Reconciliation of Changes in Unrecognized Tax Benefits Associated with Uncertain Tax Positions (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Reconciliation of Unrecognized Tax Benefits [Line Items]
Balance at beginning of year	$ 697	$ 624	$ 421
Additions based on tax positions related to the current year			326
Additions based on tax positions related to prior years	110	191
Reductions resulting from a lapse of the applicable statute of limitations	(92)	(118)	(123)
Balance at end of year	$ 715	$ 697	$ 624