Summary of Activity in Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Allowance for Sales Return and Doubtful Accounts [Line Items]
Balance at beginning of year	$ 4,784	$ 5,438	$ 4,405
Provision for doubtful accounts	233	2,140	2,922
Write-off of bad debts	(2,242)	(2,794)	(1,889)
Balance at end of year	$ 2,775	$ 4,784	$ 5,438