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Stock-Based Compensation Unrestricted Stock Awards Summary (Details) (Unrestricted Stock Award [Member], USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Unrestricted Stock Award [Member]
     
[Line Items]      
Shares of unrestricted stock granted 18,569 11,397 5,662
Weighted average grant date fair value per share $ 41.43 $ 41.19 $ 64.35