Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Aug. 31, 2013	May 31, 2013
Income Tax Contingency [Line Items]
Federal statutory corporate rate	35.00%
Estimated annualized income tax rate	29.10%	(1.90%)
Income tax payments	$ 0
Received income tax refunds (less than $0.1 million in the nine-month period ending February 29, 2012)	0
Net deferred tax assets		6.7
Net deferred tax assets classified as current	18.3	18.8
Valuation allowances		1.5
Significant reserves for uncertain tax positions including related interest and penalties	0
Tax Years 2007 Through 2010
Income Tax Contingency [Line Items]
Adjustment following IRS review of tax returns	$ 0