Note 4 - Stock-based Compensation - Stock Option Activity (Details) - $ / shares	9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Options, outstanding (in shares)	54,800
Weighted-average exercise price, outstanding (in dollars per share)	$ 3.13
Exercised (in shares)	(15,850)	(172,450)
Exercised (in dollars per share)	$ 3.97
Weighted-average exercise price, outstanding (in dollars per share)	$ 2.79
Options, outstanding (in shares)	38,950