Annual report pursuant to Section 13 and 15(d)

DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Assets and Liabilities - Canadian Entities (Details)

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DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Assets and Liabilities - Canadian Entities (Details)
CAD in Thousands, $ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2015
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Jun. 30, 2016
CAD
Mar. 31, 2016
CAD
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]            
Deconsolidation, Gain (Loss), Amount     $ (528.2)      
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]            
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]            
Deconsolidation, Gain (Loss), Amount   $ (17.5) (710.9) $ 0.0    
Wabush [Member]            
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]            
Debtor-in-Possession Financing, Borrowings Outstanding   0.0        
Bloom Lake Group [Member]            
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]            
Deconsolidation, Gain (Loss), Amount $ 818.7          
Other Current Assets [Member] | Canadian Entities [Member]            
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]            
Debtor-in-Possession Financing, Borrowings Outstanding   1.5        
Debtor-in-possession,Repayment   8.3        
Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Canadian Entities [Member]            
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]            
Loans, Associated Interest and Accounts Receivable recognized in Consolidated Financials at Fair Value   48.6 72.9      
Other Current Liabilities [Member] | Bloom Lake Group [Member]            
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]            
Contingent Liabilities recognized in Consolidated Financials   37.0 35.9      
Guarantees [Member] | Bloom Lake Group [Member]            
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]            
Contingent Liabilities recognized in Consolidated Financials   $ 0.2 $ 96.5