Share-Based Compensation Plans (Schedule of Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	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]
Outstanding at the beginning of year (in shares)	313,802
Granted (in shares)	682	0	0
Exercised (in shares)	(55,365)
Forfeited or expired (in shares)	0
Outstanding at the end of year (in shares)	259,119	313,802
Exercisable at the end of year (in shares)	258,437
Outstanding at the beginning of year, Weighted-Average Exercise Price (in dollars per share)	$ 60.93
Granted, Weighted-Average Exercise Price (in dollars per share)	152.34
Exercised, Weighted-Average Exercise Price (in dollars per share)	82.03
Forfeited or Expired, Weighted-Average Exercise Price (in dollars per share)	0.00
Outstanding at the end of year, Weighted-Average Exercise Price (in dollars per share)	56.66	$ 60.93
Exercisable at the end of the year, Weighted-Average Exercise Price (in dollars per share)	$ 56.41
Outstanding at the end of year, Weighted-Average Remaining Contractual Term (in years)	1 year 8 months
Exercisable at the end of year, Weighted-Average Remaining Contractual Term (in years)	1 year 8 months
Outstanding at the end of year, Aggregate Intrinsic Value	$ 22,148
Exercisable at the end of year, Aggregate Intrinsic Value	$ 22,148