Stock-Based Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement, Noncash Expense [Abstract]

Schedule of Stock Options Roll Forward

A summary of the stock option activity under the Incentive Plan for the year ended December 31, 2023, is presented below:

Stock Options	Number of Stock Options	Weighted Average Exercise Price Per Share		Aggregate Intrinsic Value (1) (in millions)		Weighted Average Remaining Contractual Term (in years)
Outstanding as of December 31, 2022	682,074	$	365.34
Exercised	(15,624)	333.94
Forfeited	(11,250)	374.68
Outstanding as of December 31, 2023	655,200	$	365.93	$	110.1	4.0
Exercisable as of December 31, 2023	406,288	$	352.67	$	73.3	3.7
Unvested as of December 31, 2023	248,912	$	387.58	$	36.8	4.4

(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.

Summary Of Restricted Stock Units Activity

A summary of the restricted stock unit (“RSU”) activity under the Incentive Plan for the year ended December 31, 2023, is presented below:

Restricted Stock Units	Number of Restricted Stock Units	Weighted Average Grant-Date Fair Value Per Share		Aggregate Intrinsic Value (2) (in millions)		Weighted Average Remaining Contractual Term (in years)
Outstanding as of December 31, 2022	341,228	$	169.28
Granted	22,261	454.04
Converted	(159,205)	194.97
Forfeited	(840)	462.46
Outstanding as of December 31, 2023 (1)	203,444	$	179.13	$	108.4	1.5
Vested as of December 31, 2023	163,948	$	110.92	$	87.3	1.5

(1)No RSUs outstanding at December 31, 2023 were convertible to shares of common stock.

(2)The intrinsic value of RSUs is measured by applying the closing stock price as of December 31, 2023 to the applicable number of units.

^[1]

Schedule Of Stock Based Compensation Expense

Stock-based compensation expense consists of the following:

(In millions)	For the Years Ended December 31,
	2023		2022		2021
Stock options	$	33.5	$	33.8	$	33.7
Restricted stock units	5.6		2.7		(1.1)
Restricted stock	—		—		(7.8)
Total	$	39.1	$	36.5	$	24.8

Schedule Of Future Share-Based Compensation Cost

Assuming performance targets are achieved in the periods currently estimated, we expect to recognize the remaining expense for stock-based awards outstanding as of December 31, 2023 over a weighted average period of 0.9 years, as follows:

(In millions)
For the Years Ended December 31,	Stock Options		Restricted Stock Units		Total Projected Expense
2024	$	33.4	$	5.8	$	39.2
2025	5.2		5.0		10.2
2026	1.2		3.2		4.4
2027	—		0.1		0.1
Total	$	39.8	$	14.1	$	53.9

[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.