SEGMENT REPORTING (Schedule Of Segment Reporting Information, By Segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues from product sales and services	$ 1,515.8	$ 1,546.6	$ 1,488.5	$ 1,140.5	$ 1,535.9	$ 1,544.9	$ 1,579.5	$ 1,212.4	$ 5,691.4		$ 5,872.7		$ 6,563.9
Revenues from producet sales and services, percent									100.00%		100.00%		100.00%
SALES MARGIN	294.5	348.7	268.2	237.9	238.5	198.3	443.5	291.8	1,149.3		1,172.1		2,610.9
Other operating expense									(478.3)		(1,480.9)		(314.1)
Other expense									(181.7)		(193.0)		(106.3)
Income (loss) from continuing operations before income taxes and equity income (loss) from ventures									489.3		(501.8)		2,190.5
Depreciation, depletion and amortization									593.3		525.8		426.9
Capital Additions									752.3	[1]	1,335.3	[1]	960.9	[1]
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from product sales and services									2,667.9		2,723.3		3,509.9
Revenues from producet sales and services, percent									47.00%		46.00%		53.00%
SALES MARGIN									901.9		976.2		1,679.3
Depreciation, depletion and amortization									120.3		100.9		86.2
Capital Additions									53.3	[1]	168.8	[1]	191.4	[1]
Eastern Canadian Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from product sales and services									978.7		1,008.9		1,178.1
Revenues from producet sales and services, percent									17.00%		17.00%		18.00%
SALES MARGIN									(103.3)		(121.4)		290.9
Depreciation, depletion and amortization									178.5		160.2		124.6
Capital Additions									625.5	[1]	865.2	[1]	303.1	[1]
Asia Pacific Iron Ore [Member]
Segment Reporting Information [Line Items]
Revenues from product sales and services									1,224.3		1,259.3		1,363.5
Revenues from producet sales and services, percent									22.00%		22.00%		21.00%
SALES MARGIN									367.1		311.0		699.5
Depreciation, depletion and amortization									153.7		151.9		100.9
Capital Additions									13.0	[1]	87.7	[1]	262.0	[1]
North American Coal [Member]
Segment Reporting Information [Line Items]
Revenues from product sales and services									821.9		881.1		512.1
Revenues from producet sales and services, percent									14.00%		15.00%		8.00%
SALES MARGIN									(14.5)		(1.8)		(58.4)
Depreciation, depletion and amortization									128.9		98.2		86.5
Capital Additions									55.0	[1]	144.1	[1]	181.0	[1]
All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues from product sales and services									(1.4)		0.1		0.3
Revenues from producet sales and services, percent									0.00%		0.00%		0.00%
SALES MARGIN									(1.9)		8.1		(0.4)
Depreciation, depletion and amortization									11.9		14.6		28.7
Capital Additions									$ 5.5	[1]	$ 69.5	[1]	$ 23.4	[1]

[1] Includes capital lease additions and non-cash accruals. Refer to NOTE 21 - CASH FLOW INFORMATION.