Stock-Based Compensation (Tables)

6 Months Ended

Nov. 30, 2011

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block]

	Three months ended November 30,				Six months ended November 30,
	2011		2010		2011		2010
Stock option expense	$	3.4	$	1.6	$	4.8	$	5.4
Restricted stock unit expense		2.0		0.9		2.6		2.3
Management stock purchase plan		0.2		0.5		0.2		0.5
Employee stock purchase plan		0.1		0.1		0.2		0.2
Total stock-based compensation expense	$	5.7	$	3.1	$	7.8	$	8.4