Quarterly report pursuant to Section 13 or 15(d)

SHAREHOLDERS' EQUITY Schedule of Shareholders' Equity (Details)

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SHAREHOLDERS' EQUITY Schedule of Shareholders' Equity (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Dec. 31, 2013
Dec. 31, 2012
Stockholders' Equity Attributable to Parent $ 30.7   $ 30.7   $ 6,069.5  
Stockholders' Equity Attributable to Noncontrolling Interest (208.0)   (208.0)   814.8  
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest (177.3) 6,934.6 (177.3) 6,934.6 6,884.3 5,760.9
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS (5,879.6) 117.2 (5,939.0) 370.2    
INCOME (LOSS) ATTRIBUTABLE TO NONCONTROLLING INTEREST (1,007.6) (3.3) (1,004.4) 5.8    
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (6,887.2) 113.9 (6,943.4) 376.0    
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent (5,960.8) 178.4 (5,927.5) 247.4    
Other Comprehensive Income (Loss), Net of Tax (80.7) 62.1 13.1 (119.6)    
OTHER COMPREHENSIVE INCOME ATTRIBUTABLE TO THE NONCONTROLLING INTEREST (0.5) (0.9) (1.6) (3.2)    
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest     (6,930.3) 256.4    
Stock and Other Incentive Plans     (3.4) 9.6    
Common and preferred share dividends     (107.9) (104.7)    
Undistributed Gains To Noncontrolling Interest     (20.0)      
Capital Contribution By Noncontrolling Interest       17.7    
Cliffs Shareholders Equity [Member]
            
Stockholders' Equity Attributable to Parent 30.7 5,779.7 30.7 5,779.7 6,069.5 4,632.7
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS     (5,939.0) 370.2    
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent     11.5 (122.8)    
Comprehensive Income (Loss), Net of Tax, Attributable to Parent     (5,927.5) 247.4    
Stock and Other Incentive Plans     (3.4) 9.6    
Common and preferred share dividends     (107.9) (104.7)    
Undistributed Gains To Noncontrolling Interest     0      
Capital Contribution By Noncontrolling Interest       0    
Noncontrolling Interest [Member]
            
Stockholders' Equity Attributable to Noncontrolling Interest (208.0) 1,154.9 (208.0) 1,154.9 814.8 1,128.2
INCOME (LOSS) ATTRIBUTABLE TO NONCONTROLLING INTEREST     (1,004.4) 5.8    
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest     1.6 3.2    
OTHER COMPREHENSIVE INCOME ATTRIBUTABLE TO THE NONCONTROLLING INTEREST     (1,002.8) 9.0    
Stock and Other Incentive Plans     0 0    
Common and preferred share dividends     0 0    
Undistributed Gains To Noncontrolling Interest     (20.0)      
Capital Contribution By Noncontrolling Interest       17.7    
Common Stock [Member]
            
Stock Issued During Period, Value, New Issues       285.3    
Common Stock [Member] | Cliffs Shareholders Equity [Member]
            
Stock Issued During Period, Value, New Issues       285.3    
Common Stock [Member] | Noncontrolling Interest [Member]
            
Stock Issued During Period, Value, New Issues       0    
Preferred Class A [Member]
            
Stock Issued During Period, Value, New Issues       709.4    
Preferred Class A [Member] | Cliffs Shareholders Equity [Member]
            
Stock Issued During Period, Value, New Issues       709.4    
Preferred Class A [Member] | Noncontrolling Interest [Member]
            
Stock Issued During Period, Value, New Issues       $ 0