Stock-Based Compensation (Tables)

3 Months Ended

Aug. 31, 2014

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

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan

The following table summarizes stock-based compensation expense included in Selling, general and administrative expenses for the periods indicated: 

	Three months ended
	August 31, 2014		August 31, 2013
Stock option expense	$	0.8	$	0.2
Restricted stock unit expense	0.7		0.8
Management stock purchase plan	0.0		0.0
Employee stock purchase plan	0.1		0.1
Total stock-based compensation expense	$	1.6	$	1.1