Stock-Based Compensation

6 Months Ended

Nov. 30, 2014

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

Disclosure of Compensation Related Costs, Share-based Payments

Stock-Based Compensation

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,
	2014		2013		2014		2013
Stock option expense	$	3.8	$	4.4	$	4.6	$	4.6
Restricted stock unit expense	0.6		1.2		1.3		1.9
Management stock purchase plan	0.6		0.0		0.6		0.1
Employee stock purchase plan	0.1		0.0		0.1		0.1
Total stock-based compensation expense	$	5.1	$	5.6	$	6.6	$	6.7

During the three month periods ended November 30, 2014 and 2013, respectively, approximately 0.1 million and 0.1 million shares of Common Stock were issued by the Corporation pursuant to its stock-based compensation plans. For the six month periods ended November 30, 2014 and 2013, respectively, approximately 0.5 million and 0.3 million shares of Common Stock were issued by the Corporation pursuant to its stock-based compensation plans.