GOODWILL AND OTHER INTANGIBLE ASSETS AND LIABILITIES (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Line Items]
Goodwill, Impairment Loss	$ 0	$ 0
Product	1,913,500,000	1,832,400,000	$ 3,095,200,000
Cost of Sales [Member]
Goodwill [Line Items]
Amortization expense relating to intangible assets	4,800,000	4,200,000	8,400,000
Sales Revenue, Goods, Net [Member] | Sales Revenue, Goods, Net [Member]
Goodwill [Line Items]
Product	23,100,000	$ 23,100,000	23,100,000
Permits [Member]
Goodwill [Line Items]
Impairment of Intangible Assets, Finite-lived	0		13,800,000
Asia Pacific Iron Ore [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss			$ 73,500,000
U.S. Iron Ore [Member]
Goodwill [Line Items]
Goodwill	$ 2,000,000