Warranty - Reconciliation of Accrued Warranty and Related Expenses (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	May 31, 2013
Guarantees [Abstract]
Balance at the beginning of the period	$ 5,882	$ 5,870
Accruals for warranties	4,106	4,403
Settlements made during the period	(3,867)	(3,890)
Balance at the end of the period	6,121	6,383
Non-current balance included in other deferred liabilities	2,200	2,000
Accrued warranty and related expenses	$ 3,921	$ 4,383	$ 3,682