Amount of Financial Security Plan Benefit Expense Charged to Costs and Expenses (Detail) (Financial Security Defined Benefit Plans, USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2013	Nov. 30, 2012	Nov. 30, 2013	Nov. 30, 2012
Financial Security Defined Benefit Plans
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Service cost	$ 536	$ 593	$ 1,072	$ 1,186
Interest cost	609	591	1,218	1,182
Defined benefit pension plan, total	$ 1,145	$ 1,184	$ 2,290	$ 2,368