Stock Based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Stock Based Compensation Activity

The following table shows a summary of PSU activity during the three and six months ended June 30, 2018 and 2017:

	Three Months Ended   June 30,						Six Months Ended   June 30,
	2018			2017			2018			2017
PSU compensation expense	$	3.1		$	3.2		$	7.3		$	0.1
Income tax benefit	(0.4		)	(1.1		)	(1.3		)	—
PSU compensation expense, net of tax	$	2.7		$	2.1		$	6.0		$	0.1
PSUs granted	—			—			—			237,623
Weighted average grant date fair value per unit	$	—		$	—		$	—		$	112.32
Total fair value of vested PSUs	$	25.6		$	29.4		$	25.6		$	29.4

The following table shows a summary of RSU activity during the three and six months ended June 30, 2018 and 2017:

	Three Months Ended   June 30,						Six Months Ended   June 30,
	2018			2017			2018			2017
RSU compensation expense	$	8.7		$	6.1		$	13.8		$	10.8
Income tax benefit	(1.5		)	(2.1		)	(2.3		)	(3.8		)
RSU compensation expense, net of tax	$	7.2		$	4.0		$	11.5		$	7.0
RSUs granted	32,330			31,554			421,829			205,199
Weighted average grant date fair value per unit	$	89.56		$	99.74		$	90.64		$	99.17
Total fair value of vested RSUs	$	2.6		$	3.5		$	18.8		$	23.9