Quarterly report pursuant to Section 13 or 15(d)

DISCONTINUED OPERATIONS DISCONTINUED OPERATIONS (Narrative) (Details)

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DISCONTINUED OPERATIONS DISCONTINUED OPERATIONS (Narrative) (Details)
CAD in Thousands, $ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2016
USD ($)
Sep. 30, 2015
USD ($)
Sep. 30, 2016
USD ($)
Sep. 30, 2015
USD ($)
Sep. 30, 2016
CAD
Mar. 08, 2016
CAD
Dec. 31, 2015
USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Deconsolidation, Gain (Loss), Amount       $ 528.2      
Loans to and accounts receivable from the Canadian Entities $ 69.3   $ 69.3       $ 72.9
Guarantees 0.2   0.2       96.5
Sale amount for Pointe Noire port and rail assets | CAD           CAD 66,750  
Sale Amount of the Bloom Lake Mine and Labrador Trough South mineral claims | CAD         CAD 10,500    
Canadian Entities [Member]              
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Discontinued Operation, Tax Effect of Discontinued Operation 0.0 $ (0.7) 0.0 0.0      
Deconsolidation, Gain (Loss), Amount (0.9) (13.4) 3.2 (697.4)      
Cost Method Investments 0.0   0.0        
Contingent Liabilities of Deconsolidated Entities 0.0 0.5 0.0 (203.1)      
Wabush [Member]              
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Debtor-in-Possession Financing, Amount Arranged 10.0   10.0        
Debtor-in-Possession Financing, Borrowings Outstanding 0.0   0.0        
North American Coal [Member]              
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Discontinued Operation, Tax Effect of Discontinued Operation 0.0 $ (2.1) 0.0 $ (2.6)      
Other Current Assets [Member] | Canadian Entities [Member]              
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Debtor-in-Possession Financing, Borrowings Outstanding 1.5   1.5       6.8
Debtor-in-possession,Repayment 8.3   8.3        
Other Liabilities [Member] | Bloom Lake Group [Member]              
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Contingent Liabilities recognized in Consolidated Financials $ 37.9   $ 37.9       $ 35.9