Annual report pursuant to Section 13 and 15(d)

Acquisitions And Other Investments (Freewest Purchase Price Allocation) (Details)

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Acquisitions And Other Investments (Freewest Purchase Price Allocation) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Business Acquisition [Line Items]    
Total net assets acquired   $ 1.7
Long-term deferred tax liabilities (1,041.8)  
Total net assets acquired   1.7
Freewest [Member] | Scenario, Previously Reported [Member]
    
Business Acquisition [Line Items]    
Equity instruments (4.2 million Cliffs common shares)   173.1
Cash   12.8
Fair value of total consideration transferred   185.9
Fair value of Cliffs' ownership interest in subsidiary held prior to acquisition of remaining interest   27.4
Total net assets acquired   213.3
Cash   7.7
Other current assets   1.4
Mineral rights   252.8
Marketable securities   12.1
Total identifiable assets acquired   274.0
Accounts payable   (3.3)
Long-term deferred tax liabilities   (57.4)
Total identifiable liabilities assumed   (60.7)
Total identifiable net assets acquired   213.3
Total net assets acquired   213.3
Freewest [Member] | Scenario, Adjustment [Member]
    
Business Acquisition [Line Items]    
Equity instruments (4.2 million Cliffs common shares)   173.1
Cash   12.8
Fair value of total consideration transferred   185.9
Fair value of Cliffs' ownership interest in subsidiary held prior to acquisition of remaining interest   27.4
Total net assets acquired   213.3
Cash   7.7
Other current assets   1.4
Mineral rights   244.0
Marketable securities   12.1
Total identifiable assets acquired   265.2
Accounts payable   (3.3)
Long-term deferred tax liabilities   (54.3)
Total identifiable liabilities assumed   (57.6)
Total identifiable net assets acquired   207.6
Goodwill   5.7
Total net assets acquired   213.3
Freewest [Member] | Scenario, Change [Member]
    
Business Acquisition [Line Items]    
Mineral rights   (8.8)
Total identifiable assets acquired   (8.8)
Long-term deferred tax liabilities   3.1
Total identifiable liabilities assumed   3.1
Total identifiable net assets acquired   (5.7)
Goodwill   $ 5.7