Stock-based Compensation Plans (Schedule of Stock Options by Exercise Price Range) (Details)	12 Months Ended
	Dec. 31, 2020 $ / shares shares
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Price	$ 54.61
Options Outstanding, Number | shares	66,107
Options Outstanding, Weighted Average Remaining Contractual Lives	3 years 1 month 20 days
Options Outstanding, Weighted Average Exercise Price	$ 54.61
Options Currently Exercisable, Number | shares	66,107
Options Currently Exercisable, Weighted Average Exercise Price	$ 54.61
Exercise Price Range One [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range Limit	34.66
Range of Exercise Prices, Upper Range Limit	$ 40.01
Options Outstanding, Number | shares	42,573
Options Outstanding, Weighted Average Remaining Contractual Lives	1 year 9 months 21 days
Options Outstanding, Weighted Average Exercise Price	$ 38.33
Options Currently Exercisable, Number | shares	42,573
Options Currently Exercisable, Weighted Average Exercise Price	$ 38.33
Exercise Price Range Two [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range Limit	66.14
Range of Exercise Prices, Upper Range Limit	$ 68.41
Options Outstanding, Number | shares	102,996
Options Outstanding, Weighted Average Remaining Contractual Lives	4 years 1 month 28 days
Options Outstanding, Weighted Average Exercise Price	$ 66.15
Options Currently Exercisable, Number | shares	102,996
Options Currently Exercisable, Weighted Average Exercise Price	$ 66.15
Exercise Price Range Three [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range Limit	70.51
Range of Exercise Prices, Upper Range Limit	$ 77.91
Options Outstanding, Number | shares	154,014
Options Outstanding, Weighted Average Remaining Contractual Lives	5 years 4 months 6 days
Options Outstanding, Weighted Average Exercise Price	$ 75.45
Options Currently Exercisable, Number | shares	154,014
Options Currently Exercisable, Weighted Average Exercise Price	$ 75.45
Exercise Price Range Four [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range Limit	82.39
Range of Exercise Prices, Upper Range Limit	$ 92.68
Options Outstanding, Number | shares	246,844
Options Outstanding, Weighted Average Remaining Contractual Lives	6 years 2 months 19 days
Options Outstanding, Weighted Average Exercise Price	$ 85.39
Options Currently Exercisable, Number | shares	244,951
Options Currently Exercisable, Weighted Average Exercise Price	$ 85.33
Exercise Price Range Five [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range Limit	104.11
Range of Exercise Prices, Upper Range Limit	$ 105.53
Options Outstanding, Number | shares	266,274
Options Outstanding, Weighted Average Remaining Contractual Lives	7 years 1 month 28 days
Options Outstanding, Weighted Average Exercise Price	$ 104.12
Options Currently Exercisable, Number | shares	181,613
Options Currently Exercisable, Weighted Average Exercise Price	$ 104.12
Exercise Price Range Six [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range Limit	113.32
Range of Exercise Prices, Upper Range Limit	$ 118.54
Options Outstanding, Number | shares	403,470
Options Outstanding, Weighted Average Remaining Contractual Lives	8 years 9 months
Options Outstanding, Weighted Average Exercise Price	$ 117.96
Options Currently Exercisable, Number | shares	60,550
Options Currently Exercisable, Weighted Average Exercise Price	$ 117.07