Quarterly report pursuant to Section 13 or 15(d)

Earnings Per Share (Calculation of Earnings Per Common Share on Basic and Diluted) (Details)

 v2.3.0.11
Earnings Per Share (Calculation of Earnings Per Common Share on Basic and Diluted) (Details) (USD $)
In Millions, except Share data
3 Months Ended 6 Months Ended
Jun. 30, 2011
Jun. 30, 2010
Jun. 30, 2011
Jun. 30, 2010
Earnings Per Share        
Net income attributable to Cliffs shareholders $ 407.7 $ 260.7 $ 831.1 $ 338.1
Weighted average number of shares:        
Basic 139,000,000 135,319,000 137,243,000 135,247,000
Employee stock plans 800,000 800,000 800,000 800,000
Diluted 139,783,000 136,134,000 137,987,000 136,041,000
Earnings per common share attributable to Cliffs shareholders - Basic $ 2.93 $ 1.93 $ 6.06 $ 2.50
Earnings per common share attributable to Cliffs shareholders - Diluted $ 2.92 $ 1.92 $ 6.02 $ 2.49