Share-Based Compensation Plans (Schedule of Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at the beginning of year (in shares)	106,485
Granted (in shares)	488	0
Exercised (in shares)	(105,803)
Forfeited or expired (in shares)	(488)
Outstanding at the end of year (in shares)	682	106,485
Exercisable at the end of year (in shares)	273
Outstanding at the beginning of year, Weighted-Average Exercise Price (in dollars per share)	$ 44.18
Granted, Weighted-Average Exercise Price (in dollars per share)	111.34
Exercised, Weighted-Average Exercise Price (in dollars per share)	43.48
Forfeited or Expired, Weighted-Average Exercise Price (in dollars per share)	111.34
Outstanding at the end of year, Weighted-Average Exercise Price (in dollars per share)	152.34	$ 44.18
Exercisable at the end of the year, Weighted-Average Exercise Price (in dollars per share)	$ 152.34
Outstanding at the end of year, Weighted-Average Remaining Contractual Term (in years)	7 years 1 month
Exercisable at the end of year, Weighted-Average Remaining Contractual Term (in years)	7 years 1 month
Outstanding at the end of year, Aggregate Intrinsic Value	$ 0
Exercisable at the end of year, Aggregate Intrinsic Value	$ 0