Stock-Based Compensation (Details) - Schedule of stock-based compensation (USD $) In Millions, unless otherwise specified	3 Months Ended
	Aug. 31, 2013	Aug. 31, 2012
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock option expense	$ 0.2	$ 1.0
Restricted stock unit expense	0.8	0.9
Stock-based compensation expense	1.1	2.0
Management Stock Purchase Plan [Member]
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	0	0
Employee Stock Purchase Plan [Member]
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	$ 0.1	$ 0.1