BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Investments In Unconsolidated Ventures) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Investment	$ 106.4		$ 108.4
Amapa [Member] | Investments In Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Interest Percentage	30.00%
Total percentage of Amapa sold	100.00%
Investment	96.9		101.9
Cockatoo [Member] | Other Liabilities [Member]
Schedule of Equity Method Investments [Line Items]
Interest Percentage	50.00%
Investment	(25.4)		(25.3)
Hibbing [Member] | Investments In Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Investment	1.4	[1]
Hibbing [Member] | Other Liabilities [Member]
Schedule of Equity Method Investments [Line Items]
Investment			(2.1)	[1]
Other Equity Investees [Member] | Investments In Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Investment	$ 33.5		$ 33.9
Hibbing [Member] | Hibbing [Member] | Investments In Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Interest Percentage	23.00%	[1]

[1] At December 31, 2012 the classification for Hibbing was Other liabilities.