Roll Forward of Allowance For Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of year	$ 604	$ 555	$ 457
Provision for doubtful accounts	679	591	860
Write-offs	(819)	(542)	(762)
End of year	$ 464	$ 604	$ 555