Warranty - Reconciliation of Accrued Warranty (Detail) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2016	May 31, 2015
Guarantees [Abstract]
Balance at the beginning of the period	$ 6,911	$ 5,697
Accruals for warranties	6,898	8,395
Settlements made during the period	(6,492)	(7,181)
Balance at the end of the period	7,317	6,911
Accrued warranty	$ 6,911	$ 5,697	$ 7,317	$ 6,911
Non-current balance			2,500	2,400
Accrued warranty			$ 4,817	$ 4,511