Annual report pursuant to Section 13 and 15(d)

SEGMENT REPORTING (Revenue from External Customers by Products and Services) (Details)

v3.8.0.1
SEGMENT REPORTING (Revenue from External Customers by Products and Services) (Details) - Sales Revenue, Net [Member] - Product Concentration Risk [Member]
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Revenue from External Customer [Line Items]      
Concentration Risk, Percentage 100.00% 100.00% 100.00%
Iron Ore Revenue [Member]      
Revenue from External Customer [Line Items]      
Concentration Risk, Percentage 90.00% 91.00% 91.00%
Freight and Venture Partners' Cost Reimbursements [Member]      
Revenue from External Customer [Line Items]      
Concentration Risk, Percentage 10.00% 9.00% 9.00%