Note 6 - Stock-based Compensation - Option Activity (Details) - May. 31, 2015 - $ / shares	Total
Balance (in shares)	966,692
Balance (in dollars per share)	$ 22.55
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	171,100
Granted (in dollars per share)	$ 21.71
Exercised (in shares)	(2,500)
Exercised (in dollars per share)	$ 19.91
Terminated or expired (in shares)	(750)
Terminated or expired (in dollars per share)	$ 23.28
Balance (in shares)	1,134,542
Balance (in dollars per share)	$ 22.43
Vested and exercisable (in shares)	692,283
Vested and exercisable (in dollars per share)	$ 22.22