Stock-based compensation

3 Months Ended

Mar. 31, 2023

Share-Based Payment Arrangement [Abstract]

10. Stock-based compensation

The following table presents the components of stock-based compensation expense:


(in millions)	Classification	Three months ended March 31,
		2023		2022
Stock options	Equity	$	3.6	$	4.0
RSUs	Equity	8.7		7.6
Other	Both	0.4		(0.9)
Total		$	12.7	$	10.7
Award classification:
Equity		$	12.6	$	12.0
Liability		0.1		(1.3)

At March 31, 2023, unvested awards under our plans have remaining stock-based compensation expense of $112.6 million to be recognized over a weighted average period of 2.1 years.

Stock options

The following table presents information about outstanding stock options:


(options and intrinsic value in millions)	Number of options	Weighted average exercise price per option		Aggregate intrinsic value		Weighted average remaining term
Balance at December 31, 2022	16.1	$	20.90
Granted	1.5	24.62
Exercised	(0.1)	13.19
Forfeited	(0.1)	22.39
Balance at March 31, 2023	17.4	21.26		$	40.5	6.2 years
Expected to vest	4.5	24.15		6.6		8.4 years
Vested	12.9	20.25		33.9		5.4 years

During the three months ended March 31, 2023, we granted stock options that have a contractual life of ten years and will vest annually over four years, subject to the recipient continuously providing service to us through such date.

RSUs

The following table presents information about unvested RSUs:


(awards in millions)	Number of awards	Weighted average grant date fair value per award
Balance at December 31, 2022	4.2	$	24.29
Granted	1.6	26.88
Vested	(0.9)	21.22
Forfeited	—	27.81
Balance at March 31, 2023	4.9	25.76

During the three months ended March 31, 2023, we granted RSUs that will vest annually over three to four years, subject to the recipient continuously providing service to us through each such date. Certain of those awards contain performance and market conditions that impact the number of shares that will ultimately vest. The expense recorded on such awards for the three months ended March 31, 2023 and March 31, 2022 was $2.3 million and $2.3 million, respectively.