Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	May 31, 2013	Feb. 28, 2014	Feb. 28, 2013
Income Tax Contingency [Line Items]
Federal statutory corporate rate		35.00%
Estimated annualized income tax rate	7.90%	5.40%
Received income tax refunds		$ 0.4	$ 0
Income tax payments		0	0
Net deferred tax assets	6.7	5.0
Net deferred tax assets classified as current	18.8	14.2
Tax Years 2007 Through 2010
Income Tax Contingency [Line Items]
Adjustment following IRS review of tax returns		$ 0