Long-Term Liabilities - Summary of Long-Term Liabilities Consisting of Other Deferred Liabilities and Life Insurance Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Aug. 31, 2014	May 31, 2014	Aug. 31, 2013
Other Liabilities Disclosure [Abstract]
Deferred compensation expense	$ 5,321	$ 5,386
Accrued warranty and related expenses	2,000	2,000	2,200
Total other deferred liabilities	7,321	7,386
Life insurance loans	6,334	6,334
Total	$ 13,655	$ 13,720