Summary of Accounts Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2014	May 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled revenues	$ 28,186	$ 25,516
Allowance for doubtful accounts	(5,343)	(5,438)
Total	157,988	172,108
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade accounts receivable	$ 135,145	$ 152,030