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Stock-Based Compensation Plans (Details 1) (Restricted Stock [Member], USD $)
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Restricted Stock [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Restricted stock granted 297,859 71,752 73,255
Weighted average market price $ 38.44 $ 38.43 $ 43.68
Weighted average vesting period (years) 2.27 4.74 4.42