Stock-based Compensation Plans (Summary of Stock Option Plan Activity) (Details) - $ / shares		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Shares
Outstanding, beginning of period, Shares		1,121,559	1,099,076	1,062,177
Granted, Shares	[1]	242,598	252,813	301,152
Exercised, Shares		(54,721)	(191,601)	(210,190)
Forfeited or cancelled, Shares		(27,158)	(38,729)	(54,063)
Outstanding, end of period, Shares		1,282,278	1,121,559	1,099,076
Exercisable, end of period, Shares		852,804	662,555	515,286
Weighted Average Exercise Price
Outstanding, beginning of period, Weighted Average Exercise Price		$ 87.88	$ 85.75	$ 75.53
Granted, Weighted Average Exercise Price	[1]	118.34	119.36	110.98
Exercised, Weighted Average Exercise Price		75.86	71.20	69.41
Forfeited or cancelled, Weighted Average Exercise Price		112.18	107.34	89.09
Outstanding, end of period, Weighted Average Exercise Price		93.64	87.88	85.75
Exercisable, end of period, Weighted Average Exercise Price		$ 82.76	$ 75.63	$ 69.83

[1] In accordance with plan provisions, 2019 includes 67,605 options related to special dividends paid by the Company in January 2019 and December 2019, in order to retain the intrinsic value of outstanding awards. The remaining 185,208 option awards were granted at an exercise price of $119.36.