Share-based Payments (Tables)

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

Compensation Costs Related to Share-Based Payments

The following table summarizes the components of share-based payment expense by consolidated income statement classification:

	Three months ended June 30,				Six months ended June 30,
	2024		2023		2024		2023
Selling, general and administrative:
Stock option compensation expense	$	0.8	$	1.6	$	2.3	$	4.3
Equity-classified share units	17.3		9.4		25.6		12.9
Liability-classified share units	0.2		0.5		1.5		0.5
Employee share purchase plan	1.7		0.8		4.6		1.3
	20.0		12.3		34.0		19.0
Acquisition-related and integration costs:
Acceleration of share-based payments expense	—		0.9		0.9		5.9
Share-based continuing employment costs	—		0.9		0.2		1.9
	—		1.8		1.1		7.8
	$	20.0	$	14.1	$	35.1	$	26.8

Share-Based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity

The following table summarizes share unit activity for the six months ended June 30, 2024:

	Equity-classified share units									Liability-classified share units
	PSUs with Performance Conditions			PSUs with Market Conditions			RSUs			DSUs
	Number	WA grant date fair value		Number	WA grant date fair value		Number	WA grant date fair value		Number	WA grant date fair value
Outstanding, December 31, 2023	415,429	$	58.35	174,260	$	74.83	539,671	$	53.64	100,560	$	38.36
Granted	150,461	75.42		149,444	121.25		309,807	75.46		10,103	71.43
Vested and settled	(114,315)	58.79		—	—		(223,389)	53.50		(3,759)	59.05
Forfeited	(15,175)	57.92		(10,399)	81.35		(22,832)	57.29		—	—
Outstanding at June 30, 2024	436,400	$	64.13	313,305	$	96.76	603,257	$	64.76	106,904	$	40.76

Summary of Significant Assumptions Used to Estimate the Fair Value of Stock Options

The fair value of PSUs with market vesting conditions granted during the six months ended June 30, 2024 was estimated on the respective grant dates using a Monte Carlo simulation model incorporating the following significant assumptions, presented on a weighted average basis:

Risk free interest rate	4.5	%
Expected lives of the PSUs	3 years
Expected volatility	32.3	%
Average expected volatility of comparable companies	48.3	%