Summary of Accounts Receivable (Detail) (USD $) In Thousands, unless otherwise specified	May 31, 2014	May 31, 2013	May 31, 2012	May 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled revenues	$ 14,901	$ 25,516
Allowance for doubtful accounts	(4,784)	(5,438)	(4,405)	(4,222)
Total	175,601	172,108
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade accounts receivable	$ 165,484	$ 152,030