Summary of Accounts Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2013	May 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled revenues	$ 20,569	$ 20,561
Allowance for doubtful accounts	(5,352)	(4,405)
Total	154,974	157,625
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade accounts receivable	$ 139,757	$ 141,469