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Stock-Based Compensation Plans (Details 2) (USD $)
In Millions, except Per Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Schedule of of information on performance share units      
Compensation expense $ 13.7 $ 15.4 $ 12.8
Weighted-average grant date fair value $ 31.78    
Performance Share Units [Member]
     
Schedule of of information on performance share units      
Compensation expense $ 1.7 $ 4.1 $ 1.8
Weighted-average grant date fair value $ 31.78 $ 44.85 $ 35.26
Payout levels for shares paid 0.00% 127.70% 200.00%