Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Schedule of Compensation Expense

Stock-based compensation cost by award type follows:

(in millions)	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Stock option awards	$	1.9	$	2.1	$	7.8	$	7.6
Restricted stock awards	1.7		2.0		5.6		5.8
Performance share awards	1.7		1.7		6.0		5.2
Restricted stock units	—		—		—		1.4
Stock appreciation rights	—		0.9		9.0		(2.5)
Total stock-based compensation cost incurred	5.3		6.7		28.4		17.5
Capitalized (cost) credit during the period	—		(1.1)		(9.3)		1.8
Amortization of capitalized (credit) cost during the period	—		(0.1)		14.3		0.1
Total stock-based compensation expense	$	5.3	$	5.5	$	33.4	$	19.4