Investments - Summary of Investments (Detail) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2014	May 31, 2013
Schedule of Held-to-maturity Securities [Line Items]
Gross Amortized Costs	$ 2,000	$ 4,000
U. S. Treasury Bills [Member]
Schedule of Held-to-maturity Securities [Line Items]
Gross Amortized Costs	2,000	4,000
Gross Unrealized Gains
Fair Value	$ 2,000	$ 4,000