Note 3 - Stock-based Compensation (Details Textual) - USD ($) | 1 Months Ended | 3 Months Ended |
Jul. 31, 2015 | Jun. 30, 2017 | Jun. 30, 2016 |
Stock Issued During Period, Shares, Restricted Stock Award, Gross | | 0 | |
2006 Employee Equity Compensation Restricted Stock Plan (the "Employee Plan") [Member] | Restricted Stock [Member] | | | |
Stock Issued During Period, Shares, Restricted Stock Award, Gross | | 976,461 | |
2006 Outside Director Equity Compensation Restricted Stock Plan (the "Director Plan") [Member] | Restricted Stock [Member] | | | |
Stock Issued During Period, Shares, Restricted Stock Award, Gross | | 272,000 | |
Common Stock, Capital Shares Reserved for Future Issuance | 400,000 | | |
Percentage of Automatic Increase in the Amount of Shares Available for Issuance | 10.00% | | |
2015 Outside Director Equity Compensation Restricted Stock Plan ("2015 Director Plan") [Member] | Restricted Stock [Member] | | | |
Stock Issued During Period, Shares, Restricted Stock Award, Gross | | 30,000 | |
2016 Employee Equity Compensation Restricted Stock Plan [Member] | Restricted Stock [Member] | | | |
Common Stock, Capital Shares Reserved for Future Issuance | | 1,000,000 | |
Employee and Director Plans [Member] | Restricted Stock [Member] | | | |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition | | 3 years | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number | | 232,000 | 266,000 |
Employee and Director Plans [Member] | Restricted Stock [Member] | General and Administrative Expense [Member] | | | |
Allocated Share-based Compensation Expense | | $ 494,000 | $ 463,000 |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options | | $ 2,800,000 | $ 3,200,000 |