Shareholders' Equity (Details) (USD $)	6 Months Ended
	Nov. 30, 2011
Cumulative Preferred Stock [Member]
Authorized preferred stock, shares	100,000
Series B Junior Participating Preferred Stock [Member]
Authorized preferred stock, shares	40,000
Preferred stock shares outstanding	0
Cumulative Preferred Stock (Voting) [Member]
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