Description of Business, Basis of Presentation, and Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013	May 31, 2013
Description of Business, Basis of Presentation, and Significant Accounting Policies (Textual)
Disclosure on geographic areas, Description of revenue from external customers			revenue within Germany, which represented less than one percent of the Company's total revenue	revenue within Germany, which represented less than one percent of the Company's total revenue
Disclosure on geographic areas, Long-lived assets			Long-lived assets in Germany are insignificant in relation to total long-lived assets of the Company		Long-lived assets in Germany are insignificant in relation to total long-lived assets of the Company
Maximum individual workers' compensation claims liability			$ 1.0		$ 1.0
Workers' compensation insurance costs in current liabilities	8.5		8.5		6.8
Workers' compensation insurance costs in long-term liabilities	14.8		14.8		13.7
Stock-based compensation costs recognized	$ 7.1	$ 5.4	$ 21.7	$ 16.9