Shareholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	May 31, 2012
Cumulative Preferred Stock
Class of Stock [Line Items]
Authorized preferred stock, shares	100,000
Cumulative Preferred Stock (Voting)
Class of Stock [Line Items]
Authorized preferred stock, shares	20,000
Premium on preferred stock redemption	$ 5
Preferred stock redeemable price per share	$ 105
Preferred stock price per share upon dissolution	$ 100
Preferred stock shares outstanding	0
Series B Junior Participating Preferred Stock
Class of Stock [Line Items]
Authorized preferred stock, shares	40,000
Preferred stock shares outstanding	0