Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2024

Share-Based Payment Arrangement [Abstract]

Valuation Assumptions on PSU Grants

The fair value of PSUs is estimated on the date of initial grant using the Monte-Carlo simulation model. Key assumptions used to value PSUs granted during 2020 are as follows:

	Year Ended December 31, 2020
Expected Volatility (based on our and our peer group historical daily stock prices)	23	%
Expected Life (equals the performance period)	3 years
Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant)	0.85	%

Activity for CIUs

Activity for CIUs, which are classified as a liability, is as follows:

	Units
	(000s)
Outstanding at December 31, 2023	17,028
Granted	16,187
Vested	(13,442)
Forfeited	(3,318)
Outstanding at December 31, 2024	16,455

Schedule of Cash-based Payment Award, Cash-incentive Units, Valuation Assumptions

The fair value of CIUs is estimated at each reporting period using the Monte-Carlo simulation model. Key assumptions used to value CIUs granted are as follows:

	Assumptions as of the Year Ended December 31, 2024
	2024 Grant		2023 Grant
Expected Volatility (based on our and our peer group historical daily stock prices)	30	%	30	%
Expected Life (equals the performance period)	2 years		1 year
Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant)	4.25	%	4.19	%

	Assumptions as of the Year Ended December 31, 2023
	2023 Grant		2022 Grant
Expected Volatility (based on our and our peer group historical daily stock prices)	30	%	27	%
Expected Life (equals the performance period)	2 years		1 year
Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant)	4.26	%	4.75	%

	Assumptions as of the Year Ended December 31, 2022
	2022 Grant		2021 Grant
Expected Volatility (based on our and our peer group historical daily stock prices)	30	%	33	%
Expected Life (equals the performance period)	2 years		1 year
Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant)	4.26	%	4.60	%

Activity for Restricted Stock Units

Activity for RSUs, which are classified as equity, is as follows:

		Weighted Average
	Shares	Grant Date
	(000s)	Fair Value
Outstanding at December 31, 2023	1,213	$	35.51
Granted	825	49.57
Vested	(906)	37.88
Forfeited	(145)	40.71
Outstanding at December 31, 2024	987	44.31

Schedule of Compensation Cost for Share-based Payment Arrangements

Compensation expense for the stock based plans, as reported in our consolidated statements of income, is as follows:

	Year Ended December 31
	2024		2023		2022
	(in millions of dollars)
Performance Share Units	$	—	$	0.3	$	5.7
Cash Incentive Units	12.4		21.7		12.8
Restricted Stock Units and Cash-Settled Restricted Stock Units	34.5		40.6		32.7
Stock Success Units	0.1		0.9		0.9
Other	0.8		0.6		0.6
Total Compensation Expense, Before Income Tax	$	47.8	$	64.1	$	52.7
Total Compensation Expense, Net of Income Tax	$	41.6	$	57.5	$	47.3