Summary of Activity in Allowance for Doubtful Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Allowance for Sales Return and Doubtful Accounts [Line Items]
Balance at beginning of year	$ 5,438	$ 4,405	$ 4,222
Provision for doubtful accounts	2,140	2,922	1,650
Write-off of bad debts	(2,794)	(1,889)	(1,467)
Balance at end of year	$ 4,784	$ 5,438	$ 4,405