Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [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,
	2018		2017		2018		2017
Stock option awards	$	3.2	$	1.8	$	7.8	$	5.3
Restricted stock awards	2.3		1.3		6.4		3.9
Performance share awards	2.2		1.4		6.1		4.0
Restricted stock units	—		—		1.4		1.4
Total stock-based compensation cost	$	7.7	$	4.5	$	21.7	$	14.6