Stock-Based Compensation Plans (Summary Of Restricted Stock Units Activity) (Details) - Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	12 Months Ended
		May 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, as of December 31			341,228
Granted			22,261
Converted			(159,205)
Forfeited		31,000	840
Outstanding, as of December 31			203,444	341,228
Vested			163,948
Weighted Average Grant-Date Fair Value Per Share, Outstanding as of December 31			$ 169.28
Weighted Average Grant-Date Fair Value Per Share, Nonvested, Granted			454.04	$ 488.27	$ 366.07
Weighted Average Grant-Date Fair Value Per Share, Nonvested, Converted			194.97
Weighted Average Grant-Date Fair Value Per Share, Nonvested, Forfeited			462.46
Weighted Average Grant-Date Fair Value Per Share, Outstanding as of December 31			179.13	$ 169.28
Weighted Average Grant-Date Fair Value Per Share, Vested as of December 31			$ 110.92
Aggregate Intrinsic Value, Outstanding	[1]		$ 108.4
Aggregate Intrinsic Value, Vested	[1]		$ 87.3
Weighted Average Remaining Contractual Term, Outstanding			1 year 6 months
Weighted Average Remaining Contractual Term, Vested			1 year 6 months

[1] The intrinsic value of RSUs is measured by applying the closing stock price as of December 31, 2023 to the applicable number of units.