Note 3 - Cash, Cash Equivalents and Investments (Details Textual)  | 
6 Months Ended | 
|---|---|
Mar. 31, 2017  | |
| Maximum [Member] | |
| Held-to-maturity Securities, Investment Term | 5 years | 
| X | ||||||||||
- Definition Represents information about the Company's investment term in money market accounts and bank certificates of deposit. No definition available. 
  | 
| X | ||||||||||
- Details 
  |