30, 2012
Eastern Canadian Iron Ore [Member]
Jun. 30, 2012
North American Coal [Member]
Jun. 30, 2012
Asia Pacific Iron Ore [Member]
Jun. 30, 2012
Sonoma [Member]
Loss Contingencies [Line Items]                
Total environmental and mine closure obligations $ 244.1 $ 235.7            
Mine closure obligations, number of mines     1 4 2 6 1 1