DISCONTINUED OPERATIONS (Schedule of Disposal Groups, including Discontinued Operations, Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
LOSS FROM DISCONTINUED OPERATIONS, NET OF TAX	$ (64.3)	$ (53.7)	$ (135.2)	$ (5.0)
Asia Pacific Iron Ore [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues from product sales and services	70.1	98.0	129.1	273.4
Cost of goods sold and operating expenses	106.1	97.1	230.2	225.2
Sales margin	(36.0)	0.9	(101.1)	48.2
Other operating expense	(16.2)	(3.2)	(18.8)	(3.7)
Other expense	(1.1)	(1.3)	(2.2)	(2.7)
Loss from discontinued operations before income taxes	(53.3)	(3.6)	(122.1)	41.8
Impairment of long-lived assets	0.0	0.0	(2.6)	0.0
Income tax expense	0.0	(3.7)	0.0	(0.8)
LOSS FROM DISCONTINUED OPERATIONS, NET OF TAX	$ (53.3)	$ (7.3)	$ (124.7)	$ 41.0