Note 4 - Stock-based Compensation - Summary of Stock Option Activity (Details) - Employee Stock Purchase Plan ESPP [Member] - $ / shares	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Balance (in shares)	77,285	63,915	54,307
Options granted (in shares)	63,607	55,766	52,836
Options exercised (in shares)	(17,561)	(10,893)	(15,523)
Options canceled (in shares)	(52,816)	(31,503)	(27,705)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	63,607	55,766	52,836
Balance (in shares)	70,515	77,285	63,915
Balance, Weighted Average Exercise Price (in dollars per share)
Options granted, Weighted Average Exercise Price (in dollars per share)	6.35	7.88	9.37
Options exercised, Weighted Average Exercise Price (in dollars per share)	6.69	8.34	9.57
Balance , Weighted Average Exercise Price (in dollars per share)
Shares Available for Grant, Options Granted (in shares)	(63,607)	(55,766)	(52,836)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	52,816	31,503	27,705
Shares Available For Grant [Member]
Options granted (in shares)	63,607	55,766	52,836
Options canceled (in shares)	(13,614)	(31,503)	(27,705)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	63,607	55,766	52,836
Shares Available for Grant (in shares)	365,581	389,844	414,975
Shares Available for Grant, Options Granted (in shares)	(63,607)	(55,766)	(52,836)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	13,614	31,503	27,705
Shares Available for Grant, Plan Expired (in shares)	(365,581)
Shares Available for Grant, Plan Authorized (in shares)	500,000
Shares Available for Grant (in shares)	450,007	365,581	389,844