Stock Based Compensation Plans (Summary of Stock Options Activity) (Details) - Equity Option [Member] - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, as of December 31		655,200	682,074
Exercised		(15,624)
Forfeited		11,250
Options Outstanding, as of December 31, Weighted Average Exercise Price		$ 365.93	$ 365.34
Options Exercised, Weighted Average Exercise Price		333.94
Options Forfeited, Weighted Average Exercise Price		$ (374.68)
Options Outstanding, Intrinsic Value	[1]	$ 110.1
Options Outstanding, Weighted Average Remaining Contractual Term		4 years
Options Exercisable, Number		406,288
Options Exercisable, Weighted Average Exercise Price		$ 352.67
Options Exercisable, Intrinsic Value	[1]	$ 73.3
Options Exercisable, Weighted Average Remaining Contractual Term		3 years 8 months 12 days
Options, Nonvested, Number		248,912
Options Nonvested, Weighted Average Exercise Price		$ 387.58
Options, Nonvested, Aggregate Intrinsic Value	[1]	$ 36.8
Options Nonvested, Weighted Average Remaining Contractual Term		4 years 4 months 24 days

[1] The intrinsic value of stock options is the amount by which the market price of the stock as of December 31, 2023 exceeded the exercise price of the options