Environmental and Mine Closure Obligations (Summary of Mine Closure Obligations) (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Environmental	$ 13.7	$ 13.7
Mine closure	208.1	185.4
Total environmental and mine closure obligations	221.8	199.1
Less current portion	14.3	14.2
Long term environmental and mine closure obligations	207.5	184.9
Mine closure [Member] | LTV Steel Mining Company [Member]
Mine closure	17.6	17.1
U.S. Iron Ore [Member] | Owned or Operating Facilities [Member]
Mine closure	65.9	62.7
Eastern Canadian Iron Ore [Member] | Owned or Operating Facilities [Member]
Mine closure	66.2	49.3
Asia Pacific Iron Ore [Member] | Owned or Operating Facilities [Member]
Mine closure	16.7	15.4
North American Coal [Member] | Owned or Operating Facilities [Member]
Mine closure	35.0	34.7
Owned or Operating Facilities [Member] | Other Regions [Member]
Mine closure	$ 6.7	$ 6.2