Note 2 - Net Income Per Share - Weighted Average Common Shares Outstanding (Details) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Net income	$ 747,897	$ 367,942	$ 1,249,055	$ 1,377,902
Weighted average common shares (in shares)	13,521,172	13,422,222	13,516,608	13,411,183
Dilutive potential common shares (in shares)		27,990	55,066	13,995
Weighted average dilutive common shares outstanding (in shares)	13,521,172	13,450,212	13,571,674	13,425,178
Basic (in dollars per share)	$ 0.05	$ 0.02	$ 0.09	$ 0.10
Diluted (in dollars per share)	$ 0.05	$ 0.02	$ 0.09	$ 0.10