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Share-Based Compensation (Summary of Stock Option Activity) (Details) - $ / shares
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]      
Number of Stock Options Outstanding, Beginning of period (in shares) 2,626,487 3,316,782 4,926,522
Number of Stock Options, Exercised (in shares) (1,219,820) (682,054) (1,578,050)
Number of Stock Options, Forfeited or expired (in shares) (296) (8,241) (31,690)
Number of Stock Options Outstanding, End of period (in shares) 1,406,371 2,626,487 3,316,782
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]      
Weighted-Average Exercise Price, Outstanding Beginning of period (in dollars per share) $ 27.74 $ 27.56 $ 25.21
Weighted-Average Exercise Price, Exercised (in dollars per share) 34.00 26.84 20.31
Weighted-Average Exercise Price, Forfeited or expired (in dollars per share) 23.31 28.53 24.23
Weighted-Average Exercise Price, Outstanding End of period (in dollars per share) $ 22.32 $ 27.74 $ 27.56