BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Investments In Unconsolidated Ventures) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Investment	$ 71.5		$ 108.4
Investments in Ventures [Member] | Amapa [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest, equity method investment	30.00%
Total percentage of Amapa sold	100.00%
Investment	29.4		101.9
Investments in Ventures [Member] | Hibbing [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest, equity method investment	23.00%	[1]
Investment	8.3	[1]
Investments in Ventures [Member] | Other Equity Investees [Member]
Schedule of Equity Method Investments [Line Items]
Investment	33.8		33.9
Other Noncurrent Liabilities [Member] | Cockatoo [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest, equity method investment	0.00%	[2]	50.00%	[2]
Investment			(25.3)	[2]
Other Noncurrent Liabilities [Member] | Hibbing [Member]
Schedule of Equity Method Investments [Line Items]
Investment			$ (2.1)	[1]

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

[2] At December 31, 2012 our ownership interest percentage for Cockatoo was 50 percent.