XML 18 R28.htm IDEA: XBRL DOCUMENT v3.3.0.814
Equity-Based Compensation (Fair Value Of Performance Share Awards) (Details) - Performance shares [Member] - $ / shares
9 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares granted (in shares) 78,974 87,441
Stock price as of valuation date (in dollars per share) $ 40.00 $ 39.76
Risk-free rate 1.07% 0.72%
Fair value of a performance share (in dollars per share) $ 36.71 $ 45.57