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Stock Incentive Plan (Schedule Of SSAR Exercise Price Range, Number Of Shares, Weighted Average Exercise Price And Remaining Contractual Lives) (Details) - Stock Appreciation Rights (SARs) - $ / shares
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
SSARs Outstanding (in shares) 1,060,192 1,458,611
SSARs Exercisable, Exercisable as of December 31 (in shares) 348,042  
SSARs Exercisable, Weighted Average Exercise Price (in dollars per share) $ 50.32  
$43.39 – $52.94    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Range of Exercise Prices, lower limit (in dollars per share) 43.39  
Range of Exercise Prices, upper limit (in dollars per share) $ 52.94  
SSARs Outstanding (in shares) 614,600  
SSAR Outstanding, Weighted Average Remaining Contractual Life (Years) 4 years 1 month 6 days  
SSARs Outstanding, Weighted Average Exercise Price (in dollars per share) $ 46.35  
SSARs Exercisable, Exercisable as of December 31 (in shares) 248,975  
SSARs Exercisable, Weighted Average Exercise Price (in dollars per share) $ 47.62  
$55.07 – $70.41    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Range of Exercise Prices, lower limit (in dollars per share) 55.07  
Range of Exercise Prices, upper limit (in dollars per share) $ 70.41  
SSARs Outstanding (in shares) 445,592  
SSAR Outstanding, Weighted Average Remaining Contractual Life (Years) 5 years  
SSARs Outstanding, Weighted Average Exercise Price (in dollars per share) $ 60.94  
SSARs Exercisable, Exercisable as of December 31 (in shares) 99,067  
SSARs Exercisable, Weighted Average Exercise Price (in dollars per share) $ 57.11