Inventories (Schedule Of Inventory) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Finished Goods	$ 395.7	$ 198.0
Work-in Process	132.5	71.2
Total Inventory	528.2	269.2
U.S. Iron Ore [Member]
Finished Goods	235.4	101.1
Work-in Process	21.5	9.7
Total Inventory	256.9	110.8
Eastern Canadian Iron Ore [Member]
Finished Goods	101.1	43.5
Work-in Process	28.8	21.2
Total Inventory	129.9	64.7
North American Coal [Member]
Finished Goods	7.1	16.1
Work-in Process	65.9	19.8
Total Inventory	73.0	35.9
Asia Pacific Iron Ore [Member]
Finished Goods	37.5	34.7
Work-in Process	14.0	20.4
Total Inventory	51.5	55.1
Other Segment [Member]
Finished Goods	14.6	2.6
Work-in Process	2.3	0.1
Total Inventory	$ 16.9	$ 2.7