Investments - Additional Information (Detail) (U. S. Treasury Bills [Member], USD $)	3 Months Ended	9 Months Ended	12 Months Ended
Feb. 28, 2014	Feb. 28, 2014	May 31, 2013
U. S. Treasury Bills [Member]
Schedule of Held-to-maturity Securities [Line Items]
Investment maturity period		2 months	3 months
U. S. Treasury Bills, gross amortized cost	$ 5,000,000

The aggregate value of securities held, which were categorized as held-to-maturity, for which the interest rate reset through an auction process, that failed to be liquidated through auction, and which were sold at par value during the period.

No definition available.

Name:	us-gaap_HeldtomaturitySecuritiesSoldAtPar
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration