Stock-Based Compensation (Tables)

6 Months Ended

Nov. 30, 2013

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 [Table Text Block]

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

	Three months ended November 30,				Six months ended November 30,
	2013		2012		2013		2012
Stock option expense	$	4.4	$	0.6	$	4.6	$	1.6
Restricted stock unit expense		1.2		0.8		1.9		1.8
Management stock purchase plan		0.0		0.6		0.1		0.6
Employee stock purchase plan		0.0		0.1		0.1		0.2
Total stock-based compensation expense	$	5.6	$	2.1	$	6.7	$	4.2