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Equity-Based Compensation (Fair Value Of Performance Share Awards) (Details) (Performance shares [Member], USD $)
6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Performance shares [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares granted (in shares) 83,111 85,028
Stock price as of valuation date (in dollars per share) $ 45.31 $ 31.11
Risk-free rate 0.40% 0.40%
Fair value of a performance share (in dollars per share) $ 62.78 $ 34.24