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Stock-Based Compensation (Summary Of Stock Options By Exercise Price Range) (Details)
12 Months Ended
Dec. 31, 2017
$ / shares
shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]  
Outstanding, number of shares | shares 63,000
Outstanding, average life 3 years 9 months 7 days
Outstanding, average price (usd per share) $ 63.84
Exercisable, number of shares | shares 63,000
Exercisable, average price (usd per share) $ 63.82
$57.34-$57.34  
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]  
Exercise price range, lower limit 57.34
Exercise price range, upper limit $ 57.34
Outstanding, number of shares | shares 23,000
Outstanding, average life 3 years 1 month 24 days
Outstanding, average price (usd per share) $ 57.34
Exercisable, number of shares | shares 23,000
Exercisable, average price (usd per share) $ 57.34
$66.14-$66.14  
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]  
Exercise price range, lower limit 66.14
Exercise price range, upper limit $ 66.14
Outstanding, number of shares | shares 40,000
Outstanding, average life 4 years 1 month 20 days
Outstanding, average price (usd per share) $ 66.14
Exercisable, number of shares | shares 40,000
Exercisable, average price (usd per share) $ 66.14