Stock-Based Compensation

3 Months Ended

Mar. 31, 2021

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

7. Stock-Based Compensation

The following table summarizes our stock-based compensation expense (including stock options, restricted stock units ("RSUs") and performance stock units ("PSUs")) for the three months ended March 31, 2021 and 2020:

	Three Months Ended March 31,
(in millions)	2021		2020
Stock option compensation expense	$	1.7	$	0.8
RSU compensation expense	2.5		1.0
PSU compensation expense	0.6		(0.9)
Total stock-based compensation expense	$	4.8	$	0.9

We generally recognize compensation expense for stock-based awards ratably over the vesting period. During the first quarter of 2021, the Compensation Committee of the Company's Board of Directors approved stock compensation grants which consisted of 1,526,654 stock options, 254,460 RSUs and 1,652,526 PSUs.

The following table summarizes our unrecognized compensation expense and the weighted-average period over which the expense will be recognized as of March 31, 2021:

	March 31, 2021
	Unrecognized	Weighted Average
	Compensation	Years Expense To Be
(in millions, except weighted average years)	Expense	Recognized Over
Stock options	$5.2	2.4
RSUs	$5.2	2.1
PSUs	$15.0	2.4