Quarterly report pursuant to Section 13 or 15(d)

EARNINGS PER SHARE (Earnings Per Share Computation) (Details)

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EARNINGS PER SHARE (Earnings Per Share Computation) (Details) (USD $)
In Millions, except Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Earnings Per Share [Abstract]    
Income from Discontinued Operations, net of tax $ 0 $ 5.5
NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS 107.0 375.8
PREFERRED STOCK DIVIDENDS (9.9) 0
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS $ 97.1 $ 375.8
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount 12,900,000  
Weighted Average Number of Shares:    
Basic 147,827,000 142,226,000
Employee Stock Plans 254,000 483,000
Depositary Shares 0 0
Diluted 148,081,000 142,709,000
Earnings per Common Share Attributable to Cliffs Shareholders - Basic:    
Continuing operations $ 0.66 $ 2.60
Discontinued operations $ 0.00 $ 0.04
Earnings per Common Share Attributable to Cliffs Shareholders - Basic: $ 0.66 $ 2.64
Earnings per Common Share Attributable to Cliffs Shareholders - Diluted:    
Continuing operations $ 0.66 $ 2.59
Discontinued operations $ 0.00 $ 0.04
Earnings per Common Share Attributable to Cliffs Shareholders - Diluted: $ 0.66 $ 2.63