Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	May 31, 2012	May 31, 2011
Accounts receivable, allowance for doubtful accounts	$ 532	$ 472
Claims receivable, allowance for losses	$ 3,435	$ 3,870
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, issued (in shares)	0	0
Common stock, par value	$ 0	$ 0
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, issued (in shares)	78,551,297	80,334,781
Common stock, outstanding (in shares)	78,551,297	80,334,781