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Share-Based Compensation (Stock Options) (Narrative) (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock options outstanding 2,339,667 2,420,922 2,408,917 1,995,440
Stock options exercisable 1,501,667 1,147,122 848,250  
Exercisable, average exercise price per share $ 196.37 $ 178.31 $ 143.55  
Stock Options [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expiration period, number of years 10 years      
Stock options outstanding, aggregate intrinsic value $ 38.6      
Average remaining contractual lives 6 years      
Aggregate intrinsic value for stock options exercisable $ 35.6      
Stock options exercisable 39,667      
Expiration date Jun. 30, 2021      
Exercisable, average exercise price per share $ 106.91      
Minimum [Member] | Stock Options [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period, number of years 3 years      
Maximum [Member] | Stock Options [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period, number of years 5 years      
Exercise Price Above $200 [Member] | Stock Options [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock options outstanding 1,360,000      
Range of exercise prices, upper $ 200