Stock-Based Compensation

9 Months Ended

Sep. 30, 2020

Share-based Payment Arrangement [Abstract]

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 and nine months ended September 30, 2020 and 2019:


	Three Months Ended September 30,				Nine Months Ended September 30,
(in millions)	2020		2019		2020		2019
Stock option compensation expense	$	0.5	$	0.7	$	2.1	$	2.0

RSU compensation expense	1.3		1.2		4.3		4.1
PSU compensation expense	—		(1.0)		(1.2)		0.2
Total stock-based compensation expense	$	1.8	$	0.9	$	5.2	$	6.3

We generally recognize compensation expense for stock-based awards ratably over the vesting period. Stock-based compensation expense for each of the nine months ended September 30, 2020 and 2019 includes $1.0 million of expense related to stock awards granted to eligible non-employee directors, which were fully vested on the grant date. During the third quarter of 2020, the Compensation Committee of the Company's Board of Directors approved stock compensation grants which consisted of 34,359 stock options, 10,311 RSUs and 20,618 PSUs.

The following table summarizes our unrecognized compensation expense and the weighted-average period over which the expense will be recognized as of September 30, 2020:


	September 30, 2020
	Unrecognized	Weighted Average
	Compensation	Years Expense To Be
(in millions, except weighted average years)	Expense	Recognized Over
Stock options	$4.1	1.9
RSUs	$6.9	1.9
PSUs	$0.6	2.3