Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2021

Share-based Payment Arrangement [Abstract]

Schedule of Compensation Expense

Stock-based compensation cost by award type follows:

(in millions)	Three Months Ended March 31,
	2021		2020
Stock option awards	$	3.6	$	3.2
Restricted stock awards	2.2		2.0
Performance share awards	2.5		2.0
Restricted stock units	—		1.4
Stock appreciation rights	3.1		(3.0)
Total stock-based compensation cost incurred	11.4		5.6
Capitalized (cost) credit during the period	(3.4)		2.7
Amortization of capitalized cost during the period	5.5		3.5
Total stock-based compensation expense	$	13.5	$	11.8