Note 3 - Summary of Significant Accounting Policies - Stock Options Vested and Expected to Vest (Details)	9 Months Ended
	Jun. 30, 2018 $ / shares shares
Number of shares (in shares) | shares	228,837
Weighted-average remaining contractual life (Year)	3 years 335 days
Weighted average exercise price (in dollars per share)	$ 8.48
Exercisable number of shares (in shares) | shares	188,837
Exercisable weighted- average exercise price (in dollars per share)	$ 9.31
Range One [Member]
Range of exercise prices, lower (in dollars per share)	2.01
Range of exercise prices, upper (in dollars per share)	$ 3
Number of shares (in shares) | shares	27,300
Weighted-average remaining contractual life (Year)	8 years 47 days
Weighted average exercise price (in dollars per share)	$ 2.70
Exercisable number of shares (in shares) | shares	7,700
Exercisable weighted- average exercise price (in dollars per share)	$ 2.75
Range Two [Member]
Range of exercise prices, lower (in dollars per share)	4.01
Range of exercise prices, upper (in dollars per share)	$ 5
Number of shares (in shares) | shares	36,100
Weighted-average remaining contractual life (Year)	4 years 18 days
Weighted average exercise price (in dollars per share)	$ 4.53
Exercisable number of shares (in shares) | shares	30,000
Exercisable weighted- average exercise price (in dollars per share)	$ 4.62
Range Three [Member]
Range of exercise prices, lower (in dollars per share)	5.01
Range of exercise prices, upper (in dollars per share)	$ 10
Number of shares (in shares) | shares	51,000
Weighted-average remaining contractual life (Year)	5 years 113 days
Weighted average exercise price (in dollars per share)	$ 7.80
Exercisable number of shares (in shares) | shares	36,700
Exercisable weighted- average exercise price (in dollars per share)	$ 8.02
Range Four [Member]
Range of exercise prices, lower (in dollars per share)	10.01
Range of exercise prices, upper (in dollars per share)	$ 15
Number of shares (in shares) | shares	114,437
Weighted-average remaining contractual life (Year)	2 years 94 days
Weighted average exercise price (in dollars per share)	$ 11.40
Exercisable number of shares (in shares) | shares	114,437
Exercisable weighted- average exercise price (in dollars per share)	$ 11.40