Roll Forward of Allowance For Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of year	$ 555	$ 457	$ 522
Provision for doubtful accounts	591	860	445
Write-offs	(542)	(762)	(510)
End of year	$ 604	$ 555	$ 457