CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2016	May 31, 2016	May 31, 2015
Statement of Financial Position [Abstract]
Accounts receivable, allowances for doubtful accounts	$ 0	$ 353	$ 468
Claims receivable, allowances for losses	$ 0	$ 4,868	$ 2,684
Preferred stock, par value (in dollars per share)	$ 0	$ 0	$ 0
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0	0
Common stock, par value (in dollars per share)	$ 0	$ 0	$ 0
Common stock, shares authorized (in shares)	200,000,000	200,000,000	200,000,000
Common stock, shares issued (in shares)	152,185,616	154,421,585	130,557,676
Common stock, shares outstanding (in shares)	152,185,616	154,421,585	130,557,676