Share-based compensation plans (Tables)

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Compensation expense by plan

Compensation expenses are classified as selling, general and administrative expenses in the condensed consolidated statements of operations. Compensation expenses for the share-based awards were as follows:

	Compensation Expense			Compensation Expense
	Three Months Ended September 30,			Nine Months Ended September 30,
(in millions)	2023		2022	2023		2022
Performance share units	$	3.7	10.5	$	16.6	26.3
Restricted stock units	2.4		3.3	8.0		8.7
Deferred stock units and fees paid in stock	0.3		0.3	1.0		1.0
Time-based vesting stock options	—		0.1	—		0.3
Cash based awards	0.1		0.1	1.6		1.2
Share-based payment expense	6.5		14.3	27.2		37.5
Income tax benefit	(1.5)		(3.4)	(6.3)		(8.7)
Share-based payment expense, net of tax	$	5.0	10.9	$	20.9	28.8

Option activity

The following table summarizes performance-based stock option activity during the first nine months of 2023:

	Shares (in thousands)	Weighted-Average Grant-Date Fair Value
Outstanding balance as of December 31, 2022	446.2	$	14.70
Exercised	(263.4)	12.47
Outstanding balance as of September 30, 2023	182.8	$	17.92

The following table summarizes time-based stock option activity during the first nine months of 2023: 

	Shares (in thousands)	Weighted-Average Grant-Date Fair Value
Outstanding balance as of December 31, 2022	161.6	$	21.41
Expired	—	—
Outstanding balance as of September 30, 2023	161.6	$	21.41

Nonvested share activity

The following table summarizes RSU activity during the first nine months of 2023: 

	Shares (in thousands)	Weighted-Average Grant-Date Fair Value
Nonvested balance as of December 31, 2022	309.3	$	67.25
Granted	194.8	65.76
Forfeited	(34.2)	64.86
Vested	(138.7)	68.93
Nonvested balance as of September 30, 2023	331.2	$	65.92

The following table summarizes all PSU activity during the first nine months of 2023:

	Shares (in thousands)	Weighted-Average Grant-Date Fair Value
Nonvested balance as of December 31, 2022	726.0	$	76.66
Granted	235.4	69.09
Forfeited or expired(a)	(80.9)	81.55
Vested(b)	(171.5)	82.75
Nonvested balance as of September 30, 2023	709.0	$	72.12

(a)Although the service condition had been met, 31.4 thousand TSR PSUs granted in 2020 expired in accordance with the market condition terms of the underlying award agreement. These units had a weighted average grant-date fair value of $94.52 per share.

(b)The vested PSUs presented are based on the target amount of the award. In accordance with the terms of the underlying award agreements, the actual shares earned and distributed for the performance period ended December 31, 2022 were 208.1 thousand, compared to target shares of 171.5 thousand.

The following table summarizes all DSU activity during the first nine months of 2023:

	Shares (in thousands)	Weighted-Average Grant-Date Fair Value
Nonvested balance as of December 31, 2022	19.7	$	54.74
Granted	19.2	62.43
Vested	(18.6)	54.67
Nonvested balance as of September 30, 2023	20.3	$	62.09